BOOKS ET AL.HISTORY OF PHYSICS

Before the Big Bang became scientific dogma

Simon Mitton
Flashes of Creation: George Gamow, Fred Hoyle, and the Great Big Bang Debate Paul Halpern Basic Books, 2021. 304 pp.

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Science 20 Aug 2021:
Vol. 373, Issue 6557, pp. 861
DOI: 10.1126/science.abj9479

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The serendipitous detection of the cosmic microwave background radiation in 1964 changed cosmology forever, settling a long-running debate about the origin of the Universe. The radio hiss hinted that the Universe had arisen from an instantaneous fiery beginning, a theory championed by cosmologist George Gamow, who sought to account for the origin of the chemical elements. His rival, Fred Hoyle, who developed the alternative steady-state theory, which posited an infinite Universe, had long insisted that the chemical elements formed continuously in the cores of massive stars. Both cosmic models were falsifiable by solving a simple puzzle: Has the Universe evolved? The feeble whisper detected in 1964 was an undeniable “Yes!”

In Flashes of Creation, Paul Halpern presents a scintillating account of the intellectual travails of Gamow and Hoyle, two animated, curious, provocative, and controversial figures in 20th-century physics. In this joint biography, the reader is introduced to the two physicists' theories and their efforts to explain the origin of elements.

Gamow, we learn, first encountered cosmology in the early 1920s while studying at the University of Leningrad under Alexander Friedmann, the Russian mathematician who pioneered the idea that the Universe is expanding. In Göttingen and Copenhagen, while a doctoral student in physics, he mingled with pioneers who were working on the new quantum theory. These interactions enabled his breakthrough in 1928, when he showed how an alpha particle could escape from an atomic nucleus by quantum tunneling.

Gamow's subsequent realization that quantum tunneling is reversible spurred two colleagues, Robert Atkinson and Fritz Houtermans, to demonstrate that sufficiently energetic protons could penetrate the atomic nuclei often enough to account for the source of stellar energy. Physicist Hans Bethe made the next advance, finding that proton-proton collisions in the cores of stars like the Sun fuse hydrogen to helium. For more-massive stars, he suggested a cycle of nuclear reactions in which carbon, nitrogen, and oxygen catalyze hydrogen to helium. This scheme left open the question that Gamow and Hoyle would confront head on: How did the elements from carbon to uranium come into existence?

Hoyle entered the Cavendish Laboratory at the University of Cambridge in 1936 as a doctoral student supervised by Rudolf Peierls. As academics, including Peierls, later fled the Cavendish Laboratory to professorships elsewhere, Hoyle remained at Cambridge until the war years, working alone on extending Enrico Fermi's theory of beta decay. By peacetime, he had developed the steady-state theory and witheringly dismissed Gamow's cosmology as a mere “big bang.”


Fred Hoyle (left) and George Gamow disagreed about the origins of the Universe

.PHOTOS (LEFT TO RIGHT): A. BARRINGTON BROWN/SCIENCE SOURCE; GRANGER

Hoyle could perceive no merit in Gamow's notion that the elements were created in a flash by the eruption of a primeval atom—it violated the conservation laws of physics. His ageless steady-state approach envisaged that new matter trickled continuously into the empty space left by the expansion of the Universe. The buildup of chemical elements then arose as a consequence of the evolution of massive stars, he postulated. When the hydrogen fuel in a star's core became exhausted, it would implode gravitationally, thereby sparking the physical conditions conducive to the rapid assembly of heavier elements.

The Gamowian school had considered the role of neutrinos in core collapse, but Hoyle's powerful rebuttal of their model in 1946 was vastly more efficient at building heavy elements. By 1957, Hoyle's team had completed its brilliant synthesis of element building via neutron capture reactions. However, steady-state theory came under relentless attack as report after report by observational astronomers cemented Big Bang cosmology.

In 1964, Hoyle reluctantly conceded that “a small residue of Gamow's idea”—the synthesis of light elements in the Big Bang—had merit. Within months, news broke of the discovery of the cosmic microwave background. Hoyle never accepted this as evidence that “the entire cosmos had a start date.” By contrast, Gamow opportunistically seized the moment, claiming primary credit for a neglected prediction of the background temperature made in 1948 by his associates Ralph Alpher and Robert Herman.

In the book's closing pages, Halpern sensitively handles with commendable candor the tragic endgames of these two giants. Gamow's alcoholism, we learn, destroyed him and much of his reputation. And while Hoyle commanded great respect after resigning from Cambridge in 1972, his little tweaks to steady-state cosmology failed to find a following.

Gamow and Hoyle were friendly rivals who seldom interacted in person. Halpern nonetheless renders their contributions and clashes vividly in this expertly crafted biography of two contentious cosmologists who thrived on ingenious invention.
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Simulation provides images from the carbon nucleus

International study with participation of the University of Bonn also provides new insights into the puzzling Hoyle state

Peer-Reviewed Publication

UNIVERSITY OF BONN

 

IMAGE: ARE PRESENT IN THE CARBON NUCLEUS AS THREE CLUSTERS OF FOUR. DEPENDING ON THE ENERGY STATE OF THE NUCLEUS, THESE CAN BE ARRANGED INTO AN EQUILATERAL TRIANGLE (LEFT) OR LIKE A SLIGHTLY BENT ARM (RIGHT). view more 

CREDIT: IMAGE: PROF. SERDAR ELHATISARI/UNIVERSITY OF BONN

What does the inside of a carbon atom’s nucleus look like? A new study by Forschungszentrum Jülich, Michigan State University (USA) and the University of Bonn provides the first comprehensive answer to this question. In the study, the researchers simulated all known energy states of the nucleus. These include the puzzling Hoyle state. If it did not exist, carbon and oxygen would only be present in the universe in tiny traces. Ultimately, we therefore also owe it our own existence. The study has now been published in the journal “Nature Communications.”

The nucleus of a carbon atom normally consists of six protons and six neutrons. But how exactly are they arranged? And how does their configuration change when the nucleus is bombarded with high-energy radiation? For decades, science has been searching for answers to these questions. Not least because they could provide the key to a mystery that has long puzzled physicists: Why is there a significant amount of carbon in space at all - an atom without which there would be no life on Earth?

After all, shortly after the Big Bang, there was only hydrogen and helium. The hydrogen nucleus consists of a single proton, that of helium of two protons and two neutrons. All heavier elements were only created many billions of years later by aging stars. In them, helium nuclei fused into carbon nuclei at immense pressure and extremely high temperatures. This requires three helium nuclei to fuse together. “But it's actually very unlikely for this to happen,” explains Prof. Dr. Ulf Meißner of the Helmholtz Institute of Radiation and Nuclear Physics at the University of Bonn and the Institute for Advanced Simulation at Forschungszentrum Jülich. The reason: The helium nuclei together have a much higher energy than a carbon nucleus. However, this does not mean that they fuse particularly readily - on the contrary: It is as if three people wanted to jump onto a merry-go-round. But since they run much faster than the merry-go-round turns, they do not succeed.

Simulation on the supercomputer

As early as the 1950s, the British astronomer Fred Hoyle therefore postulated that the three helium nuclei first come together to form a kind of transition state. This "Hoyle state" has a very similar energy to the helium nuclei. To stay in the picture: It is a faster-spinning version of the merry-go-round, which the three passengers can therefore easily jump onto. When that happens, the carousel slows down to its normal speed. “Only by taking a detour via the Hoyle state can stars create carbon at all in any appreciable quantity,” says Meißner, who is also a member of the Transdisciplinary Research Areas “Modeling” and “Matter” of the University of Bonn.

About ten years ago, together with colleagues from the USA, Forschungszentrum Jülich and Ruhr-Universität Bochum, he succeeded in simulating this Hoyle state for the first time. “We already had an idea then of how the protons and neutrons of the carbon nucleus are arranged in this state,” he explains. “However, we were not able to prove with certainty that this assumption was true.” With the help of an advanced method, the researchers have now succeeded. This is essentially based on confinement: In reality, the protons and neutrons - the nucleons - can be located anywhere in space. For their calculations, however, the team restricted this freedom: “We arranged our nuclear particles on the nodes of a three-dimensional lattice,” Meißner explains. “So we allowed them only certain strictly defined positions.”

Computing time: five million processor hours

Thanks to this restriction, it was possible to calculate the motion of nucleons. Since nuclear particles affect each other differently depending on their distance from each other, this task is very complex. The researchers also ran their simulation several million times with slightly different starting conditions. This allowed them to see where the protons and neutrons were most likely to be. “We performed these calculations for all known energy states of the carbon nucleus,” Meißner says. The calculations were performed on the JEWELS supercomputer at Forschungszentrum Jülich. They required a total of about five million processor hours, with many thousands of processors working simultaneously.

The results effectively provide images from the carbon nucleus. They prove that the nuclear particles do not exist independently of each other. “Instead, they are clustered into groups of two neutrons and two protons each,” the physicist explains. This means that the three helium nuclei can still be detected after they have fused to form the carbon nucleus. Depending on the energy state, they are present in different spatial formations - either arranged into an isosceles triangle or like a slightly bent arm, with the shoulder, elbow joint and wrist each occupied by a cluster.

The study not only allows researchers to better understand the physics of the carbon nucleus. Meißner: “The methods we have developed can easily be used to simulate other nuclei and will certainly lead to entirely new insights.”

Participating institutions and funding:

Forschungszentrum Jülich, Michigan State University (USA), the China Academy of Engineering Physics and the University of Bonn were involved in the study. The work was made possible by funding from the German Research Foundation, the National Natural Science Foundation of China, the Chinese Academy of Sciences (CAS), the Volkswagen Foundation, the European Research Council (ERC), the U.S. Department of Energy, the Nuclear Computational Low-Energy Initiative (NUCLEI), and the Gauss Center for Supercomputing e.V.

