In their ongoing hunt for extraterrestrial life, astronomers are searching for three key ingredients: liquid water, a source of energy, and complex organic molecules, which make up the basic building blocks of life as we know it.

If a planet has all three, it’s considered a more promising location for life to emerge — but it’s not as easy to discover as it sounds. 

Evidence for life? Tantalizingly, all three of these ingredients may exist on some of the moons of Jupiter and Saturn, which host vast oceans of liquid water below crusts of ice kilometers thick. 

As they orbit their host planets, both Europa (Jupiter’s fourth largest moon) and Enceladus (Saturn’s sixth largest) are stretched and squeezed by tidal forces, a source of energy that helps heat their subsurface oceans to far more comfortable temperatures than their frigid exteriors would suggest.

That leaves just the third key ingredient. That one is ultimately far more difficult to detect from Earth, yet across several missions to Jupiter and Saturn over the past few decades, astronomers have now gathered enticing evidence that complex organics may be abundant on both Europa and Enceladus. 

In 2015, NASA’s Cassini probe passed directly through an icy plume that had erupted from a crack on Enceladus’ south pole. With its in-built Cosmic Dust Analyzer, the probe identified the signature of complex organic molecules in the ice grains. However, the measurements were not enough to pin down the origin or identity of the molecules.

The challenge: As ice grains in the plume were ejected into space at speeds of over 400 meters per second, they would have impacted Cassini’s detector at colossal speeds. 

According to some astronomers, these impacts may have been violent enough to break apart any organic molecules riding along inside the grains, degrading any samples picked up by the probe. Yet due to the limited resolution of Cassini’s measurements, we can’t be sure whether or not this really happened. 

Ultimately, without a clear understanding of what happens to complex organics during these detector impacts — be it with Cassini or any future missions to Europa or Enceladus — astronomers can’t make any particularly reliable predictions about the life-harboring potential of these icy moons. 

The experiment: In a new study published in PNAS, Robert Continetti and a team of astronomers at UC San Diego have shed new light on the problem. They wanted to imitate the impacts taking place as Cassini passed through Enceladus’ icy plume, combined with measurements from a state-of-the-art mass spectrometer.

The researchers started by preparing a water-based solution of various amino acids — those are the molecular building blocks of proteins, which are essential to all life on Earth. Through a technique named “electrospray ionization,” they then pushed the solution through a thin capillary tube while subjecting it to a high voltage.

In the process, the liquid became charged, creating a fine spray of charged droplets just a few hundred nanometres across as it emerged from the end of the tube. Continetti’s team then injected the droplets into a vacuum, where they immediately froze into tiny, solid ice grains, much like those picked up by Cassini. 

From here, the grains were accelerated by strong electric fields and then passed into a custom-built instrument named the Hypervelocity Ice Grain Impact Mass Spectrometer. Crucially, this device could select grains with specific ratios between their mass and charge — a value determined by their amino acid contents — to impact an ion detector at the back of the instrument. 

Withstanding impacts: Remarkably, the team found that each type of amino acid they studied survived the impact, even when the grains were accelerated to speeds of over four kilometers per second, which is much faster than the speeds of the ice grains picked up by Cassini.

Their results were consistent with Cassini’s data and also showed that the amino acids became less detectable when prepared in salty solutions. Since Enceladus’ ocean is likely very salty, this result goes further to explaining the probe’s observations.

Altogether, the results provide the first unambiguous evidence that, using similar instruments, future missions could safely fly through the icy plumes of Europa and Enceladus and study them without damaging any complex organic molecules in the process. 

Continetti’s team now hopes their results could offer important guidance for future missions to the icy moons of Jupiter and Saturn — including NASA’s Europa Clipper Mission, due for launch in October this year. In turn, they may even bring us a step closer to knowing whether life may yet exist on other worlds in our solar system.

This article Ice plumes could reveal signs of life on Europa and Enceladus is featured on Big Think.

In all of the Universe, there is nothing quite so mind-bending as a black hole. Black holes are usually the corpses of long-dead stars — ones that lived and died in a blinding flash called a supernova. This cataclysmic explosion crushes the core to densities billions of times greater than any substance found on Earth.

The result is a stellar corpse with a mass typically between 5 and 50 times that of the Sun, with all of the mass crushed to a volume smaller than an atom. What then emerges is a strong gravitational field — so strong that, close to the tiny mass, not even light can escape.

The area around the crushed star from which light cannot escape is called the event horizon. For the simplest black hole, the event horizon is a sphere with a radius called the Schwarzschild radius, named after the German physicist Karl Schwarzschild, who first calculated it. For a black hole with the mass of the Sun, the Schwarzschild radius is about 3 kilometers (1.9 miles). In comparison, the radius of the Sun is about 700,000 km.

Much has been written about what happens to someone who falls into the event horizon of a black hole, but what is less known is the claim that as you fall into a black hole, you will be ripped apart by the gravitational force of the hole in a process called “spaghettification.” If you fall feet-first into a black hole, your feet will be pulled harder than your head, resulting in you being stretched out like a long piece of spaghetti.

So, is spaghettification real? Will any object get stretched as it falls into a black hole?

Spaghettification

Here’s where things get interesting. Yes, spaghettification is real — but several parameters determine whether it will happen in any specific situation. For example, a very small object will not experience spaghettification. This is because the force that pulls apart any object isn’t the gravity itself — it’s the difference in the gravitational force between the ends of the object. For a human, that would be the feet and the head. The name of this kind of force is called a tidal force: It’s the same phenomenon that gives Earth its twice-daily tides, as the force of gravity from the Sun on one side of the Earth differs from the other.

The tidal force between the ends of the object depends on the length of the object (L), the mass of the body creating the gravitational field (M), and the distance between them cubed (R³). (For the mathematically savvy, a = 2GML/R³, where G is the gravitational constant and a is the acceleration.)

From this, we see that the mass of the gravitating body is important, but even more important is the distance between it and the object being subjected to tidal forces. Here are some numbers that can help make sense of it all. On the surface of the Earth, the difference in gravity between the head and the feet of a 6-foot-tall man is about 0.00007% the force of gravity itself. So, it’s no surprise at all that we don’t perceive differences in gravity as we stand up.

In contrast, for a black hole with the mass of our Sun, the head and feet of that same man located about 100 kilometers above the hole would experience a difference in gravity about six million times the force of gravity on Earth — a force difference that would definitely pull a person apart.

This raises another point: Not all materials are equally strong. For example, a steel cable is much stronger than the human body, so it can withstand tidal forces much more easily than a human.  

If we want to calculate how far away a person would need to be from a solar-mass black hole and not die, we need to know the force at which a human body fails. As it happens, 19th-century military manuals give numbers for the correct way to hang a human. Too little force and the hanging will not break the neck of the condemned; too much and the force will decapitate them. Very roughly, a force of about 2,000 pounds (9,000 Newtons) will pull a human apart. From this, we can calculate the closest safe distance a human can get to a solar-mass black hole: about 700 km (440 miles). And, of course, the tidal force would hurt for much larger distances.

We have seen that falling into a solar-mass black hole would be deadly. Long before you approached the event horizon, you would be painfully disassembled. But what about falling into a supermassive black hole?

Bigger is less dangerous

Supermassive black holes can be found at the center of nearly every galaxy. These cosmic leviathans have masses that are millions or even billions of times more than our Sun. Surely, with such huge masses, the effect will be much stronger, right?

Let’s see what happens when for the black hole at the center of our Milky Way galaxy.  It has a mass of about 4.3 million solar masses. The Schwarzschild radius for this black hole is about 12 million kilometers. So, for a person at the Schwarzschild radius of this huge black hole, the gravity difference between head and feet is about 0.02% — barely noticeable.

This demonstrates a very surprising point: At least as far as spaghettification is concerned, larger black holes are less dangerous than small ones. For a supermassive black hole, you could fall through the event horizon past the point of no return without feeling even a twinge. In contrast, for a small black hole, you will be ripped apart long before you ever get close to the event horizon.

The final message is that falling into a black hole is a bad thing to do no matter what.  But, if you do, pick a big one. 

This article “Spaghettification”: How black holes stretch objects into oblivion is featured on Big Think.

My colleague Ian Crawford and I recently made a bet — a little bet with potentially big consequences. 

In a paper recently published in Nature Astronomy, Ian — a planetary scientist and astrobiologist at the University of London — discussed possible solutions to the Fermi paradox, also commonly referred to as the “Great Silence.” This refers to the mismatch between the widely held expectation that advanced technological life should be common in the Universe and the apparent lack of evidence to support that belief. The discovery in this century of thousands of planets beyond our Solar System, along with recent interest by NASA and others in investigating Unidentified Aerial Phenomena (UAP), make a re-analysis of the Fermi paradox timely.

Our conclusion is that advanced extraterrestrial intelligent life (ETI) is either (1) extremely rare or non-existent in our galaxy or (2) these civilizations are deliberately hiding from us. No other possibility seems very likely. While Ian tends to favor the first explanation, I lean toward the second one. We settled on a wager, a bottle of whiskey, on whether convincing evidence for technological life elsewhere in the Universe will be found within the next 15 years.

What makes us conclude that there are only two likely answers to the Fermi paradox? We started by grouping all previously suggested solutions into categories. Some are based on the view that interstellar travel is unlikely or impossible, an argument that seems easy to dismiss. Even with spaceship velocities as low as tens of kilometers per second — speeds already attained by our “primitive” Pioneer, Voyager, and New Horizons spacecraft — it should be possible for aliens, whether biological or artificial, to reach nearby stars if they really wanted to, even if it takes millions of years. 

Then there are what might be termed “sociological” solutions. Maybe extraterrestrials always destroy themselves before they master interstellar travel. Or maybe they all opt to stay home rather than venture out into space. (If that’s true, we’re now arriving at the point in our own evolution where we might detect technosignatures from these stay-at-home societies via remote sensing.) Amri Wandel at The Hebrew University of Jerusalem has made the intriguing suggestion that non-technological life is so common across the galaxy that ETIs only bother to visit planets with similarly advanced technology. But that certainly wouldn’t apply to us on Earth — we’d be excited to visit any planet with life on it, advanced or not. Besides, these kinds of behaviors only plausibly resolve Fermi’s paradox if they apply to every civilization in the Milky Way. And that seems unlikely given the huge number of civilizations that may have arisen over our galaxy’s 13-billion-year history.

The “Great Filter”

Related to these sociological explanations is the idea of a “Great Filter” — an evolutionary hurdle that most life forms in the galaxy never or hardly ever manage to survive. It may happen right at the point when life originates, and for some reason, we made it through. Or maybe, ironically, it’s the development of technology itself that spells doom. Many other intelligent species have arisen on our own planet, from parrots to octopuses to dolphins, and many of these have been around much longer than Homo sapiens. But none of them have developed nuclear weapons or other means of mass destruction. Is there perhaps a key evolutionary trait, perhaps related to human language or our specific type of culture or our tribalistic nature, that contains the seeds of our own destruction? Perhaps there are several Great Filters at different stages of evolution. Maybe the worst ones lay ahead of us (the scariest possibility).

Of course, if ETIs are extremely rare in the galaxy, there is no paradox. The reason we don´t see them is because they aren’t there. On Earth, it took about four billion years — most of our planet’s lifetime — to advance from simple microbial life to advanced technological life. And as far as we know, it has only happened here once. 

The “zoo hypothesis”

The other possibility, however—the one I’ve bet a bottle of whiskey on—is that the aliens are here. They just don’t want us to know it. Following up on a 1973 proposal by John Ball, this “zoo hypothesis” holds that Earth is effectively a fenced-off game preserve, with extraterrestrial visitors not allowed to interfere. The idea was anticipated in Olaf Stapledon´s 1937 science-fiction epic Star Maker and was implicit in Star Trek’s “Prime Directive” in the 1960s.

It seems reasonable that any ETI with the technical ability to cross interstellar space could remain hidden from us if they choose to. One problem with this hypothesis, though, is that all such visitors would have to agree not to enter the zoo, at least for some time, perhaps until we reach some stage of advanced technology. It could be that some early galactic civilizations established rules governing non-interference for subsequent alien visitors to follow. Such a policy might be hard to enforce, however, and it’s tempting to speculate that a small fraction of reported UAP sightings are due to interstellar visitors not playing by the rules. Maybe the “zookeepers” mean to initiate contact gradually, depending on humanity’s stage of technological evolution. All we can do right now is guess, unfortunately.

To those who consider all of this idle speculation, here’s a challenge: How would you reconcile the Copernican principle — that humans don´t occupy a privileged position in the cosmos — with the idea that we really are the only advanced civilization in the Universe (in which case, consider the enormous responsibility weighing on our species!).

If ETIs are at least somewhat common, the only other way out of Fermi’s famous dilemma is the zoo hypothesis. And the good news is that, given our current rate of technological progress, it will be increasingly hard for the aliens to hide from us. We’re now discovering their planets at a rapid clip, and soon we may be able to detect their technosignatures remotely. I just hope it happens within 15 years. I have a bottle of whiskey riding on it. And more importantly, both of us, Ian and I, simply want to know.

This article Life in the Universe: It’s either everywhere or nowhere is featured on Big Think.

At a recent meeting of the American Astronomical Society, researchers announced a surprising discovery — one that will add to a growing list of astronomical anomalies that run afoul of one of the guiding principles of cosmological research.

Humanity has long imagined itself to be somehow special in the Universe: The Bible told us we have dominion over other living things, while the Greek philosopher Plato wrote that the Earth lies at the center of the Universe.

Yet science has told a different story. Darwin realized that humanity was but one species on a vast tree of life and, as early as the early 16th century, Polish scientist Nicolaus Copernicus made the bold claim that the Earth was not the object around which the Universe revolved. Indeed, the scientific community has come to realize that our astronomical neighborhood isn’t special, and Earth doesn’t necessarily grant us a special vantage point from which to view the cosmos. Our planet orbits an ordinary star inside an ordinary galaxy. More broadly, astronomers have come to believe that on the very largest scales, the Universe is uniform — all places are pretty much the same. This proposition has come to be called the Copernican principle.

Challenging the Copernican principle

On the face of it, the Copernican principle seems to be violated when we look out into the Universe. Matter congregates in stars, surrounded by vast swathes of interstellar space. On galactic scales, the story is much the same, with galaxies containing countless stars but separated by enormous distances. However, the situation is different on the very largest scales. When one zooms back far enough — to a scale where individual galaxies are dots on a much bigger picture — the distribution of matter begins to look quite uniform. 

There’s a good reason for this. When the Universe began, it was smaller and hotter and filled with hot plasma. Plasma, like air, can transmit sound waves. And sound waves mean that some locations have slightly denser plasma than others.

Over the eons, those places with slightly denser plasma exerted a force on their neighbors, drawing nearby gas (plasma becomes gas when it cools). Those locations become denser over time, forming galaxies, stars, and all of the familiar inhabitants of the cosmic zoo.

But it’s a slow process — especially for large objects. Stars can collapse from gas clouds in millions of years, while galaxies might take a billion years. Bigger objects take longer. Since the Universe is about 13.8 billion years old, this sets an upper limit on how large of a structure can form while still being held together by gravity. So, astronomers do not expect to see gravitationally bound objects much bigger than 1 to 2 billion light-years in size. 

If objects larger than that are seen, this could invalidate the Copernican principle. Given the centrality of the Copernican principle in modern cosmology, this would require some significant head-scratching among the scientific community.

