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An international research team has succeeded in developing a new type of material in the rather young research field of covalent organic frameworks. The new two-dimensional polymer is characterized by the fact that its properties can be controlled in a targeted and reversible manner. This has brought the researchers a step closer to the goal of realizing switchable quantum states.

An international research team has succeeded in developing a new type of material in the rather young research field of covalent organic frameworks. The new two-dimensional polymer is characterized by the fact that its properties can be controlled in a targeted and reversible manner. This has brought the researchers a step closer to the goal of realizing switchable quantum states.

A new study has found that the United States does not have a housing shortage, contrary to popular belief. An analysis of Census data shows the majority of the nation's metropolitan and micropolitan markets have enough housing units for the number of househoulds in the area. However, median incomes indicate many people cannot afford the housing available in the area, indicating policy needs to address income and housing prices instead of trying to build out of the problem, authors argue.

Brain-computer interfaces or BCIs hold immense potential for individuals with a wide range of neurological conditions, but the road to implementation is long and nuanced for both the invasive and noninvasive versions of the technology. Scientists have now successfully integrated a novel focused ultrasound stimulation to realize bidirectional BCI that both encodes and decodes brain waves using machine learning in a study with 25 human subjects. This work opens up a new avenue to significantly enhance not only the signal quality, but also, overall nonivasive BCI performance by stimulating targeted neural circuits.

Researchers developed software that can simulate the growth of field crops. To do this, they fed thousands of photos from field experiments into a learning algorithm. This enabled the algorithm to learn how to visualize the future development of cultivated plants based on a single initial image. Using the images created during this process, parameters such as leaf area or yield can be estimated accurately.

Astronomers have discovered a double-record-breaking pair of quasars. Not only are they the most distant pair of merging quasars ever found, but also the only pair confirmed in the bygone era of the Universe's earliest formation.

A team of scientists used NASA's James Webb Space Telescope to parse the composition of the Crab Nebula, a supernova remnant located 6,500 light-years away in the constellation Taurus.

The early Universe was a strange place. Early in its history—in the first quintillionth of a second—the entire cosmos was nothing more than a stunningly hot plasma. And, according to researchers at the Massachusetts Institute of Technology (MIT), this soup of quarks and gluons was accompanied by the formation of weird little primordial black holes (PHBs). It’s entirely possible that these long-vanished PHBs could have been the root of dark matter.

MIT’s David Kaiser and graduate student Elba Alonso-Monsalve suggest that such early super-charged black holes were very likely a new state of matter that we don’t see in the modern cosmos. “Even though these short-lived, exotic creatures are not around today, they could have affected cosmic history in ways that could show up in subtle signals today,” Kaiser said. “Within the idea that all dark matter could be accounted for by black holes, this gives us new things to look for.” That means a new way to search for the origins of dark matter.

Dark matter is mysterious. No one has directly observed it yet. However, its influence on regular “baryonic” matter is detectable. Scientists have many suggestions for what dark matter could be, but until they can observe it, it’s tough to tell what the stuff is, exactly. Black holes could be likely candidates. But the mass of all the observable ones isn’t enough to account for the amount of dark matter in the cosmos. However, there may be a connection to black holes after all.

Black Holes Through Cosmic Time

Most of us are familiar with the idea of at least two types of black holes: stellar-mass and supermassive. There is also a population of intermediate-mass black holes, which are rare. The stellar-mass objects form when massive stars explode as supernovae and collapse to form black holes. These exist throughout many galaxies. The supermassive ones aggregate many millions of solar masses together. They form “hierarchically” from smaller ones and exist in the hearts of galaxies. The intermediate-mass ones probably form hierarchically as well and could be a hidden link between the other two types.

An image based on a supercomputer simulation of the cosmological environment where primordial gas undergoes the direct collapse to create black holes. Credit: Aaron Smith/TACC/UT-Austin.

Black holes have formed throughout the history of the Universe. That’s why the idea of primordial black holes isn’t too much of a surprise, although they remain elusive. In their very primitive state, they’d be ultradense objects with the mass of an asteroid punched down into something the size of an atom. They probably didn’t last very long—maybe another quintillionth of a second. After formation, they either blinked out of existence or got scattered across the expanding Universe.

The Link Between Primordial Black Holes and Dark Matter

So, how could these weird PHBs affect the formation of dark matter if they winked in and out of existence so quickly? That’s where Kaiser and his student’s work come in. They suggest that as the first PHBs scattered, they somehow “tugged” on space-time and changed something that could explain dark matter. That same process could have produced even smaller black holes with a curious property called “color charge.” And, there’s a dark matter connection.

