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I’m at that age, 67 going in 68, where it is reasonable to yell at the clouds. Which, come to think of it, may be a good title for another collection of my SBM essays. Aging does indeed suck, but it is, usually, better than the alternative. As we, and by we I mean my family and me, age we get the […]

The post Old Doctor Yells At Clouds first appeared on Science-Based Medicine.

Physicists have created a 3D shape called the cosmohedron, which can be used to reconstruct the quantum wavefunction of the universe - and potentially do away with the idea of space-time as the underlying fabric of the universe

The newer the data, and the longer we've had to study the epidemiology, the less harm we find that Agent Orange caused.

Learn about your ad choices: dovetail.prx.org/ad-choices

After a close look with a powerful radio telescope, astronomers are still puzzled by a pair of objects with strange characteristics first spotted in 2021

What came first, galaxies or planets? The answer has always been galaxies, but new research is changing that idea.

Could habitable planets really have formed before there were galaxies?

In the immediate aftermath of the Big Bang, there were no heavy elements. There was only hydrogen, which comprised about 75% of the mass, and helium, which comprised the remaining 25%. (There were probably also trace amounts of lithium, even beryllium.) There was nothing heavier, meaning there was nothing for rocky planets to form from. After a few hundred million years, the first stars and galaxies formed.

As successive generations of stars lived and died, they forged heavier elements and spread them out into the Universe. Only after that could rocky planets form, and by extension, habitable planets. That’s been axiomatic in astronomy.

However, new research that’s yet to be published suggests that habitable worlds could’ve formed in the early stages of the Cosmic Dawn, prior to galaxies forming. Its title is “Habitable Worlds Formed at Cosmic Dawn,” and it’s available at the pre-press site arxiv.org. The lead author is Daniel Whalen from the Institute of Cosmology and Gravitation at the University of Portsmouth in the UK.

The research hinges on primordial supernovae, the first stars in the Universe to explode. These massive stars lived fast and died young in cataclysmic explosions. They peaked at about redshift 20 when population III stars, which were extremely massive, exploded as pair-instability supernovae. Simulations show that these stars formed in dark matter haloes where the temperature allowed large amounts of molecular hydrogen to gather.

According to Whalen and his co-researchers, when these stars exploded, low-mass stars formed in the aftermath. Planetesimals formed around those stars, leading to the formation of potentially habitable, rocky worlds. This all happened before the first galaxies formed. These results are based on simulations the research team performed with Enzo.

It starts with a star forming with about 200 solar masses. It lives for only about 2.6 million years before it explodes as a PI supernova. The explosion enriches the supernova bubble to high metallicity. In the aftermath, hydrostatic instabilities cause a dense core to form about 3 million years later, with 35 solar masses.

“All known prerequisites for planet formation in this core are fulfilled: dust growth, dust enhancement in a dead zone, the onset of the streaming instability, and conversion of dust to planetesimals,” the authors explain.

This figure from the research shows a PI supernova exploding (a) and a dense core forming (b) about 3 million years later containing 35 solar masses. Image Credit: Whalen et al. 2025.

Here’s where this study differs from previous ones. Since the PI supernova explodes and creates high-metallicity gas, the gas cools more quickly. That allows the next star to form sooner, and hence, planetesimals and planets.

Eventually, a protostar with 0.3 solar masses formed. Then planetesimals formed between 0.46 and 1.66 AU from their star. Life needs water, and the researchers’ simulations also showed that the young solar system contained an amount of water similar to our own Solar System.

This figure from the research shows the protoplanetary disk. Gas, dust and planetesimal distributions are shown 39 kyr after the formation of the protostar in (a) – (c), respectively, where b and c show the central 4 AU of the disk. The green dashed circles indicate where water can exist in liquid form. Image Credit: Whalen et al. 2025.

Planetesimals formed in the circumstellar disk around the low-mass star, and over time, they combined to form planets. Since the original primordial supernovae created elements like carbon, oxygen, and iron, all of the necessary ingredients were likely present to form rocky planets, even life.

The remarkable part is that this could’ve happened before the first galaxies formed. If true, it would change our understanding of the Universe and of life. However, this is just one simulation. How could observations support it?

“These planets could be detected as extinct worlds around ancient, metal-poor stars in the Galaxy in future exoplanet surveys,” Whelan and his fellow researchers write in their paper.

According to the authors, if conditions were just right, rocky planets could have formed even earlier than their simulations show. If that’s true, then it changes the entire course of events in the evolution of the Universe.

However, this is only a single study. And it hinges on primordial supernovae. Did they even exist? There’s at least some evidence that they did.

Clearly, attempting to observe primordial supernovae is extremely difficult. They occurred so long ago that they’re extraordinarily distant and faint. It’s likely impossible with current technology.

Also, there is much uncertainty about the Population III stars that were the progenitors of primordial supernovae. Their exact masses, lifetimes, and explosion mechanisms are uncertain. Astronomers don’t have a clear understanding of the early Universe’s extreme conditions. It’s still evolving, as is our understanding of supernovae. Combined, that’s a lot of uncertainty.

An artist’s illustration of some of the Universe’s first stars. Called Population 3 stars, they formed a few hundred million years after the Big Bang. Image Credit: By NASA/WMAP Science Team – https://www.nasa.gov/vision/universe/starsgalaxies/fuse_fossil_galaxies.html (image link), Public Domain, https://commons.wikimedia.org/w/index.php?curid=1582286

Still, all of these challenges don’t mean that primordial supernovae didn’t exist. So astronomers can’t rule them out, nor can they rule out very early habitable planets.