The “Big Ring”

At a recent meeting of the American Astronomical Society, astronomers from the University of Central Lancashire (UCLanc) in England announced the discovery of a ring of galaxies located about 9.2 billion light-years from Earth. The diameter of the ring is about 1.3 billion light-years, giving it a circumference of approximately 4 billion light-years. Researchers have taken to calling this structure the “Big Ring.” If confirmed, this structure would certainly pose a challenge to accepted cosmology.

The Big Ring isn’t the first large structure reported by astronomers. In 2021, the same group at UCLanc reported what was called the “Great Arc,” an arc of stars about 3.3 billion light-years long, located about 9.2 billion light-years away. Interestingly, the Great Arc and the Big Ring were found in the same basic location in space.

It’s not only the UCLan group that has discovered unexpected and large structures in the Universe. In 2014, a group of astronomers reported a possible structure called the Hercules-Corona Borealis Great Wall. This structure is about 10 billion light-years long and was discovered by a significant concentration of gamma-ray bursts. A few years earlier, in 2012, a different group reported a structure called the Huge Large Quasar Group, consisting of 73 quasars. This structure is about 4 billion light-years long.

So, does the discovery of an ever-proliferating number of large structures spell the death knell of accepted cosmology? This would be a hasty conclusion. There are a couple of reasons to be cautious. The first is simple: If you wish to overturn a central principle of cosmology, you had better use impeccable data. While the reported large structures were discovered by reputable researchers, in most cases the data was not entirely conclusive. When astronomers restrict themselves to observations that are inarguable, no structures larger than about 1.4 billion light-years have been observed.

Another consideration is the role of chance in observation. The Universe is huge, with an estimated 2 trillion visible galaxies distributed over a volume of approximately 400 trillion cubic light-years. With so many galaxies, some configurations will inevitably occur purely by chance. It may be that the observed large structures are simply two smaller ones that occurred near one another. Such an unfortunate occurrence could fool astronomers.

However, the possibility that a bedrock assumption of cosmology like the Copernican principle could be overturned means scientists will continue to search for robust observations of large structures. If confirmed, the scientific community will have to revisit their core ideas. Next-generation surveys like the Euclid telescope, launched in the summer of 2023, will give researchers a cornucopia of new data to study. Once the facility is fully operational, it is expected to make stringent tests of the Copernican principle, perhaps nailing it down once and for all.

This article Surprising discovery challenges key principle of modern cosmology  is featured on Big Think.

On a spring night in 2019, in the bowels of Tornado Alley, nature documentarian Hank Schyma was out photographing a storm when he captured something mysterious. A “ghost,” but not of the paranormal sort. In the distance, this specter appeared as a faint green blob over a red flash of light.

The red flash was familiar to Schyma, a savvy citizen scientist. The technical name for it is a sprite, an electrical discharge that occurs in the upper atmosphere during intense thunderstorms, glowing red in the sky because of excited nitrogen molecules in the air. He happened to be out looking for this exact phenomenon and other forms of upper-atmosphere “lightning” known as transient luminous events (TLEs) that night.

“Multiple vibrant red sprites and a couple secondary jets were captured with great excitement,” Schyma recalls. A blue jet is another type of TLE that appears as a spray of cerulean light aimed upward. “Upon reviewing the footage later that night and the next morning, I noticed a green afterglow proceeding two of the larger red sprite events. On video, the green appeared to be a faint aurora lasting about a second.” Schyma says he’d never seen or heard of such a thing, so he called up self-described sprite chaser Paul Smith, who Schyma deems a “TLE expert.”

Together, they named it the “green ghost,” with “ghost” being a close-enough backronym for “Green excitation of Oxygen in Sprite Tops,” which was Smith’s initial hypothesis. The discovery piqued the interest of astrophysicists abroad, who spent the following four years trying to document the foggy blob and figure out what causes it. Finally, they found a green ghost.

“The connection with green ghosts and asteroid dust is interesting.”

According to their research, published in the journal “Nature Communications” on December 12, 2023, these rare mesospheric emissions require a cocktail of atmospheric conditions or, one might say, the perfect storm. There is excited atomic oxygen, as Smith suggested, but the study found that various metal ions were also present, including some that came from asteroids.

Upper-atmospheric lightning and electrical-discharge phenomena. Green ghosts appear in the footprint of a red sprite. (Wikimedia / public domain)

“The connection with green ghosts and asteroid dust is interesting, but I am not surprised,” says Thomas Ashcraft, a NASA Citizen Scientist who runs an observatory in New Mexico. Ashcraft says he documented a green ghost years before Schyma’s discovery, but chalked it up to “common green air glow.” He credits Schyma’s keen eye for recognizing its significance and ultimately inspiring the research campaign that followed.

To investigate the mysterious emission, the authors of the study, led by María Passas-Varo of the Institute of Astrophysics of Andalusia, aimed a spectrograph at the sky above Castellgalí, in Spain’s Catalonia region. Over four years, they recorded 42 sprites, and only one of them produced a green ghost.

The U.S. Great Plains are “notorious for their large quantities of sprites.”

The instance occurred in September 2019 over a jellyfish sprite, named for its characteristic tentacles of red light, just as it did when Schyma observed it in Oklahoma months before. It turns out amateur green ghost hunters have had much more success in finding the phenomenon than the researchers. Ashcraft has documented the specter about 15 times and Schyma 25 times since his initial 2019 encounter.

“I chase storms pretty much all year. Though I’ve documented TLEs in Argentina and Thailand, it’s hard to compete with the high frequency of monster storm complexes here in the United States,” says Schyma.

Dr. Oscar van der Velde, one of the authors of the study, says the U.S. Great Plains are “notorious for their large quantities of sprites.”

Sprites above Rome seen from Antibes. (Denis Huber / CC BY-SA 4.0)

He also says one reason why the study in Spain only recorded one green ghost could additionally come down to methodology. “The spectrograph works with a slit which must be aimed manually exactly to the right altitude of the sprite top. And then, many regular sprites do not display any ghost, only the tallest and brightest ones.” In short, operating a spectrograph is much different than pointing a DSLR at the sky.

Ashcraft says that although he’s documented more than a dozen green ghosts, he’s never seen one with the naked eye. “A person with acute vision should be able to see a green ghost, since they take a little longer to quench before they disappear,” he says. But the ghost appears only once out of every 100 sprites, and a sprite lasts just a few milliseconds. In other words, most of us don’t stand a chance without a decent camera or telescope—and a lot of luck.

This article Scientists finally find mysterious mesospheric ghosts is featured on Big Think.

Astronomers have known for nearly a century that our Universe is expanding. For decades, scientists expected this expansion to be slowing down due to the force of gravity. However, that all changed in the 1990s when astronomers realized that not only is the Universe expanding, but it’s doing so at an accelerating rate, like a runaway train on a downward slope. The Universe is literally blowing itself apart.

The culprit for this expansion is a phenomenon called dark energy. This invisible and undetectable substance is effectively a form of antigravity, pushing distant galaxies apart and making empty space ever emptier. While the scientific community is confident that dark energy exists, this energy is very weak — equivalent to just a couple of protons per cubic meter — and determining its properties is very difficult. But after a decade of effort, astronomers have just released a very precise measurement of the amount of dark energy as it has existed over the last 9 billion years. 

The Dark Energy Survey

The Dark Energy Survey (DES) is a collaboration of astronomers who used a powerful telescope in Chile to scan about an eighth of the sky, looking for supernovas. A supernova is the explosion of a star that leads to a flash so bright that it can be seen for billions of light-years. While there are a couple of different kinds of supernovae, a specific kind — called an “SN-Ia” — is very special. SN-Ia supernovae are all very similar, meaning they all generate about the same amount of light. Given that more distant objects appear dimmer than nearby ones, astronomers can compare how bright a supernova appears in their telescope to its original brightness and use that information to determine how far away the supernova is from Earth.

Given that light travels at a fixed speed, knowing how far away something is tells us how old it is. After all, light from more distant objects takes longer to get to Earth. So, by looking at ever more distant objects, astronomers effectively have a time machine. Nearby galaxies tell us about the expansion of the Universe now, while distant objects tell us what happened in the very distant past.

Astronomers can also image the galaxies in which these supernovae occur to determine the spectrum of light they emit. Because of the Doppler effect, galaxies that are moving away from Earth will appear redder than if they were stationary, with the amount of redness being related to the galaxies’ speed. (The Doppler effect mentioned here is the visual equivalent of the change of a train whistle’s pitch as the train goes by you.)

Scientists can combine the measurement of the distance and the measurement of the velocity to work out the expansion history of the Universe — this is how the original observation of the accelerating expansion of the Universe was accomplished back in 1998.

The original measurement used a mere 52 supernovae to make their discovery. Recently, DES used about 1,500 supernovae for their new measurement. The team also used advanced AI techniques to make sure that the supernovae it was looking at were the desired SN-Ia type. This result is a huge advance in the understanding of dark energy.

The density of dark energy

Scientists have long known that dark energy currently constitutes about two-thirds of the energy in the Universe. It remains an open question whether this ratio is a constant. And it’s here that the situation gets complicated. According to the currently accepted theory of the Universe, what is constant is the density of dark energy. As the volume of the Universe increases, the fraction of the universe made up of dark energy increases.

Previous measurements suggest that the density of dark energy is constant, but those early measurements had some uncertainty associated with them, leading to uncertainty in our understanding of the evolution of the Universe. Precisely determining the density of dark energy would have profound consequences on cosmological theories.

If the density of dark energy in the Universe is constant, a parameter of the theory represented by the letter w should equal negative one (w = -1). When DES scientists used their data to measure the parameter, they found a value of (w = -0.80), but with an uncertainty ranging from -0.66 to -0.96. The discrepancy between prediction and measurement is about the same size as the uncertainty, meaning that dark energy density could be constant.

DES is not the only group looking at the amount of dark energy. When they combined their measurements with earlier ones by the Planck group, the combined result was more precise: w = -0.955, with an uncertainty range of -0.923 to -0.992. 

The bottom line is that the measurement is very close to prediction, leading scientists to conclude that dark energy density is probably constant, but the tiny residual discrepancy means that they are not completely certain. They will continue to look at their data and combine other measurements to refine their result.

The dark energy density is one of the most important parameters in terms of predicting the future evolution of the cosmos: whether the expansion will continue to accelerate like it has been or whether the acceleration will slow down or speed up. Future measurements, like those planned at the Vera C. Rubin Observatory will help nail down this important measurement.

This article Astronomers use AI to shed light on dark energy is featured on Big Think.

A black hole is one of the most fascinating of all cosmic phenomena. Essentially, black holes are locations in space that completely overturn our intuition of how space and time behave. In movies, they are often depicted as the ultimate danger — ravenous monsters that will reach out and grab any unwitting spaceship that falls into their gravitational field. Even weirder, their interior is cloaked in mystery. Scientists using Einstein’s theory of general relativity tell us that the center of a black hole is a singularity: a place where an amount of mass equivalent to at least five times that of our Sun is compressed into a spot with zero volume.

So, what is the reality of black holes? And is there any truth to that singularity idea?

Approaching a black hole

Let’s start with the easiest. Far outside of a black hole, the gravity they exert is really quite ordinary. Replace the Sun with a black hole with the same mass, and the Earth would continue its stately march through the Solar System, circling the black hole every 365.25 days. Admittedly, the Earth would be dark and begin to freeze, but gravitationally speaking there would be no change.

When one gets closer to the black hole, however, the story becomes different. What does “closer” mean? When talking about black holes, there are a couple of radii that are noteworthy. The first is the singularity. General relativity says that all of the mass of the black hole has been crushed by gravity down to literally zero size. So, it might be sensible to say that the radius of a black hole is zero (though, as we shall see in a moment, this is a hasty characterization).

Another important feature is a sphere called the event horizon. The event horizon is defined by the behavior of light. Light, like mass, is affected by gravity. In the same way that it takes energy to lift a rocket from the surface of the Earth into space, it takes energy for light to leave a heavy object. The stronger the gravity, the more energy it takes for light to escape.  

As one gets closer and closer to the center of a black hole, gravity becomes stronger and stronger. There is a radius at which an object traveling at the fastest speed possible — the speed of light — can no longer escape the black hole.

The size of the event horizon depends on the mass of the black hole, but other important parameters include whether it is rotating and whether it has electric charge. However, for the simplest possible black hole — one that is both uncharged and not rotating — the radius of the event horizon is called the Schwarzschild radius, named after the German physicist and astronomer Karl Schwarzschild. For distances closer to the center of the black hole than the Schwarzschild radius, nothing can escape — not even light. Outside it, objects can escape, at least in principle.

For an object with the mass of the Sun, the Schwarzschild radius is approximately 3 kilometers (1.9 miles). In contrast, the radius of the Sun is about 700,000 kilometers or 435,000 miles. The Schwarzschild radius of the Earth is just shy of a centimeter. At distances of about 2.5 times the Schwarzschild radius, objects can orbit the black hole. From about 2.5 to 1.5 times the Schwarzschild radius, orbiting is difficult and unstable, requiring enormous effort to sustain the orbit.

At about 1.5 times the radius of the event horizon lies the “photon sphere.” At this distance, the black hole bends space so much that photons of light actually orbit the black hole. If you were at this distance from a black hole, the light from the back of your head would circle the hole and hit you in the face. You wouldn’t need a mirror to see if you combed your hair properly.

Getting closer to the black hole, things get even stranger. A person far from the black hole would see objects approach the event horizon moving slower and slower, and eventually fade from view. However, as a person approaches the event horizon, nothing much changes, though the view one has of the surrounding sky becomes heavily distorted by the gravitational field of the black hole. (Note: Depending on the size of the black hole and the size of the object approaching the event horizon, gravitational forces might pull the object apart. Or not. Many things determine whether an object is destroyed and one cannot generalize. I’m ignoring this effect.)

Once a person passes the event horizon, that’s the point of no return. Once there, you can never leave. And here’s the interesting thing: Because nothing can leave the event horizon, we have no data about what occurs inside. Our understanding of the nature of space and time inside a black hole is entirely theoretical, and these ideas may or may not be right. However, according to theory, space and time become reversed inside the event horizon. As you move toward the center of the black hole, you are moving in time, not space. This is a crazy idea, but it might be true.

The singularity 

It’s when one approaches the center of the black hole that our ignorance of measurement is joined by an ignorance of theory; the theory breaks down. It is common to hear that the center of a black hole is a singularity: a theoretical place where the mass of the hole is compressed into zero size. But this isn’t what a singularity really means.  

A singularity is a place where the theory breaks down. If one takes general relativity seriously, the zero-size option is real. But that would also mean a place of infinite density. And what all of this really means is that our theory no longer works.

Among practicing scientists, the consensus is that the singularity means that general relativity fails. As such, what we need is a new theory of gravity — what scientists call quantum gravity. And here is an unsettling truth: Scientists don’t really know what that theory looks like. There are some ideas, but none have been validated.

Thus, the truth about the center of a black hole is two-fold. Inside the event horizon, all we have are theories and speculation. It is reasonable to suppose that Einstein’s theories work at locations within the event horizon, but far from the center. But we’re not sure. And scientists are sure that Einstein’s theory utterly fails at the center. So, if we’re being honest, we’re pretty clueless about what lurks at the center of a black hole.

Because we’ll never be able to see inside a black hole, it may well be that we’ll never know what goes on within them. It is quite likely that the interior of a black hole will forever be a mystery.

This article What does the center of a black hole look like? is featured on Big Think.