“Color charge” is a property of quarks and gluons, and it ends up gluing them together. Think of it as a “super-charge”. Kaiser and Alonso-Monsalve suggest that some of the very early PHBs had this “supercharge” in the same way as the quarks and gluons had it. If that’s true, then the earliest super-color-charged PHBs would have been an entirely new state of matter. We don’t see them around anymore because they likely evaporated a fraction of a second after they spawned. But, their existence was necessary, particularly to the formation of dark matter.

Even during their short life span, however, the earliest supercharged PHBs could have influenced a key cosmological transition: the time when the first atomic nuclei were forged. Those color-charged black holes could have affected the balance of fusing nuclei. And, they could have done it in a way that astronomers might someday detect with future measurements. Such an observation would point convincingly to primordial black holes as the root of all dark matter today.

What Were Those Early PHBs Made Of?

If those PHBs did exist, what were THEY made of? Unlike other black holes, there’s not much evidence for something like a star or another black hole that “birthed” these early ones. To figure that one out, Alonso-Monsalve and Kaiser did some exploration. They calculated the PHB formation “era” as happening just after the Big Bang. “Typical” microscopic black holes formed within this short “flash of time.” Those would have been as massive as an asteroid and as small as an atom. But, they also found that a tiny population of exponentially smaller black holes came into being. Those had the mass of a rhino and a size much smaller than a single proton.

This process probably started around one second after the Big Bang. That gave all these PBHs plenty of time to disrupt the equilibrium conditions that would have prevailed when the first nuclei began to form from the quark-gluon plasma. The super-charged black holes would have quickly evaporated. That probably happened about the time when the first atomic nuclei began to form. “These objects might have left some exciting observational imprints,” Alonso-Monsalve said. “They could have changed the balance of this versus that, and that’s the kind of thing that one can begin to wonder about.”

From Plasma to PHBs to Dark Matter

The backdrop for the formation of these short-lived black holes? The quark-gluon plasma. And, it should have a distribution of “color charge”. Kaiser and Alonso-Monsalve determined the size of an area in the plasma that could collapse to form a PBH. It turns out there wouldn’t have been much color charge in most typical black holes formed in the moment. That’s because they probably formed by absorbing a huge number of regions that had a mix of charges. Thus, they wouldn’t be “supercharged.”

But the smallest black holes would have been highly color-charged. They would have contained the maximum amount of any type of charge allowed for a black hole. And, by their formation, they could well have produced the tiniest bit of change that led to the formation of dark matter.

For More Information

Exotic Black holes Could be a Byproduct of Dark Matter
Preprint: Primordial Black Holes with QCD Color Charge

The post A New Way to Prove if Primordial Black Holes Contribute to Dark Matter appeared first on Universe Today.

The vicinity of Sagittarius A* (Sgr A*), the supermassive black hole at the Milky Way’s center, is hyperactive. Stars, gas, and dust zip around the black hole’s gravitational well at thousands of kilometers per hour. Previously, astronomers thought that only mature stars had been pulled into such rapid orbits. However, a new paper from the University of Cologne and elsewhere in Europe found that some relatively young stars are making the rounds rather than older ones, which raises some questions about the models predicting how stars form in these hyperactive regions.

Astronomers have known about the highly mobile stars surrounding Sgr A* for over thirty years now. They even have their own categorization, known as S stars. However, researchers lacked the equipment to analyze the age of some of these stars, and theories pointed to older, dimmer stars being the most likely to survive near a black hole.

But then, as it does so often with science, evidence that challenged the old and dim star theory began to pile up. Twelve years ago, researchers found an object they believed was a cloud of gas that was in the process of being eaten by Sgr A*. More recently, evidence has begun to hint that that gas cloud might surround a newly born star, known as a “Young Stellar Object” (YSO) in astronomy jargon.

Video showing the motion of stars around Sgr A*, from the corresponding author of the new paper.
Credit – Florian Peißker YouTube Channel

As Sgr A* started to receive more observational time with more powerful telescopes over the years, researchers were able to focus in on other interesting objects, the paper describes dozens of potential YSOs in the vicinity of the previously known S stars. Interestingly, they also seem to follow similar orbits.

Those orbits have the new YSOs zipping in front of the black hole at thousands of kilometers per hour, much faster than typical star formation theories allow. Maybe some intricacy of the black hole’s gravitational field is causing this dramatic motion, or maybe there is some other unknown aspect of stellar formation that can account for these fast-moving young stars, but for now, how they are formed remains a mystery.

However, the researchers made another interesting discovery as part of their work. They found that these YSOs, along with their S star counterparts, orbit in very well-defined formations. In a press release from the University of Cologne, they compare this to how bees from the same hive fly in formation when together. In this case, the black hole appears to be forcing them into this common formation, though other explanations could also account for it, and that analysis wasn’t part of the current research.

Fraser digs into the long term future of our supermassive black hole.

The pattern they formed was three-dimensional, so it wasn’t as simple as one stellar object following the orbital path of another around the black hole. However, the complexity still needs to be studied in detail, and theories that would account for this new information about orbital patterns are hard to come by.