As things stand, there’s no way to prove or disprove this research. However, it does open another line of thinking and new possibilities.

The post Habitable Worlds Could Have Formed Before the First Galaxies appeared first on Universe Today.

The Andromeda galaxy is our closest galactic neighbour, barring dwarf galaxies that are gravitationally bound to the Milky Way. When conditions are right, we can see it with the naked eye, though it appears as a grey smudge. It’s the furthest object in the Universe that we can see without telescopic help.

The Hubble Space Telescope has created a massive 2.5-gigapixel panorama of Andromeda. It took 10 years and more than 1,000 orbits to capture all of the images.

We’re stuck inside the Milky Way and will never escape it. (Yes, there’s a tiny possibility we will in some far-off future.) The ESA’s powerful Gaia telescope has given us our best look at our own galaxy from inside it, but even it has its limitations.

That’s one of the reasons that observing Andromeda, also known as M31, is important. Like the Milky Way, M31 is also a barred spiral. By observing M31 in detail, we can learn more about our own galaxy. M31 is like a proxy for the Milky Way, and astronomers’ chief tool for studying our galactic proxy is the Hubble.

“With Hubble we can get into enormous detail about what’s happening on a holistic scale across the entire disk of the galaxy. You can’t do that with any other large galaxy,” said principal investigator Ben Williams of the University of Washington.

The image is a mosaic comprising at least 2.5 billion pixels. It resolves about 200 million individual stars, all of them hotter than our Sun. That’s only a small fraction of the galaxy’s stellar population, as dim stars like red dwarfs aren’t detected. The image contains bright blue star clusters, background galaxies, foreground stars, satellite galaxies, and dust lanes.

This is the largest photomosaic ever made by the Hubble Space Telescope. Andromeda is seen almost edge-on, tilted by 77 degrees relative to Earth’s view. The galaxy is so large that the mosaic is assembled from approximately 600 separate fields of view taken over 10 years of Hubble observing. The Andromeda galaxy is shown at the top of the visual. It is a spiral galaxy that spreads across the image. It is tilted nearly edge-on to our line of sight so that it appears very oval. The borders of the galaxy are jagged because the image is a mosaic of smaller, square images against a black background. The outer edges of the galaxy are blue, while the inner two-thirds are yellowish with a bright, central core. Five callout squares highlight interesting features of the galaxy. Image Credit: NASA, ESA, B. Williams (U. of Washington)

This vast image is the result of two observing programs: the Panchromatic Hubble Andromeda Southern Treasury (PHAST) and the Panchromatic Hubble Andromeda Treasury (PHAT). PHAT and PHAST have made a large contribution to galactic science. PHAT started acquiring the images for this mosaic about a decade ago, and now we have this new image thanks to both efforts.

New research in the Astrophysical Journal presents the latest results from PHAST, including the new image. It’s titled “PHAST. The Panchromatic Hubble Andromeda Southern Treasury. I. Ultraviolet and
Optical Photometry of over 90 Million Stars in M31.” the lead author is Zhuo Chen from the Department of Astronomy at the University of Washington in Seattle.

Andromeda is not only our nearest neighbour but also the nearest spiral to us and the largest galaxy in the Local Group. Those facts aren’t just answers to trivia questions. They explain why astronomers can study the galaxy in detail, including assessing its stellar population, without some of the problems they face observing other galaxies.

“M31 studies circumvent complications from line-of-sight reddening, uncertain distances, and background/foreground confusion,” the researchers write in their paper. “Furthermore, such studies can be put into the context of the surrounding local environment, such as the ISM structure, the star formation rate (SFR), and the metallicity of the stars and gas, and even larger environment as mapped by
the Pan-Andromeda Archeological Survey.”

“Thus, M31 provides a unique and interesting comparison to the detailed information we have for our
Milky Way,” the authors explain.

This is a zoom-in of the full-resolution version of the image. You can download the full image and explore it for yourself here. Image Credit: NASA, ESA, B. Williams (U. of Washington)

One of the main takeaways from this massive observing effort is that the southern disk, which hadn’t been studied as intently as the northern disk, is fundamentally different from its counterpart. The southern disk appears to be more disturbed, indicating that it shows the effects of M31’s merger history more than the northern disk. The presence of M32, an early-type dwarf galaxy, hints at some of that merger history.

This image from the research shows the locations of the 13 “bricks” in PHAST (grey) and the 23 bricks from PHAT (blue.) Each of the new PHAST bricks consists of 15 HST pointings, each of which includes observations in two HST cameras: the Advanced Camera for Surveys and the Wide Field Camera 3. M32 is marked with an arrow in Brick 28. Image Credit: Chen et al. 2025.

Astronomers think that M32 could be what’s left of a galaxy that merged with Andromeda. Its properties are difficult to explain with our galaxy formation models. It could be the remnant core of a much more massive galaxy that was absorbed by Andromeda about two or three billion years ago.

“Andromeda’s a train wreck. It looks like it has been through some kind of event that caused it to form a lot of stars and then just shut down,” said study co-author Daniel Weisz at the University of California, Berkeley. “This was probably due to a collision with another galaxy in the neighborhood.”

One strong piece of evidence for that merger is the Giant Southern Stream. It’s a tidal debris stream made up of stars in Andromeda’s halo that could be a remnant from the ancient merger. The metallicity of its stars is generally lower than the stars in Andromeda’s bulge and disk.

This figure from older research shows Andromeda’s Giant Southern Stream and its proximity to M32. Image Credit: The Pan-Andromeda Archaeological Survey (PandAS).