The history of theoretical physics is chock-full of quirky characters with eccentric personalities. To travel down mind-bending mathematical and universal rabbit holes, one must be a bit mad, after all.

One of those personalities belonged to Austrian theoretical physicist Wolfgang Pauli. Among his many contributions to our fundamental understanding of reality, Pauli predicted the existence of the neutrino in 1930, which was subsequently discovered 26 years later. He also formulated what would later become known as the Pauli exclusion principle, for which he would be nominated by the illustrious Albert Einstein for a Nobel Prize in Physics. Pauli won the award in 1945. The principle states that two or more identical fermions (particles with half-integer spin like an electron, proton, or neutron) cannot occupy the same quantum state within a quantum system simultaneously.

Pauli’s discoveries are what he’s most regarded for publicly, but within the theoretical physics community of the early to mid-20th century — which included legendary thinkers such as Albert Einstein, Paul Ehrenfest, Freeman Dyson, Paul Dirac, Richard Feynman, Werner Heisenberg, and Robert Oppenheimer — Pauli was both revered and feared as a biting critic that held everyone accountable for their ideas, protecting the integrity of theoretical physics as a whole.

Pauli was known for policing novel theories, making sure that they were coherent and would enhance the discipline. When attending lectures that did not live up to those standards, he could be scathing. “What you just said was so confused that one could not tell whether it was nonsense or not,” he often said. Pauli eventually distilled this critique to a now-famous aphorism: “This isn’t right. This isn’t even wrong,” he would say of balderdash ideas.

He also saved sharp rebuttals for physicists who would publicize novel concepts before they were ready. “I do not mind if you think slowly, but I do object when you publish more quickly than you think,” he proclaimed.

Pauli often elected not to publish his own ideas in scientific journals, choosing instead to present them in personal letters to his friends and colleagues, who, in turn, circulated them.

Though Pauli could be rather cruel to his colleagues — or, at least, to their ideas he found fault with — they generally liked him. Freeman Dyson’s account of meeting Pauli exemplifies this well:

“He had nasty things to say about almost everybody. I remember the very first time I met him at a conference in Zurich. He was talking with a whole group of people about Julian Schwinger, who had just come to Switzerland. Schwinger was a brilliant young American who had done some very fine work. He was a rival of Feynman; they were the two geniuses then. Pauli was saying that Schwinger told us all this stuff that actually made sense, not like that nonsense Dyson has been writing. At that point I came walking up with a friend of mine, Markus Fierz, who was also a Swiss scientist. With a twinkle in his eye, Fierz came up to Pauli and said, “Please allow me to introduce you to my friend, Freeman Dyson.” Pauli said, “Oh that doesn’t matter. He doesn’t understand German.” Which of course I did. That was a good beginning and we were friends right from the very first day.”

Historian of science Jagdish Mehra recalled some of the “nasty” things Pauli would say about his colleagues in a conversation with Nobel Prize-winning physicist Richard Feynman:

“About Oppenheimer, Pauli had said: ‘He always acts like the caricature of God in action!’ About Hermann Weyl: ‘One must first penetrate his façade in order to understand his thoughts.’ About Leon Rosenfeld: ‘He is the choirboy of the Pope [Niels Bohr]!’ About Freeman Dyson: ‘Everyone wants to learn something from me; no one wants to teach me anything. I had hoped Dyson would do it, but he’s only a mathematician!’ By now, Feynman was becoming quite eager: ‘Did you ask Pauli about me?’ I said, ‘Yes.’ ‘Well, what did he say?’ I replied, ‘When I asked Pauli what he thought of you, he was amused, and replied, “Oh, Feynman, that Feynman, he talks like a gangster!”‘ This story made Feynman’s day; nothing could have pleased him more.”

This article The “sharp-tongued” physicist who everyone was scared of is featured on Big Think.

In the 1930s, the bolo-tie-wearing astronomer Fritz Zwicky found something strange in the motions of galaxies. They were moving far too quickly within their clusters than they should be, based on their mutual gravitational attraction. The clusters also should have scattered themselves apart billions of years ago, but yet they remained intact. Figuring that there was some component of the clusters at work that he could not directly see, the Swiss scientist named this material “dunkle Materie”—dark matter—and moved on.

Decades later, astronomer Vera Rubin found a similar oddity. In the 1970s, she discovered that stars within galaxies were orbiting much faster than they should be, meaning that there had to be an invisible substance, one that was suffusing every galaxy, keeping everything from flying apart like an out-of-control merry-go-round. It must be something like Zwicky’s dark matter.

Today, modern cosmologists have dozens of independent lines of evidence that point to the existence of dark matter, from the behavior of individual galaxies to the evolution of the universe itself. And yet we can only detect its presence through gravity, meaning that we have no idea what dark matter really is—despite estimates that it accounts for more than 85 percent of the mass of every galaxy in the universe.

After nearly a century of hunting, cosmologists are now worried that the search for dark matter is growing cold. Is dark matter a sort of highly technical, scientific version of magical thinking? A tidy way of explaining away gaps in our limited, human understanding? If scientists don’t find more concrete evidence for dark matter soon, we might need to radically revamp our understanding of fundamental physics—and with it, the universe itself.

To solve numerous long-standing problems in physics, including dark matter, in the 1980s, some theorists proposed a new kind of particle, known as a WIMP: a weakly interacting massive particle. Despite their name, these particles would be rather hefty, easily outweighing more familiar particles like protons and neutrons. But otherwise, these dark matter particles would share nothing in common with those we know; WIMPs would not participate in the electromagnetic force, rendering them invisible to direct observation (with the small exception of the extremely rare interaction with normal matter through the weak nuclear force).

For decades, scientists have been searching for traces of the dark matter that seem to explain the otherwise unexplainable in our universe. But big experiment, after big experiment (such as the Large Underground Xenon experiment, pictured here, which was built 4,850 feet underground at an abandoned mine in South Dakota) have failed to turn up traces of proposed particles known as WIMPs. So cosmologists are expanding their ideas of what dark matter might be. (Credit: Gigaparsec / Wikimedia Commons)

Cue the ensuing particle (and Nobel) chase, with advanced efforts, like the Cryogenic Dark Matter Search, popping up around the globe, charged with the mission of catching a stray heavy WIMP.

Decades after the initiation of these missions, the grand total of captured or detected WIMPs is … zero.

These results have not been entirely unproductive. Particle physics and cosmology can tell us the gross properties of this mysterious particle (or particles, if there happens to be more than one type comprising the universe’s dark matter), but it has not been able to provide the specifics. Null results in these experiments can at least tell us what the dark matter is not. And as the years go on, the range of possibilities of what the WIMP could be have gotten narrower and narrower.

But now the constraints are so narrow that physicists are wondering if we’ve gotten dark matter all wrong. Our experiments are tuned to find WIMPs. These WIMPs are heavy particles motivated by theories in particle physics. So perhaps our continued null results are telling us that WIMPs aren’t the answer. Maybe it’s something else, even more ghostly, even more effervescent, even lighter.

The idea that dark matter is made of a particle that is much, much lighter than we previously thought doesn’t come out of nowhere. For one, we already know of one kind of particle that is both lightweight and invisible: the neutrino. We have not yet ascertained the precise mass of the neutrino, but our upper limits place its mass at no higher than about 500,000 times lighter than the electron (the electron itself is about 2,000 times lighter than the proton).

Second, other outstanding problems in high-energy physics have suggested their own classes of new particles, known as axions, that would also happen to fit the bill of ultra-light and otherwise invisible particles. These particles would sail through our detectors without a hint of their existence, potentially explaining why we have yet to find the dark matter that seems so integral to explain our observations of the universe.

Just as in the case of the WIMPs, there is a wide variety of potential masses for this form of ultra-light dark matter. In the most extreme cases, the dark matter particle could be a trillion-trillion times lighter than the electron.

And this is where things get strange. The proposed WIMPs are exotic because they are largely invisible but otherwise act like normal particles. They would zoom around through space like tiny little dark bullets, exactly like any other particle of nature would do.

But the ultra-light dark matter is so light that it would look more like, well, light. All objects in nature exhibit wave-particle duality, sometimes manifesting their behaviors as waves and sometimes as particles. Most fundamental particles spend most of their lives acting like particles, bouncing and wiggling at will. But ultra-light particles act more like waves, sloshing and scattering around. The lightest particles we know are the photons, the carriers of the electromagnetic force, and are completely massless, and they are often very wavy: You can squeeze light through narrow channels, bend it around corners, and add the particles together just like waves of water.

Ultra-light dark matter would behave in the same way. Instead of buzzing around like billions of furious invisible bees in the cosmos, this form of dark matter would slosh back and forth, with waves of dark matter lapping against the stellar shores of every galaxy. An ocean of dark matter, with the galaxies as nothing more than brightly lit buoys bobbing up and down in their gravitational embrace.

Just as waves of water can converge into tremendous freak tidal waves, researchers have discovered that ultra-light dark matter could theoretically clump up on itself, forming invisible “dark stars” made of concentrated dark matter. If the ultra-light dark matter interacts with itself, these dark stars could become extremely dense, right on the precipice of forming black holes, before ripping themselves apart in a singular burst of energy, completely invisible to any telescope.

But searching for these ultra-light ghost particles requires a far different approach than a quest for WIMPs. Newer experiments, such as the Axion Dark Matter eXperiment at the University of Washington’s Center for Experimental Nuclear Physics and Astrophysics, use resonant cavities buried deep underground. The hope is that when an axion encounters an incredibly strong magnetic field, it could occasionally find itself turning into a photon. So, if we design an experiment with an incredibly strong magnetic field and find more photons in the apparatus than we expect, it might be a sign of axions floating around us. If dark stars exploded, these kinds of experiments might see a burst of axions (signaled by a sudden surge of extra photons) flooding through their detectors, just as we see a flash of light when stellar supernovas go off.

Nature is unforgiving. Our best ideas, no matter how motivated by theory, by elegance, or even by sheer will must all stand up to experimental scrutiny. If there’s no evidence to support an idea, we must discard it.

The dark matter hypothesis—that there is a substance that dominates the mass of the universe that is largely invisible—can only remain viable if we someday find direct evidence for these new kinds of particles. The nearly 40-year-old WIMP paradigm is becoming increasingly untenable. But it could be that axions and their ultra-light cousins are no more likely to exist.

It could be that we are completely, totally off base. That there is no new particle; that what we know of the universe from our current understanding of particle physics is it. In this scenario, we must still explain our cosmic observations. We could do this by modifying our understanding of the force of gravity. Einstein’s general relativity has proven itself in every experimental trial it has faced, but past results are no guarantee of future returns.

Unfortunately, every single attempt to go beyond Einstein’s theory to explain away dark matter as a great cosmic misunderstanding has failed in their own way. Today, there are no viable alternatives to general relativity that are able to explain the totality of evidence we have so far in favor of dark matter (in other words, theories that modify general relativity to explain one observation or another, like the motions of stars within galaxies, still require at least some “dunkle Materie” to explain the remaining observations).

If we fail to find direct evidence for dark matter in any form, whether WIMP or ultra-light, we’ll have some serious work to do. Something must explain the observations that we are making in the wider universe. Perhaps some brilliant mind will come up with a revolution of our understanding of gravity, wiping away the need for dark matter in a new, all-encompassing paradigm. Perhaps another genius will devise an extension to particle physics and find an entirely new class of particles that can account for the dark matter with properties that we can detect with new methods.

Or, perhaps we will be doomed to decades more of frustration, with all evidence pointing to the existence of dark matter despite our inability to directly detect it, forcing us to revise our understanding of the relationship and role of all forms of matter in the universe.

In the meantime, we can hold out hope for the possibility that we are awash in a vast sea of particles so faint that only in the motions of galaxies can we find evidence for their subtle but essential machinations, unseen dark stars exploding around us.

This article Have we gotten dark matter all wrong? is featured on Big Think.

Of all of the fundamental forces known to humanity, gravity is both the most familiar and the one that holds the Universe together, connecting distant galaxies in a vast and interconnected cosmic web. With that in mind, a fascinating question to ponder is whether gravity has a speed. It turns out that it does, and scientists have precisely measured it.

Let’s start with a thought experiment. Suppose at this very instant, somehow the Sun was made to disappear — not just go dark, but vanish entirely. We know that light travels at a fixed speed: 300,000 kilometers per second, or 186,000 miles per second.  From the known distance between the Earth and the Sun (150 million kilometers, or 93 million miles), we can calculate how long it would take before we here on Earth would know the Sun had disappeared. It would take about eight minutes and 20 seconds before the noon sky would go dark.

But what about gravity? If the sun disappeared, it would not only stop emitting light, but also stop exerting the gravity that holds the planets in orbit. When would we find out?  

If gravity is infinitely fast, gravity would also disappear as soon as the Sun poofed into nonexistence. We’d still see the Sun for a little over eight minutes, but the Earth would already start wandering off, heading for interstellar space. On the other hand, if gravity traveled at the speed of light, our planet would continue to orbit the Sun as usual for eight minutes and 20 seconds, after which it would stop following its familiar path.

Of course, if gravity traveled at some other speed, the interval between when beachgoing Sun worshipers noticed the Sun was gone and when astronomers observed that the Earth was going in the wrong direction would be different. So, what is the speed of gravity?

Different answers have been proposed throughout scientific history. Sir Isaac Newton, who invented the first sophisticated theory of gravity, believed the speed of gravity was infinite. He would have predicted that the Earth’s path through space would change before Earth-bound humans noticed that the Sun was gone.

On the other hand, Albert Einstein believed that gravity traveled at the speed of light.  He would have predicted that humans would simultaneously notice the disappearance of the Sun and the change of Earth’s path through the cosmos. He built this assumption into his theory of general relativity, which is currently the best accepted theory of gravity, and it very precisely predicts the path of the planets around the Sun. His theory makes more accurate predictions than Newton’s. So, can we conclude that Einstein was right?

No, we can’t. If we want to measure the speed of gravity, we need to think of a way to directly measure it. And, of course, since we can’t just “disappear” the Sun for a few moments to test Einstein’s idea, we need to find another way.

Einstein’s theory of gravity made testable predictions. The most important one is that he realized that the familiar gravity we experience can be explained as a distortion of the fabric of space: the greater the distortion, the higher the gravity. And this idea has significant consequences. It suggests that space is malleable, similar to the surface of a trampoline, which distorts when a child steps on it. Furthermore, if that same child jumps on the trampoline, the surface changes: it bounces up and down.

Similarly, space can metaphorically “bounce up and down,” although it is more accurate to say that it compresses and relaxes similar to how air transmits sound waves. These spatial distortions are called “gravitational waves” and they will travel at the speed of gravity. So, if we can detect gravitational waves, we can perhaps measure the speed of gravity. But distorting space in ways that scientists can measure is quite difficult and well beyond current technology. Luckily, nature has helped us out.

Measuring gravitational waves

In space, planets orbit stars. But sometimes stars orbit other stars. Some of those stars were once massive and have lived their lives and died, leaving a black hole — the corpse of a dead, massive star. If two such stars have died, then you can have two black holes orbiting one another. As they orbit, they emit tiny (and currently undetectable) amounts of gravitational radiation, which makes them lose energy and draw closer to one another. Eventually, the two black holes get close enough that they merge. This violent process releases enormous amounts of gravitational waves. For the fraction of a second that the two black holes come together, the merging releases more energy in gravitational waves than all of the light emitted by all of the stars in the visible Universe during the same time.