Publication: Shihang Shen, Serdar Elhatisari, Timo A. Lähde, Dean Lee, Bing-Nan Lu & Ulf-G. Meißner: Emergent geometry and duality in the carbon nucleus; Nature Communications; https://www.nature.com/articles/s41467-023-38391-y

---

JOURNAL

Nature Communications

DOI

10.1038/s41467-023-38391-y 

METHOD OF RESEARCH

Computational simulation/modeling

SUBJECT OF RESEARCH

Not applicable

ARTICLE TITLE

Emergent geometry and duality in the carbon nucleus

ARTICLE PUBLICATION DATE

15-May-2023

PAPER: CULTURE, COMPUTING SHOULD BE CONSIDERED “LIFE FORMS”

The idea of broadening the definition of life isn’t wholly new. Astronomer Fred Hoyle wrote a sci-fi novel about intelligent gaseous clouds

NEWS AUGUST 21, 2021

Some researchers are urging us to broaden our definition of life, which may have an impact on the search for life on exoplanets.

In a new paper, published in the Journal of Molecular Evolution, Santa Fe Institute researchers Chris Kempes and David Krakauer argue that in order to recognize life’s full range of forms, we must develop a new theoretical frame.

Although there are many definitions of life, they all assume a strict separation between life and non-life — and that is what the researchers challenge:


Culture, computation, and forests are all forms of life in this frame. As Kempes explains, “human culture lives on the material of minds, much like multicellular organisms live on the material of single-celled organisms.”

Their broader definition of life includes the idea that life has multiple origins; all life did not begin with a single cell; it may not even require cells. Viruses would certainly be considered alive in their scheme.

When researchers focus on the life traits of single organisms, they often neglect the extent to which organisms’ lives depend upon entire ecosystems as their fundamental material, and also ignore the ways that a life system may be more or less living. Within the Kempes-Krakauer framework, by contrast, another implication appears: life becomes a continuum rather than a binary phenomenon. In this vein, the authors point to a variety of recent efforts that quantitatively place life on a spectrum.

On one hand, this broader approach might make it easier to envision, thus look for, extraterrestrial life. We would not insist that it be like life on Earth.

The idea is not entirely new. Astronomer Fred Hoyle (1915–2001) wrote a science fiction novel, The Black Cloud (1957) in which the extraterrestrials turn out to be a dark, gaseous cloud, much more intelligent than humans. The cloud is creating havoc by accidentally blocking the sun but, being so informed, it expresses surprise that there are life forms that are actually solids.

On the other hand, there is a danger is losing a grip on what makes life on Earth unique. Culture, for example, originates as ideas, which are immaterial in character. That makes culture quite different from cells. And, while forests are full of life forms, the concept of a “forest” is an idea in the human mind.

Similarly, however powerful computers may become, insisting that they are “life” could only have the effect of diminishing the importance of biological life. If all computers “went extinct,” the effect on the environment would be negligible compared to what would happen if most pollinators did.

Kempes and Krakauer’s approach sounds like one of those ideas that is better explored in a conference workshop than used for definitions or enacted into law.

The paper is open access.

You may also wish to read: Scientists try to understand how one-celled life forms learn. Artificial intelligence may offer a model for learning without a brain.


MIND MATTERS NEWS

Breaking and noteworthy news from the exciting world of natural and artificial intelligence at MindMatters.ai.

CTHULHU STUDIES

A Weird Paper Tests The Limits of Science by Claiming Octopuses Came From Space


(PlanctonVideo/iStock)

MIKE MCRAE
28 DECEMBER 2021

A summary of decades of research on a rather 'out-there' idea involving viruses from space raises questions on just how scientific we can be when it comes to speculating on the history of life on Earth.

It's easy to throw around words like crackpot, rogue, and maverick in describing the scientific fringe, but then papers like this one, from 2018, come along and leave us blinking owlishly, unsure of where to even begin.

A total of 33 names were listed as authors on this review, which was published by Progress in Biophysics and Molecular Biology back in August 2018. The journal is peer reviewed and fairly well cited. So it's not exactly small, or a niche pay-for-publish source.

Science writer Stephen Fleischfresser goes into depth on the background of two of the better known scientists involved: Edward Steele and Chandra Wickramasinghe. It's well worth a read.

For a tl;dr version, Steele is an immunologist who has a fringe reputation for his views on evolution that relies on acquiring gene changes determined by the influence of the environment rather than random mutations, in what he calls meta-Lamarckism.

Wickramasinghe, on the other hand, has had a somewhat less controversial career, recognized for empirically confirming Sir Fred Hoyle's hypothesis describing the production of complex carbon molecules on interstellar dust.

Wickramasinghe and Hoyle also happened to be responsible for another space biology thesis. Only this one is based on more than just the origins of organic chemistry.

The Hoyle Wickramasinghe (H-W) thesis of Cometary (Cosmic) Biology makes the rather simple claim that the direction of evolution has been significantly affected by biochemistry that didn't start on our planet.

In Wickramasinghe's own words, "Comets are the carriers and distributors of life in the cosmos, and life on Earth arose and developed as a result of cometary inputs."

Those inputs, Wickramasinghe argued, aren't limited to a generous sprinkling of space-baked amino acids, either.

Rather, they include viruses that insert themselves into organisms, pushing their evolution into whole new directions.

The report, titled "Cause of Cambrian Explosion – Terrestrial or Cosmic?", pulls on existing research to conclude that a rain of extra-terrestrial retroviruses played a key role in the diversification of life in our oceans roughly half a billion years ago.

"Thus retroviruses and other viruses hypothesized to be liberated in cometary debris trails both can potentially add new DNA sequences to terrestrial genomes and drive further mutagenic change within somatic and germline genomes," the authors wrote.

Let that sink in for a moment. And take a deep breath before continuing, because that was the tame part.

It was during this period that a group of mollusks known as cephalopods first stretched out their tentacles from beneath their shells, branching into a stunning array of sizes and shapes in what seemed like a remarkably short time frame.

The genetics of these organisms, which today include octopuses, squid, and cuttlefish, are as weird as the animals themselves, due in part to their ability to edit their DNA on the fly.

The authors of the paper make the rather audacious claim that these genetic oddities might be a sign of life from space.

Not of space viruses this time, but the arrival of whole genomes frozen in stasis before thawing out in our tepid waters.

"Thus the possibility that cryopreserved squid and/or octopus eggs, arrived in icy bolides several hundred million years ago should not be discounted," they wrote.

In his review of the paper, medical researcher Keith Baverstock from the University of Eastern Finland conceded that there's a lot of evidence that plausibly aligns with the H-W thesis, such as the curious timeline of the appearance of viruses.


But that's just not how science advances.

"I believe this paper justifies skepticism of the scientific value of stand alone theories of the origin of life," Baverstock argued at the time.

"The weight of plausible, but non-definitive, evidence, great though that might be, is not the point."

While the idea is as novel and exciting as it is provocative, nothing in the summary helps us better understand the history of life on Earth any better than existing conjectures, adding little of value to our model of evolution.

Still, with solid caveats in place, maybe science can cope with a generous dose of crazy every now and then.

Journal editor Denis Noble concedes that 'further research is needed', which is a bit of an understatement.

But given the developments regarding space-based organic chemistry in recent years, there's room for discussion.

"As space chemistry and biology grows in importance it is appropriate for a journal devoted to the interface between physics and biology to encourage the debates," said Noble.

"In the future, the ideas will surely become testable."

Just in case those tests confirm speculations, we recommend being well prepared for the return of our cephalopod overlords. Who knows when they'll want those eggs back?

This research was published in Progress in Biophysics and Molecular Biology.

A version of this article was first published in August 2018.

Why is there something not nothing? The big bang isn’t the only answer

News Post || Tech News

The idea that the universe started in the big bang revolutionised 20th-century cosmology. But it seems increasingly unlikely it was a case of something from nothing

17 November 2021
By Joshua Howgego
Louis Koo/Getty Images

“NO QUESTION is more sublime than why there is a Universe: why there is anything rather than nothing,” philosopher Derek Parfit once wrote.
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Sublime it might be, but the question has traditionally exercised philosophers and theologians. Creation myths, a feature of many cultures, satisfied a deep-seated need for meaning and narrative drive in our existence (see “Why do we exist?”). Scientific thought, insofar as it paid attention to such matters, assumed the cosmos had always been there in an eternal, unchanging state.

Then came the greatest scientific revelation of the past century, arguably of all time: what came to be known as the big bang.

Its seeds were sown by Albert Einstein with general relativity, his theory of gravity, back in 1915, and by Edwin Hubble and others in the 1920s. Their astronomical measurements showed that far-off galaxies were receding from us, as if the universe were expanding.

As late as the 1940s, physicists including Hermann Bondi, Thomas Gold and Fred Hoyle were explaining these observations in terms of an eternal, steady state universe that expanded through the continuous creation of matter. Today, we can cross this possibility off the list. 

“That’s not a stable state for a universe that is structured in the way we see ours is,” says cosmologist Katie Mack at North Carolina State University.

That is partly because it is hard to square with the way gravity works, only pulling inwards, not pushing outwards. But it is mainly down to the discovery of the cosmic microwave background radiation in the 1960s. This all-pervasive radiation was exactly what you would expect to see …

HIS MOTHER WAS A WITCH

Why Johannes Kepler is a scientist’s best role model

When people pick the greatest scientist of all-time, Newton and Einstein always come up. Perhaps they should name Johannes Kepler, instead.

Johannes Kepler, whose life spanned from the late 1500s to the early 1600s, was perhaps most remarkable as a scientist for his discovery that planets moved in ellipses around the Sun. Without the ability to throw out his own brilliant idea, he never could've gotten there.
(Credits: August Köhler/public domain (L); Datumizer/Wikimedia Commons (R)

KEY TAKEAWAYS

The annals of history are filled with scientists who had incredible, revolutionary ideas, sought out and found the evidence to support them, and initiated a scientific revolution.