As more telescope time on increasingly powerful systems is devoted to watching one of the most intriguing parts of our galaxy, there will be plenty of data for future astronomers to puzzle over. But for now, this is a step toward understanding the hyperactive world around Sgr A* and the world of stellar birth more generally and how extreme forces play a role in both.

Learn More:
University of Cologne – High-speed baby stars circle the supermassive black hole Sgr A* like a swarm of bees
Peißker et al. – Candidate young stellar objects in the S-cluster: Kinematic analysis of a subpopulation of the low-mass G objects close to Sgr A*
UT – Three Baby Stars Found at the Heart of the Milky Way
UT – Baby Stars Discharge “Sneezes” of Gas and Dust

Lead Image:
Image of the galactic center, including Sgr A*
Credit – NASA/JPL-Caltech/ESA/CXC/STSci

The post Baby Stars are Swarming Around the Galactic Center appeared first on Universe Today.

Cashew nut shells are a source of low-emissions biofuel, which is being tested in several ships, but it is unlikely there will be enough to make much of a dent in the industry’s emissions

Extremely cold atoms that perpetually move in repeating patterns could be a promising building block for quantum computers

A few months ago, I wrote about how antivaxxers misrepresent vaccine safety studies to portray vaccines as dangerous, using a large study of outcomes in adults as an example.. They're doing it again, but this time it's a large study of COVID-19 vaccines in children.

The post How antivaxxers weaponize vaccine safety studies to falsely portray vaccines as dangerous, part 2: The children first appeared on Science-Based Medicine.

In his classic book On the Structure of Scientific Revolutions, the philosopher Thomas Kuhn posited that, for a new scientific framework to take root, there has to be evidence that doesn’t sit well within the existing framework. For over a century now, Einstein’s theory of relativity and gravity has been the existing framework. However, cracks are starting to show, and a new paper from researchers at Case Western Reserve University added another one recently when they failed to find decreasing rotational energy in galaxies even millions of light years away from the galaxy’s center.

Galaxies are known to rotate – even our solar system travels in a circle around the center of the Milky Way galaxy at around 200 km per second, though we can’t perceive any motion on human time scales. According to Newtonian dynamics, this rotational speed should slow down the farther away a star is from the center of a galaxy. However, observations didn’t support this, showing that the speed kept up no matter how far away the star is.

That led scientists to create another force impacting the speed of rotation of the farthest-out stars. Today, we commonly call it dark matter. However, scientists have also spent decades trying to puzzle out what exactly dark matter is made of and have yet to come up with a coherent theory.

Anton dives into a weird quirk of galaxy rotation.
Credit – Anton Petrov YouTube Channel

But in some cases, even the existence of dark matter as we know it doesn’t match the observational data. Dr. Tobias Mistele, a post-doc at Case, found that the rotational speed of galaxies doesn’t drop off, no matter how far out they are and no matter how long they’ve been doing so. This data flies in the face of a traditional understanding of dark matter, where its gravitational influence is felt by a “halo” surrounding the dark matter itself. Even these dark matter halos have an effective area. Dr. Mistele and his co-authors found evidence of maintained rotational speed that should be well outside the sphere of influence of any dark matter halo existing in these galaxies.

To collect this data, the authors used a favorite tool of cosmologists – gravitational lensing. They collected data on galaxies that were far away and had their light amplified by a galaxy cluster or similarly massive object that was nearer. When collecting the data, Dr. Mistele analyzed the speed of rotation of the stars in a galaxy and plotted it against the distance of those stars from the galaxy’s center. This is known as a “Tully-Fisher” relation in cosmology.

The result was an almost perfectly straight line – the rotational speed of stars in a galaxy did not seem to diminish with distance from the galaxy’s center, as both traditional Newtonian dynamics and relativity via dark matter predicted it would. So, what alternative explanations are there?

Why do galaxy rotation curves matter? Nora explains.
Credit – Nora’s Guide to the Galaxy YouTube Channel

Paper co-author Stacy McGaugh points out in a press release that one theory in physics accurately predicted the data his team had collected—the modified Newtonian Dynamics (or MOND) theory. Designed explicitly to account for things like galaxy rotations, MOND was developed in 1983 and remains controversial to this day. It struggles with things like the gravitational lensing with which the paper’s data was collected. 

That disconnect points to the need for a deeper understanding of gravity – what Kuhn called a “crisis,” which many cosmologists already believe is afflicting the discipline. While there is no current consensus on what might resolve that crisis, the evidence is mounting for the need for resolution. If we’re truly going to understand our place in the universe, we will eventually need to figure out a solution – it just might take a while.

