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A ‘Very Exciting’ Anomaly Detected in Major Experiment Could Be Huge News For Physics

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A strange gap between theoretical predictions and experimental results in a major neutrino research project could be a sign of the elusive ‘sterile’ neutrino – a particle so quiet, it can only be detected by the silence it leaves in its wake.

 

It’s not the first time the anomaly has been seen, adding to previous experimental data hinting at something odd in the world of neutrino research. This time around, it’s been detected at the Baksan Experiment on Sterile Transitions (BEST).

Unambiguous evidence of the hypothetical sterile neutrino could provide physicists with a solid candidate for the Universe’s mysterious supply of dark matter. On the other hand, it could simply all come down to a problem in the models used to describe the quirky behaviors of old school neutrinos.

Which would also make for a significant moment in the history of physics.

“The results are very exciting,” says Los Alamos National Laboratory physicist Steve Elliott.

“This definitely reaffirms the anomaly we’ve seen in previous experiments. But what this means is not obvious. There are now conflicting results about sterile neutrinos. If the results indicate fundamental nuclear or atomic physics are misunderstood, that would be very interesting, too.”

In spite of ranking among the most abundant particles in the Universe, neutrinos are notoriously difficult to catch. When you’ve got barely any mass, no electric charge, and only make your presence known through the weak nuclear force, it’s easy to slip through even the densest of materials unimpeded.

 

The neutrino’s ghost-like movement isn’t its only interesting quality. Each particle’s quantum wave morphs as it zips along, oscillating between characteristic ‘flavors’ that echo their negatively charged particle cousins – the electron, muon, and tau.

Studies on the oscillations of neutrinos at the US Los Alamos National Laboratory in the 1990s noticed gaps in the timing of this flip-flopping that left room for a fourth flavor, one that wouldn’t make so much as a ripple in the weak nuclear field.

Cloaked in silence, the sterile flavor of neutrino would only be conspicuous by a brief pause in its interactions.

BEST is shielded from cosmic neutrino sources beneath a mile of rock in Russia’s Caucasus Mountains. It features a double-chambered tank of liquid gallium which patiently collects neutrinos erupting from a core of irradiated chromium.

After measuring the amount of gallium that had transformed into a germanium isotope in each tank, the researchers could work backwards to determine the number of direct collisions with neutrinos while they were oscillating through their electron flavor.

Similar to the Los Alamos experiment’s own ‘gallium anomaly’, researchers calculated a fifth to a quarter less germanium than expected, hinting at a deficit in the expected number of electron neutrinos.

 

This isn’t to say with certainty that the neutrinos had briefly adopted a sterile flavor. Many other searches for the pale little particle come up empty-handed, leaving open the possibility that the models used to predict the transformations are on some level misleading.

That isn’t itself a bad thing. Corrections in the basic framework of nuclear physics could have significant ramifications, potentially revealing gaps in the Standard Model which could lead to explanations for some of science’s big remaining mysteries.

If this is indeed the mark of the sterile neutrino, we might at last have evidence of a material that exists in tremendous quantities, yet makes only a gravitational dimple in the fabric of space.

Whether that is the sum of dark matter or a mere piece of its puzzle would depend on further experimentation on the most ghostliest of ghost particles.

This research was published in Physics Review Letters and Physical Review C.

 

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Earth’s Magnetic Poles Probably Won’t Flip After All, Scientists Predict

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Our planet’s protective shell isn’t quite what it used to be. Over the past two centuries its magnetic strength has taken a nosedive, and nobody has the foggiest idea why. 

At the same time, a concerning soft-spot in the field called the South Atlantic Anomaly has blistered over the Atlantic ocean, and has already proven problematic for delicate circuitry on orbital satellites.

 

Both of these troubling observations fuel concerns that we might be seeing signs of an imminent reconfiguration that would turn the compass points all topsy-turvy in what’s known as a magnetic pole reversal.

But researchers behind a new investigation modelling the planet’s magnetic field in the recent past warn that we shouldn’t be too hasty in assuming that’s going to happen.

“Based on similarities with the recreated anomalies, we predict that the South Atlantic Anomaly will probably disappear within the next 300 years, and that Earth is not heading towards a polarity reversal,” says geologist Andreas Nilsson from Lund University in Sweden.

Not any time soon, at least. So for now we can breathe easy.

Still, if our geological history is anything to go by, it’s likely the flowing lines of our planetary magnetic field will eventually point the other way around.