 
But much rarer is someone who has a brilliant idea, discovers that the evidence doesn't quite fit, and instead of doggedly pursuing it, tosses it aside in favor of a newer, better, more successful idea.

 
That's exactly what separates Johannes Kepler from all of the other great scientists throughout history, and why, if we have to choose a scientific role model, we should admire him so thoroughly.

Ethan Siegel

For a great many people in the world, the three hardest words to say are simply, “I was wrong.” Even if the evidence is overwhelmingly decisive that your idea or conception is unsupported, most people will instead find a way to discount or ignore that evidence and stick to their guns. People’s minds are notoriously resistant to change, and the greater their own personal stake in the outcome of the issue under debate, the less open they are to even the possibility that they might be mistaken.

Although it’s often asserted that science is the exception to this general rule, that’s only true of science as a collective enterprise. On an individual basis, scientists are just as susceptible to confirmation bias — overweighting the supporting evidence and discounting the evidence to the contrary — as anyone in any other walk of life. In particular, the greatest difficulties await those who themselves have formulated ideas and invested tremendous efforts, often amounting to years or even decades of time, in hypotheses that simply cannot explain the full suite of data that humanity has amassed. This applies even to the greatest minds in all of history.Albert Einstein could never accept quantum indeterminism as a fundamental property of nature.

Arthur Eddington could never accept quantum degeneracy as a source for holding white dwarfs up against gravitational collapse.

Newton could never accept the experiments that demonstrated the wave nature of light, including interference and diffraction.

And Fred Hoyle could never accept the Big Bang as the correct story of our cosmic origins, even nearly 40 years after the critical evidence, in the form of the Cosmic Microwave Background, was discovered.

But one person stands above the rest as an exemplar for how to behave when the evidence comes in against your brilliant idea: Johannes Kepler, who showed us the way more than 400 years ago. Here’s the story of his scientific evolution, an example we should all strive to emulate.

This chart, from around 1660, shows the signs of the zodiac and a model of the solar system with Earth at the centre. For decades or even centuries after Kepler clearly demonstrated that not only is the heliocentric model valid, but that planets move in ellipses around the Sun, many refused to accept it, instead hearkening back to the ancient idea of Ptolemy and geocentrism.

(Credit: Johannes Van Loon, Andreas Cellarius Harmonia Macrocosmica, 1660/61)

For thousands of years, humans assumed that the Earth was a static, stable, and unchanging point in the Universe, and that all the heavens literally moved around us. Observations seemed to support this: there was no detectable motion occurring on our surface that supported an Earth that either rotated on its axis or revolved around the Sun through space. Instead, there were three key observations that had been made that helped people determine what our best model of the Universe would be.

The entire sky appeared to rotate a full 360 degrees over the course of 24 hours, most evident at night, as the stars rotated about either the northern or southern celestial pole.

The stars themselves appeared to remain fixed in their relative position to one another from night-to-night and even over much longer timescales.

However, there were a few objects that did move relative to one another from night-to-night or day-to-day: the planets, or “wanderers” of the sky.

Additionally, the Sun and Moon shifted in the night as well, as did the entire canopy of stars over longer periods of time. However, it was the first observation that led to the static, stable, unchanging conception of the Universe.

This timelapse view of the night sky from Hyatt Lake shows the sky as it appeared just after the summer solstice on June 21, 2020. The apparent motion of the objects in Earth’s sky could either be explained by the Earth rotating beneath our feet or by the heavens above rotating about a fixed Earth. Simply by watching the skies, we cannot tell these two explanations apart.

(Credit: Bureau of Land Management OR & WA/Kyle Sullivan)

Think about the above observation: that everything in the sky appears to rotate a full 360 degrees over the span of a full day. This could be caused by one of two potential explanations. Either the Earth itself was rotating about some axis, and that our world completed a full rotation once per 24 hours, or the Earth was stationary and everything in the heavens was rotating around it, also once per 24 hours.

How, physically, could we tell these two situations apart? The answers were twofold.

First, it should be possible, if the Earth were rotating, to note a curved trajectory to falling objects. The higher they fell from, the greater the curve would be. Yet no curve was ever observed; in fact this effect wouldn’t be measured until the demonstration of the Foucault pendulum in the 19th century.

Second, a rotating Earth would lead to a difference in the relative positions of the stars from dusk until dawn. The Earth was big, and its diameter had been measured precisely by Eratosthenes in the 3rd century B.C.E., so if any of the stars were closer than most of them, a parallax would appear: similar to holding your thumb out and watching it shift relative to the background as you alternated which eye you used to view it. But no parallax could be seen; in fact this wouldn’t be observed until the 19th century as well! 

The stars that are closest to Earth will appear to shift periodically with respect to the more distant stars as the Earth moves through space in orbit around the Sun. Before the heliocentric model was established, we weren’t looking for “shifts” with a ~300,000,000 kilometer baseline over the span of ~6 months, but rather a ~12,000 kilometer baseline over the span of one night: Earth’s diameter as it rotated on its axis.(Credit: ESA/ATG medialab)

It’s easy to see, based on what we knew and could observe at the time, how we’d conclude that the Earth was static and fixed, while the heavenly bodies all moved around us.

Then, there were those additional observations that required an explanation: why did the stars remain fixed relative to one another while the planets appeared to “wander” through the sky?

It was quickly modeled that the planets, as well as the Sun and the Moon, must be closer to Earth than the stars were, and that these bodies must be in motion relative to one another.

With a fixed, static Earth, that meant that it must be the planets themselves that were in motion. The motion must have been incredibly complex, however. While the planets overwhelmingly appeared to move in one direction relative to the backdrop of stars on a night-to-night basis, every once in a while, the planets would:slow down in their usual motion,
come to a complete stop,
reverse their motion to move opposite their original direction (a phenomenon known as retrograde motion),
would then slow and stop again,
and finally would continue on in their normal (prograde) direction of motion.

This phenomenon was the most challenging aspect of planetary motion to model and understand.

Mars, like most planets, normally migrates very slowly across the sky in one predominant direction. However, a little less than once a year, Mars will appear to slow down in its migration across the sky, stop, reverse directions, speed up and slow down, and then stop again, resuming its original motion. This retrograde (west-to-east) period stands in contrast to Mars’s normal prograde (east-to-west) motion.(Credit: E. Siegel/Stellarium)

The prevailing assumption, since the Earth had already been deemed to be static, was that the planets themselves each typically moved in circular paths around the Earth, but atop those circles were smaller circles known as “epicycles” that they moved about as well. When the motion through the smaller circle proceeded in the opposite direction from the main motion through the larger circle, the planet would appear to reverse course for a brief while: a period of retrograde motion. Once the two motions lined up in the same direction again, prograde motion would resume.

Although epicycles did not start with Ptolemy — with whose name they are now synonymous — Ptolemy did make the best, most successful model of the Solar System that incorporated epicycles. In his model, the following occurred.Each planet’s orbit was dominated by a “great circle” that it moved along, moving around the Earth.
Atop each great circle, a smaller circle (an epicycle) existed, with the planet moving along the outskirts of that small circle, with the center of the small circle always moving along the larger one.
And the Earth, rather than being at the center of the great circle, was offset from that center by a particular amount, with the specific amount differing for each planet.

That was the Ptolemaic theory of epicyclic motion, leading to a geocentric model of the Solar System.

One of the great puzzles of the 1500s was how planets moved in an apparently retrograde fashion. This could either be explained through Ptolemy’s geocentric model (L), or Copernicus’ heliocentric one (R). However, getting the details right to arbitrary precision was something that would require theoretical advances in our understanding of the rules underlying the observed phenomena, which led to Kepler’s laws and eventually Newton’s theory of universal gravitation.(Credit: E. Siegel/Beyond the Galaxy)

Going all the way back to ancient times, there was some evidence — from Archimedes and Aristarchus, among others — that a Sun-centered model for planetary motion was considered. But once again, the lack of any detectable motion for the Earth or of any detectable parallax for the stars failed to provide the corroborating evidence. The idea languished in obscurity for centuries, but was finally revived in the 16th century by Nicolaus Copernicus.

The great idea of Copernicus was that if the planets moved in circles around the Sun, then during most times, the inner planets would orbit more quickly than the outer ones. From the perspective of any one planet, the others would appear to migrate relative to the fixed stars. But whenever an inner planet passed by and overtook an outer planet, then retrograde motion would occur, as the normal apparent direction-of-motion would appear to reverse.

Copernicus realized this and put forth his theory of a Sun-centered Solar System, or a heliocentric (rather than geocentric) one, offering it up as an exciting and possibly superior alternative to Ptolemy’s older Earth-centered model

.
This simulation of the Solar System over the duration of one Earth-year shows the innermost planet, Mercury, “overtaking” the Earth from an interior orbit three independent times during the year. With Mercury’s orbital period of just 88 days, three or four retrograde periods exist every year for Mercury: the only planet annually with more than one. The outer planets, by contrast, experience retrograde only when Earth overtakes them: roughly once per year for all planets except Mars, which experiences them less frequently.(Credit: dynamicdiagrams.com, 2011, now defunct)

But in science, we always have to follow the evidence, even if we loathe the path it leads us down. It’s not aesthetics, elegance, naturalness, or personal preference that decides the issue, but rather the success of the model in predicting what can be observed. Leveraging circular orbits for both the Ptolemaic and the Copernican models, Copernicus was frustrated to discover that his model gave less successful predictions when compared against Ptolemy’s. The only way Copernicus could devise to equal Ptolemy’s successes, in fact, relied on employing the same ad hoc fix: by adding epicycles, or small circles, atop his planetary orbits!