Learn More:
CWRU – New, groundbreaking research shows that rotation curves of galaxies stay flat indefinitely, corroborating predictions of modified gravity theory as an alternative to dark matter
Mistele et al. – Indefinitely Flat Circular Velocities and the Baryonic Tully-Fisher Relation from Weak Lensing
UT – Will Wide Binaries Be the End of MOND?
UT – New Measurements of Galaxy Rotation Lean Towards Modified Gravity as an Explanation for Dark Matter
UT – The Earliest Galaxies Rotated Slowly, Revving up Over Billions of Years

Lead Image:
Illustration of the galaxy rotation curve used in the research.
Credit – Mistele et al.

The post Rotation Curves of Galaxies Stay Flat Indefinitely appeared first on Universe Today.

In the years before the JWST’s launch, astronomers’ efforts to understand the early Universe were stymied by a stubborn obstacle: the light from the early Universe was red-shifted to an extreme degree. The JWST was built with extreme redshifts in mind, and one of its goals was to study Galaxy Assembly.

Once the JWST activated its segmented, beryllium eye, the Universe’s most ancient, red-shifted light became visible.

The light emitted by the first galaxies is not only faint but has been stretched by billions of years of cosmic expansion. The galaxies that emitted that light are called high-redshift galaxies, where redshift is indicated by the letter z. Since its shifted into the red, only infrared telescopes can see it. Telescopes like the Hubble and the Spitzer can see some redshifted light. But the JWST has far more power than its predecessors, allowing it to effectively see further back in time.

“Using advanced instruments such as JWST allows us to study more distant galaxies with greater detail than ever before.”

Yicheng Guo, Department of Physics and Astronomy, University of Missouri

Observations have shown that galaxies grow large through mergers and collisions and that up to 60% of all galaxies are spirals. But how did the process play out? When did the first spirals emerge? An answer to that question trickles down and affects other outstanding questions about galaxies.

Spiral arms host active star formation, where successive generations of stars create heavier elements. Those elements allow rocky planets to form and are also a requirement for life. So, an understanding of when spiral galaxies formed helps astronomers understand the parameters of star formation, rocky planet formation, and even, potentially, the appearance of life.

“Knowing when spiral galaxies formed in the universe has been a popular question in astronomy because it helps us understand the evolution and history of the cosmos.”

Vicki Kuhn, Department of Physics and Astronomy, University of Missouri

One of the JWST’s observing efforts is CEERS, the Cosmic Evolution Early Release Science Survey. In CEERS, the JWST was the first telescope to capture images of the Universe’s early galaxies. CEERS found the most distant active supermassive black hole and galaxies that existed in the distant past when the Universe was only about 500 to 700 million years old.

Image of CEERS scientists looking at the Epoch 1 NIRCam color mosaic in TACC’s visualization lab at UT Austin. Credit: R. Larson

New research published in The Astrophysical Journal Letters examined galaxies from CEERS to determine how many of these ancient galaxies were spirals. The title is “JWST Reveals a Surprisingly High Fraction of Galaxies Being Spiral-like at 0.5 ≤ z ≤ 4.” The first author is Vicki Kuhn, a graduate student in the University of Missouri’s Department of Physics and Astronomy.

“Scientists formerly believed most spiral galaxies developed around 6 to 7 billion years after the universe formed,” said Yicheng Guo, an associate professor in Mizzou’s (University of Missouri) Department of Physics and Astronomy and co-author of the study. “However, our study shows spiral galaxies were already prevalent as early as 2 billion years afterward. This means galaxy formation happened more rapidly than we previously thought.”

In their research letter, the authors examined 873 galaxies from CEERS with redshift 0.5 ≤ z ≤ 4 and stellar mass ≤ 1010 solar masses. They found that 216 of them had spiral structures. “This fraction is surprisingly high and implies that the formation of spiral arms, as well as disks, was earlier in the Universe,” the authors write in their paper.

This figure from the research shows some of the galaxies in the sample. Redshift increases from left to right, and the rows from top to bottom show the range of galaxies classified as spiral to nonspiral. “Spiral structure is easier to see at the lower redshift ranges and becomes less pronounced at higher redshifts.” the authors write. The top three rows show galaxies identified as spirals with strong confidence, the middle three rows show galaxies identified as spirals with less confidence, and the bottom row shows non-spirals. Image Credit: Kuhn et al. 2024

“Knowing when spiral galaxies formed in the universe has been a popular question in astronomy because it helps us understand the evolution and history of the cosmos,” said lead author Kuhn. “Many theoretical ideas exist about how spiral arms are formed, but the formation mechanisms can vary amongst different types of spiral galaxies. This new information helps us better match the physical properties of galaxies with theories — creating a more comprehensive cosmic timeline.”