The only way to understand Andromeda’s history is by surveying its stars. Thanks to PHAT and PHAST, astronomers now know 200 million individual stars. The observations are limited to stars brighter than the Sun, but the images are still scientifically rich. Together, they hint at a galaxy in transition.

“Andromeda looks like a transitional type of galaxy that’s between a star-forming spiral and a sort of elliptical galaxy dominated by aging red stars,” said Weisz. “We can tell it’s got this big central bulge of older stars and a star-forming disk that’s not as active as you might expect given the galaxy’s mass.”

“This detailed look at the resolved stars will help us to piece together the galaxy’s past merger and interaction history,” added PHAST’s Principal Investigator Ben Williams.

This figure from the research shows how the stellar density varies between regions in Andromeda. The zoom-in panels highlight the rich detail available at full HST resolution. Image Credit: Chen et al. 2025.

PHAST, together with PHAT, is a rich resource for astronomers studying Andromeda and, by extension, barred spirals everywhere, including our own Milky Way. However, before long, astronomers will get even better looks at Andromeda.

If all goes well, NASA will launch the Nancy Grace Roman Space Telescope in the near future. It’s an infrared telescope with a wide field of view, though it has the same size mirror. In a single exposure, the Roman can capture the equivalent of 100 high-resolution Hubble images, maybe more. It will help astronomers study the Giant Southern Stream in detail, along with other things, and will provide critical clues to Andromeda’s history.

The post Hubble Takes a 2.5 Gigapixel Image of Andromeda appeared first on Universe Today.

On a day that’s dolorous for many of us, let’s have some music. Here is a fantastic song by a fantastic band, featuring one of the greatest guitar solos in the history of rock: fifty short seconds of sublime inventiveness. The song is “Kid Charlemagne,” the band is of course Steely Dan, and the guitar solo is by Larry Carlton (b. 1948), a great studio musician who isn’t well known because he mostly backed up others. (I once saw him play as a solo act.)

Nearly all Steely Dan’s songs have opaque lyrics, but at least these lyrics were explained by the writers:

Writers Walter Becker and Donald Fagen have stated that the lyrics of “Kid Charlemagne” were loosely inspired by the rise and fall of the San Francisco-based LSD chemist Owsley Stanley, augmented with other images of the counterculture of the 1960s:

On the hill the stuff was laced with kerosene
But yours was kitchen clean
Everyone stopped to stare at your Technicolor motor home

The first two lines draw on the fact that Owsley’s LSD was famed for its purity. The “Technicolor motor home” of the third line is likely a reference to Furthur, the Merry Pranksters‘ modified school bus; Stanley supplied them with LSD.

The final verse describes Stanley’s 1967 arrest after his car reportedly ran out of gas:

Clean this mess up else we’ll all end up in jail
Those test tubes and the scale
Just get it all out of here
Is there gas in the car?
Yes, there’s gas in the car
I think the people down the hall know who you are.

More from Wikipedia:

Larry Carlton’s guitar solo starts at 2:18 into the song and ends at 3:08. Pete Prown and HP Newquist described it as consisting of “twisted single-note phrases, bends, and vibrant melody lines”; they called it and Carlton’s “joyous, off-the-cuff break” during the song’s fade-out “breathtaking.”  According to Rolling Stone, which ranked “Kid Charlemagne” at #80 in its list of the “100 Greatest Guitar Songs”: “In the late seventies, Steely Dan made records by using a revolving crew of great session musicians through take after take, which yielded endless jaw-dropping guitar solos. Larry Carlton’s multi-sectioned, cosmic-jazz lead in this cut may be the best of all: It’s so complex it’s a song in its own right.”  In 2022, Far Out Magazine listed it as the fourth-greatest guitar solo on a Steely Dan song, calling Carlton’s playing “intense, fluid, and frequently on the brink of spinning out of control”.[10] Nick Hornby, in Songbook, spoke of the solo’s “extraordinary and dexterous exuberance”, though he questioned its relationship with the “dry ironies of the song’s lyrics”.[11]

“It’s my claim to fame,” Carlton told Guitar World in 1981. “I did maybe two hours worth of solos that we didn’t keep. Then I played the first half of the intro, which they loved, so they kept that. I punched in for the second half. So it was done in two parts and the solo that fades out in the end was done in one pass.”

. . . Carlton called his solo on “Kid Charlemagne” the high point of his career at the time, saying, “I can’t think of anything else that I still like to listen to as strongly as that.”

Carlton also plays the “outro” at the end.

Rick Beato’s third episode of his well know What Makes This Song Great series was an analysis of “Kid Charlemagne”, and you can hear it here. It’s a good one.

Listening to Steely Dan songs and reading comments, I see that many people think that Donald Fagen has a horrible voice. I disagree. Yes, it’s nasal, but I thinks it fits very well with their unusual songs.

The band, which included many studio musicians, is vastly underrated, and I wonder if today’s young people even listen to its music. It is sui generis and unmistakable: a melange of jazz, rock, and ballads. Some of my other favorites are “Dr. Wu,” “Dirty Work,” “Bad Sneakers” (totally opaque), and, of course, the song below,” which mentions my alma mater William & Mary—one of the few rock songs to mention a college or university (can you name two others?) Oh, and the guitar-rich stop time during the song is great.

Becker (left) and Fagen:

Kotivalo, CC BY-SA 4.0, via Wikimedia Commons

There’s a Universe full of black holes out there, spinning merrily away—some fast, others more slowly. A recent survey of supermassive black holes reveals that their spin rates reveal something about their formation history.