In the decades following Copernicus, others took interest in the Solar System. Tycho Brahe, for example, constructed the best naked eye astronomy setup in history, measuring the planets as precisely as human vision allows: to within one arc-minute (1/60th of a degree) during every night that planets were visible towards the end of the 1500s. His assistant, Johannes Kepler, attempted to make a glorious, beautiful model that fit the data precisely.

Given that there were six known planets (if you included the Earth as one of them), and exactly five (and only five) perfect polyhedral solids — the tetrahedron, cube, octahedron, icosahedron, and dodecahedron — Kepler constructed a system of nested spheres called the Mysterium Cosmographicum

.
Kepler’s original model of the Solar System, the Mysterium Cosmographicum, consisted of the 5 Platonic solids defining the relative radii of 6 spheres, with the planets orbiting around the circumferences of those spheres. As beautiful as this is, it couldn’t describe the Solar System as well as ellipses could, or even as well as Ptolemy’s model could.(Credit: Johannes Kepler, 1597)

In this model, each planet orbited along a circle defined by the circumference of one of the spheres. Outside of it, one of the five Platonic solids was circumscribed, with the sphere touching each of the faces in one spot. Outside of that solid, another sphere was circumscribed, with the sphere touching each of the solid’s vertices, with the circumference of that sphere defining the orbit of the next planet out. With six spheres, six planets, and five solids, Kepler made this model where “invisible spheres” held up the Solar System, accounting for the orbits of each of Mercury, Venus, Earth, Mars, Jupiter, and Saturn.

Kepler formulated this model in the 1590s, and Brahe boasted that only his observations could put such a model to the test. But no matter how Kepler did his calculations, not only did disagreements with observation remain, but Ptolemy’s geocentric model still made superior predictions.

In the face of this, what do you think Kepler did?Did he tweak his model, attempting to save it?
Did he distrust the critical observations, demanding new, superior ones?
Did he make additional postulates that could explain what was truly occurring, even if it was unseen, in the context of his model?

No. Kepler did none of these. Instead, he did something revolutionary: he put his own ideas and his own favored model aside, and looked at the data to see if there was a better explanation that could be derived from demanding that any model needed to agree with the full suite of observational data.
Kepler’s second law states that planets sweep out equal areas, using the Sun as one focus, in equal times, regardless of other parameters. The same (blue) area is swept out in a fixed time period. The green arrow is velocity. The purple arrow directed towards the Sun is the acceleration. Planets move in ellipses around the Sun (Kepler’s first law), sweep out equal areas in equal times (his second law), and have periods proportional to their semimajor axis raised to the 3/2 power (his 3rd law).

(Credit: Gonfer/Wikimedia Commons, using Mathematica)

If only we could all be so brave, so brilliant, and at the same time, so humble before the Universe itself! Kepler calculated that ellipses, not circles, would better fit the data that Brahe had so painstakingly acquired. Although it defied his intuition, his common sense, and even his personal preferences for how he felt the Universe ought to have behaved — indeed, he thought that the Mysterium Cosmographicum was a divine epiphany that had revealed God’s geometrical plan for the Universe to him — Kepler was successfully able to abandon his notion of “circles and spheres” and instead used what seemed to him to be an imperfect solution: ellipses.

It cannot be emphasized enough what an achievement this is for science. Yes, there are many reasons to be critical of Kepler. He continued to promote his Mysterium Cosmographicum even though it was clear ellipses fit the data better. He continued to mix astronomy with astrology, becoming the most famous astrologer of his time. And he continued the long tradition of apologetics: claiming that ancient texts meant the opposite of what they said in order to reconcile the acceptability of the new knowledge that had emerged.

But it was through this revolutionary action, of abandoning his model for a new one that he himself devised to explain the observations more successfully than ever before, that Kepler’s laws of motion became elevated to scientific canon.

Tycho Brahe conducted some of the best observations of Mars prior to the invention of the telescope, and Kepler’s work largely leveraged that data. Here, Brahe’s observations of Mars’s orbit, particularly during retrograde episodes, provided an exquisite confirmation of Kepler’s elliptical orbit theory.(Credit: Wayne Pafko)

Even today, more than four full centuries after Kepler, we all learn his three laws of planetary motion in schools.Planets move in ellipses around the Sun, with the Sun at one of the ellipse’s two focal points.
Planets sweep out equal areas, with the Sun at once focus, in equal amounts of time.
And planets orbit in time periods proportional to their semimajor axes (half of the longest-axis of the ellipse) to the 3/2 power.

These were the first calculations that advanced the science of astronomy beyond the stagnated realm of Ptolemy, and they paved the way for Newton’s theory of universal gravitation, which transformed these laws from simple descriptions of how motion occurred to one that was physically motivated. By the end of the 17th century, all of Kepler’s laws could be derived simply from the laws of Newtonian gravity.

But the greatest achievement of all was the day Kepler put his own idea of a Mysterium Cosmographicum — an idea that he was arguably more emotionally attached to than any other — in order to follow the data, wherever it led him. That brought him to elliptical orbits for the planets, which kicked off the revolution in our understanding the physical universe around us, i.e., the modern sciences of physics and astronomy, that continues to the present day. Like all scientific heroes, Kepler certainly had his faults, but the ability to admit when you’re wrong, to reject your insufficient ideas, and to follow the data wherever it leads are traits we should all aspire to. Not only in science, of course, but in all aspects of our lives.

AFTER ALL THEY ORIGINATED IN SPACE

Viruses may exist ‘elsewhere in the universe’, warns scientist

#PANSPERMIA

Prof Paul Davies suggests viruses may form vital part of ecosystems on other planets

A range of microbes and other microscopic agents may be needed to support life on other planets, including viruses. 

Photograph: Alamy Stock Photo


Nicola Davis Science correspondent
@NicolaKSDavis
Mon 6 Sep 2021 11.55 BST


The Covid pandemic has already turned life as we know it upside down – and no doubt prompted some people to want to leave the planet.

Now a leading scientist has warned that viruses may not only be found on Earth, but might occur – should life exist – elsewhere in the universe.

Prof Paul Davies, an astrobiologist, cosmologist and director of the Beyond Center for Fundamental Concepts in Science at Arizona State University, said that the idea of aliens ranges from microbial life to super advanced civilisations that might be signalling to us.

But Davies backed the idea that a wide range of microbes and other microscopic agents would probably be needed to support life as a whole, whatever form it takes. And it seems viruses – or something that performs a similar role – could be part of the equation.

“Viruses actually form part of the web of life,” said Davies. “I would expect that if you’ve got microbial life on another planet, you’re bound to have – if it’s going to be sustainable and sustained – the full complexity and robustness that will go with being able to exchange genetic information.”

Viruses, said Davies, can be thought of as mobile, genetic elements. Indeed, a number of studies have suggested genetic material from viruses has been incorporated into the genomes of humans and other animals by a process known as horizontal gene transfer.

“A friend of mine thinks most, but certainly a significant fraction, of the human genome is actually of viral origin,” said Davies, whose new book, What’s Eating the Universe?, was published last week.

According to Davies, while the importance of microbes to life is well known, the role of viruses is less widely appreciated. But he said if there is cellular life on other worlds, viruses or something similar, would probably exist to transfer genetic information between them.

What’s more, he said, it is unlikely alien life would be homogenous.

“I don’t think it’s a matter that you go to some other planet, and there will just be you one type of microbe and it’s perfectly happy. I think it’s got to be a whole ecosystem,” he added.

While the thought of extraterrestrial viruses may seem alarming, Davies suggests there is no need for humans to panic.

“The dangerous viruses are those that are very closely adapted to their hosts,” he said. “If there is a truly alien virus, then chances are it wouldn’t be remotely dangerous.”

Davies’ comments come after a study, published in late August, suggested that signs of life may be detected beyond our solar system within two to three years.

But the need to consider entire ecosystems does not only apply when considering alien life.

Davies – whose conversation is peppered with nods to former colleagues and associates from Stephen Hawking to Fred Hoyle, the great if unconventional former director of the Institute of Astronomy at Cambridge University – said it is also important should humans attempt to colonise another planet.

“Most people think about, well, we would need to have very large spacecraft, and then sort of recycle things for the very long journey, and then all the technology you’d need to take,” he said.

“Actually, the toughest part of this problem is what would be the microbiology that you’d have to take – it’s no good just taking a few pigs and potatoes and things like that and hoping when you get to the other end it’ll all be wonderful and self sustainable.”


Safe space: the cosmic importance of planetary quarantine – podcast

While Covid has left most of us with a dim view of viruses, Davies said they are not all bad. “In fact, mostly, they’re good,” he said.

Among their positive roles, viruses that infect bacteria – known as phages – can help keep bacterial populations in check, while viruses have also been linked to a host of other important processes, from helping plants survive in extremely hot soils to influencing biogeochemical cycles. And, as Davies notes, a significant fraction of the human genome may be remnants of ancient viruses.

“We hear about the microbiome inside us, and there’s a planetary microbiome,” said Davies. But, he argues there is also a human and planetaryvirome, with viruses playing a fundamental role in nature.

“I think without viruses, there may be no sustained life on planet Earth,” he said.

“Consciousness” –Existing Beyond Matter, Or in the Central Nervous System as an Afterthought of Nature?



Does human consciousness exist separate from matter, or is it embodied in the body –a critical player in anything that has to do with mind? “We are not thinking machines that feel; rather, we are feeling machines that think.” answers neuroscientist Antonio Damasio, who pioneered the field of embodied consciousness –the bodily origins of our sense of self. “We may smile and the dog may wag the tail, but in essence,” he says. “we have a set program and those programs are similar across individuals in the species. There is no such thing as a disembodied mind.”

Consciousness is considered by leading scientists as the central unsolved mystery of the 21st Century: “I have a much easier time imagining how we understand the Big Bang than I have imagining how we can understand consciousness,” says Edward Witten, theoretical physicist at the Institute for Advanced Study in Princeton, New Jersey who has been compared to Isaac Newton and Einstein about the phenomena that has been described as assuming the role spacetime did before Einstein invented his theory of relativity.