Spiral galaxies started as disks of gas. These results, when combined with other studies of high-redshift galaxies, paint a picture of the history of galaxy evolution in the early Universe. Dynamically hot gaseous disks appear around z = 4 to 5. These disks settled down to become dynamically cold gaseous disks around z = 3 to 4. Since stars form when gas cools and clumps together, large numbers of dynamically cold stellar disks appeared at z = 3 to 4, as indicated by their spiral arms.

This research also illuminates the relationships between spiral arms and other galaxy substructures. Gas-rich disks at high redshifts are very turbulent, and gravitational instabilities form giant clumps of star formation. Later, hot stars disperse young galaxies’ velocities, allowing them to settle down and become less turbulent. These bulges of star formation can also merge, helping to further stabilize the disks. The conclusion is that gravitational instabilities primarily lead to spiral arms, with clumps playing a secondary role since they co-exist with spirals at high redshifts.

The authors point out some caveats in their work. Galaxies that are merging can appear as spirals. The long tails prevalent during mergers can look like spiral arms, so their numbers could be off a little. But on the other hand, spirals can also look like mergers, adding to the uncertainty. “This situation is more severe for galaxies at z > 2, as the merger fraction is believed to be higher then,” the authors write.

But these facts likely don’t affect the conclusion much. “The observed spiral fraction decreases with increasing redshift, from ~43% at z = 1 to ~4% at z = 3,” the researchers conclude. So, while spirals are rarer the further we look back in time, they’re still more plentiful earlier than thought.

“Using advanced instruments such as JWST allows us to study more distant galaxies with greater detail than ever before,” Guo said. “A galaxy’s spiral arms are a fundamental feature used by astronomers to categorize galaxies and understand how they form over time. Even though we still have many questions about the universe’s past, analyzing this data helps us uncover additional clues and deepens our understanding of the physics that shaped the nature of our universe.”

The post Almost a Third of Early Galaxies Were Already Spirals appeared first on Universe Today.

Many years ago, there was a viral YouTube video called “History of the entire world, i guess,” which has been an endless source of internet memes since its release. One of the most prominent is also scientifically accurate—when describing why animals couldn’t start living on land, the video’s creator, Bill Wurtz, intones, “The Sun is a deadly laser.” 

Early in planetary development, the X-ray and ultraviolet radiation level of a planet’s host stars could sterilize the entire planet’s surface, even if it is in the so-called “habitable zone.” To narrow down the search for potentially habitable planets, the team at the Chandra X-ray Observatory and XMM-Newton telescopes took a look at stars that had planets in their habitable zone and analyzed them for whether the star’s radiation itself might preclude life as we know it from developing there.

Over ten observational days on Chandra and 26 on XMM-Newton, scientists observed 57 stars close enough to Earth to have their exoplanets explored by the next generation of exoplanet-hunting telescopes, such as the Habitable Worlds Observatory. While not all of them had known exoplanets, at least some did. 

YouTube Video detailing the research.
Credit – Chandra X-ray Observatory YouTube Channel

However, those exoplanets were typically much larger than Earth, even if they were in the habitable zone. It is much easier to detect giant planets orbiting close to their stars using modern date exoplanet detection techniques like transiting and astrometry. A press release from Chandra notes how many more rocky exoplanets the size of Earth are likely hiding around these stars, but our limited detection methods are not yet capable of finding them.

That isn’t to say we can’t learn much about their host stars, though, and that is where the data from the paper presented to the 244 meeting of the American Astronomical Society in Madison, Wisconsin, comes in. Watching the X-ray emissions of these local stars allowed the team to narrow down what stars to look at for potentially habitable exoplanets, thereby allowing the future powerful planet hunters to focus their observational time on candidates that are more likely to produce results.

Fraser details the path towards detecting 100 million exoplanets over the next thirty years.

Some of the stars in the study were indeed promising, with X-ray exposure similar to, or even less than, that of Earth when life began forming here billions of years ago. The data measured several aspects of the star’s output, including their brightness, how much energy those X-rays pack, and how powerful the star’s flares are. All of those could significantly impact the ability of life to form on any orbiting planets.

Fifty-seven stars is a relatively small sample size. Still, the proof of concept for how Chandra and XMM-Newton can be used to scout potential systems for habitability can be scaled up before any long-term observing mission for the new planet finders—no doubt they will be shortly as HWF and other missions get closer to fruition.

However, Chandra itself is facing budgetary challenges, causing many in the media to speculate that it might soon go “dark.” XMM-Newton itself is almost a quarter century old at this point, and a new joint X-ray mission, XRISM, is facing its own technical challenges, with a stuck door limiting it from observing in some of its potential wavelengths.

With luck, X-ray astronomy will continue to evolve over the next few decades. Part of that mission might be leading the scouting team for one of the most important astronomical searches humanity is currently undergoing.