What such a reversal would mean for humanity isn’t clear. The last time such a monumental event occurred, a mere 42,000 years ago, life on Earth seemed to go through a rough period as a rain of high-speed charged particles ripped through our atmosphere.

 

Whether we humans noticed – perhaps responding by spending a bit more time sheltering – is a matter of speculation.

However, given today’s reliance on electronic technology that could be vulnerable without the protection of a magnetic umbrella, even the most rapid of field reversals in the foreseeable future would leave us exposed.

So geologists are keen to know which wiggles, wobbles, and wanderings in the field herald catastrophe, and which imply business as usual.

Much of what we know of the magnetic field’s history comes from the way its orientation forces particles in molten materials to line up before being locked in place as they solidify. Digging through layers of mineralized arrows provides a fairly clear record of which way the compass pointed throughout the millennia.

Similarly, pottery artifacts from archaeological sites can also provide a snapshot of the field in more recent times, capturing its direction in clay before firing.

In the new study, researchers from Lund University and Oregon State University reconstructed a detailed timeline of our planet’s magnetic shell stretching back towards the last ice age, by analyzing samples of volcanic rocks, sediments, and artifacts from around the world.

 

“We have mapped changes in the Earth’s magnetic field over the past 9,000 years, and anomalies like the one in the South Atlantic are probably recurring phenomena linked to corresponding variations in the strength of the Earth’s magnetic field,” says Nilsson.

With thousands of years of perspective, it quickly becomes clear the South Atlantic soft-spot isn’t completely out of the ordinary. Starting around 1600 BCE, a similar geological change took place, lasting some 1,300 years before evening out once more.

Assuming the same basic mechanics are at work, it’s likely the current patch of weakening will soon regain strength and fade away without ending in global reconfiguration. It’s even likely the magnetic field as a whole will bounce back to a vigor we haven’t seen since the early 19th century.

This isn’t proof against a reversal occurring soon, however – just new evidence suggesting we shouldn’t interpret present anomalies of diminishing strength as strong signs of a polar flip.

In some ways, that’s good news. But it leaves us in the dark on exactly what such a massive geological process will look like in the scale of a human lifetime.

Having detailed records like this one goes a long way towards building a clearer picture, so maybe if the worst happens, we’ll be prepared for it.

This research was published in PNAS.

 

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These Record-Breaking Simulations of The Universe Aim to Solve a ‘Tiny’ Problem

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What’s the mass of a neutrino? This problem has vexed physicists for decades. It’s tiny, no doubt, but by virtue of one of the particle’s most fundamental features, it can’t be zero. This still leaves plenty of room for guesswork. 

 

Like most riddles, the solution might be found by thinking outside of the box.

Physicists from the University of Tsukuba, Kyoto University, and the University of Tokyo in Japan have taken this advice to heart, using a revolutionary new method for modeling a significant chunk of the Universe to act as a testing ground for the subtle influence of neutrinos on the evolution of the cosmos.

It’s an idea that’s been tested before. But by applying a simulation used in other areas of physics, the researchers behind this new model think they can iron out some of the previous method’s shortcomings.

Neutrinos have been a theoretical part of the standard model of physics since 1930, and a confirmed member since their experimental discovery in the mid-1950s.

Technically, this ghost-like particle should be as massless as a photon. But a little over twenty years ago scientists worked out that not only do they come in a variety of forms, or ‘flavors’, they oscillate between them as they move.

For this very reason, physicists are confident neutrinos must have some kind of mass. Even if it’s a whisker off nothing. If neutrinos didn’t have mass, they would move at the speed of light in a vacuum, and if that was the case, time would stand still for them, so they wouldn’t be changing at all.

 

Searches for a precise mass using laboratory methods have put upper limits on how chunky a neutrino could potentially get, capping it at 1/500,000 of a single electron. So, it’s safe to say that somewhere between zip and 1/500,000th of an electron’s mass, we have our answer.

This new method might just bring us a little closer to that number, though admittedly, reconstructing most of a Universe to weigh something that barely exists isn’t without its irony.

Fortunately, what the humble neutrino lacks in punch it makes up for in sheer numbers.

From the very earliest moments in time, neutrinos have been a part of the Universe in significant amounts, churned out of the roiling vacuum itself within the first second of the Big Bang.

Just like the static hum of leftover radiation we still see as a cosmic microwave background, a neutrally-charged background of these neutrino relics surround us to this day.