Some scientists have asked how can we be sure that the source of consciousness lies within our bodies at all? One popular, if mystical, idea, writes astrophysicist Paul Davies in The Demon in the Machine, “is that flashes of mathematical inspiration can occur by the mathematician’s mind somehow ‘breaking through’ into a Platonic realm of mathematical forms and relationships that not only lies beyond the brain but beyond space and time altogether.”

The English astronomer, Fred Hoyle, infamous for his rejection of the Big Bang theory, suggested an even more radical hypothesis: that quantum effects in the human brain leave open the possibility of a “superintelligence in the cosmic future using a subtle but well-known backwards-in-time property of quantum mechanics in order to steer scientific progress.”

Four billion years ago, writes Damasio, in The Strange Order of Things: Life, Feeling, and the Making of the Cultural Mind, “the first primitive organisms monitored changes in their bodily state – equivalent to hunger, thirst, pain and so on – and had feedback mechanisms to maintain equilibrium. The relic of those primitive mechanisms is our autonomic nervous system, which controls bodily functions such as heartbeat and digestion, and of which we are largely unconscious.

Then, about half a billion years ago, the central nervous system, featuring a brain, evolved an afterthought of nature,” says Damasio who a proposes three layered theory of consciousness based on a hierarchy of stages, with each stage building upon the last. The most basic representation of the organism is referred to as the Protoself, next is Core Consciousness, and finally, Extended Consciousness.

Damasio, who is an internationally recognized leader in neuroscience, was educated at the University of Lisbon and currently directs the University of Southern California Brain and Creativity Institute. The human brain, he argues, became the “anchor” of what had once been a more distributed mind. Changes in bodily state were projected onto the brain and experienced as emotions or drives – the emotion of fear, say, or the drive to eat. Subjectivity evolved later again, he argues. “It was imposed by the musculoskeletal system, which evolved as a physical framework for the central nervous system and, in so doing, also provided a stable frame of reference: the unified ‘I’ of conscious experience.”

Life was regulated at first without feelings of any sort; here was no mind and no consciousness. 

“There was,” Damasio writes, “a set of homeostatic mechanisms blindly making the choices that would turn out to be more conducive to survival. The arrival of nervous systems, capable of mapping and image making, opened the way for simple minds to enter the scene. During the Cambrian explosion, after numerous mutations, certain creatures with nervous systems would have generated not just images of the world around them but also an imagetic counterpart to the busy process of life regulation that was going on underneath. This would have been the ground for a corresponding mental state, the thematic content of which would have been valenced in tune with the condition of life, at that moment, in that body. The quality of the ongoing life state would have been felt.”

Enter Sarah Garfinkel, at the University of Sussex, UK, who joins Damasio in arguing that our thoughts, feelings and behaviors are shaped in part by the internal signals that arise from our body. But, she reports in New Scientist: “it goes beyond that. It is leading her and others to a surprising conclusion: that the body helps to generate our sense of self and is a key part of consciousness. This idea has practical implications in assessing people who show little sign of consciousness. It may also force us to reconsider where we draw the line between life and death, and provide a new insight into how consciousness evolved.”

Since 2000, concludes Damasio, “I have been defending the idea that the body is a critical player in anything that has to do with mind.”

The Daily Galaxy, Max Goldberg, via New Scientist and Antonio R. Damasio, Descartes Error and the Strange Order of Things: Life, Feeling, and the Making of the Cultural Mind and Paul Davies, The Demon in the Machine –All Kindle editions

Image credit: Shutterstock License

SPACE/COSMOS

In Photos: See NASA Juno’s Jaw-Dropping New Images Of Jupiter

Jamie Carter
Senior Contributor
Jamie Carter is an award-winning reporter who covers the night sky.

Nov 5, 2024





Jupiter, as seen during NASA Juno's 66th perijove on Oct. 23, 2024. NASA / JPL / SwRI / MSSS / Gerald Eichstädt / Thomas Thomopoulos © cc by

NASA’s Juno spacecraft has returned new images of Jupiter after its 66th close flyby as it enters the final year of its mission. The $1 billion spacecraft completed its latest close flyby on Oct. 23, 2024, dipping close to its poles, the first mission to do so.



Juno, which has been in orbit around Jupiter since July 2016, has sent back thousands of unprecedented high-resolution images of the planet’s atmosphere and several of its moons. It’s latest tranche are equally as spell-binding.



Jupiter, as seen during NASA Juno's 66th perijove on Oct. 23, 2024. NASA / SwRI / MSSS / Jackie Branc © cc by


During this latest flyby, the spacecraft passed close to Amalthea, Jupiter's fifth-largest moon, characterized by its potato-like shape and small size. With a radius of 52 miles (84 kilometers), it is significantly smaller than Earth's moon and orbits closer to Jupiter than Io.



A collage of images of Jupiter, as seen by NASA Juno during its 66th perijove on Oct. 23, 2024. NASA/JPL-Caltech/SwRI/MSSS/Brian Swift © cc by
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Its two-megapixel camera, JunoCam, continues to capture images that reveal intricate details of Jupiter’s weather patterns, including its colorful bands and storms. Besides JunoCam, the spacecraft has a magnetometer, a gravity science system and a microwave radiometer.






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Jupiter, as seen during NASA Juno's 66th perijove on Oct. 23, 2024. NASA / SwRI / MSSS / Jackie Branc © cc by

Remarkably, the Juno mission has no dedicated team of image-processing scientists. Instead, citizen scientists download the raw data — which JunoCam captures as it spins — who painstakingly process them and upload them to a dedicated mission website, many of them in creative versions.


Jupiter, as seen during NASA Juno's 66th perijove on Oct. 23, 2024. NASA / JPL / SwRI / MSSS / Gerald Eichstädt / Thomas Thomopoulos © cc by

There are now two missions on their way to the gas giant planet to replace Juno. Jupiter’s moon Callisto will be imaged 21 times during close flybys by the European Space Agency's JUICE spacecraft, which launched last year and will reach the Jovian System in 2031.


Jupiter, as seen during NASA Juno's 66th perijove on Oct. 23, 2024. NASA / SwRI / MSSS / Jackie Branc © cc by

JUICE will also photograph Europa before eventually going into orbit around Ganymede for 18 months. NASA’s Europa Clipper, launched earlier this month, will reach Jupiter in 2030 to tour Jupiter’s moons, focusing on Europa.

Juno’s next close flyby of Jupiter, perijove 66, will occur on Nov. 25, 2024. The Juno mission is scheduled to end on Sept. 15, 2025, when Juno will perform a “death dive” into the gas giant during its 76th perijove to be destroyed. This will ensure it doesn't crash into one of the moons of Jupiter that could potentially host life, specifically Europa.

Wishing you clear skies and wide eyes.

Follow me on Twitter or LinkedIn. 

Check out my website or some of my other work here.

Jamie Carter
Jamie Carter is an award-winning reporter and experienced stargazer who covers the night sky, astro-tourism, the northern lights and space exploration..

Nearly three years since launch, Webb is a hit among astronomers

Demand for observing time on Webb outpaces supply by a factor of nine.

Stephen Clark – Nov 6, 2024 

ARS TECHNICA


Astronomers combined images from two of Webb's infrared science instruments to create this view of Crab Nebula, the remnants of a violent supernova explosion in 1054. Credit: NASA, ESA, CSA, STScI, T. Temim (Princeton University)

From its halo-like orbit nearly a million miles from Earth, the James Webb Space Telescope is seeing farther than human eyes have ever seen.

In May, astronomers announced that Webb detected the most distant galaxy found so far, a fuzzy blob of red light that we see as it existed just 290 million years after the Big Bang. Light from this galaxy, several hundreds of millions of times the mass of the Sun, traveled more than 13 billion years until photons fell onto Webb's gold-coated mirror.

A few months later, in July, scientists released an image Webb captured of a planet circling a star slightly cooler than the Sun nearly 12 light-years from Earth. The alien world is several times the mass of Jupiter and the closest exoplanet to ever be directly imaged. One of Webb's science instruments has a coronagraph to blot out bright starlight, allowing the telescope to resolve the faint signature of a nearby planet and use spectroscopy to measure its chemical composition.

These are just a taste of the discoveries made by the $10 billion Webb telescope since it began science observations in 2022. Judging by astronomers' interest in using Webb, there are many more to come.

Breaking records

The Space Telescope Science Institute, which operates Webb on behalf of NASA and its international partners, said last week that it received 2,377 unique proposals from science teams seeking observing time on the observatory. The institute released a call for proposals earlier this year for the so-called "Cycle 4" series of observations with Webb.

This volume of proposals represents around 78,000 hours of observing time with Webb, nine times more than the telescope's available capacity for scientific observations in this cycle. The previous observing cycle had a similar "oversubscription rate" but had less overall observing time available to the science community.



This composite image of Arp 107, created with data from two of the James Webb Space Telescope’s infrared instruments, reveals a wealth of information about the star formation taking place in these two galaxies and how they collided hundreds of million years ago. Credit: NASA, ESA, CSA, STScI

More than 600 scientists will review the proposals and select the most promising ones for time on Webb. The largest share of proposals would involve observing "high-redshift" galaxies among the first generation of galaxies that formed after the Big Bang. Galaxies this old and distant have their light stretched to longer wavelengths due to the expansion of the Universe. Research involving exoplanet atmospheres and stars and stellar populations were the second- and third-most popular science categories in this cycle.

Webb is a joint project of NASA, the European Space Agency, and the Canadian Space Agency. The observatory's 21.3-foot (6.5-meter) primary mirror and four infrared instruments, tuned to detect faint thermal energy coming from the cold blackness of space, make it a particularly useful general-purpose research platform. In this cycle, astronomers asked for time on Webb to look at targets within the Solar System, exoplanets in our stellar neighborhood, gas and dust suspended in the space between the stars, supermassive black holes, and nearby galaxies.