Learn More:
Chandra Press Room – Coming in Hot: NASA’s Chandra Checks Habitability of Exoplanets
UT – Chandra’s X-ray Vision Combined With JWST Reveals Even More Details About the Universe
UT – A Collection of New Images Reveal X-Rays Across the Universe
UT – Chandra and JWST Join Forces in a Stunning Series of Images

Lead Image:
Illustration of hot exoplanet.
Credit – NASA/CXC/M.Weiss

The post Which Stars are Lethal to their Planets? appeared first on Universe Today.

Not content with shapes in two or three dimensions, mathematicians like to explore objects in any number of spatial dimensions. Now they have discovered shapes of constant width in any dimension, which roll like a wheel despite not being round

I’ve been meaning to write about this issue for a while, as I covered the beginning of it (see all posts here).  And the longer I delayed, the more complicated the issue became, until I became unable to remember everything, much less synthesize it.

The story in short: two people made a documentary movie, “The Fall of Minneapolis” (watch it here) maintaining that George Floyd was not murdered by Minneapolis police officer Derek Chauvin, but died of his many ailments (including a big titer of fentanyl in his blood), not from having his neck compressed so that he was asphyxiated. (Nor, the movie maintained, was his neck really compressed: Chauvin was supposedly using procedures taught him by his department).  The movie convinced both John McWhorter and Glenn Loury, as well as me, that Chauvin was not guilty of murder—at least if you use the “reasonable doubt” standards mandated in such a case.

Then a former Washington Post reporter, Radley Balko, wrote a multipart attack on the movie on his webpage arguing that the thesis of “The Fall of Minneapolis” was wrong on several counts, including its claim that Floyd was not asphyxiated.  Balko’s analysis was enough to convince Loury (and, to some extent, McWhorter) that they were wrong—that perhaps Chauvin really did murder Floyd. Having read all this stuff, and intending to post on it, the sheer magnitude of the task defeated me. But I felt remiss in not calling attention to Balko’s attack. And I couldn’t come to my own conclusions, for essential material, like the training procedure for Minneapolis police, was missing.

In January, Coleman Hughes, now an essayist for The Free Press, wrote a piece arguing that Chauvin was not a murderer but a scapegoat for all those who wanted him convicted for supposedly killing a black man.  Hughes and Balko went back and forth about having a debate, and eventually had one, but one that, says Coleman, was stacked because the moderators were on Balko’s side.

Now we have the longest article yet published in the Free Press, a second piece by Coleman Hughes reiterating his claim that Chauvin should not have been found guilty of the murder of Floyd. His claim, as you’ll see below (click on the headline to read) is not that Chauvin was clearly innocent, but that the standards of evidence supposed to be applied by the jury, involving “reasonable doubt,” would have found such doubt in the prosecution’s evidence against Chauvin. Ergo, Chauvin should have been found not guilty.

The article is informative and, to me, convincing—Chauvin seems to have gotten a bad trial, including jurors biased against the prosecution, a prosecution that didn’t properly give the evidence, a defense that didn’t do its job, a judge who didn’t seem to know what was going on, and the venue (and the judge’s instructions) terrifying the jurors that if they didn’t find Chauvin guilty, there would be riots.

Read it; it has all the links that you need, including to Balko’s work and the debate.

Here’s Coleman’s main points in the essay:

The purpose of this essay is to set the record straight on Balko’s claims, which range from useful counterarguments to misleading assertions and outright errors. Our disagreements fall into two basic categories: the first is the question of how exactly Floyd died. And the second pertains to whether or not Chauvin was following his training.

One final, important note before I dive in: Balko’s series generally mischaracterizes my essay as arguing for the definite truth of various propositions—or doing a “just asking questions” routine—when in fact I was arguing for the existence of reasonable doubt.

In a typical debate, each side is trying to prove a claim by summoning more evidence than the other side—“guns are helpful” vs. “guns are harmful,” for instance. The burden assigned to each side is symmetric. If either side summons more evidence than the other, then that side wins.

Criminal trials are deliberately not like this. They are highly asymmetric—and that’s intentional.

It’s not enough for a majority of the evidence to indicate guilt. And it’s not enough if the defendant’s guilt is “highly and substantially more likely to be true than untrue.” That is the “clear and convincing evidence” standard.

Rather, “beyond a reasonable doubt” means that “there is no other reasonable explanation that can come from the evidence presented at trial” other than the defendant having committed the crime in question. Keep that phrase—no other reasonable explanation—at the top of your mind. My Free Press piecewas written from the perspective of reasonable doubt. In the essay, I summed up my thesis like this: “In short, there are two major justifications to reasonably doubt Chauvin’s felony murder charge: whether he caused Floyd’s death and whether he committed a felony.”

There remains significant uncertainty about the death of George Floyd—uncertainty that was not settled at trial. My purpose in this essay, as in my original column, is not to settle that uncertainty for good by putting forward a definitive version of events—that is not the defense’s burden anyway. My purpose is to convey the existence of other reasonable explanations.