While gravitational radiation was predicted back in 1916, it took scientists nearly a century to develop the technology to detect it. To detect these distortions, scientists take two tubes, each about 2.5 miles (4 kilometers) long, and orient them at 90 degrees, so they form an “L.” They then use a combination of mirrors and lasers to measure the length of both of the legs. Gravitational radiation will change the length of the two tubes differently, and if they see the right pattern of changes of length, they have observed gravitational waves.

The first observation of gravitational waves occurred in 2015, when two black holes located more than 1 billion light years away from Earth merged. While this was a very exciting moment in astronomy, it didn’t answer the question of the speed of gravity. For that, a different observation was needed.

Although gravitational waves are emitted when two black holes collide, that’s not the only possible cause. Gravitational waves are also emitted when two neutron stars slam together. Neutron stars are also burned-out stars — similar to black holes, but slightly lighter. Furthermore, when neutron stars collide, not only do they emit gravitational radiation, they also emit a powerful burst of light that can be seen across the Universe.  To determine the speed of gravity, scientists needed to see the merging of two neutron stars.

In 2017, astronomers got their chance. They detected a gravitational wave and a little over two seconds later, orbital observatories detected gamma radiation, which is a form of light, from the same location in space originating in a galaxy located 130 million light years away. Finally, astronomers found what they needed to determine the speed of gravity.

The merging of two neutron stars emits both light and gravitational waves at the same time, so if gravity and light have the same speed, they should be detected on Earth at the same time. Given the distance of the galaxy that housed these two neutron stars, we know that the two types of waves had traveled for about 130 million years and arrived within two seconds of one another.  

So, that’s the answer. Gravity and light travel at the same speed, determined by a precise measurement. It validates Einstein once again, and it hints at something profound about the nature of space. Scientists hope one day to fully understand why these two very different phenomena have identical speeds.

This article How fast is gravity, exactly? is featured on Big Think.

In the turbulent forging of the early Earth, density was destiny. Heat from asteroid impacts and radioactive decay turned a mass of primordial rubble, held together by gravity, into a seething, molten orb. In this feverish state, the matter that makes up the Earth separated into distinct layers; the densest materials sank, forming an iron-nickel core, while lighter silicate matter rose to form the rocky mantle.

Geologists have long assumed that these layers were permanent—and that no physical matter could cross the ancient boundary between Earth’s core and mantle. A new paper published in Nature challenges this view, providing evidence that the core may leak gasses stored there since the formation of the planet “up” into the mantle—and that these gasses can find their way, via volcanic rocks, to Earth’s surface.

Although it begins just 20 miles beneath our feet and constitutes more than 80 percent of the planet’s volume, Earth’s mantle is a wild and uncharted place. Our deepest drill holes have never reached the mantle, and inferences about its makeup and roiling motions come from indirect sources, like earthquake-generated seismic waves that rumble through it, revealing it to be solid, though languidly flowing, rock. Other clues come from the chemistry of basaltic lavas, high temperature magmas which, when they erupt, have a viscosity close to that of ketchup. These lavas are generated by the partial melting of the mantle, and erupt through vents and volcanoes where the Earth’s crust—its uppermost layer—is thin, mainly in the ocean.

In the 1960s, soon after the emergence of the theory of plate tectonics—which explains global patterns of volcanic and seismic activity—geologists noticed subtle differences in the chemistry of basaltic lavas released from sites like Iceland, known as mid-ocean ridge basalts or MORBS, versus those from places like Hawaii, called hotspots. MORBS lie along underwater volcanic ridges, while hotspots are areas of the Earth’s mantle from which isolated columns of hot magma rise, forming volcanoes on the overlying crust.

In particular, the chemistry of Iceland-type MORBs suggests that these lavas originate in a shallow mantle source. In contrast, the chemistry of Hawaiian-type hotspot basalts suggests they come from a deeper mantle source. Although the mantle churns itself through convection—the density-driven process whereby cold rock sinks and hot rock rises—many geoscientists believe that the upper and lower mantle churn separately, intermingling only via the hotspot plumes, or columns of magma, that rise from depth. In this view, pockets of “original” material—unchanged by melting, or other geological processes such as subduction, which recycle parts of the Earth’s crust—could persist in the deeper parts of Earth’s mantle, even after 4.5 billion years.

This idea of an upper mantle chemically distinct from the lower mantle has generally been supported by studies of noble gasses—like helium and neon—trapped in tiny amounts within mineral crystals in basalts. In particular, scientists have looked at concentrations of two helium isotopes, ⁴He and ³He. Whereas ⁴He is more abundant in both rocks and the atmosphere, the much rarer ³He is generally understood to be gas from the beginning of the world. In previous studies, researchers have found that upper crust MORB basalts typically have more ⁴He and primordial hot-spot basalts have more ³He.

The new study, however, rewrites this tidy view of the mantle and its helium budget. The researchers found that basalts from Baffin Island, in Canada’s Arctic Archipelago, though related to a hotspot, have MORB-like chemistry, and yet have higher ³He/⁴He ratios than any previously measured—higher, in fact, than any plausible primordial mantle values. While the researchers acknowledge that there may be more than one way to explain this unexpected combination, the simplest scenario is that MORB-type ocean crust sank to the base of Earth’s mantle, where it was infused with primordial ³He seeping out of the core. Some of this hybrid material then made the long ascent up to Baffin Island.

This is a radical new view of Earth’s mantle and core as open rather than closed, where rocks from the crust may sink through the mantle and mingle with matter from the core—and then return to the surface with news of their journey to the center of the Earth.

This article Earth’s core has a gas leak is featured on Big Think.

After a multi-year review, the U.S. particle physics community has announced its vision for research spanning the next five to ten years. The various projects could, if funded, help researchers develop a much better understanding of the laws of nature.

The recommendations were released in a report called “Exploring the Quantum Universe: Pathways to Innovation and Discovery in Particle Physics.” It was written by the Particle Physics Projects Prioritization Panel (P5), a sub-panel of the High Energy Physics Advisory Panel (HEPAP), and will be submitted to funding agencies like the U.S. Department of Energy Office of Science and the National Science Foundation to guide their funding decisions over the next decade.

The future of particle physics

Particle physicists study the behavior of matter under the most extreme conditions ever achieved in the laboratory. They accelerate subatomic particles like protons and electrons to nearly the speed of light and crash them together using large and powerful particle accelerators. At the world’s most powerful accelerator, scientists can achieve temperatures as hot as an unfathomable 7 trillion degrees Celsius. That’s well over 100,000 times the temperature within the center of the Sun and nearly 100 times hotter than the center of a supernova, which is the explosion of a star so bright that it can be seen across half the Universe. The last time that temperature was common throughout the Universe was less than a trillionth of a second after the Big Bang.

The deep connections between the laws that govern the quantum realm and those that govern the entire Universe have long been known, and researchers have been studying them for decades. These sorts of experiments require very large particle accelerators and detectors, involving thousands of physicists, engineers, computer professionals, technicians, and various support staff. Such a considerable effort requires careful planning and independent oversight.

About every five years, the U.S. particle physics community evaluates the progress made from the previous five years. It uses that information to determine which efforts are the most likely to provide progress in the near term. The community must take into account real-world considerations, like budgets and whether the necessary technology exists or is in advanced development. They also consider things like scientific impact. Both P5 and HEPAP are merely advisory and governmental funding agencies that make the final determination as to which projects should be pursued.

The P5 report recommends projects of a variety of sizes and impacts. One of the larger projects is a fourth-generation effort to study the cosmic microwave background of the Universe. These microwaves are the oldest detectable remnant of the Big Bang and are a direct look at the Universe in its infancy.  Another big project involves upgrading the Fermilab accelerator complex to improve its already world-class neutrino research program. Fermilab is America’s flagship particle physics laboratory, and it is developing an unprecedented effort to study the behavior of neutrinos, which interact so rarely that they can pass through the entire Earth with only a very small chance of interacting. Neutrino studies may shed light on why the Universe seems to consist of only matter when our best theories suggest that antimatter should be equally present.

The P5 report also recommends the creation of a third-generation dark matter experiment, which would search for a ghostly form of matter that is thought to be five times more prevalent than ordinary matter. If dark matter exists, it should pass through the Earth with little chance of interacting. Any hope of detecting this theoretical form of matter will require a focused effort and advanced technology.

Also recommended is American involvement in a future accelerator in either Europe or Asia that would conduct detailed studies of the Higgs boson, which is the particle discovered in 2012 that gives mass to other subatomic particles.

One ambitious recommendation is that scientists explore the creation of a high-energy muon collider. Muons are similar to electrons but heavier. Another difference is that muons decay in a fraction of a second. To make a muon collider, researchers will have to create muons, capture them, and then accelerate them and smash them together in a very short period. It is not yet clear that such a facility is possible, but it is suggested that the nation’s accelerator scientist community collaborate to see if such an accelerator is feasible.

More modestly priced possible future facilities include an upgrade of the IceCube detector. IceCube uses a cubic kilometer of ice in Antarctica to study cosmic neutrinos, including some of the most energetic neutrinos ever made. The study of cosmic neutrinos can give astronomers an insight into some very violent astronomical phenomena, including supernovae, colliding neutron stars, and matter accelerated in the vicinity of huge black holes. A second generation of IceCube could use as much as ten cubic kilometers of ice to make even more precise measurements.

While the recommendations of the P5 committee are not binding, they do reflect the judgment of the American particle physics community. Before the convening of P5, thousands of physicists worked together in the Snowmass Process. Over several years, researchers came up with their best ideas and met in large conferences to discuss them. Through discussion, criticism, and refinement, the proposals from Snowmass represent some of the most creative ideas for improving our understanding of the laws of nature.

The P5 committee took the Snowmass proposals — refining some and pruning others — and will pass the remainder along to funding agencies. The next step in the process will be for agencies like DOE and NSF to consult with their international counterparts and consider fiscal realities. Over the next year or so, it will become clear what the future of particle physics research in America will look like.

This article Physicists unveil 10-year plan for exploring the quantum Universe is featured on Big Think.

This is T-Minus, where we count down the biggest developments in space, from new rocket launches to discoveries that advance our understanding of the universe and our place in it. Humanity is reaching new heights in space exploration. Make sure you’re part of the journey by subscribing here.

An alien-hunter’s big gift

Rather than waiting for little gray aliens to swing by Earth and ask to rendezvous with our leader, scientists at the SETI Institute are actively searching the cosmos for extraterrestrial life, primarily by using telescopes to hunt for signs of alien technology.

The non-profit institute, which spun out of a small “search for extraterrestrial intelligence” program at NASA in the 1980s, relies solely on donations, private funding, and grants to support the work of its more than 100 scientists, which currently cost about $25-$30 million annually.

On November 8, the non-profit announced a $200 million donation from the estate of Franklin Antonio, co-founder of the telecom company Qualcomm. Antonio, who passed away in 2022, had been working with the SETI Institute for more than a decade, providing both funding and technical knowledge to advance its mission.

“[W]e now have the opportunity to elevate and expedite our research and make new discoveries to benefit all humanity for generations to come,” said Bill Diamond, the institute’s president and CEO. “In his memory, the SETI Institute will continue its pursuit of one of the biggest and most profound questions in all of science, a question as old as humanity itself — are we alone in the universe?”

The “dark mysteries” telescope

In July 2023, the European Space Agency (ESA) launched Euclid, a space telescope with the ambitious mission to record incredibly sharp images of billions of galaxies — including ones that are up to 10 billion light years away — over the next six years.

Astronomers plan to use those images to construct the world’s largest 3D map of the cosmos and — they hope — unravel some of the mystery surrounding dark matter and dark energy.

“Dark matter pulls galaxies together and causes them to spin more rapidly than visible matter alone can account for; dark energy is driving the accelerated expansion of the universe,” said Carole Mundell, ESA’s Director of Science. “Euclid will for the first-time allow cosmologists to study these competing dark mysteries together.”

Euclid is expected to begin its routine science observations from Lagrange point 2 — the same neighborhood in space occupied by the James Webb Space Telescope — in early 2024, but on November 7, ESA shared the first stunning full-color images captured by the telescope, giving the world of taste of what’s to come.

“Euclid will make a leap in our understanding of the cosmos as a whole, and these exquisite Euclid images show that the mission is ready to help answer one of the greatest mysteries of modern physics,” said Mundell.

SpaceX’s in-development Starship, the biggest rocket in the world, is expected to return astronauts to the moon, deliver people to Mars for the first time, and maybe even transport people anywhere on Earth in less than an hour.

Before any of that can happen, though, SpaceX needs to prove the rocket can survive a flight — the company’s first launch attempt ended with an explosion about 4 minutes after liftoff.

On November 18, SpaceX tried again, and this time, Starship soared to an altitude of 91 miles — officially putting it in space — before SpaceX lost contact with the rocket, triggering it to self-destruct.

According to SpaceX CEO Elon Musk, the next Starship will be ready to fly again in December, but the company won’t be able to test it until the FAA finishes its investigation into this launch and issues a license for the next one.

That might not happen until 2024, but after more than 7 years of development, we’re now tantalizingly close to seeing Starship deliver on its promise to transport people to the moon and beyond.

This article T-Minus: Starship’s big flight, an alien hunter’s gift, and more is featured on Big Think.

At the center of nearly every galaxy in the cosmos sits a monster: a black hole with a mass millions or even billions of times heavier than our Sun. When and how these enormous objects formed is an open question in the astrophysics community.

Recently, in a paper published in Nature Astronomy, scientists reported the discovery of an ancient supermassive black hole, one that existed very early in life of the Universe. While some enthusiasts have claimed that the observation of these gigantic black holes has disproved the theory of the Big Bang, this is a hasty conclusion. However, it is certainly true that the existence of very early supermassive black holes will require astronomers to rethink some things.

Supermassive black holes

Most black holes are made when a very massive star burns through its fuel and then collapses under the weight of its own gravity. Stellar-mass black holes are typically in the range of 5 to 100 times the mass of the Sun. 

In contrast, the supermassive black holes at the centers of galaxies are much bigger. The black hole at the center of the Milky Way galaxy, called Sagittarius A* (Sgr A*), has a mass equal to about 4.3 million suns. But even that pales compared to the heaviest black hole known: TON 618, found at the center of a quasar, weighs in at a staggering 66 billion solar masses.

Just how these giant black holes were formed remains a mystery even today. While one idea is that individual stellar-mass black holes combined, it is difficult to envision that there has been enough time since the Universe began 13.8 billion years ago for enough mergers to have occurred to account for the observed distribution of supermassive black holes. And it’s even harder to imagine that giant black holes formed early in the Universe.

JWST weighs in

The James Webb Space Telescope (JWST) is able to image ancient galaxies, ones that existed a few hundred million years after the Universe began. In the aforementioned paper, astronomers combined a JWST observation with separate data from the Chandra X-ray Observatory to identify a distant galaxy that contained a supermassive black hole. (When black holes absorb matter from their surroundings, that matter heats up as it falls inward and emits characteristic X-rays.)

Astronomers were surprised when they found that the mass of the black hole at the center of the ancient galaxy was about the same as the total mass of the stars in that same galaxy. (To put this into perspective, the supermassive black hole at the center of the Milky Way is only about 0.1% the mass of the entire galaxy.) 

Given that this ancient supermassive black hole formed so quickly after the Universe began, it cannot have been created by the merging of stellar-mass black holes. Instead, another mechanism is required.

Gassy black holes

Sophisticated simulations have shown that early in the history of the Universe, it is possible for giant clouds of gas to have collapsed directly into very large black holes — ones with masses about 100,000 times that of the Sun. It is thought that these very massive black holes transformed into supermassive ones by a combination of merging and absorbing gas from their surroundings.