This is a remarkable range of scientific targets. Only the Hubble Space Telescope can match the breadth of Webb's scientific targets, but Webb's larger mirror allows it to observe objects 100 times fainter than Hubble can see.

This image of the gas-giant exoplanet Epsilon Indi Ab was taken with the coronagraph on the James Webb Space Telescope’s Mid-Infrared Instrument A star symbol marks the location of the host star Epsilon Indi A, whose light has been blocked by the coronagraph. Credit: ESA/Webb, NASA, CSA, STScI, E. Matthews (Max Planck Institute for Astronomy)

In less than two-and-a-half years of science operations, Webb has only teased astronomers of its potential productivity. There is a high probability that Webb will see galaxies even older and more distant than the faint red beacon announced in May. There are thousands more known exoplanets for Webb to study, worlds of all sizes in our own Solar System, and unspeakable grandeur Webb will assuredly reveal in the years ahead.

It seems astronomers have no shortage of ideas about where to look. Maybe one day, new super heavy-lift rockets or advancements in in-space assembly will make it possible to deploy space telescopes even more sensitive than Webb. Until then, we can be thankful that Webb is performing well and has a good shot of far outliving its original five-year design life. Let's continue enjoying the show.


Stephen Clark Space Reporter
Stephen Clark is a space reporter at Ars Technica, covering private space companies and the world’s space agencies. Stephen writes about the nexus of technology, science, policy, and business on and off the planet.

It all started with a Big Bang – the quest to unravel mystery behind birth of the universe

The Conversation
November 6, 2024 

NASA's Goddard Space Flight Center/CI Lab

How did everything begin? It’s a question that humans have pondered for thousands of years. Over the last century or so, science has homed in on an answer: the Big Bang.

This describes how the Universe was born in a cataclysmic explosion almost 14 billion years ago. In a tiny fraction of a second, the observable universe grew by the equivalent of a bacterium expanding to the size of the Milky Way. The early universe was extraordinarily hot and extremely dense. But how do we know this happened?

Let’s look first at the evidence. In 1929, the American astronomer Edwin Hubble discovered that distant galaxies are moving away from each other, leading to the realisation that the universe is expanding. If we were to wind the clock back to the birth of the cosmos, the expansion would reverse and the galaxies would fall on top of each other 14 billion years ago. This age agrees nicely with the ages of the oldest astronomical objects we observe.

The idea was initially met with scepticism – and it was actually a sceptic, the English astronomer Fred Hoyle, who coined the name. Hoyle sarcastically dismissed the hypothesis as a “Big Bang” during an interview with BBC radio on March 28 1949.

This is article is part of our series Cosmology in crisis? which uncovers the greatest problems facing cosmologists today – and discusses the implications of solving them.

Then, in 1964, Arno Penzias and Robert Wilson detected a particular type of radiation that fills all of space. This became known as the cosmic microwave background (CMB) radiation. It is a kind of afterglow of the Big Bang explosion, released when the cosmos was a mere 380,000 years old.




NASA

The CMB provides a window into the hot, dense conditions at the beginning of the universe. Penzias and Wilson were awarded the 1978 Nobel Prize in Physics for their discovery.

More recently, experiments at particle accelerators like the Large Hadron Collider (LHC) have shed light on conditions even closer to the time of the Big Bang. Our understanding of physics at these high energies suggests that, in the very first moments after the Big Bang, the four fundamental forces of physics that exist today were initially combined in a single force.

The present day four forces are gravity, electromagnetism, the strong nuclear force and the weak nuclear force. As the universe expanded and cooled down, a series of dramatic changes, called phase transitions (like the boiling or freezing of water), separated these forces.

Experiments at particle accelerators suggest that a few billionths of a second after the Big Bang, the latest of these phase transitions took place. This was the breakdown of electroweak unification, when electromagnetism and the weak nuclear force ceased to be combined. This is when all the matter in the Universe assumed its mass.




Edwin Hubble discovered that galaxies were moving away from one another. NASA, ESA, and The Hubble Heritage Team (STScI/AURA)-ESA/Hubble Collaboration

Moving on further in time, the universe is filled with a strange substance called quark-gluon plasma. As the name suggests, this “primordial soup” was made up of quarks and gluons. These are sub-atomic particles that are responsible for the strong nuclear force. Quark-gluon plasma was artificially generated in 2010 at the Brookhaven National Laboratory and in 2015 at the LHC.


Quarks and gluons have a strong attraction for one other and today are bound together as protons and neutrons, which in turn are the building blocks of atoms. However, in the hot and dense conditions of the early universe, they existed independently.

The quark-gluon plasma didn’t last long. Just a few millionths of a second after the Big Bang, as the universe expanded and cooled, quarks and gluons clumped together as protons and neutrons, the situation that persists today. This event is called quark confinement.


The early universe was extremely hot and dense, much like the centre of the Sun. NASA/SDO

As the universe expanded and cooled still further, there were fewer high energy photons (particles of light) in the universe than there had previously been. This is a trigger for the process called Big Bang nucleosynthesis (BBN). This is when the first atomic nuclei – the dense lumps of matter made of protons and neutrons and found at the centres of atoms – formed through nuclear fusion reactions, like those that power the Sun.

Back when there were more high energy photons in the universe, any atomic nuclei that formed would have been quickly destroyed by them (a process called photodisintegration). BBN ceased just a few minutes after the Big Bang, but its consequences are observable today.


Observations by astronomers have provided us with evidence for the primordial abundances of elements produced in these fusion reactions. The results closely agree with the theory of BBN. If we continued on, over nearly 14 billion years of time, we would reach the situation that exists today. But how close can we get to understanding what was happening near the moment of the Big Bang itself?

Scientists have no direct evidence for what came before the breakdown of electroweak unification (when electromagnetism and the weak nuclear force ceased to be combined). At such high energies and early times, we can only stare at the mystery of the Big Bang. So what does theory suggest?

When we go backwards in time through the history of the cosmos, the distances and volumes shrink, while the average energy density grows. At the Big Bang, distances and volumes drop to zero, all parts of the universe fall on top of each other and the energy density of the universe becomes infinite. Our mathematical equations, which describe the evolution of space and the expansion of the cosmos, become infested by zeros and infinities and stop making sense.

We call this a singularity. Albert Einstein’s theory of general relativity describes how spacetime is shaped. Spacetime is a way of describing the three-dimensional geometry of the universe, blended with time. A curvature in spacetime gives rise to gravity.


But mathematics suggests there are places in the universe where the curvature of spacetime becomes unlimited. These locations are known as singularities. One such example can be found at the centre of a black hole. At these places, the theory of general relativity breaks down.


The universe cooled as it continued to expand. NASA, ESA, CSA, STScI, J. Diego (Instituto de Física de Cantabria, Spain), J. D’Silva (U. Western Australia), A. Koekemoer (STScI), J. Summers & R. Windhorst (ASU), and H. Yan (U. Missouri).


From 1965 to 1966, the British theoretical physicists Stephen Hawking and Roger Penrose presented a number of mathematical theorems demonstrating that the spacetime of an expanding universe must end at a singularity in the past: the Big Bang singularity.

Penrose received the Nobel Prize in 2020. Hawking passed away in 2018 and Nobel Prizes are not awarded posthumously. Space and time appear at the Big Bang singularity, so questions of what happens “before” the Big Bang are not well defined. As far as science can tell, there is no before; the Big Bang is the onset of time.

However, nature is not accurately described by general relativity alone, even though the latter has been around for more than 100 years and has not been disproven. General relativity cannot describe atoms, nuclear fusion or radioactivity. These phenomena are instead addressed by quantum theory.


Theories from “classical” physics, such as relativity, are deterministic. This means that certain initial conditions have a definite outcome and are therefore absolutely predictive. Quantum theory, on the other hand, is probabilistic. This means that certain initial conditions in the universe can have multiple outcomes.

Quantum theory is somewhat predictive, but in a probabilistic way. Outcomes are assigned a probability of existing. If the mathematical distribution of probabilities is sharply peaked at a certain outcome, then the situation is well described by a “classical” theory such as general relativity. But not all systems are like this. In some systems, for example atoms, the probability distribution is spread out and a classical description does not apply.

What about gravity? In the vast majority of cases, gravity is well described by classical physics. Classical spacetime is smooth. However, when curvature becomes extreme, near a singularity, then the quantum nature of gravity cannot be ignored. Here, spacetime is no longer smooth, but gnarly, similar to a carpet which looks smooth from afar but up-close is full of fibres and threads.

Thus, near the Big Bang singularity, the structure of spacetime ceases to be smooth. Mathematical theorems suggest that spacetime becomes overwhelmed by “gnarly” features: hooks, loops and bubbles. This rapidly fluctuating situation is called spacetime foam.

In spacetime foam, causality does not apply, because there are closed loops in spacetime where the future of an event is also its past (so its outcome can also be its cause). The probabilistic nature of quantum theory suggests that, when the probability distribution is evenly spread out, all outcomes are equally possible and the comfortable notion of causality we associate with a classical understanding of physics is lost.

Therefore, if we go back in time, just before we encounter the Big Bang singularity, we find ourselves entering an epoch where the quantum effects of gravity are dominant and causality does not apply. This is called the Planck epoch.

Time ceases to be linear, going from the past to the future, and instead becomes wrapped, chaotic and random. This means the question “why did the Big Bang occur?” has no meaning, because outside causality, events do not need a cause to take place.

In order to understand how physics works at a singularity like the Big Bang, we need a theory for how gravity behaves according to quantum theory. Unfortunately, we do not have one. There are a number of efforts on this front like loop quantum gravity and string theory, with its various incarnations.