If you want to describe a supermassive black hole’s characteristics, there are two important numbers to use. One is its mass and the other is its spin rate. Some black hole spin rates are thought to be very close to the speed of light. According to Logan Fries, a PhD student at the University of Connecticut, those numbers are tough to get. “The problem is that mass is hard to measure, and spin is even harder,” he said. Yet, having accurate numbers is important if we want to understand black hole evolution.

Fries and his colleagues in the Sloan Digital Sky Survey’s Reverberation Mapping Project took on a tough job. They measured the spin rates of black holes over cosmic history. “We have studied the giant black holes found at the centers of galaxies, from today to as far back as seven billion years ago,” said Fries, a primary author of a paper about this work. The mapping project also made detailed observations of the associated accretion disks. Those are the areas nearest the black hole where matter accumulates and heats up as it spirals in. Measuring that region is important since knowing the black hole’s mass and its accretion disk’s structure provides data that allows them to measure the spin rate. Astronomers typically estimate the spin rate by observing how matter behaves as it falls into the black hole.

The typical morphology of supermassive black holes. This artist’s impression depicts one surrounded by an accretion disc. Credit: ESO, ESA/Hubble, M. Kornmesser/N. Bartmann Black Holes and their Archaeology

The results of the SDSS Survey of mass measurements of hundreds of black holes were a surprise, according to Fries. That’s because the spin rates reveal something about the black holes’ formation history. “Unexpectedly, we found that they were spinning too fast to have been formed by galaxy mergers alone,” he said. “They must have formed in large part from material falling in, growing the black hole smoothly and speeding up its rotation.”

Fries described his work at a recent meeting of the American Astronomical Society. “I have read research papers that examine black hole spin, theoretically, from the lens of like black hole mergers, and I was curious if spin could be observationally measured,” said Fries. He pointed out that the history of black hole growth requires more precise measurements than have been available. And, they’re not easy, according to Fries’s thesis advisor, Physics professor Jonathan Trump. “The challenge lies in separating the spin of the black hole from the spin of the accretion disk surrounding it,” said Trump. “The key is to look at the innermost region, where gas is falling into the black hole’s event horizon. A spinning black hole drags that innermost material along for the ride, which leads to an observable difference when we look at the details in our measurements.”

Examples of black holes and accretion disks with various spin configurations: retrograde (black hole rotates in the opposite direction as the accretion disk), zero spin (does not rotate), and prograde (black hole rotates in the same direction as the accretion disk) from top to bottom, respectively. Examples of spectral energy distributions (SEDs) for each spin configuration are shown to the right of each cartoon with a vertical line drawn at the peak of the SED. The differences in the peak of the SEDs and how bright they are for different spin configurations demonstrate how astronomers measure black hole spin by fitting these models to observational data. (Contributed image using NASA illustrations)

Digging into the mass and spin of a black hole requires spectral measurements. Those made by the SDSS contain subtle shifts in the spectra toward shorter wavelengths of light. That shift is a major clue to the black hole’s rotation rate. “I call this approach ‘black hole archaeology,'” said Fries “because we’re trying to understand how the mass of a black hole has grown over time. By looking at the spin of the black hole, you’re essentially looking at its fossil record.”

What The Black Holes Tell Us

So, what does that fossil record tell us? First of all, it challenges the prevailing wisdom that black holes are always created in galaxy collisions. In other words, when galaxies merged, so did their central black holes. Each galaxy brings a rotation rate and orientation to the merger. The rotations could just as easily cancel each other out as they are to add together. If that is true, then the astronomers should have seen a wide range of spins. Some black holes should have a lot of spin, others… not so much.

The big surprise is that many black holes appear to spin very quickly. Even more amazing, the most distant ones seem to be spinning faster than the ones nearest to us (i.e. the “nearby” Universe). It’s as if they spin faster in the early Universe, and more slowly in more recent epochs. “We find that about 10 billion years ago, black holes acquired their mass primarily through eating things,” Fries explained.

The early fast spin rate implies that most supermassive black holes (like the one in our own Milky Way Galaxy) built up over time by taking in gas and dust in a very smooth and controlled manner. In other words, the more they eat (in the way of stars and gas), the faster their spin rate. It also turns out that merger growth actually slows the spin of supermassive black holes. That could explain why those we measure today have a mix of spin rates, rather than the more uniform rates of earlier epochs.

Future Directions

The idea of black holes forming smoothly over time provides a new direction for black hole research. Observations by JWST will help give more targets to study. Surveys such as the SDSS Reverberation Mapping project will follow up with more precise measurements of the huge supermassive black holes JWST continually finds as it studies the Universe.

For More Information

Spinning Black Holes Reveal How They Grew
‘Black Hole Archaeology’: Understanding How Black Holes Gained Their Mass

Black Hole Archaeology: Mapping the Growth History of Black Holes Across Cosmic Time (PDF of AAS presentation)

The post Black Holes are Spinning Faster Than Expected appeared first on Universe Today.

This article, published in the Journal of Anatomy four years ago, was also highlighted in ScienceAlert this January 18, which is how Matthew Cobb found it.  And although the results aren’t new, I find them interesting from an evolutionary point of view and sure didn’t know about them before. (I’m not sure why ScienceAlert chose to highlight them this week.)