While this is a single example of an ancient galaxy already hosting a supermassive black hole, it is expected that others will be found; after all, JWST only began operations in the summer of 2022. Data like that reported in the recent article will help scientists get a better handle on just exactly what went on when the Universe was in its infancy.

For example, outstanding questions include: Which came first, supermassive black holes or galaxies? Did the galaxy attract nearby extragalactic gas that created the conditions that allowed supermassive black holes to form? Or did the black holes form first, and thereby draw in the gas that formed the stars and galaxies? How did the heat generated by gas flowing into early black holes affect star formation? And what role did dark matter play in the process?

The answers to these and similar questions are slowly coming into focus.

This article Ancient black hole challenges our understanding of the early Universe is featured on Big Think.

A consensus has arisen in the astronomical community that familiar matter made of atoms is not the dominant form of matter in the Universe. Instead, an invisible form of matter, called dark matter, is thought to be far more prevalent. However, a small group of researchers deny the existence of dark matter, instead saying our understanding of how objects move is incomplete. A recent paper in the Monthly Notices of the Royal Astronomical Society seems to have ruled this out definitively.

Dark matter vs. MOND

Stars, planets, and galaxies move under the direction of the force of gravity, and Isaac Newton worked out the laws that govern that motion, which we now call Newtonian dynamics. However, despite the enormous success of Newtonian dynamics, this success is not universal. Indeed, when Newton’s equations are applied to certain astronomical phenomena, they do not make the correct predictions. One such example is the speed at which galaxies rotate. When astronomers measure the speed of stars in the periphery of a galaxy, they move faster than can be explained by accepted theory. Instead, the galaxies should fly apart.

The solution to this mystery favored by most scientists is that beyond the familiar stars and clouds of gas, our galaxy also hosts a large amount of invisible matter, called dark matter. This dark matter adds to the gravitational force holding the galaxy together. Thus, the evidence for dark matter is indirect. It has never been observed in the laboratory; yet its ability to explain the motion of galaxies is strong circumstantial evidence that it exists.

Still, because dark matter remains unobserved, alternative hypotheses should be considered. One idea, called MOND (Modified Newtonian Dynamics), suggests that the Newtonian laws of motion taught in introductory physics classes are not quite right. For accelerations larger than about 10^-11 times the gravity felt on the surface of Earth, Newton’s familiar equations work. For accelerations smaller than that, a new set of equations applies. MOND theory was first devised by Israeli physicist Mordehai Milgrom in 1983, and while the model is not accepted by the majority of astronomers, it has some passionate supporters.

When astronomers apply MOND theory to predicting the rotation of galaxies, it works quite well, essentially as well as dark matter theory does. Thus, a measurement is needed that will definitively distinguish between the two. 

Testing MOND

In the newly released paper, researchers used data recorded using the Gaia satellite to study wide binary stars, which are two stars that orbit one another at large distances. In this study, binary stars were included if their separation was in the range of 2,000 to 30,000 times the average separation between Earth and the Sun. Binary stars with these characteristics experience a range of accelerations that allow scientists to try to determine if MOND or Newtonian theory is correct.

So, what did they find? The study very clearly favors Newtonian theory over MOND as an accurate description of the orbital behavior of wide binary stars. (The measurement ruled out MOND by sixteen sigma, which is far larger than a five-sigma result that is considered definitive.)

In their paper, researchers also tackled earlier reports that wide binaries actually supported the MOND hypothesis. They separated their data into wide binaries in which the measurements were precise and ones in which there was significant uncertainty in the numbers. They found that an analysis that included poorly measured wide binaries favored MOND, but when only precisely measured results were included, the data strongly favored Newtonian dynamics.

Does this measurement prove that dark matter is real? No. That would be too strong of a conclusion. If confirmed, what it demonstrates is that the specific theory called MOND is incorrect. It does not rule out all alternative theories to dark matter. Others remain viable. Indeed, there are other proposed solutions to the mystery of rapidly rotating galaxies, including changes to the laws of gravity, as well as different modifications to the laws of motion. In addition, while the distance separating wide binary stars is very large, it is very small compared to the size of galaxies. It remains possible that MOND theory could apply on galactic sizes, but not on the scale of large stellar systems.

Sherlock’s approach to astrophysics

Still, the result, if confirmed, is a very important advance in our search for the answer of why galaxies rotate so quickly. While not as satisfying as a definitive discovery, definitive refutations of other theories is how science advances. As fictional detective Sherlock Holmes once said in the story “The Sign of Four”: “Once you eliminate the impossible, whatever remains, no matter how improbable, must be the truth.”

This article Scientists rule out a popular alternative theory to dark matter is featured on Big Think.

The rise of Big Science after World War II was pushed by massive Cold War and Space Race spending. There was, however, one fundamental area of physics that didn’t see federal dollars, at least at first. This was research into gravity and general relativity.

Observations of light bending around the sun in 1919 confirmed Albert Einstein’s “elegant theory of gravitation,” as historians of science David Kaiser and Dean Rickles call this aspect of the general theory of relativity. After that confirmation, though, gravitational physics cooled down. Nuclear and quantum physics became where the action was. (The Nazi’s “crushing displacement of world’s most active centers for gravitational research” didn’t help.)

In the late 1940s, there wasn’t a physics department in the US that required their graduate students to study gravitation/relativity. Yet starting in the mid 1960s, there was what has been called a “renaissance in relativity,” culminating in the work of Stephen Hawking and Roger Penrose on black holes.

As Kaiser and Rickles show, that renaissance was seeded by money from private patrons. Businessmen Robert Ward Babson (1875–1967) and Agnew Hunter Bahnson (1915–1964) funded the burgeoning of gravitational physics when no one else would. But since plutocrats usually want a say in where their money is going, that funding was somewhat eccentric: both men were absolutely obsessed by anti-gravity.

Roger Babson was famous for predicting the 1929 stock market crash. In 1948, with something of a personal grudge against “Gravity: Our Enemy Number One,” he set up the Gravity Research Foundation sixty miles from Boston. The location was chosen because it was supposed to be outside the blast radius of an atomic bomb over Boston.

Babson blamed Gravity (he capitalized it) for the deaths of both his sister and a grandson, both of whom drowned in separate swimming accidents. What Babson most wanted from his gravity researchers was a “partial insulator, reflector, or absorber of gravity”—something, anything, that would stop or dampen the damn stuff.

His interest in slaying what he called “that ‘dragon’ Gravity” led into fantasies about perpetual motion machines and free and limitless electrical power. He also marketed patent medicine “gravity pills,” which he sold for sore legs. He even built the Thomas Edison Bird Museum, with 5,000 specimens. This was named after his inventor friend: Edison had once suggested birds could fly because they had the secret of anti-gravity.

Along with block grants to colleges and universities, Babson’s foundation also contributed actual blocks of stone to thirteen institutions. The foundation’s monument at the Tufts Institute of Cosmology is inscribed “to remind students of the blessings forthcoming when a semi-insulator is discovered in order to harness gravity as a free power and reduce airplane accidents.”

In 1952, the popular science writer Martin Gardner parodied Babson and his foundation in a book on pseudoscience. But Babson’s money was certainly real enough and hard to say no to. The foundation’s essay competition’s first prize was $1,000 in the early 1950s, equal to a graduate student stipend. (Stephen Hawking won six awards from the foundation in the 1960s and 1970s.) Turning away from trying to control gravity to understanding it, the foundation fought its way to respectability. Their first conference on gravitation in 1951 saw twenty-two attendees. By 1958, 280 people were attending.

Agnew Bahnson, meanwhile, was rather younger than Babson but just as fascinated with anti-gravity. A Gravity Research Foundation trustee, Bahnson worked with Bryce DeWitt, the 1953 winner of the foundation’s essay contest, and Cécile Morette DeWitt, a renowned physicist in her own right, to set up the Institute of Field Physics at the University of North Carolina, Chapel Hill (1956). He was a tireless fundraiser, even though the institute’s physicists and administrators made a point of saying that they had “no connection with anti-gravity research.” (Anti-gravity being impossible under general relativity.)

Bahnson signed off on that official statement but continued his own dabbling in would-be anti-gravity machines. His 1959 novel The Stars Are Too High features “a gravity-defying flying saucer” helping to ease Cold War tensions. (Gravity claimed Bahnson at the age of forty-eight when his private plane crashed.)

The “renaissance of relativity” may be an apt term in more ways than one. Babson and Bahnson were like the patrons of the Renaissance, only instead of funding artists, they funded gravitational physics—and physicists. But were the Medici ever so eccentric?

This article The physicists who wanted to put an end to gravity is featured on Big Think.

The archetypal image of chemistry is a set of glassware, full of colorful liquids about to be mixed. Froth, bubbles, and smoke ensue. Much of industrial chemical synthesis is a tamer version of this. But could we replace the bubbling flask with the slow grind of a ball mill? A scientific review article details progress in the field of mechanochemistry, investigating this question.

When chemists start grinding

Most traditional chemical syntheses rely on random thermal motion driven by mixing to bring reactants together. Solvents dissolve materials into fluid form, and the dissolved materials are comingled, stirred, heated, filtered, and distilled to create and isolate new compounds. Electrochemical synthesis drives a reaction with an electrical current. Electrolysis of water to liberate hydrogen and oxygen is one example. Photochemistry uses light to drive reactions, with photosynthesis being an abundant natural demonstration. The breakdown of plastic under prolonged sunlight is another. (Nanofabrication, if it is possible, would synthesize molecules by using tiny machines to pluck atoms out of bins and poke them together.)

Mechanochemistry, by contrast, uses mechanical force to combine reactants. A simple form of mechanochemistry is grinding reactants with a mortar and pestle until a product forms in the pestle. Simple studies have found that many compounds can be synthesized by human hands without resorting to liquid solutions and solvents.

Grinding is more efficient when performed with an instrument called a ball mill, which grinds down a substance into a fine powder. The simplest ball mill consists of a cylindrical reaction vessel mounted on its side and spun around its central axis. The vessel is a jar filled with powdered chemical reactants and a number of hard balls. In some cases, additional liquid or salt compounds are added to catalyze the reaction. As a motor rotates the vessel, the balls roll up the vessel wall and then fall back down onto the other balls in the chemical mixture. Each ball-on-ball strike crushes and mixes small amounts of powder at the strike point. In this way, the rotation and colliding balls churn the materials.

There are other ways to grind. The jar can be stood upright and shaken side-to-side at certain frequencies. A more powerful and industrially scalable method is to spin the jar about its central axis while also rolling it along the inside of a larger cylinder. This can rotate the jar rapidly enough to throw the balls and mixture back and forth with more force than gravity alone could impart. It’s a bit like putting a brick in a laundry machine. (Don’t try this at home.)

The balls and jars are generally made of the same material, chosen for several reasons. Harder and denser balls, such as stainless steel, tungsten carbide, or agate, grind and smash the material more easily. Polytetrafluorethylene (PTFE), better known by its commercial trademark Teflon, or a clear polymer like polymethylmethacrylate (PMMA) are also used as they clean easily and don’t tend to shed material that contaminates the product. Copper balls and jars also can catalyze reactions, such as cycloaddition.

Mechanochemistry under pressure

The mechanochemistry review paper discusses how various chemical syntheses that were previously performed with solvents can be replicated using solvent-free mechanical grinding methods that are simpler, faster, and cleaner. It also points out that a few rare or entirely new syntheses have been achieved. Why, then, is the technique not standard in industry?

Mechanochemistry, they argue, is still qualitative and intuitive rather than quantitative and precise. Ironically, mechanochemical reactivity is not understood mechanically. For instance, the mechanics vary by the type of stress involved. Effects of normal stress, a head-on pressure felt by a molecule directly smashed between two colliding balls, differ in important ways from those of shear stress, a perpendicular force felt by molecules caught between two balls sliding across one another. Kinetic effects (those described by impacts of rigid bodies) and thermodynamic effects (those involving compression, heating, and energy transmutation) must be separated. The prevalence and importance of localized heating at ball impact locations are also unclear.

To study the reactions, real-time measurements of reactants and products are required. Transparent polymer jars allow a laser to access the contents, performing Raman spectroscopy to fingerprint individual compounds. Some jars efficiently pass X-rays, and the diffraction of the X-rays through the powder identifies the crystalline grains present within it. Measuring the fractions of different molecules present throughout the grind is a crucial way to quantify the dynamics of the reaction and provide data for modeling. Models that consider the particles as a pseudo-fluid may help chemists understand and predict reactions.

New techniques and a better theoretical understanding could encourage the commercialization of mechanochemistry. External factors such as environmental and emissions regulations may provide additional incentives. However, while it may be possible to replace bubbling flasks with ball mills, we don’t yet fully know how.

This article Grinding scientists: How mechanochemistry could revolutionize the creation of new materials is featured on Big Think.

Since October 2023, thousands of earthquakes have shaken the Reykjanes peninsula of Iceland. The small town of Grindavík, a fishing village on the southern coast, has been evacuated. In some instances, residents had only ten minutes to grab possessions and pets before leaving their homes — possibly forever.

Already, clouds of gas billow from massive fissures that have opened in roads, playgrounds, and parking lots. Toxic sulfur dioxide has also been detected. Not only do these telltale signs herald an imminent eruption that could threaten the town, they suggest that Iceland — whose volcanoes go through roughly 1,000-year cycles — may be about to enter a new era of increased volcanism that could last for hundreds of years.

Up and down

The Reykjanes peninsula of southwest Iceland juts out into the Atlantic Ocean and sits over a tectonic plate boundary called the Mid-Atlantic Ridge. It has a raw type of beauty, with kaleidoscopic geothermal springs and moss covering ancient lava fields. This peninsula is the center of Iceland’s volcanic activity, yet it has been relatively quiet for the past 800 years. 

That may soon change. After three eruptions in the area in the last few years, it appears that Iceland might be gearing up for a fourth. A swarm of over 1,000 earthquakes hit the region on October 25th within a two-hour period. Since then, hundreds of earthquakes per day have been recorded. Most of these earthquakes are minor, but they indicate a significant change in the conditions belowground.

To understand what is happening, geologists turn to interferometry, a technique that uses radars and wave interference patterns to detect small changes in land elevation. Interferograms produced around November 10th to 11th showed that the region around Grindavík sank drastically – about a meter to a meter and a half. A more recent interferogram produced on November 18th to 19th showed that the same region has rapidly risen. The Icelandic Met Office reported that this change in elevation corresponds to an intrusion of magma, called a dike intrusion, pushing up against the ground of Iceland. It likely began forming on November 10th.

As of November 17th, scientists estimate that this magma intrusion is only 500 to 800 meters below the surface in a magma tunnel about 15 kilometers long. An eruption could occur anywhere along this tunnel. Situated nearby is the town of Grindavík, the Svartsengi geothermal power plant, and the popular tourist destination Blue Lagoon. Grindavík and Blue Lagoon have been evacuated, while Iceland’s largest bulldozer is creating a massive trench around Svartsengi in an attempt to divert lava if it heads that way. 

The Icelandic Met Office also has been updating and releasing maps indicating where an eruption is likely. If an eruption is to occur, it is likely to happen within the next three weeks. 

Iceland’s volcanoes

Volcanoes form in a few different locations on Earth. In the first, two tectonic plates converge. One plate is pushed under the other, forcing the other plate upward. The sinking plate, located in the subduction zone, eventually meets the mantle and begins to melt. Subduction zone regions are known for powerful earthquakes (like in California) and explosive, devastating volcanic eruptions (like Mount St. Helens).