There’s little doubt that masses of relic neutrinos would have had some kind of influence on the emerging structures of the Universe. Precisely what kind of effect isn’t so easy to figure out.

 

In a typical physics model of something like a solar system, or even a bunch of atoms, you might select a number of objects, define their behaviors with respect to one another, map them in 3D space, and let a computer calculate what happens over time.

Want more objects? Get a faster computer and add them in.

Such ‘N-body’ simulations can work well for large-scale simulations. But they have their limits, especially when rubbed up against physics of a more quantum nature.

Quantum objects like massive neutrinos don’t play by the same rules as classical particles. Neutrinos are only known to interact with gravity and weak subatomic forces, so it’s hard to say how different types of neutrinos stirred up the early Universe.

In this new model, the researchers borrowed an equation from plasma physics called a Vlasov simulation. Rather than treat relic neutrinos as discrete classical objects, the plasma-based equations allowed the team to describe them as if they were a continuous medium.

Running the simulation on a supercomputer at RIKEN Center for Computational Sciences in Japan demonstrated that the program could be used on a range of scales, resulting in fairly accurate representations of the structure of most of the observable Universe.

 

“Our largest simulation self-consistently combines the Vlasov simulation on 400 trillion grids with 330 billion-body calculations, and it accurately reproduces the complex dynamics of cosmic neutrinos,” says lead author of the study, physicist Koji Yoshikawa from the University of Tokyo.

Future work will be needed to tweak the details to hopefully zoom in on a more precise figure for the relic neutrino’s mass. Yet it’s an innovation that has already earned the team recognition in the form of a finalist’s place in the 2021 ACM Gordon Bell Prize.

Their revolutionary new way of modeling large-scale structures this way isn’t just a potential win for physicists eager to learn precisely how much mass a neutrino commands, either; it could have applications in plasma physics as well.

This research was published in SC ’21: Proceedings of the International Conference for High Performance Computing, Networking, Storage and Analysis.

 

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This One Tiny Animal Has Found a Way to Give Up Sex Completely, And Still Do Fine

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Let’s face it. Sex isn’t always worth the effort. For many animals, the whole mating game is so inconvenient, going it alone and reproducing asexually is the best option.

As appealing as it might sound, however, evolution puts a heavy price on a population that gives up sex for too long. Sooner or later, a eukaryotic species will either need to swap chromosomes in a DNA shake-up that increases genetic variation, or risk fading into extinction.

 

That’s the rule, at least – but the beetle mite (Oppiella nova) is having none of it.

By comparing its genome with that of its sexually active cousin, O. subpectinata, a team of researchers from across Europe has found that this micrometer-sized arthropod has been doing quite all right living a chaste lifestyle for… millions of years.

Like us, these tiny mites have a copy for every chromosome making up their genome, which makes them a diploid organism.

Swapping chromosomes and subjecting them to a bit of mix-and-match every now and then helps give a population a diverse choice in genetic combinations, meaning when catastrophe strikes – be it a plague, a temperature change, or introduction of a new predator – there’s bound to be at least a few individuals that will cope.

Strip away all the bells and whistles, and that’s sex all summed up. Unfortunately, those bells and whistles (searching out mates, competing with them, producing all that sperm, the whole pregnancy thing) impose a toll on maximizing genetic diversity.

There are other ways to maintain a degree of variation that don’t rely on sexual reproduction. These processes cause mutations to build up differently in types of the same gene (or allele), creating a unique signature among the genes of asexual organisms.

 

Known as the Meselson effect, named after Harvard geneticist Matthew Meselson, this mutation pattern could in theory be used to identify a diploid organism as a bona fide, long-term asexual species.

The only problem is none of the evidence for this effect has been clear-cut, leaving too much room for doubt. Some ancient lineages of species thought to be asexual have since been found to have only recent converts, or – scandalous as it is to suggest – have peppered their genes with the occasional licentious tryst over the eons.  

What researchers needed was a strong, unambiguous signal of variation in genes in an animal suspected of having given up sex long, long ago, and never looked back.

Which brings us back to O. nova – a little mite with sublineages that went their separate ways between 6 and 16 million years ago, suggesting it’s a species that’s been around for quite a while.

More importantly, it’s a species known to be asexual, in contrast with others on its branch of the family tree, making it a prime specimen to study for evidence of the Meselson effect.

 

As one might imagine of an animal that could form a conga-line inside a single millimeter, the task of collecting them and analyzing their DNA wasn’t exactly easy.