The paper (and the shorter popular summary) describes an Australian study of a variable trait: an extra artery in the forearm and hands of humans called “the median artery”.  It is present in fetuses, where it feeds the growing arm and hand, but regresses during development so that it’s not usually present in newborns. However, in a substantial number of cases—now about 30%—it remains as a functioning artery in adults.  The paper describes a present study of the incidence of this “vestigial artery” in modern adult Australians, and compares this incidence with that seen in adults going back to the late 19th century. There has been a marked increase in persistence—threefold!—over that period.  What we don’t know is why this is happening.  It could be strong natural selection, an environmental change we don’t understand, or both.

You can see the paper by clicking on the title below, or download a pdf here.

First, here’s what the artery looks like in an adult (caption from the paper). I’ve put a red oval around the artery:

Median artery and superficial palmar arch (anterior dissection of the left lower forearm, wrist and hand) – Median artery accompanied the median nerve and completed the superficial palmar arch laterally.

Now although the artery feeds the arm and hand, we don’t know whether it actually benefits those who have it.  The authors and ScienceAlert appear to favor natural selection as the reason for the increase over time, but we don’t know that. To know for sure, we’d have to do long-term studies of the reproductive output of individuals having the artery versus those lacking it, or perhaps genetic studies (see below). We don’t have that data and therefore cannot say anything about natural selection.

Further, perhaps its increased persistence into adulthood is due to some environmental effect. We have no data on that, either. All we can say, and we can’t even say that with a high degree of confidence, is that the percentage of adults having the artery seems to have increased drastically over time.

But I’m getting ahead of myself. The authors dissected 78 arms of Australians aged from 51 to 101 years who died between 2015 and 2016, determining how many of them had the persisting median artery.  Individuals were excluded who might have skewed the studies, including individuals with only the hands and not arms examined, people who had carpal tunnel syndrome (possibly caused by persistence of the artery), and examinations using angiography, which has a greater ability to detect arteries.  Exactly a third of adults (33.3%) showed the artery.

The authors then went back and scoured the literature, using data on adults from 47 published papers going back to 1897. Using data from that arms in individuals who died at a known age, we have a dataset of individuals born from about 1846 to 1997—a span of roughly 150 years, or about 5 human generations.  That’s a remarkably short span of time from an evolutionary viewpoint.

Nevertheless, they found a significant increase over this period of the proportion of individuals having a median artery nearly tripled—from about 10% to 30%. Here’s the most relevant graph plotting the percentage of individuals showing the artery as adults born between 1880 and 2000. (There’s considerable scatter because sample sizes at each date are small.). The authors gives a probability of less than 0.0001 that this temporal trend would be due to chance, so it’s highly statistically significant (they don’t specify whether they’re testing the regression coefficient or the correlation coefficient, but it doesn’t really matter with p values that low.

They also extrapolate this trend and say that one “could predict that the median artery will be present in 100% of individuals born in the year 2100 or later.”  It will then no longer be a persisting fetal trait, but a trait that persists throughout life, and the persisting adult trait could no longer be seen as “vestigial”, like persisting wisdom teeth in some people.

The authors do suggest that environmental factors could play a role in this increase, but also that it could be due to natural selection. Such selection, to cause such a strong change in just a few generations, would have to be strong! The ScienceAlert article plays up the selection part, saying this:

“This increase could have resulted from mutations of genes involved in median artery development or health problems in mothers during pregnancy, or both actually,” said Lucas.

We might imagine having a persistent median artery could give dexterous fingers or strong forearms a dependable boost of blood long after we’re born. Yet having one also puts us at a greater risk of carpal tunnel syndrome, an uncomfortable condition that makes us less able to use our hands.

Nailing down the kinds of factors that play a major role in the processes selecting for a persistent median artery will require a lot more sleuthing.

Indeed, a TON of more sleuthing. What would be required to show selection would be either or both of two things:

1.) Show that, over a long period of time, individuals with median arteries as adults leave more offspring than individuals lacking these arteries. This is how the Framingham Heart Study, which began in 1948, showed that there appeared to be natural selection in women for reduced height, increased stoutness, reduced total cholesterol levels, and lower systolic blood pressure. Further, there appears to have been selection for women to produce their first child earlier and to reach menopause later. This is what I tell people who ask me, as they inevitably do when I lecture on human evolution, where our spercies is going. Not that exciting, is it? But of course the time span of such studies are necessarily limited.

2.) Find the genes responsible for the persistence of the artery and show, by population-genetic analysis, that those genes leading to persistence have been undergoing positive selection. This would be even harder because we have no idea what those genes are.

Absent those two types of studies, all we can say is that we have a putative case of evolution occurring over a short period of human evolution.

Caveats: The authors offer these caveats, and I have one more:

Limitations of the present study include the fact that the number of whole cadavers that were available for the study was not adequate. In addition, our search of the literature may have missed some publications not listed in Google Scholar. Finally, the definitions of ‘persistent median artery’ may have differed somewhat among the various published studies included in the present study.