Volcanic eruptions can also occur where two tectonic plates move apart from one another. At this divergent plate boundary, the mantle rises to fill the gap between the separating plates, creating volcanoes that erupt gently and gradually. The Mid-Atlantic Ridge is a prime example. Here, the North American and Eurasian plates move apart by roughly two cm per year. Iceland is part of this ridge, created by volcanic eruptions that occurred millions of years ago. Thingvellir National Park in Iceland is one of the only locations on the planet where the boundary of two tectonic plates can be seen on Earth’s surface.

Finally, volcanoes can form over a hot spot, where unusually hot magma rises through the mantle toward the crust. These can occur anywhere on a plate, sometimes even in the middle (like in Hawaii or Yellowstone) or near the edge, like in Iceland. Hot spot volcanoes typically erupt gently, but lava can still cause significant damage, covering roads and towns, starting fires, and explosively entering the sea. 

A thousand-year cycle

Iceland‘s volcanism is due to a combination of a divergent plate boundary and a hot spot, but the region largely has been dormant for the past 800 years. Along with the eruption of Fagradalsfjall in March 2021, followed by eruptions in August 2022 and July 2023, this most recent activity indicates that the region has reawakened.

This article Iceland earthquakes hint at a new era of increased volcanic activity is featured on Big Think.

Back in 1966, Richard Fleischer directed a movie called Fantastic Voyage. The premise was that scientists were able to shrink a submarine-like craft (complete with humans inside) and inject the craft into a human body. The craft then was piloted to the location of a blood clot in the brain of a patient, and the clot was removed using a laser. Although the premise of the movie is obviously fictitious, a recent development described in the journal Nature involving miniature particle accelerator technology could make the movie a smidge closer to reality.

Pocket-sized particle accelerator

Particle accelerators are devices that use a combination of electric and magnetic fields to accelerate charged particles like protons or electrons to very high velocities and then form beams of these particles. Those beams can have many purposes, including conducting fundamental research into the laws of nature or recreating the conditions of the Universe just fractions of a second after it began. However, a much more pragmatic usage of these beams is to treat cancer patients using radiation.

Particle accelerators are generally large pieces of equipment, ranging from the size of a minivan in many hospital settings to the Large Hadron Collider, which is 16.5 miles (26.6 km) in circumference. This new accelerator, however, is much smaller — smaller than a dime.

Researchers at the Friedrich-Alexander University of Erlangen-Nuremberg (FAU) in Germany made what is called a nano-photonic particle accelerator. It uses laser pulses to accelerate electrons from an injection energy of 28,000 electron-volts to an energy of just over 40,000 electron-volts, an increase of 43%. This is the energy of extremely potent X-rays. Furthermore, the accelerating force is comparable to traditional accelerators, with only the short accelerator length restricting the total energy increase.

Tiny, but a mighty punch

The “business end” of the accelerator is a tube that is only 0.02 inches (0.5 mm) long. The inner diameter of the tube is merely 225 nanometers wide. To give a sense of just how small that is, a million nanometers is the same as a millimeter, and the diameter of a human hair ranges between 80,000 and 100,000 nanometers. When in operation, a tiny laser located on an electronic chip fires at about one thousand individual “pillars,” which look a bit like a tiny forest. The interaction of the laser and the pillars is responsible for the acceleration.

The total energy is small compared to much larger accelerators, but researchers think that perhaps by using a series of these nano-photonic devices, they could reach higher energies. Currently, the number of electrons accelerated in these first prototypes is very low, thus the beam does not generate enough radiation to have commercial value.

Treating cancer

While the technology is not yet ready, researchers imagine that it could one day revolutionize radiation therapy. Attaching the accelerator to a miniature submarine in the manner depicted in Fantastic Voyage is unlikely, but the accelerator could be attached to what is called an endoscope, which is used to probe inside the human body. Oncologists could then put the output of the accelerator immediately adjacent to a tumor to treat the cancer.

This would be advantageous for a couple of reasons. Today, radiation used in treatment is usually strong enough that it also irradiates healthy tissue beyond the tumor. In theory, the new technology could have an energy output that is tunable, so that it minimizes damage to nearby tissues, which also would reduce any side effects experienced by the patient. Furthermore, current treatments utilize radiation that is created outside the body, which is then aimed at the tumor. Because radiation is absorbed as it travels through human tissue, the tissues nearest the skin get the most radiation, while the deeper tumor gets less — and it can result in what appears to be a sunburn. The tiny particle accelerators could avoid this.

Miniaturization of medical instrumentation is becoming a reality. The invention of micro- and nano-electronics has the potential to treat patients in ways that were once unimaginable.

This article How pocket-sized particle accelerators could treat cancer is featured on Big Think.

Scientists at a high-tech facility on America’s West Coast have fired up the world’s most powerful X-ray laser for the first time. With these ultra-bright pulses of X-ray light, they will make measurements that will teach us a great deal about the atomic and molecular world.

Brighter and more powerful

The LCLS-II facility is an upgrade of the Linac Coherent Light Source. It is located at the U.S. Department of Energy’s SLAC National Accelerator Laboratory, near Stanford University in Menlo Park, California. LCLS-II is what is called a free electron laser, which means that it accelerates a beam of electrons to near the speed of light and then sends the beam through a series of magnetic fields. Those magnetic fields cause the path of the electrons to wiggle and, because of the wiggling, the electrons emit very intense X-rays that can be used to image things like molecules and see how the atoms within them interact.

LCLS-II can emit as many as a million X-ray pulses every second, or 8,000 times more than the earlier LCLS laser could. When one combines the increased pulse rate with an increased number of electrons per pulse, the new facility is over 10,000 times brighter than its predecessor.

Each pulse is very short. For high-energy (short-wavelength) X-rays, the pulses range from 10 to 50 femtoseconds; for low-energy (long-wavelength) X-rays, the pulses can be stretched to as long as 250 femtoseconds. It is also possible to make very short pulses (less than 10 femtoseconds), although for such short time periods, each pulse is less bright than usual. (A femtosecond is 10^-15 second.)

With such short wavelengths, short pulses, and rapid repetition, scientists can use this facility to watch chemical reactions as they occur. Essentially, each pulse can image the configuration of the atoms participating in the reaction, and then the individual images can be chained together like a molecular Claymation movie. Back in 2018, the LCLS facility was able to make a movie of a chemical process that occurs in human vision and photosynthesis. The entire process takes a mere 1,000 femtoseconds (10^-12 second).

More broadly, the LCLS-II facility will be able to image objects as small as one angstrom (10^-10 meter). This capability will allow researchers to study many different atomic processes, from those in biological systems to those in photovoltaics and fuel cells. The laser will also help illuminate superconductivity, ferroelectricity, and magnetism.

A pretty cool technology

One of the key components of the upgrade was the installation of some revolutionary technology. While the earlier accelerator operated at room temperature, the upgraded LCLS-II uses superconducting accelerator components, which allows it to operate at cryogenic temperatures close to absolute zero (-456° F or -271° C). The LCLS-II also has better magnets to wiggle the electron beams.

While LCLS-II has just begun operations, the success of the earlier LCLS accelerator has researchers optimistic. Over 3,000 scientists have used the facility, resulting in over 1,450 publications. Time will reveal whatever new insights this powerful laser has in store.

This article World’s most powerful X-ray laser fires for the first time is featured on Big Think.

“A fool and his money are soon parted” is a proverb that dates back to at least the 16th century. Scammers and conmen are always looking for an angle to fleece the gullible, including the use of realistic sounding pseudoscientific babble.

Look at my email inbox. I am told that my life will be improved by the manipulation of my aura or that crystal channeling will align my chakras or something. Then there are the utterly ineffective homeopathic remedies. But these are small potato scams, merely asking me to buy something. Even if they were successful, they wouldn’t deplete my bank account too much.

Much bigger scams ask me to invest in schemes to utilize new sources of energy — ones that will supposedly make me rich if I get in on the ground floor. Some purport to have invented a perpetual motion machine, but the newest and jazziest offer to land in my email inbox promises to exploit what is called “zero-point energy.”

The very name sounds a bit mysterious and science-y. And it has the advantage of being a real thing. However, even though zero-point energy is a valid scientific concept, it most certainly isn’t something in which you should invest your hard-earned money.

What is zero-point energy?

The term zero-point energy has at least two meanings, one that is innocuous — and one that is a great deal sexier. In the simpler definition, zero-point energy is the lowest energy any system can have. Take a pendulum, like a ball on a string. If the ball is moving, the pendulum has energy. The pendulum also has energy if you raise the ball above the lowest point and hold it stationary in place. And, of course, if the ball is swinging from the highest point of oscillation, through the bottom and up to the other side, the pendulum has energy there too.

However, there is one situation in which the pendulum has the absolute minimum amount of energy, and that’s when the ball is stationary at the lowest possible location. In any other configuration, the ball will have more energy than this configuration. This is the zero-point energy configuration of the pendulum.

Now, if you think a bit outside the box, you realize that if you were to cut the string of the pendulum, the ball could fall and end in an even lower state of energy. Thus, while the example of the pendulum has illustrative value, it is only good within certain limitations. A true zero-point energy environment will have no possible lower energy configurations.

Enter the conmen

The sexier definition of zero-point energy is much grander and is the one that con artists claim to be able to exploit. This supposed panacea is the energy of space itself.

By “empty space,” we mean no matter, no external energy fields, nothing. Thus, a volume of empty space can be considered the zero-point energy of the Universe. However, and this is where the scam artists come in, empty space isn’t truly empty. Because of the laws of quantum mechanics, at the ultra-subatomic level, there is a constant energy field that permeates the Universe. And, if you had the right equipment, you could zoom into the microcosm and see that this energy field has consequences (what is called the “quantum foam”). Because of the laws of quantum mechanics, this energy is manifested in the ephemeral creation and annihilation of subatomic particles, called virtual particles.

Virtual particles are not visible to the human eye, but they most certainly exist. In 1948, Dutch physicist Hendrik Casimir predicted that virtual particles would have detectable consequences for researchers using sensitive equipment. A decade later, researchers qualitatively validated his predictions, and in 1997, a more refined approach made a precise measurement that confirmed his calculations. Zero-point energy is a real thing.

But subtle interactions with sensitive equipment isn’t what the scammers are promising. Instead, they are promising limitless and free energy. And when one calculates the amount of zero-point energy stored in a small volume, it is huge. Indeed, according to quantum theory, the amount of zero-point energy contained in a volume the size of a light bulb is enough, if it were liberated, to boil all the Earth’s oceans.

However, “if it were liberated” is the sticky point. Remember that we are talking about literally empty space — space that contains absolutely no matter and external energy. The only energy is the energy of space itself, which is to say, zero-point energy. But you cannot remove space from space, thus you cannot remove the zero-point energy. And zero-point energy, being a property of space, is the same everywhere. You cannot move some of the energy of this space over to that space, or vice versa. Nor is there any place with less zero-point energy.

How to harness energy

Such uniformity of energy is what disproves the claims of the zero-point energy fraudsters. Uniform energy cannot be exploited. Energy can only be exploited if it is moved or changes form. For example, fire heats your coffee by releasing energy from chemical reactions. Oxygen combines with carbon, and this chemical transformation releases energy. The situation is conceptually similar to a nuclear reactor, in which atomic nuclei are split into lighter ones, resulting in the release of energy.

Perhaps an example that more nearly mirrors zero-point energy is a hydroelectric dam holding back a huge lake. If you shut off the sluices in the dam so that no water flows, you cannot get any energy out. The water is the same everywhere, and there are no energy differences to exploit. However, when you open the sluices, the higher energy contained within the water pressure is released as it flows to areas of lower pressure. It’s that transfer of energy that turns turbines and creates electricity. However, without the motion of energy from a place of high energy density to one of lower density, no energy can be extracted from the lake.

With zero-point energy, there is no lower point. That’s the bottom line (no pun intended). Because the energy of empty space is everywhere constant, there is no impetus for the energy to move. And without the motion of energy, none can be extracted. Zero-point energy is a scam.

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Two cosmological mysteries continue to fascinate scientists and science enthusiasts alike. The first is understanding in detail how the Universe came into existence. The second is the nature of dark matter, a substance which is thought to be far more prevalent than all the stars and galaxies in the Universe. A recent paper explores a possible intricate connection between these two phenomena and proposes that the beginning of the Universe included not one, but two, Big Bangs.

To understand the implications of this interesting new idea, we must first consider the prevailing understanding of both the Big Bang and dark matter.

In the beginning

According to the accepted theory of the beginning of the Universe, a tiny fraction of a second after the Universe began, there was a period called “inflation.” During inflation, the Universe expanded very quickly — faster than the speed of light. Inflation was driven by the existence of a form of energy called “vacuum energy.” Inflation persisted only for a very short time, lasting far less than a second, during which our visible Universe expanded from a size smaller than an atom to about the size of a football stadium.

As the inflation period ended, the energy driving the expansion changed form and created the matter that evolved into the Universe we see today. The moment that the Universe transitioned from being governed by inflation to being filled with a hot and dense plasma is the beginning of what scientists call the Big Bang.

The other interesting phenomenon is dark matter, a proposed substance that, if it exists, explains some observed astronomical anomalies. Galaxies, like people, are made of ordinary matter, and we can use the laws of physics to predict how they should move. However, when astronomers study the heavens, they see some surprises. One example is that galaxies rotate faster than expected. A second example is that certain galaxy clusters shouldn’t exist, as individual galaxies are moving so fast that they should escape the gravitational attraction of their neighbors.

While there are several possible explanations for these and other astronomical mysteries, most scientists believe that in addition to the visible matter of stars and galaxies, there exists another form of matter, called dark matter. If dark matter exists, it is five times more prevalent than ordinary matter, and this additional mass exerts additional gravity, which means that galaxies can rotate faster and move more quickly than expected. The only way researchers have inferred the existence of dark matter is by how it affects nearby ordinary matter through gravitational attraction. There is no evidence that dark matter interacts in any other way.

Two Big Bangs

In the prevailing theory of the origins of the Universe, both familiar matter and dark matter were created at the same time, less than a second after the Universe began. Effectively, it is thought that a series of steps converted the energy that governed inflation into matter and dark matter.

However, the new paper raises a different possibility. Given that ordinary matter and dark matter only interact via gravity, perhaps they didn’t appear at the same time in the early Universe. This paper suggests that while the energy of inflation eventually transitioned into ordinary matter, dark matter might have had a different origin. In the new theory, there was a second form of energy, similar to the vacuum energy that caused inflation, but this new energy was dark vacuum energy, which became the origin of dark matter.

If it is true that ordinary vacuum energy and dark vacuum energy are different, it is not necessary that they convert into particles at the same time. Indeed, the new theory suggests that instead of being created a split second after the Universe began, vacuum dark energy could have created dark matter particles as long as a month later. This is still a short time compared to the lifetime of the Universe, but a long time compared to the timescales involved in particle physics.

Testing the idea

Can this new idea be tested? If dark matter and ordinary matter interact only via gravity, the dozens of dark matter experiments currently underway will fail. All of them depend on dark matter and ordinary matter experiencing some sort of interaction beyond gravity. Thus, if this new theory is right, that would be disappointing. 

However, when the dark vacuum energy transitioned into dark matter particles, that change of energy would have shaken the structure of space and time, creating gravitational waves that would fill the Universe. Metaphorically at least, this would appear to be a “hum” in the structure of space. 