“These mites are only one-fifth of a millimeter in size and difficult to identify,” says reproductive biologist Jens Bast from the University of Lausanne in Switzerland.

The team even required specialized computer programs to decipher the genomes, but it was all worth it in the end.

“Our results clearly show that O. nova reproduces exclusively asexually,” says Bast.

“When it comes to understanding how evolution works without sex, these beetle mites could still provide a surprise or two.”

This isn’t to say asexual reproduction isn’t without its problems. The beetle mite appears to be an exception to an otherwise fairly consistent rule in biology.

But the discovery of an animal that’s managed to leave sex millions of years in the past does demonstrate it’s possible to thrive without it.

This research was published in PNAS.

 

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Scientists Just Identified Another Mysterious Surge in The Atmosphere Due to Humans

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Levels of molecular hydrogen (H2) in the atmosphere have surged in modern times due to human activity, according to new research.

When scientists analyzed air samples trapped in drilled cores of Antarctica’s ice, they found atmospheric hydrogen had increased 70 percent over the course of the 20th century.

 

Even as recent air pollution laws have sought to curb fossil fuel emissions, hydrogen emissions have continued to surge with no signs of slowing down. And there’s a chance that leakage is to blame.

Molecular hydrogen is a natural component of our atmosphere due to the breakdown of formaldehyde, but it is also a byproduct of fossil fuel combustion, especially from automobile exhaust, and biomass burning.

While hydrogen doesn’t trap heat in the atmosphere on its own, it can indirectly impact the distribution of methane and ozone. After carbon dioxide, these are the two most important greenhouse gases, which means global hydrogen levels can also perturb the climate.

Nevertheless, the sources and sinks of atmospheric hydrogen are rarely studied. We don’t even have a good estimate of how much humans have emitted since industrial times.

The current study is the first to offer up a solid figure. Between 1852 and 2003, air samples from near the South Pole of Antarctica suggest atmospheric hydrogen jumped from 330 parts per billion to 550 parts per billion.

“Aging air is trapped in the perennial snowpack above an ice sheet, and sampling it gives us a highly accurate account of atmospheric composition over time,” explains Earth scientist John Patterson from the University of California Irvine.

 

“Our paleoatmospheric reconstruction of H2 levels has greatly enhanced our understanding of anthropogenic emissions since the beginning of the industrial revolution.”

The news isn’t exactly good. As it turns out, we may have been significantly underestimating our hydrogen emissions.

Some tailpipe emissions have been mitigated in recent years with the use of catalytic converters, and ideally we would have seen hydrogen emissions decrease or even plateau as well.

Yet hydrogen levels have continued to rise in the atmosphere, almost uninterrupted.

“[W]e are likely underestimating nonautomotive sources of the gas,” says Patterson.

Instead, there must be another rapidly increasing source that is offsetting our progress in the automobile industry – we just don’t know where it’s coming from.

This isn’t the only dataset to identify such a discrepancy. Prior research has also shown a consistent rise in hydrogen from 2000 and 2015, distinct from trends in other forms of exhaust pollution.

In terms of human-caused emissions, hydrogen emissions are thought to mostly come from automobile exhaust, but hydrogen leakage from industrial processes is rarely considered.

No one has directly measured how much hydrogen leaks from these processes, but initial estimates suggest it could be significant. 

 

A 10 percent leakage rate between 1985 and 2005 would account for roughly half the rise in recent hydrogen emissions, researchers estimate.

They can’t be sure this is where the hydrogen is coming from – hydrogen emissions from coal combustion are also seriously understudied – but the authors argue it’s worth investigating more.

Especially since green hydrogen processes, which split hydrogen from water to create carbon-free power, could also result in substantial leakage if they are one day scaled up, as some climate scientists and environmentalists hope they will be.

This isn’t a new worry. It’s a concern scientists have been pointing out for years now.

If hydrogen one day leaks from industrialized hydrogen gas plants, experts are troubled it could increase the lifetime of methane in our atmosphere, a greenhouse gas 20 times more potent than carbon dioxide.

Although, even with a small percentage of leaks, a global hydrogen economy would likely have far lower climate impacts than our existing fossil fuel-based energy system, researchers estimate.

Scientists are now on the hunt to find the mysterious source of hydrogen we seem to have been missing all along. If at least some of it turns out to be leakage, the future of green hydrogen might have a problem in need of solving.

The study was published in PNAS.

 

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