Finally, as far as I can determine from looking at a few of the papers they cite in the older literature, the samples of arms came not just from Australia, but from other countries like Brazil and South Africa. Given that we know that at present populations from different places differ in the persistence of the artery, this could also throw some bias into the data. However, to create a time course this significant, I don’t think that using arms from different places could be the explanation, for it would require that arms from older people tended to come from places which had a lower incidence of the artery in general.

h/t: Matthew Cobb

Research is revealing the complex relationship between sleep and the gut microbiome, raising the prospect that eating better during the day might help you get a better night’s rest

All seven of the other planets in our solar system are about to become visible at once in a great planetary alignment – here’s how to spot the celestial show

A man with paralysis was able to fly a virtual drone through a complex obstacle course simply by thinking about moving his fingers, with signals being interpreted by an AI model

The benefits of taking GLP-1 agonists seem to outweigh the risks, at least when taken for approved uses, according to an assessment of how the drugs affect 175 conditions

The benefits of taking GLP-1 agonists seem to outweigh the risks, at least when taken for approved uses, according to an assessment of how the drugs affect 175 conditions

Urine is rich in nitrogen, which is important for plant growth, and now scientists have found an efficient way of utilising this to make human wastewater into fertiliser

Supernovae are one of the most useful events in all of astronomy. Scientists can directly measure their power, their spin, and their eventual fallout, whether that’s turning into a black hole or a neutron star in some cases or just a much smaller stellar remnant. One of these events happened around 350 years ago (or around 11,000 years ago from the star’s perspective) in the constellation Cassiopeia. The James Webb Space Telescope recently caught a glimpse of the aftereffects of the explosion, and it happened to shed light (literally) on a familiar area of study – interstellar gas.

The supernova in Cassiopeia ejected a massive amount of X-rays and ultraviolet light into the area surrounding the now-dead star. That energy is now hitting a clump of gas gathered in the interstellar medium about 350 light years from the star. An effect called a “light echo” is created in the process.

A light echo can be thought of as a giant photographer’s bulb. A bright flash (i.e., the energy from the supernova) travels in an ever-extending sphere outwards, gradually illuminating everything in its path, then moving on and leaving the objects it just passed back in darkness. As the material is illuminated, telescopes back on Earth can see this otherwise invisible matter existing in the interstellar medium.

Evolution of the lit-up gas and dust cloud over the course of months.
Credit – STScI YouTube Channel

The Cassiopeia A explosion caused dozens of light echoes, but one in particular caught the attention of astronomers. From our perspective, gas and dust located past the now-dead star have been gradually lit up as the flash from the supernova passes through it, creating a spectacular image.

Spitzer, one of NASA’s great observatories that ended its observations in 2020, examined this same clump of gas and dust back in 2008. Its image was fascinating but not as complete as the one by its successor, JWST.

The image from JWST, admittedly falsely colored since humans can’t see infrared light, is spectacular, both aesthetically and scientifically. It shows a series of “sheets” that are remarkably small for an interstellar structure, measuring only about 400 AU across. They seem to be influenced by interstellar magnetic fields, as video of still images shows them twisting and writhing around.

Image from Spitzer of the dust cloud taken in 2008.
Credit – NASA / JPL-Caltech / Y. Kim (U of Arizona / U of Chicago)

Another feature of the image is described as “knots in wood grain” in a press release from the Webb telescope researchers. It also twists and moves over months as if dragged by some invisible force.

Light echoes can also be seen in the visible light range. However, infrared wavelengths, which are better thought of as the heat emitted from this gas and dust as the light echo passes through it, are more capable of showing the 3D structure as the wavelengths themselves aren’t blocked by the dust as visible light would be.

Consistently taking images over the course of months also provides another advantage. As Armin Rest of the Space Telescope Science Institute puts it, “We have three slices taken at three different times,” comparing the layered result as equivalent to a CT scan commonly used in medicine.

Context for the area of the image in the Cassiopeia
Credit – NASA / ESA / CSA / STScI

While the first picture from these studies might be fantastic, there is plenty of science left to do on these clouds of matter. Future work will continue to watch as the supernova flash-bulb illuminates and darkens different parts of the collected material. Some of that might even be destroyed, as the high-power supernovae that are strong enough to cause infrared light echoes could potentially vaporize some of the matter it hits.

JWST will continue to monitor the evolving situation, but a helping hand is coming. The Nancy Grace Roman Space Telescope, due to launch in 2027, will help scan the sky for evidence of other infrared light echoes. JWST will then follow up with closer observations using its powerful infrared instruments. If we’re lucky, we’ll see plenty more astonishing pictures soon, like the ones released last week.

Learn More:
Webb Space Telescope – NASA’s Webb Reveals Intricate Layers of Interstellar Dust, Gas
UT – A Fast-Moving Star is Colliding With Interstellar gas, Creating a Spectacular bow Shock
UT – Local Interstellar Gas Mapped in 3-D
UT – A Black Hole Has Cleared Out Its Neighbourhood

The post Webb Sees Light Echoes in a Supernova Remnant appeared first on Universe Today.

The video of Day 1 of our “Censorship in the Sciences” conference is up (and down below), and this baby is nearly seven hours long.  Few people have the patience to listen to the first day’s sessions all at 0ne go, but I want to single out a few talks. The first is by Jonathan Rauch, author of The Constitution of Knowledge: A Defense of Truth, an excellent book. His talk begins at 12:01, outlines how knowledge acquisition should work, and is quite eloquent.

Later, the four-member panel on “Examples of Censorship” gives a good account of how ideology has led to suppression of science.  Luana introduces it at 2:43:26 and Lawrence Krauss kicks it off at 2:44:45 via Zoom. His examples are numerous and disturbing—and not just from physics.  He pulls no punches, and even calls out America’s National Academy of Sciences (NAS), the most prestigious honorary organization of scientists in the U.S. It so happened that the NAS President (Marcia McNutt) was in the audience, and heard Krauss call out her organization for identity-based choosing of candidates for a supposedly meritocratic society (see 2:55:45). As Krauss shows, the NAS even admitted this explicitly in a quote from an executive of the organization, and it’s widely admitted by Academy members themselves. (Note that at the end of her later talk, at 4:39:30, President McNutt denies this. accusing Krauss implicitly of ignorance, but her own organization’s stated policies belie her words.)  Finally, Krauss gives evidence that both the NSF and DOE have likewise been captured by ideology in their funding of grants.