With that throat-clearing out of the way, let’s move on to Balko’s substantive arguments.

The arguments turn on what really killed George Floyd (he had several medical conditions and was full of drugs), whether the restraint technique used by Floyd really involved asphyxiation, whether that technique was part of the regular training, verbal or written, by the Minneapolis police, what “homicide” means to a coroner versus a jury, whether the jury was tainted by people who were pro-Floyd to begin with, and what are the criteria for conviction.  And more.

Read it for yourself; I’ll simply give Hughes’s conclusions in brief:

I think there was clearly reasonable doubt on whether Chauvin caused Floyd’s death. There were two rival theories of his death: the positional asphyxia theory (put forth by Dr. Tobin and endorsed by the prosecution), and the adrenaline surge theory (put forth by Dr. Baker and rejected by the prosecution). Both were reasonable theories, but only the former implicated Chauvin. That alone should have introduced reasonable doubt on all three charges.

As for whether Chauvin assaulted Floyd—that is, whether he used unlawful force outside the scope of MPD training—reasonable people can disagree on whether there was reasonable doubt. Balko would emphasize that MPD [Minneapolis Police Department] officers were trained to worry about positional asphyxia, move people to the side-recovery position as soon as possible, and use the hobble.

. . . .What are the odds that Chauvin received a trial in accordance with these instructions? Given the jurors who spoke about their fears for their physical safety, given the juror who was found wearing a “GET YOUR KNEE OFF OUR NECKS” t-shirt before the trial, given that everyone knew the city would burn if he was acquitted yet the trial location wasn’t changed, and given that the jury wasn’t sequestered in one of the most talked-about trials in modern American history—I would submit that the odds are close to zero.

Ultimately, we’ll never know how a jury might have weighed the evidence under even halfway normal conditions. And it is probably too late for any of this to matter for Chauvin himself. What is clear, however, is that there were many reasons to doubt that Chauvin was guilty of the crimes he was charged with, and the American public should not be afraid to say so.

Once again, this is a complicated issue that you should judge for yourself, ideally after having watched the movie, read Balko’s ripostes, and having read at least Hughes’s second essay: the one quoted here.  Chauvin’s conviction for murdering Floyd spawned the “racial reckoning” that has persisted until today, and regardless of whether we need a reckoning or not, the conviction that started it all needs to be carefully examined. More important, the conviction of a man for a “crime” that carries reasonable doubt is a miscarriage of justice that needs to be rectified (Chauvin is serving 22 years in prison, and will be 60 when he’s released). In my view, they need to try Chauvin again, but bringing in all the evidence and with a jury that is not intimidated.

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This new paper in Nature gives a rare picture of human sacrifice among ancient Mayans from the Yucatán peninsula in Mexico.  Paleoanthropologists had found remains before, mostly children, preserved by being tossed in sacred cenotes (wells), but this group of 64 ancient individuals was not only collected, but their DNA was analyzed from the ear bones, giving surprising results about genetic relatedness.

As with the Aztecs, human sacrifice was a fixture of ancient Mayan society, though the people killed (in this case, children) were probably captives rather than residents of the place where the killers lived. Sacrifice could have occurred via either decapitation, extraction of the heart from living individuals, or killing with arrows.

Click below to read the piece, or find the pdf here.  

The figure below shows where the remains were found: in a chultún (an underground cistern) next to an airport runway near the ancient Mayan city of Chichén Itzá (now a World Heritage Site), which flourished between about 600 and 1200 A.D. This map gives the location:

(From the paper) a, Location of the Maya region in the Americas. b, Geographical locations of Chichén Itzá and Tixcacaltuyub in the Yucatan Peninsula. c, Stratigraphy for the chultún and the adjacent cave in which the burial was found (adapted from ref. 4). d, Location of the chultún within the archaeological site of Chichén Itzá and its relation to El Castillo (adapted from ref. 10). Modern roads are marked in light grey; the chultún abuts an airport runway.

They found the bones of 64 individuals, carbon-dated as being from the 7th to the 12 centuries AD. How did they know how many individuals were represented in their sample? Because they recovered 64 left petrous parts, the bit of the skull’s temporal bone that surrounds the inner ear (this bone, sequestered away from the outside of the skull, is often used to extract ancient DNA).  64 left petrous bones means 64 individuals.

First, every one of the individuals was a male between 3 and 6 years old, showing that the Mayans preferred to sacrifice young boys. Why? It’s not clear, but there’s speculation that sacrifices helped local maize crops flourish (the method of sacrifice wasn’t specified in the paper).  However, other sacrificed individuals recovered, as in the famous sacred cenote, have been mixtures of males and females, but also overrepresented with children. The authors don’t speculate why, in this location, only boys were killed.