Near the Big Bang singularity, spacetime takes on a structure similar to foam. NASA/CXC/M.Weiss

However, these efforts are at best incomplete, because the problem is notoriously difficult. This means that spacetime foam has a totemic, powerful mystique, much like the ancient Chaos of Hesiod which the Greeks believed existed in the beginning.

So how did our expanding and largely classical universe ever escape from spacetime foam? This brings us to cosmic inflation. The latter is defined as a period of accelerated expansion in the early universe. It was first introduced by the Russian theoretical physicist Alexei Starobinsky in 1980 and in parallel, that same year, by the American physicist Alan Guth, who coined the name.

Inflation makes the universe large and uniform, according to observations. It also forces the universe to be spatially flat, which is an otherwise unstable situation, but which has also been confirmed by observations. Moreover, inflation provides a natural mechanism to generate the primordial irregularities in the density of the universe that are essential for structures such as galaxies and galaxy clusters to form.
Theory vindicated

Precision observations of the cosmic microwave background in recent decades have spectacularly confirmed the predictions of inflation. We also know that the universe can indeed undergo accelerated expansion, because in the last few billion years it started doing it again.

What does this have to do with spacetime foam? Well, it turns out that, if the conditions for inflation arise (by chance) in a patch of fluctuating spacetime, as can occur with spacetime foam, then this region inflates and starts conforming to classical physics.

According to an idea first proposed by the Russian-American physicist Andrei Linde, inflation is a natural – and perhaps inevitable – consequence of chaotic initial conditions in the early universe.

The point is that our classical universe could have emerged from chaotic conditions, like those in spacetime foam, by experiencing an initial boost of inflation. This would have set off the expansion of the universe. In fact, the observations by astronomers of the CMB suggest that the initial boost is explosive, since the expansion is exponential during inflation.

In March 20 of 2014, Alan Guth explained it succinctly: “I usually describe inflation as a theory of the ‘bang’ of the Big Bang: It describes the propulsion mechanism that we call the Big Bang.”

So, there you have it. The 14 billion year story of our universe begins with a cataclysmic explosion everywhere in space, which we call the Big Bang. That much is beyond reasonable doubt. This explosion is really a period of explosive expansion, which we call cosmic inflation. What happens before inflation, though? Is it a spacetime singularity, is it spacetime foam? The answer is largely unknown.

In fact, it might even be unknowable, because there is a mathematical theorem which forbids us from accessing information about the onset of inflation, much like the one that prevents us from knowing about the interiors of black holes. So, from our point of view, cosmic inflation is the Big Bang, the explosion that started it all.

Konstantinos Dimopoulos, Professor in Particle Cosmology, Lancaster University

This article is republished from The Conversation under a Creative Commons license. Read the original article.

NASA runs first engine tests on supersonic X-59 research aircraft


NASA's X-59 quiet supersonic research aircraft, pictured on Dec. 12, sits on the apron outside Lockheed Martin's Skunk Works facility in Palmdale, Calif. 

NASA File Photo by Steve Freeman/UPI

Nov. 6 (UPI) -- NASA engineers fired the engines on the X-59 research aircraft in advance of planned test flights to determine if the aircraft can reduce sonic booms and make supersonic flight over land quieter.

Engineers began test-firing the experimental aircraft's jet engine at the Lockheed Martin Skunk Works facility in Palmdale, Calif., on Oct. 30 to see if the aircraft's systems work properly while the engine is in use before its inaugural test flight sometime in the near future.

The single-engine aircraft that Lockheed Martin designed and built is the research aircraft for NASA's Quiet SuperSonic Technology mission that NASA officials refer to as the Quesst mission. NASA first unveiled the experimental aircraft on Jan. 12.

The mission's intent is to make supersonic flight quieter and safer over residential areas.

The experimental aircraft has a very long needle-like nose with no windshield due to the inability of pilot to see what is below the nose.

The X-59's nose accounts for 38 feet of its 99.7 foot length, and pilots will use an External Vision System that uses forward-facing cameras linked to cockpit displays to enable its lone pilot to safely fly the aircraft

The aircraft's delta-shaped wings give it a wingspan of 29.5 feet, and it has a maximum takeoff weight of 32,300 pounds.

General Electric Aviation designed and built the engine that is expected to enable the X-59 to fly at up to 925 mph, which is equal to Mach 1.4, with a maximum altitude of 55,000 feet.

Instead of causing a loud sonic boom while flying over land, the aircraft is supposed to produce more of a soft thud.

NASA pilots will fly the aircraft over between four and six residential areas in 2026 and record data on how the public experiences the sonic disturbances caused while the aircraft exceeds the speed of sound.

NASA will ask residents of respective flyover communities their impression of the X-59 and the amount of noise it produces.

Mighty radio bursts linked to massive galaxies

Results from Caltech's Deep Synoptic Array-110 provide new clues about how magnetars form

California Institute of Technology

 

image: 

This photo montage shows the antennas of the Deep Synoptic Array-110, which are used to discover and pinpoint the locations of fast radio bursts (FRBs). Above the antennas are images of some of the FRB host galaxies as they appear on the sky. The galaxies are remarkably large, challenging models that describe FRB sources.

view more 

Credit: Annie Mejia/Caltech

 

Since their discovery in 2007, fast radio bursts—extremely energetic pulses of radio-frequency light—have lit up the sky repeatedly, leading astronomers on a chase to uncover their origins. Currently, confirmed fast radio bursts, or FRBs, number in the hundreds, and scientists have assembled mounting evidence for what triggers them: highly magnetized neutron stars known as magnetars (neutron stars are a type of dead star). One key piece of evidence came when a magnetar erupted in our own galaxy and several observatories, including Caltech's STARE2 (Survey for Transient Astronomical Radio Emission 2) project, caught the actionin real time. 

 

Now, reporting in the journal Nature, Caltech-led researchers have uncovered where FRBs are more likely to occur in the universe—massive star-forming galaxies rather than low-mass ones. This finding has, in turn, led to new ideas about how magnetars themselves form. Specifically, the work suggests that these exotic dead stars, whose magnetic fields are 100 trillion times stronger than Earth's, often form when two stars merge and later blow up in a supernova. Previously, it was unclear whether magnetars form in this way, from the explosion of two merged stars, or whether they might form when a single star explodes.

 

"The immense power output of magnetars makes them some of the most fascinating and extreme objects in the universe," says Kritti Sharma, lead author of the new study and a graduate student working with Vikram Ravi, an assistant professor of astronomy at Caltech. "Very little is known about what causes the formation of magnetars upon the death of massive stars. Our work helps to answer this question."

 

The project began with a search for FRBs using the Deep Synoptic Array-110 (DSA-110), a Caltech project funded by the National Science Foundation and based at the Owens Valley Radio Observatory near Bishop, California. To date, the sprawling radio array has detected and localized 70 FRBs to their specific galaxy of origin (only 23 other FRBs have been localized by other telescopes). In the current study, the researchers analyzed 30 of these localized FRBs. 

 

"DSA-110 has more than doubled the number of FRBs with known host galaxies," says Ravi. "This is what we built the array to do."

Although FRBs are known to occur in galaxies that are actively forming stars, the team, to its surprise, found that the FRBs tend to occur more often in massive star-forming galaxies than low-mass star-forming galaxies. This alone was interesting because the astronomers had previously thought that FRBs were going off in all types of active galaxies. 

 

With this new information, the team started to ponder what the results revealed about FRBs. Massive galaxies tend to be metal-rich because the metals in our universe—elements that are manufactured by stars—take time to build up over the course of cosmic history. The fact that FRBs are more common in these metal-rich galaxies implies that the source of FRBs, magnetars, are also more common to these types of galaxies. 

 

Stars that are rich in metals—which in astronomical terms means elements heavier than hydrogen and helium—tend to grow larger than other stars. "Over time, as galaxies grow, successive generations of stars enrich galaxies with metals as they evolve and die," Ravi says.

 

What is more, massive stars that explode in supernovae and can become magnetars are more commonly found in pairs. In fact, 84 percent of massive stars are binaries. So, when one massive star in a binary is puffed up due to extra metal content, its excess material gets yanked over to its partner star, which facilitates the ultimate merger of the two stars. These merged stars would have a greater combined magnetic field than that of a single star. 

 

"A star with more metal content puffs up, drives mass transfer, culminating in a merger, thus forming an even more massive star with a total magnetic field greater than what the individual star would have had," Sharma explains. 

 

In summary, since FRBs are preferentially observed in massive and metal-rich star-forming galaxies, then magnetars (which are thought to trigger FRBs) are probably also forming in metal-rich environments conducive to the merging of two stars. The results therefore hint that magnetars across the universe originate from the remnants of stellar mergers.

 

In the future, the team hopes to hunt down more FRBs and their places of origin using DSA-110, and eventually the DSA-2000, an even bigger radio array planned to be built in the Nevada desert and completed in 2028.

 

"This result is a milestone for the whole DSA team. A lot of the authors on this paper helped build the DSA-110," Ravi says. "And the fact that the DSA-110 is so good at localizing FRBs bodes well for the success of DSA-2000."

 

The paper is titled "Preferential Occurrence of Fast Radio Bursts in Massive Star-Forming Galaxies." Other Caltech authors include Liam Connor, Casey Law, Stella Koch Ocker, Myles Sherman, Nikita Kosogorov, Jakob Faber, Gregg Hallinan, Charlie Harnach, Greg Hellbourg, Rick Hobbs, David Hodge, Mark Hodges, James Lamb, Paul Rasmussen, Jean Somalwar, Sander Weinreb, David Woody, Shreya Anand, Kaustav Kashyap Das, Yu-Jing Qin, Sam Rose, Dillon Z. Dong, Jessie Miller, and Yuhan Yao. Joel Leja from The Pennsylvania State University is also an author.