If you want to hear about how indigenous peoples are preventing anthropologists and forensic scientists from studying relics likes bones and objects used by Native Americans, Elizabeth Weiss’s short talk in that panel, beginning at 3:23:43,  gives a good idea. She has a new book about these issues.

I heard all the talks, and some of the others engaged me as well, but I’ve just mentioned the ones I enjoyed the most.

Here is the first day’s schedule (from here)

And here’s some of the press as detailed by Heterodox at USC:

Press Coverage

Censorship in the Sciences conference speakers call on peers to organize, defend free speech, writes Jennifer Kabbany in The College Fix.

Rauch’s opening speech highlighted surveys which found that almost half of Americans think that colleges have a negative effect on the country.

“It really is a crisis,” he said, adding a combination of factors are to blame, including students’ emotional fragility, the politicization of hiring, tenure and funding based on ideology, and a newer trend of academic journals refusing to publish findings that allegedly harm some communities.

Kabbany also covered Musa al-Gharbi’s presentation at the conference. Read that article here.

Alice Dreger, managing editor at the Heterodox Academy, wrote a recap on HxA’s Free the Inquiry Substack:

On the issue of censorship of research publication, many speakers at the conference objected to the idea that claims about potential harm to vulnerable populations should be used as a reason to stop, force changes to, or retract research reports. Some raised the question of the harms that arise from alleged-harm-reduction censorship–that is, the harms that arise from stopping valuable research out of fear of harm

In response to a Saturday morning presentation by Nature editor Stavroula Kousta, journalist Jesse Singal, also a speaker at our event, published a critique of some the ideas presented.

Conference organizer and panelist Lee Jussim wrote about the conference (and whether we should just burn academia down).

Panelist Jerry Coyne wrote several dispatches about the conference on his blog Why Evolution is True (which reaches nearly 75,000 readers).

Attendee Zvi Shalem wrote up his take-ways from the conference here.

Panelist Michael Bowen of Free Black Thought reflected on attending conference on his Substack.

Natalya Murakhver wrote about her experience debuting her documentary 15 Days at the conference.

Panel chair Abhishek Saha wrote up excellent Twitter threads (in real time!) detailing conference proceedings. Here is one on the first day of conference.

Is 8 hours of sleep really the right amount for you? Understanding your personal chronotype could be a better way to approach how much time you should spend in bed

There really is a significant mystery in the world of cosmology. This, in my opinion, is a good thing. Such mysteries point in the direction of new physics, or at least a new understanding of the universe. Resolving this mystery – called the Hubble Tension – is a major goal of cosmology. This is a scientific cliffhanger, one which will unfortunately take years or even decades to sort out. Recent studies have now made the Hubble Tension even more dramatic.

The Hubble Tension refers to discrepancies in measuring the rate of expansion of the universe using different models or techniques. We have known since 1929 that the universe is not static, but it is expanding. This was the famous discovery of Edwin Hubble who notice

d that galaxies further from Earth have a greater red-shift, meaning they are moving away from us faster. This can only be explained as an expanding universe – everything (not gravitationally bound) is moving away from everything else. This became known as Hubble’s Law, and the rate of expansion as the Hubble Constant.

Then in 1998 two teams, the Supernova Cosmology Project and the High-Z Supernova Search Team, analyzing data from Type 1a supernovae, found that the expansion rate of the universe is actually accelerating – it is faster now than in the distant past. This discovery won the Nobel Prize in physics in 2011 for  Adam Riess, Saul Perlmutter, and Brian Schmidt. The problem remains, however, that we have no idea what is causing this acceleration, or even any theory about what might have the necessary properties to cause it. This mysterious force was called “dark energy”, and instantly became the dominant form of mass-energy in the universe, making up 68-70% of the universe.

I have seen the Hubble Tension framed in two ways – it is a disconnect between our models of cosmology (what they predict) and measurements of the rate of expansion, or it is a disagreement between different methods of measuring that expansion rate. The two main methods of measuring the expansion rate are using Type 1a supernovae and by measuring the cosmic background radiation. Type 1a supernovae are considered standard candle because they have roughly the same absolute magnitude (brightness). The are white dwarf stars in a binary system that are siphoning off mass from their partner. When they reach a critical point of mass, they go supernova. So every Type 1a goes supernova with the same mass, and therefore the same brightness. If we know an object’s absolute magnitude of brightness, then we can calculate its distance. It was this data that lead to the discovery that the universe is accelerating.

But using our models of physics, we can also calculate the expansion of the universe by looking at the cosmic microwave background (CMB) radiation, which is the glow left over after the Big Bang. This gets cooler as the universe expands, and so we can calculate that expansion by looking at the CMB close to us and farther away. Here is where the Hubble Tension comes in. Using Type 1a supernovae, we calculate the Hubble Constant to be 73 km/s per megaparsec. Using the CMB the calculation is 67 km/s/Mpc. These numbers are not close enough – they are very different.

At first it was thought that perhaps the difference is due to imprecision in our measurements. As we gather more and better data (such as building a more complete sample of Type 1a supernovae), using newer and better instruments, some hoped that perhaps these two numbers would come into alignment. The opposite has happened – newer data has solidified the Hubble Tension.