The ancestry of the sacrificed individuals was compared among each other, as well as to 68 individuals of Mayan descent living the nearby town of Tixcacaltuyub. One surprising finding was that those sacrificed included two pairs of identical (monozygotic) twins (easily seen in DNA, which is identical among two different earbones).  The authors note that twins held a special position in Mayan mythology.  But, as the plot of “pairwise mismatch rates” shows below), 11 pair of individuals were “close relatives”, represented by the hollow diamonds (the twins, with a mismatch rate of zero, are the two pairs of twins.  The authors speculate (see below) that the individuals came from a single big event of mass killing.

The paper doesn’t say how “close” the “close relatives were”, or whether they were contemporaneous, like brothers, but given the age of the individuals, it seems likely that the related pair members came from the same family.

(From paper): e, Genetic pairwise mismatch rate (PMR) for child pairs in the chultún identifies 11 close relative pairs (hollow diamonds), including two pairs of monozygotic twins (highlighted in grey). A low overall PMR for unrelated individuals (black triangles) confirms low genetic diversity in the population; only pairs with PMR < 0.20 are visualized in the plot. See Supplementary Fig. 2 for individual annotations.

The comparison of the DNA of the sacrificed children with that of living people in Tixcacaltuyub, as in the principal-component cluster graph below, showed that the sacrificed individuals )”YCH”, dark purple stars) fell into a cluster of Native Americans, other Mayan individuals, people from Belize, and individuals from the nearby town (“TIX”, light blue stars), and were considerably different from individuals in Africa, Asia, and Oceania, as expected. (This shows diagnostic genetic differences between geographic groups, demonstrating that the idea of “races”—defined as “diagnostically genetically differentiated populations”—is not purely a social construct, but contains biological information.)  However, the ancient sacrificed individuals, which also had a dollop of genes from the Caribbean, didn’t particularly cluster with the present day Mayans living nearby, who had their own admixture of genes from Africa and Europe, perhaps reflecting turnover of populations over time. In the sixteenth century there was a big poulation bottleneck, perhaps due to diseases introduced by Europeans. In fact, this bottleneck reduced the population of what is now Mexico by 90%!)

(From paper): (From paper): a, PCA showing ancient Chichén Itzá (YCH) individuals and present-day Tixcacaltuyub (TIX) in a worldwide PCA plot.

One other bit of information. We are able, looking at contemporary DNA sequences of a population, to judge whether natural selection is acting on genes or groups of genes. If variable genes such as the HLA (“human leukocyte antigen”) genes involved in immune response show coordinated variation (that is, variant “A” of one gene tends to co-occur with variant “B” of another gene in individuals), this gives evidence that selection is acting on groups of genes—in this case genes affecting immunity. The authors identified several HLA variants that look like they were subject to selection, and also tested some by making copies of sequences of some HLA variants and seeing how strongly they bound to proteins derived from Salmonella bacteria (strong binding means that the HLA proteins were reacting and presumably neutralizing the bacterial proteins). The authors suggest that the selection acting to promote the rise in frequency of some HLA variants was due to typhoid or paratyphoid-like infections.

The upshot:  Although the data from HLA genes does indicate that there was selection for immunity in both ancient and historic times, what I find most interesting is that the sacrifice involved children, all male children, and many were close relatives. This, at least, gives us a pretty strong sociological picture of one aspect of ancient Mayan culture. To quote the authors,

In comparing the subadults in the chultún to other ancient and present-day populations in the Maya region, we find evidence of long-term genetic continuity, which also suggests that the sacrificed children and sibling pairs at Chichén Itzá were obtained from nearby ancient Maya communities. Among present-day individuals at TIX, we detect evidence of European and African admixture since the Contact period.

and

Overall, 25% of the children had a close relative within the assemblage, suggesting that the sacrificed children may have been specifically selected for their close biological kinship. Moreover, this may underestimate the true number of relatives present in chultún as only 64 of the estimated 106 individuals in the chultún had a preserved petrous portion of the left temporal bone available for analysis. The further finding that the closely related children in each set seem to have consumed a similar diet and died at a similar age suggests that they have been sacrificed during the same ritual event as a pair or twin sacrifice.

and, finally,

The discovery of two sets of identical twins, as well as other close relatives, in a ritual mass burial of male children suggests that young boys may have been selected for sacrifice because of their biological kinship and the importance of twins in Maya mythology. We show that, at a genome-wide level, the present-day Maya of Tixcacaltuyub exhibit genetic continuity with the ancient Maya who once inhabited Chichén Itzá and we demonstrate through several lines of evidence the involvement of the HLA region in a pathogen-driven selection event(s) probably caused by infectious diseases brought into the Americas by Europeans during the colonial period.

The interest of the Mayans in identical twins reminds me of Josef Mengele in Auschwitz, who also took a particular interest in twins, but in his case he did gruesome experiments on them before killing them.