Very precise experiments have already reported detecting a cosmic hum, but a bit of caution is warranted. There are several astronomical phenomena that can generate a similar hum. Thus, the recent detection is not a confirmation this new theory. That will take more data and far more sophisticated analysis. However, the fact that facilities exist that can detect the right kind of gravitational waves gives us hope that researchers will be able to confirm or disprove this idea within a few years.  

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Quantum mechanics — the creation of several surpassing geniuses in a period of just three years — is the finest example of “collective” or “group genius” in the history of science. The expression “group genius,” inseparable from the then-prevailing zeitgeist, refers to genius traits and legacies far transcending the sum of its parts. Its underlying principles, promulgated in the Copenhagen interpretation under the group’s “father confessor” Niels Bohr, are counterintuitive and indeterministic in distinction to classical mechanics (including relativity), where they are intuitive and deterministic. Just like great art, quantum mechanics is open-ended and porous. The most successful scientific theory in history may forever remain as tantalizing and enigmatic as Mona Lisa’s smile, resonating with a message from nature: “It was my destiny to know more than you!”

The celebrated fifth Solvay Conference (1927) had been organized to debate the credibility of quantum mechanics based on the matrix mechanics and uncertainty principle of Heisenberg, the wave mechanics of Schrödinger, along with the probabilistic interpretation of wave functions set down originally by Max Born. Like two tennis champions facing each other across the net, Einstein served gedankenexperiment after gedankenexperiment with blinding speed and perfect placement. Bohr returned the serves with top-spin, slices, and scattershot effects. And he won all the points. The Bohr-Einstein debates were continued at the sixth Solvay Conference in 1930 and they would have continued at the seventh conference in 1933 had Einstein chosen to attend. The controversy has had monumental significance for the philosophy underlying quantum mechanics and the fundamental nature of reality. To his dying day Einstein was never able to reconcile himself with the uncertainty principle. In a memorable exchange, one that was repeated again and again with minor variation, Einstein decried the uncertainty principle: “God does not play dice with the universe!” Bohr offered the riposte: “Einstein, stop telling God what he can and cannot do!” 

In 1935, Einstein, in collaboration with Boris Podolsky and Nathan Rosen, wrote a paper claiming quantum mechanics was incomplete, that there existed “hidden variables” (the actual expression was introduced much later), and for that reason quantum mechanics was forced to be probabilistic and not exact. 

The puzzling assessment in the quotation above was offered by John Stewart Bell (1928–1990). Bell, lacking the academic pedigree of many of the creators of quantum mechanics, was an unlikely candidate to delve deeper into the firmament of the theory than anyone else. Yet this veritable quantum mechanics hobbyist, hailing from Northern Ireland, formulated a remarkable theorem testing the theory’s veracity. Bell’s theorem (1964) states: 

If [a hidden-variable theory] is local it will not agree with quantum mechanics, and if it agrees with quantum mechanics it will not be local. 

With experiments suggested by Bell, his theorem and its subsequent variations have been put to repeated experimental tests since 1972, most prominently by the French physicist Alain Aspect in the 1980s. Bell himself confessed to having been initially in Einstein’s corner in examining the Bohr-Einstein debates, but came to change his mind. At the submicroscopic scale we cannot examine nature without disturbing it, without insinuating ourselves into the process. Orthodoxy in physics fully accepts this concept. Late in the 20th century, the legendary Rudolf Peierls of Oxford described the Copenhagen interpretation as “battle tested.” But it is also the nature of human warfare that the defeated side is bound to resurrect the challenge.

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Modern science can rule out some ideas, but not all of them. The possibility of the existence of parallel universes — which crucially depends on the definition of “parallel” — might be one of those ideas.

A 2D thought experiment

We live in three dimensions, meaning that we can go left/right, up/down, and forward/backward. Living in our 3D world, it is difficult to envision a fourth spatial dimension, so let’s explore the concept with two dimensions existing in a three-dimensional space. Suppose we could only live in two dimensions. If those two dimensions were flat, this means that we would live on a plane. In this two-dimensional world, we would go about our lives moving east/west and north/south — but never climbing a set of stairs.

Now, imagine that despite our two-dimensional experience, the actual universe is three-dimensional. Suppose further that another two-dimensional universe exists, and that universe is oriented parallel to our own, with a tiny separation in between. Now imagine another and another. If such a situation existed, it very much would resemble a stack of large sheets of paper, with each sheet a complete, two-dimensional universe, stacked in three dimensions. Could parallel universes defined in this way exist? And what strange phenomena might arise?

The ghost hypothesis

You could imagine that creatures living on two adjacent sheets of paper could move in tandem, separated by only a tiny gap in the third dimension. Some people have imagined that this explains “ghosts.” According to this hypothesis, what some people believe are ghosts are actually individuals in a parallel dimension. The fact that they are seen only faintly is because their images just barely cross from their dimension to ours.

But science has something to say about this. We know from many experiments that the intensity of light decreases with the square of the distance between the source and your eyes. (Known as the inverse square law, it shows that the intensity of light is proportional to 1/distance².) What is less well known is that this reduction of light intensity is a measure of the number of dimensions through which light can travel.

Light from a source, such as a light bulb, spreads out through a series of concentric spheres that are centered on the source. The surface area of a three-dimensional sphere is proportional to the square of the radius (surface area = 4πr²), and the intensity of the light spreads out evenly over the sphere. As it turns out, the “2” (which means “squared” in the 1/distance² formula) is equivalent to one less than the number of dimensions through which light can travel. In other words, light can travel through three spatial dimensions, and 3 – 1 = 2, which is the number in the formula.

This means that a “ghost” cannot be explained by light coming from a parallel dimension. If that was actually true, then light could travel through four dimensions instead of three, and the light intensity formula would be 1/distance³ (since 4 – 1 = 3). But we know from measurements that light intensity decreases as the distance squared, not distance cubed — so light travels in only three spatial dimensions.

Strange attraction

This observation is also relevant to another astronomical mystery. Astronomers have known for half a century that galaxies rotate faster than the known laws of gravity and motion can explain. Essentially, the galaxies act as if they have more mass than can be observed. This is one reason why astrophysicists posit the existence of dark matter. Sci-fi enthusiasts have speculated that perhaps what we are seeing is the effect of mass from parallel worlds. In this conjecture, the rotation of galaxies is so fast because gravity from parallel universes adds to the mass we can see.

While creative, this explanation can be disproved using the same logic that disproves parallel universes as an explanation for ghosts. If gravity could indeed travel between parallel worlds, its strength would not drop off as the square of the distance between two bodies but as the cube of the distance. But we know from measurements that isn’t true.

Case closed on parallel universes?

If precise measurements of the behavior of light and gravity rule out the possibility that they can travel in more than three dimensions, does that rule out the possibility of parallel worlds? Not entirely. After all, the argument depends on matter and energy from one universe interacting with the matter and energy of another. If no interaction is allowed, then we have no data that can rule out that conjecture.

On the other hand, we also have no data that rules out invisible pixies who live in your broom closet and leave no trace. But, with no data to suggest they exist, we conclude that they probably don’t. Similarly, with no data that suggests that parallel worlds exist — in the sense of individual universes that exist in higher dimensions and can interact with one another — we can conclude that parallel universes defined thusly probably don’t exist.

Mind you, there are other possible meanings to the phrase “parallel worlds,” and this logic doesn’t apply in those cases. So, it is not possible, merely on the basis of scientific data, to make a global statement on the matter. But ruling out one conjecture is a start. And stepping over the bodies of discarded theories is how science progresses.

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This is T-Minus, where we count down the biggest developments in space, from new rocket launches to discoveries that advance our understanding of the universe and our place in it. Humanity is reaching new heights in space exploration. Make sure you’re part of the journey by subscribing here.

Blue Origin’s lander reveal

On May 19, Jeff Bezos’ Blue Origin became the second company — after SpaceX — to secure a NASA contract to develop a lander for the Artemis program’s upcoming crewed missions to the moon.

As part of the $3.4 billion contract, the company will need to design, develop, test, and demonstrate a spacecraft that can transport astronauts from the Lunar Gateway — an in-development moon-orbiting space station — to the moon’s surface. The plan is for the spacecraft, Blue Moon, to be used during Artemis V, a mission currently scheduled for 2029.

On October 27, Blue Origin unveiled a full-sized mockup of a cargo version of the Blue Moon lander. Once actually built, this spacecraft will be used to deliver three tons of payload to the lunar surface and test technologies for the later crewed Blue Moon lander.

Blue Origin’s plan is to use its in-development New Glenn rocket to deploy future Blue Moon landers, but when that might happen is TBD — the rocket still hasn’t flown, and while its maiden launch is currently scheduled for 2024, it has been repeatedly delayed in the past.

SpaceX, meanwhile, is well on its way to building its NASA moon lander. In September, it wrapped a series of key engine tests on the Starship Human Landing System, which is expected to be used for the first two crewed Artemis moon missions (Artemis III and IV).

Mars’ molten layer

Once again, a marsquake has shaken up our understanding of the Red Planet.

As mentioned in last week’s T-Minus, NASA’s InSight Lander used its seismometer to detect more than 1,300 marsquakes during its mission on Mars. This included a powerful September 2021 quake that was caused by a meteorite slamming into the planet’s surface.

Because this meteorite hit the side of Mars opposite to where Insight was stationed, the seismic waves it produced traveled through the planet’s interior before reaching Insight’s seismometer — something that had never happened before. 

Using that seismometer data, two teams of researchers have now published papers detailing how the Red Planet’s liquid-metal core is likely smaller than previously thought and surrounded by a layer of molten rock.

“This new discovery of a molten layer is just one example of how we continue to learn new things from the completed InSight mission,” said Vedran Lekic, a professor of geology at the University of Maryland and co-author of one of the papers. 

“We hope that the information we’ve gathered on planetary evolution using seismic data is paving the way for future missions to celestial bodies like the moon and other planets like Venus,” he continued.

Varda’s stranded space drugs

California startup Varda Space Industries is on a mission to create the world’s first “space factories,” autonomously manufacturing products that are easier to make in microgravity, in orbit, than here on Earth, such as semiconductors, fiber optic cables, and certain drugs.

On June 12, it launched the first of these space factories, dubbed “Winnebago 1,” with the help of a SpaceX rocket. The plan was for the spacecraft to orbit Earth for about a month, allowing Varda to test the system by attempting to synthesize the HIV-AIDS drug ritonavir.

The experiment went off without a hitch — “Space drugs have finished cooking baby!” co-founder Delian Asparouhov tweeted on June 30 — but more than four months after launch, Winnebago 1 has yet to bring the drugs home, and it still doesn’t have a return date.

Varda blames the delayed capsule return on the FAA’s inability to keep pace with the quickly growing commercial space industry, an issue SpaceX and others in the industry recently brought before Congress.

“We just need a more responsive agency from the FAA,” Asparouhov told IEEE Spectrum on October 24.  “And obviously that has to do with funding and staffing levels not lining up to the huge increase in activity in commercial space.”

The FAA, however, told IEEE Spectrum on October 20 that Varda hasn’t submitted the required paperwork — meaning the stranded space drugs could have less to do with government delays and more to do with a space startup still learning the regulatory ropes.

This article T-Minus: Stranded space drugs, a new moon lander, and more is featured on Big Think.

This is T-Minus, where we count down the biggest developments in space, from new rocket launches to discoveries that advance our understanding of the universe and our place in it. Humanity is reaching new heights in space exploration. Make sure you’re part of the journey by subscribing here.

SpaceX’s wild pace

SpaceX has been launching rockets at a blistering rate of about once every four days in 2023, a record-breaking pace, and it hopes to increase its launch rate to once every 2 to 3 days in 2024.

It also hopes some of those launches will be of its Starship rocket — the biggest in the world — which NASA plans to use to return astronauts to the moon in 2025 (and which SpaceX wants to use to colonize Mars).

None of this will happen, however, unless U.S. regulators can also step up their pace, according to William Gerstenmaier, SpaceX’s VP for build and reliability — on October 18, he testified to a Senate subcommittee that regulators are taking too long to approve SpaceX’s launch requests, including one for the in-development Starship’s next test flight.

“Our Starship, Falcon, and Dragon programs are encountering regulatory headwinds and unnecessary bureaucracy that has nothing to do with public safety … It’s a shame when our hardware is ready to fly, and we’re not able to go fly because of regulations or re-review,” said Gerstenmaier.

He urged Congress to double the FAA’s licensing staff, streamline the regulatory process, and spin off some jobs to NASA and the US Space Force to “modernize” the whole process — or risk falling behind China in the new space race.

Marsquake mystery solved

NASA’s Insight lander has detected more than 1,300 “marsquakes” since landing on the Red Planet in 2018, but the one that shook its seismometer on May 4, 2022, was five times stronger than any previously recorded.

Here on Earth, quakes are usually caused by sudden movements at the fault lines between tectonic plates. But Mars’ crust is just one solid plate, so NASA assumed this massive quake was caused by the same thing behind other big ones: a meteorite impact.

To cause such a quake, a meteorite impact would have left a blast zone an estimated 111 miles wide, but University of Oxford researchers couldn’t find any matching impact in images of Mars taken by orbiting spacecraft on the day of the quake.

On October 17, they published their research, concluding that the source of the marsquake was tectonic, caused by the release of stress from within Mars’ crust.

“These stresses are the result of billions of years of evolution, including the cooling and shrinking of different parts of the planet at different rates” said lead author Benjamin Fernando. 

“We still do not fully understand why some parts of the planet seem to have higher stresses than others, but results like these help us to investigate further,“ he continued. “One day, this information may help us to understand where it would be safe for humans to live on Mars and where you might want to avoid!”

India’s historic flight

While citizens of more than 40 countries have visited space, only three nations — the U.S., Russia, and China — have the capability to send people off-world. India aims to be the fourth, with the crewed Gaganyaan mission to Earth’s orbit, currently scheduled for 2025.

On October 21, the Indian Space Research Organization (ISRO) completed the first in a series of test flights of the Gaganyaan spacecraft. The purpose of this test, dubbed the TV-D1 (Test Vehicle Demonstration 1) mission, was to test its escape module — a key safety feature. 

During this test, the Gaganyaan spacecraft separated from its launch rocket at an altitude of 7.5 miles — this was to simulate what might happen if the mission needed to be aborted after launch.

Once it reached an altitude of 10.6 miles, Gaganyaan’s crew module (CM) detached from the crew escape system (CES). Slowed by a system of parachutes, the module then splashed down in the Indian Ocean, 6.2 miles from the launch site. 

Gaganyaan aced the test, so the next step will be a 2024 launch in which an AI-powered humanoid named Vyommitra will be aboard to mimic the activities ISRO has planned for its real astronauts.

This article T-Minus: SpaceX’s wild pace and a marsquake mystery solved is featured on Big Think.

Is there any way to speed up the search for life on Mars? It has been nearly half a century since the Viking landers gave an ambiguous answer to that ancient scientific question, and it often seems — at least to the general public — that we have made little progress since. Sophisticated rovers have found the conditions for Martian life, as well as the building blocks of life, but never life itself. 

Life or no life?

Now a new paper published in Proceedings of the National Academy of Sciences offers a possible tool for picking up the pace. A research team headed by James Cleaves of Howard University applied artificial intelligence (AI) to the challenging science of life detection to see whether a machine learning program could tell the difference between non-biological samples containing carbon and samples from living organisms. They tested 134 carbon-containing samples, including coal, rice grains, human hair, and amino acids (both synthesized and from meteorites) and had the AI vote yay or nay on the presence of life. The AI got it right in about 90% of cases.