A recent study, for example, uses the Dark Energy Spectroscopic Instrument (DESI) to make more precise measurements of Type 1a’s in the nearby Coma cluster. This is used to make a more precise calibration of our overall measurements of distance in the universe. With this more precise data, the authors argue that the Hubble Tension should now be considered a “Hubble Crisis” (a term which then metastasized throughout reporting headlines). The bottom line is that there really is a disconnect between theory and measurements.

Even more interesting, another group has used updated Type 1a supernovae data to argue that perhaps dark energy does not have to exist at all. This is their argument: The calculation of the Hubble Constant throughout the universe used to establish an accelerating universe is based on the assumption of isotropy and homogeneity at the scale we are observing. Isotropy means that the universe is essentially the same density no matter which direction you look in, while homogeneity means that every piece of the universe is the same as every other piece. So no matter where you are and which direction you look in, you will observe about the same density of mass and energy. This is obviously not true at small scales, like within a galaxy, so the real question is – at what scale does the universe become isotropic and homogenous? Essentially cosmologists have used the assumption of isotropy and homogeneity at the scale of the observable universe to make their calculations regarding expansion. This is called the lambda CDM model (ΛCDM), where lambda is the cosmological constant and CDM is cold dark matter.

This group, however, argues that this is not true. There are vast gaps with little matter, and matter tends to clump along filaments in the universe. If instead you take into account these variations in the density of matter throughout the universe, you get different results for the Hubble Constant. The primary reason for this is General Relativity. This is part of Einstein’s (highly verified) theory that matter affects spacetime. Where matter is dense, time relatively slows down. This means as we look out into the universe, the light that we see is travelling faster through empty space than it is through space with lots of matter, because that matter is causing time to slow down. So if you measure the expansion rate of the universes it will appear faster in gaps and slower in galaxy clusters. As the universe expands, the gaps expand, meaning the later universe will have more gaps and therefore measure a faster acceleration, while the older universe has smaller gaps and therefore measures a slower expansion. They call this the timescape model.

If the timescape model is true, then the expansion of the universe is not accelerating (it’s just an illusion of our observations and assumptions), and therefore there is no need for dark energy. They further argue that their model is a better fit for the data than ΛCDM (but not by much). We need more and better data to definitively determine which model is correct. They are also not mutually exclusive – timescape may explain some but not all of the observed acceleration, still leaving room for some dark energy.

I find this all fascinating. I will admit I am rooting for timescape. I never liked the concept of dark energy. It was always a placeholder, but also just has properties that are really counter-intuitive. For example, dark energy does not dilute as spacetime expands. This does not mean it is false – the universe can be really counterintuitive to us apes with our very narrow perspectives. I will also follow whatever the data says. But wouldn’t it be exciting if an underdog like timescape overturned a Nobel Prize winning discovery, and for at least a second time in my lifetime radically changed how we think about cosmology. Timescape may also resolve the Hubble Tension to boot.

Whatever the answer turns out to be – clearly there is something wrong with our current cosmology. Resolving this “crisis” will expand our knowledge of the universe.

The post The Hubble Tension Hubbub first appeared on NeuroLogica Blog.

Today’s photos come from mathematician and Hero of Intellectual Freedom Abby Thompson of UC Davis, whose avocation is photographing California tide pools and their invertebrates. Abby’s captions are indented, and you can enlarge her photos by clicking on them.

New year’s tidepool pictures from Dillon Beach in northern California, plus a few older photos.  It’s not that much colder during the winter here- August can be freezing, December delightful.   To see much in December you have to be willing to go out after dark, which is a little spooky, but has the advantage that you often get to see racoons foraging on the rocks.    Sadly the only pictures I get of them look like two red dots (their eyes) on a black background.

As usual I got help with some of the IDs from people on inaturalist.

Schuchertinia milleri (tentative):

This is through a microscope, taken with my iphone.  In the tidepools it appears as a small very pink blob stuck to a rock. These are hydroids, closely related to jellyfish, unlikely as that seems.

Kelp crab:

These crabs are one of the few things you should be cautious about in the tidepools here- they are reported to have a strong bite with their claws (I haven’t tested this), and they’re not shy.

The next four pictures are all nudibranchs. As you can see, their coloration is quite varied, but nevertheless they are all the same species. Keep this in mind for when we get to pictures 7,8 and 9.

Triopha maculata 1:

 

Triopha maculata 2:

 

Triopha maculata 3:

 

Triopha maculata 4:

 

Ok, the next two pictures are two distinct species of nudibranch.    To my eye, the difference in coloration here is a bit more subtle than for the Triophas; H. crassicornis has white “stripes” on the frilly stuff on its back.

Hermissenda opalescens:

Hermissenda crassicornis:

And the next picture is of these two local species of Hermissenda hanging out together.  Not exactly in flagrante (nudibranchs spend an awful lot of their time mating and laying eggs), but still, looking pretty friendly. Maybe Jerry will chime in with some info on delimiting species?  and how exactly it is done, for us non-experts. [JAC: two different forms copulating doesn’t resolve their species status!]

Hermissenda opalescens and Hermissenda crassicornis:

Clam siphons:

There is not enough appreciation of bivalves in the world, except as dinner,  Their siphons can be lovely (I admit this may be in the eye of the beholder).

Coryphella trilineata:

A pretty nudibranch. There are lots of this species at the moment.

Pycnogonid stearnsi:

There are several species of “sea spiders” locally.   They’re small (this one was less than an inch across), and lively.      This is the most common here.

Anthopleura artemisia (Moonglow anemone):

You may remember from earlier pictures that this is another species with many dramatically different color variants.

Camera info:  Mostly Olympus TG-7, in microscope mode, pictures taken from above the water.