 

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Journal

Nature

Asteroid grains shed light on the outer solar system’s origins

A weak magnetic field likely pulled matter inward to form the outer planetary bodies, from Jupiter to Neptune.

Massachusetts Institute of Technology

 

image: 

MIT scientists analyzed one of several particles (shown in black) from the asteroid Ryugu, and found evidence that a weak magnetic field likely existed in the outer solar system where the asteroid is thought to have first formed, more than 4.6 billion years ago.

 

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Credit: Elias Mansbach

Tiny grains from a distant asteroid are revealing clues to the magnetic forces that shaped the far reaches of the solar system over 4.6 billion years ago. 

Scientists at MIT and elsewhere have analyzed particles of the asteroid Ryugu, which were collected by the Japanese Aerospace Exploration Agency’s (JAXA) Hayabusa2 mission and brought back to Earth in 2020. Scientists believe Ryugu formed on the outskirts of the early solar system before migrating in toward the asteroid belt, eventually settling into an orbit between Earth and Mars. 

The team analyzed Ryugu’s particles for signs of any ancient magnetic field that might have been present when the asteroid first took shape. Their results suggest that if there was a magnetic field, it would have been very weak. At most, such a field would have been about 15 microtesla. (The Earth’s own magnetic field today is around 50 microtesla.) 

Even so, the scientists estimate that such a low-grade field intensity would have been enough to pull together primordial gas and dust to form the outer solar system’s asteroids and potentially play a role in giant planet formation, from Jupiter to Neptune.

The team’s results, which are published today in the journal AGU Advances, show for the first time that the distal solar system likely harbored a weak magnetic field. Scientists have known that a magnetic field shaped the inner solar system, where Earth and the terrestrial planets were formed. But it was unclear whether such a magnetic influence extended into more remote regions, until now. 

“We’re showing that, everywhere we look now, there was some sort of magnetic field that was responsible for bringing mass to where the sun and planets were forming,” says study author Benjamin Weiss, the Robert R. Shrock Professor of Earth and Planetary Sciences at MIT. “That now applies to the outer solar system planets.”

The study’s lead author is Elias Mansbach PhD ’24, who is now a postdoc at Cambridge University. MIT co-authors include Eduardo Lima, Saverio Cambioni, and Jodie Ream, along with Michael Sowell and Joseph Kirschvink of Caltech, Roger Fu of Harvard University, Xue-Ning Bai of Tsinghua University, Chisato Anai and Atsuko Kobayashi of the Kochi Advanced Marine Core Research Institute, and Hironori Hidaka of Tokyo Institute of Technology. 

A far-off field

Around 4.6 billion years ago, the solar system formed from a dense cloud of interstellar gas and dust, which collapsed into a swirling disk of matter. Most of this material gravitated toward the center of the disk to form the sun. The remaining bits formed a solar nebula of swirling, ionized gas. Scientists suspect that interactions between the newly formed sun and the ionized disk generated a magnetic field that threaded through the nebula, helping to drive accretion and pull matter inward to form the planets, asteroids, and moons. 

“This nebular field disappeared around 3 to 4 million years after the solar system’s formation, and we are fascinated with how it played a role in early planetary formation,” Mansbach says.

Scientists previously determined that a magnetic field was present throughout the inner solar system — a region that spanned from the sun to about 7 astronomical units (AU), out to where Jupiter is today. (One AU is the distance between the sun and the Earth.) The intensity of this inner nebular field was somewhere between 50 to 200 microtesla, and it likely influenced the formation of the inner terrestrial planets. Such estimates of the early magnetic field are based on meteorites that landed on Earth and are thought to have originated in the inner nebula. 

“But how far this magnetic field extended, and what role it played in more distal regions, is still uncertain because there haven’t been many samples that could tell us about the outer solar system,” Mansbach says. 

Rewinding the tape

The team got an opportunity to analyze samples from the outer solar system with Ryugu, an asteroid that is thought to have formed in the early outer solar system, beyond 7 AU, and was eventually brought into orbit near the Earth. In December 2020, JAXA’s Hayabusa 2 mission returned samples of the asteroid to Earth, giving scientists a first look at a potential relic of the early distal solar system. 

The researchers acquired several grains of the returned samples, each about a millimeter in size. They placed the particles in a magnetometer — an instrument in Weiss’ lab that measures the strength and direction of a sample’s magnetization. They then applied an alternating magnetic field to progressively demagnetize each sample.

“Like a tape recorder, we are slowly rewinding the sample’s magnetic record,” Mansbach explains. “We then look for consistent trends that tell us if it formed in a magnetic field.”

They determined that the samples held no clear sign of a preserved magnetic field. This suggests that either there was no nebular field present in the outer solar system where the asteroid first formed, or the field was so weak that it was not recorded in the asteroid’s grains. If the latter is the case, the team estimates such a weak field would have been no more than 15 microtesla in intensity. 

The researchers also reexamined data from previously studied meteorites. They specifically looked at “ungrouped carbonaceous chondrites” — meteorites that have properties that are characteristic of having formed in the distal solar system. Scientists had estimated the samples were not old enough to have formed before the solar nebula disappeared. Any magnetic field record the samples contain, then, would not reflect the nebular field. But Mansbach and his colleagues decided to take a closer look. 

“We reanalyzed the ages of these samples and found they are closer to the start of the solar system than previously thought,” Mansbach says. “We think these samples formed in this distal, outer region. And one of these samples does actually have a positive field detection of about 5 microtesla, which is consistent with an upper limit of 15 microtesla.”

This updated sample, combined with the new Ryugu particles, suggest that the outer solar system, beyond 7 AU, hosted a very weak magnetic field, that was nevertheless strong enough to pull matter in from the outskirts to eventually form the outer planetary bodies, from Jupiter to Neptune. 

“When you’re further from the sun, a weak magnetic field goes a long way,” Weiss notes. “It was predicted that it doesn’t need to be that strong out there, and that’s what we’re seeing.”

The team plans to look for more evidence of distal nebular fields with samples from another far-off asteroid, Bennu, which were delivered to Earth in September 2023 by NASA’s OSIRIS-REx spacecraft. 

“Bennu looks a lot like Ryugu, and we’re eagerly awaiting first results from those samples,” Mansbach says. 

This research was supported, in part, by NASA.

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Written by Jennifer Chu, MIT News

Paper: “Evidence for Magnetically-Driven Accretion in the Distal Solar System”

https://agupubs.onlinelibrary.wiley.com/doi/10.1029/2024AV001396

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Journal

AGU Advances

DOI

10.1029/2024AV001396 

Article Title

Evidence for Magnetically-Driven Accretion in the Distal Solar System”

Interstellar methane as progenitor of amino acids?

Gamma radiation converts methane into glycine and other complex molecules

Wiley

Gamma radiation can convert methane into a wide variety of products at room temperature, including hydrocarbons, oxygen-containing molecules, and amino acids, reports a research team in the journal Angewandte Chemie. This type of reaction probably plays an important role in the formation of complex organic molecules in the universe—and possibly in the origin of life. They also open up new strategies for the industrial conversion of methane into high value-added products under mild conditions.

With these research results, the team led by Weixin Huang at the University of Science and Technology of China (Hefei) has contributed to our fundamental understanding of the early development of molecules in the universe. “Gamma rays, high-energy photons commonly existing in cosmic rays and unstable isotope decay, provide external energy to drive chemical reactions of simple molecules in the icy mantles of interstellar dust and ice grains,” states Huang. “This can result in more complex organic molecules, presumably starting from methane (CH4), which is widely present throughout the interstellar medium.”

Although higher pressures and temperatures reign on Earth and on planets in the so-called habitable zone, most studies of cosmic processes are only simulated under vacuum and at extremely low temperatures. In contrast, the Chinese team studied the reactions of methane at room temperature in the gas and aqueous phases under irradiation with a cobalt-60 emitter.

The composition of the products varies depending on the starting materials. Pure methane reacts—with very low yield—to give ethane, propane and hydrogen. The addition of oxygen increases the conversion, resulting mainly in CO2 as well as CO, ethylene, and water. In the presence of water, aqueous methane reacts to give acetone and tertiary butyl alcohol; in the gas phase, it gives ethane and propane. When both water and oxygen are added, the reactions are strongly accelerated. In the aqueous phase, formaldehyde, acetic acid, and acetone are formed. If ammonia is also added, acetic acid forms glycine, an amino acid also found in space. “Under gamma radiation, glycine can be made from methane, oxygen, water, and ammonia, molecules that are found in large amounts in space,” says Huang. The team developed a reaction scheme that explains the routes by which the individual products are formed. Oxygen (∙O2−) and ∙OH radicals play an important role in this. The rates of these radical reaction mechanisms are not temperature-dependent and could thus also take place in space.

In addition, the team was able to demonstrate that various solid particles that are components of interstellar dust—silicon dioxide, iron oxide, magnesium silicate, and graphene oxide—change the product selectivity in different ways. The varied composition of interstellar dust may thus have contributed to the observed uneven distribution of molecules in space.

Silicon dioxide leads to a more selective conversion of methane to acetic acid. Says Huang, “because gamma radiation is an easily available, safe, and sustainable source of energy, this could be a new approach for using methane as a carbon source that can be efficiently converted into value-added products under mild conditions—a long-standing challenge for industrial synthetic chemistry.”

(3427 characters)

About the Author

Dr Weixin Huang is the Changjiang Professor in Physical Chemistry at USTC appointed by the Ministry of Education of China. His research focuses on surface chemistry and catalysis of solid catalysts with well-defined structures.

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Journal

Angewandte Chemie International Edition

DOI

10.1002/anie.202413296 

Method of Research

Experimental study

Subject of Research

Not applicable

Article Title

γ-Ray Driven Aqueous-Phase Methane Conversions into Complex Molecules up to Glycine