The paper raises hopes that AI might revolutionize life detection, but several challenges need to be overcome first. The AI algorithm works by recognizing functional groups in chemical compounds known to be associated with biology. Alien life might use vastly different functional groups, however. And the more alien, the less certain will be the detection because AI is only trained on life as we know it on Earth.

The miss rate in the Cleaves study was about 10%. Although that is expected to improve with more sampling data to train the AI, in science we often require at least three standard deviations for proof —meaning 99.7%. So, as impressive as the AI is, it is still not accurate enough to unambiguously identify life. And of course, none of the samples in its training set would be alien lifeforms, until we have such samples in hand.

Don’t get me wrong. AI can and will play an important role in life detection. My own research group uses it for detecting specific movement patterns (the “motility”) of microbial life and comparing it to non-biotic sediment particles. Another great application of Cleaves’ approach will be to identify ancient life on Earth. One major question is when life first originated on our planet, and Cleaves’ AI could be used to screen samples suspected of being fossilized life. The more samples, the better it will get. This alone represents a major breakthrough.

Martian chronicles

As for Mars, the Cleaves paper suggests that AI could be used to analyze molecules detected by a gas chromatograph-mass spectrometer on a planetary lander. Both the Curiosity and Perseverance rovers carry such instruments, so some of the data analysis could be done right there on Mars, albeit not with the same accuracy you could achieve in a lab on Earth. Personally, I would love to see an AI analysis of samples of thiophenes (sulfur-rich organic compounds) already detected by Curiosity. Or we could have it investigate the Martian meteorite ALH 84001, which was claimed in the 1990s to contain fossilized Martian life. While that claim remains controversial, with most scientists in the “non-believer” camp, I would still be curious what Cleaves’ algorithm would say. Life on Mars could be related to life on Earth due to an exchange of meteoritic material, so the AI might have a better chance of succeeding.

How does all this affect the long-standing question of whether we need a sample return mission to identify life on Mars, or whether that identification could be done on the planet itself? Each approach has its unique selling points. If the samples are returned to Earth, you can apply the full power and range of high-tech analysis in cutting-edge labs, now and in the future. On the other hand, in situ life detection has the advantage that you might be able to detect active life. If you put your sample in a box for the long return to Earth — as is planned for Mars Sample Return — you are probably limited to studying dead and possibly decayed remnants. Considering astrobiology only, in situ life detection would be preferable. But a sample return mission is meant to fulfill other planetary science goals, too, including the study of Martian geology, geophysics, climate science, and atmospheric science.

Best of all would be a combination of both methods — in situ and sample return. But this isn’t the greatest time for such a discussion. Despite decades of planning, there is a real danger that neither mission will happen soon. An independent review board examining NASA’s Mars sample return plans recently found that the mission faces major challenges. In fact, it’s basically impossible given the currently projected schedule and costs. NASA set up its own review team in response, which is expected to report back next spring. While the outside committee emphasized the great importance of sample return, the U.S. Senate could still decide to scrap the program.

Either way, a 2028 launch (to collect and return samples gathered by Perseverance) now seems more than unlikely. The negative review has rattled the Mars science community, and even though my own preference as an astrobiologist would be for a life detection mission, cancelling the sample return mission would be a colossal loss for science. It could even derail, or at least damage, NASA’s entire planetary exploration program. Hopefully, there will only be a delay instead of an outright cancellation.

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The question of the shape of space certainly seems a bit nonsensical. Space just is. It’s the place that holds stars and planets, and it’s big enough to allow comets and asteroids to buzz about the Sun, with very little chance of any of them colliding. Asking whether space has a shape doesn’t seem to make much sense.

But the question of the shape of space has very real implications for the future of the cosmos — playing a role in whether the Universe will expand forever, or reverse its current expansion in a cataclysmic Big Crunch. Furthermore, space could be infinite, or it could be that if you travel far enough in one direction, you’ll return to your starting point.

3 possible shapes of space

The idea of space having a shape arose with Einstein’s theory of general relativity in 1915. In it, he discovered that he could describe the effect of gravity not as a force between two astronomical bodies, but rather as the bending of space and time. While Newton described the motion of the Moon around the Earth as the Moon traveling in a circle, Einstein described it as the Moon traveling in a straight line, but in a curved space. It’s not so different from how a person walking in what seems like a straight line along the Earth’s equator is actually following a giant curve.

In Einstein’s theory, close to every astronomical body, space is curved and distorted from the shape it would be without any matter nearby. Near a black hole, space is distorted enough to trap even light itself, despite classical physics saying that massless light does not experience gravity at all. If space can be distorted, and the Universe consists of space, what is the shape of the Universe?

Imagining the curvature of our familiar three-dimensional space is rather difficult, so it is valuable to think about the curvature of a two-dimensional one. Three shapes of space are commonly discussed: flat (like a tabletop), spherical (described by the surface of a globe), and hyperbolic or “saddle” (which looks essentially like a giant saddle). Flat and saddle space are infinite in extent, while spherical space is not.

The 270° triangle

The behavior of flat space is taught in high school geometry courses. In it, two parallel lines never cross, and the sum of the angles of a triangle add to 180°. In spherical space, things are quite different. Here, parallel lines cross, and the sum of angles in a triangle are more than 180°. 

Don’t see it? Take a city like Quito, Ecuador, which sits directly on the equator. The angle separating north and west is 90°. Follow the equator to a location 90º west of there. At that location, north and east are also separated by 90º. If you follow the two lines northward, which are parallel at the equator, they meet at the North pole and form a 90º angle. And, if you sum the angles of the triangle described by the two cities and the North pole, they add to 270°. 

Saddle space has similar surprises, however in saddle space, two parallel lines diverge, drawing farther apart. And the sum of the angles in a triangle in saddle space is less than 180°.

Determining the shape of space

So, is it possible for researchers to determine the shape of the Universe? It turns out that it is. Astronomers have employed a very clever approach to answer the question. And it begins by using radio antennas to image the Universe shortly after the Big Bang.

Shortly after the Universe began, it was filled with a hot plasma, which glowed white hot. The plasma also was full of soundwaves with a preferred wavelength. Just like sound waves in the air, this caused density differences in the plasma. Where the plasma was denser, it was a little hotter; conversely, areas with lower density were colder.  The distance between the hot and cold spots was determined by the wavelength of the sound waves.

In the 13.8 billion years since that time, the Universe has expanded and cooled. What once was white hot, has cooled to a temperature of about -450°F (-268°C). At this temperature, that early temperature variation cannot be seen by the human eye, but it can be imaged using sensitive radio telescopes. 

Light travels at a fixed speed, which means that light from distant objects was emitted far in the past. This also means that if we look at light emitted far enough away, we can literally see the conditions of the Universe shortly after the Big Bang. Indeed, light of the Big Bang emitted 13.8 billion years ago can now be seen on a sphere that encircles the Earth.

The wavelength of sound in the early Universe set the distance between two adjacent hot spots. The distance between the hot spots and the Earth is determined by the speed of light and how long it took the light to get to Earth. The centers of two adjacent spots and the Earth form a triangle. And astronomers can use geometry to calculate the angle between two adjacent hot spots as seen in an Earthbound telescope.

Remember that the shape of space can distort triangles. If space is flat, the spots should be separated by 1°; if space is spherical, the angle should be bigger than 1°; and if space is saddle-shaped, the angle should be smaller than 1°.

A flat Universe

When astronomers examined their data, they measured the angle to be 1°. From this, they concluded that the shape of space in the Universe is flat, which means it is infinitely large — much larger than the Universe we can see with telescopes.

However, no measurement is 100% accurate. They all have uncertainty. So, it remains possible that the Universe is slightly curved, and our equipment isn’t precise enough to measure it. Or perhaps the Universe is curved and very big, and it is only because we see only a little piece of it that it looks flat.

Given that flat is one unique possible shape out of countless alternatives, explaining its flatness is one of the unanswered mysteries of science.

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Ah, New Hampshire, home to extensive granite formations and quarries, the first presidential primary in the U.S., delicious apple cider donuts — and the worst weather on Earth.

Of course, that weather isn’t widespread across the Granite State, which for the most part has a pleasantly mild, temperate climate, but is rather concentrated at one location in particular: Mount Washington.

Miserable Mount Washington

Standing 6,288 feet above sea level, Mount Washington is positively short compared to the rampant “fourteeners” of the West’s Rocky Mountains. It is, however, the tallest mountain for about a thousand miles, looming large over the surrounding terrain. And its horrid weather firmly trounces that of any grander peak.

Kenneth Jones, a longtime board member for the Mount Washington Observatory, which sits atop the mountain, ardently defends the area’s claim to the worst weather on Earth. It combines rain, cold, and wind as no other place does, he says. Sure, there are places like Antarctica’s Vostok Station, which the Russians claim is the “coldest and most inhospitable place in the world,” that are chillier. But Vostok gets almost no precipitation and has winds that blow at a pitiful average of just 11 mph (18 kph). And many other locations are wetter, but they aren’t nearly as cold or windy.

Mount Washington, on the other hand, has it all. The annual average temperature there is 27°F (-2.8°C), with a winter average of 7°F (-13.9°C), and a record low of -47°F (-43.9°C). This frigid air combines with gusty winds to chill visitors’ bones. The average annual wind speed is 35 mph (56 kph), and winds are at or above hurricane force (at least 74 mph, or 119 kph) every other day on average in winter. Then there’s the copious precipitation: about 100 inches (254 cm) of rain and 281 inches (714 cm) of snow each year, with fog cover about 60% of the time.

For nearly 62 years, Mount Washington held the record for the fastest measured wind gust over the surface of the Earth: 231 mph (372 kph). It was dethroned in 1996 by winds from Typhoon Ophelia at Barrow Island, Australia, which clocked in at an astounding 253 mph (407 kph). Mount Washington also has the record for the lowest recorded wind chill in the U.S., -109°F (-78°C), set earlier this year when the ambient temperature was -47°F (-43.9°C) and the winds howled at 122 mph (196 kph). Such conditions would cause exposed skin and the underlying tissues to freeze in a couple of minutes.

Masochists on the mountain

The brutal conditions at Mount Washington naturally have attracted the curiosity of scientists. Researchers have shacked up at the mountain’s observatory since 1932, meticulously measuring the weather conditions outside, in person, every hour, 365 days a year. When the weather is especially awful — in charmingly masochistic fashion — they venture out every 15-20 minutes. One way the scientists at the observatory fund their operations is by weather-testing products for manufacturers. “If they can survive Mount Washington, they can survive anywhere,” the researchers claim.

So what explains Mount Washington’s worst weather on Earth? First, its lofty standing among its surroundings mightily contributes. “There’s not a lot of terrain that’s going to slow down the jet stream,” Francis Tarasiewicz, an engineer at the Mount Washington Observatory, told PBS Terra.

Once the winds of the jet stream arrive at Mount Washington, they get funneled in by the White Mountains that flank Mount Washington to the north and south. The natural triangle they form constricts and focuses winds directly to the peak. Thanks to the Bernoulli principle, when air passes through a confined space, its velocity increases.

Second, Mount Washington rests almost exactly at the midpoint between Earth’s equator and the North Pole. “Cold air from the north is clashing with more tropical air to the south,” Tarasiewicz explained to PBS. Where warm and cold fronts meet, storms arise.

Despite Mount Washington’s ominous reputation, it’s a lovely place to visit for the avid outdoor-lover or hiker. Just make sure you go in summer!

This article Why the worst weather on Earth is in New Hampshire is featured on Big Think.

At first blush, asking if gravity is a force seems quite silly. After all, when you were a toddler, you experimented with gravity by dropping tidbits from your highchair down to a grateful puppy. The food always fell. And, when you were much older, the story was still true — like perhaps on your 21st birthday when you had a few too many and lost your footing, hitting the ground was a clear sign that gravity still worked.

But the question is rather complicated. To answer it, we first need to define the term. A force can be thought of as something that, when applied to a free body, can cause it to move or deform or both. Thus, when you push a car out of a snowbank, that’s a force. So is smashing a watermelon with a sledgehammer. And, since objects fall when they are dropped, it would seem that there is no question that gravity is indeed a force.

Defining gravity

Putting aside some early attempts at understanding gravity, it was first described in a quantitative way back in the mid-1600s by Isaac Newton. While the oft-told story of an apple falling on his head is apocryphal, what Newton did was to work out the mathematical laws that govern the gravitational attraction between two bodies. The gravitational force depended on the mass of each object and the distance separating them. 

Despite the breathtaking success of Newton’s equations, he was never completely satisfied with his theory. He didn’t see the mechanism that would connect two astronomical bodies, like the Moon and the Sun. For forces like picking up a glass, what caused the force was clear. But that wasn’t true for gravity. He was always uncomfortable with this idea of “action at a distance” (action being his word for force). He even wrote to a colleague, telling him that any competent thinker shouldn’t believe his theory.

Regardless, it worked. Astronomers used his equations to predict the motions of planets and comets, as well as the location and timing of solar eclipses. (And, one day, NASA used them to land on the Moon.) No matter how philosophically unsatisfying, gravity seemed to be a force of some sort.

Upsetting the apple cart

The situation changed in 1915, when Albert Einstein devised his own theory of gravity. His ideas were staggeringly different from Newton’s. Einstein imagined that space and time were equivalent, where one could be transformed into the other. Because they were the same, he joined them into a single concept: spacetime. 

When Einstein married his spacetime concept with gravity, he found that gravity was actually the distortion of spacetime. Heavy objects like stars and planets distorted spacetime in a way that made objects move toward them, so gravity is simply a result of the geometry of spacetime. As bizarre as this sounds, it has been validated over and over again.

A disturbance in the force

While Einstein’s ideas are very well regarded, they are also known to be incomplete. His theory fails in the subatomic world. When scientists try to use his equations to describe the nature of gravity at atomic scales (and smaller), they fail miserably, predicting non-physical infinities. When a theory predicts something to be infinite, this is a sign not that infinities are real, but that the theory is broken. 

Accordingly, researchers have tried to devise a theory of gravity that describes the world of the ultra-small. To do so, they look to theories of electromagnetism and other subatomic forces of the quantum world, which work very well. Stealing from these successful theories, scientists call any theory of super-small gravity “quantum gravity.”

While no successful theory of quantum gravity has yet been devised, scientists use other theories as a guide to help envision what a quantum theory of gravity might predict. In electromagnetism, the force is transmitted by particles called photons. An electrically charged particle emits a photon, which then travels to another one. Both the sending and receiving particles recoil, changing their direction. Because the particles change their motion, electromagnetism is most certainly a force.

For gravity, physicists imagine that force-carrying particles called “gravitons” jump between massive subatomic particles, which will cause them to recoil and move. Thus, on the quantum scale, gravity is a force in much the way that electromagnetism is. It’s only when the effects of many gravitons work together that, on larger scales, gravity appears to be the distortion of spacetime.

So, is gravity a force?

All this takes us back to the original question: Is gravity a force? The answer is murky. It is clearly a force in the simplest definition of the word. But we also know that Einstein’s theory positing gravity to result from the distortion of spacetime is an incredibly successful model. So perhaps we have reached a moment of scientific Zen: Gravity just is. Or, to paraphrase Forrest Gump, “Gravity is as gravity does.” 

This article Is gravity a force? It’s complicated is featured on Big Think.