March science readings.
https://arxiv.org/pdf/2202.10719.pdf
What's this one about? Well, the author (single author - always an amber flag ; Rajagopal Anand) thinks that the initiation and continuation of plate tectonics on Earth was important in several ways for the origin and development of life. Which itself isn't a bad idea. Earth is the only planet with (ahemm) "Earth Like" plate tectonics in the solar system, though there are some hints that something similar operated on Mars way back in the Hesperian or Noachian (3-4 Gyr ago). And people are still trying to figure out what is (or was, or does occasionally) going on on Venus. Our author sees that the rotation period of the Earth on it's axis and the time for the Earth to travel 1° around in it's orbit are about the same, and shows that isn't true for any other "rocky" planet in the Solar System. Which is true, and conuld conceivably be important. Or it could be numberology - what is special about 1°, compared to, for example, 1/32 radian?
It's an interesting idea, but whether it's an important idea ... I'm a lot less than convinced.
Dynamical origin of the Dwarf Planet Ceres
https://arxiv.org/pdf/2202.09238.pdf
Ceres is an odd one. It comprises about 1/3 of the mass of the Asteroid Belt, but it's composition is considerably different - more "volatile" rich - to the average asteroid. As witnessed by the cryovolcanoes revealed by the
Dawn mission.
This paper suggests that Ceres could have been formed in the Kuiper Belt, then migrated inwards during the period of Jupiter-Saturn interaction that rearranged the rest of the Solar system's planets (and incidentally, moved Pluto and the Plutinos into 3:2 resonance orbits with Neptune, fed small bodies into Jupiter's Trojan regions, and generally created interplanetary havoc. With a variety of not-particularly demanding assumptions, they get Solar system evolution models that indeed move about 1 Ceres-size "minor bodies" into the main belt of the Asteroids.
Interesting idea. It should be testable with (particularly) small atom stable isotopes (C-13:C-12, N14:N15, etc). Which really looks for a sample-return mission at the moment.
Three-dimensional imaging of convective cells in the photosphere of Betelgeuse
https://arxiv.org/pdf/2202.12011.pdf
Betelgeuse should be well-known to most people - only those in the very far north and even further south can't see it at some point in the year, and it's about the 6th brightest star in the sky. Exactly which position on the "bright star list may vary, because it is moderately variable. The first records of it's brightness (by "manual" optical comparison with other nearby stars was in the 1830s when John Herschel (son of William Herschel, the discoverer of Uranus (leave the jokes out, please!) set up an observatory in South Africa and recorded about a half-magnitude of variability. Variation in the brightness of Betelgeuse is, very literally, old news.
During the first pandemic of the 21st century, there was a degree of excitement when Betelgeuse went through a profound dimming - then returned to normal brightness. (The last time I looked, using the BetelBot, it was at 107% of "normal" brightness. Meh.) Everyman and their dogs were howling that we were going to get a supernova. Except, of course, for those who knew that Betelgeuse has this long-standing variability.
Yes, very likely, Betelgeuse is going to go "bang" at some point. But it's in a phase in it's evolution where it is losing a significant amount of matter to it's solar wind, and how much mass it will eventually lose remins unpredictable. It may remain big enough to go out with a bang, it may lose enough mass to go out with a whimper. Nobody really knows. (Also, it could go next year, or it could go in a few tens of thousand years ; again, nobody knows.) Finally, it's far enough away (200 persec, 650-odd light years) that we're unlikely to get anything worse than a light show when it does go bang (or whimper).
On the other hand, being a big star, at an interesting phase of it's development, and relatively nearby, it's also a site for trying all sorts of innovative imaging techniques. Since the 1910s, we've occasionally got a view of it's surface and it's changes from year to year, and day to day. This paper is about that, taking a look into the sub-surface of the star. ("Surface" needing a little elaboration - in this case it means the "surface of last scattering", where photons emitted by a hot gas molecule then travel to our eyeas without scattering off any other molecules. That gives us both the surface we can see, and it's height compared to some datum. This analysis shows around 8 rising (and falling) columns of plasm in the stars surface. That's (to me) surprisingly low - the Sun has tens of thousands of cells, if not millions. But for a bigger body that doesn't astonish me.
Fun science, pretty pictures.
AMATEUR OBSERVERS WITNESS THE RETURN OF VENUS’ CLOUD DISCONTINUITY
https://arxiv.org/pdf/2202.12601.pdf
Another area of science where amateurs contribute (the monitoring of variable stars is also utterly dependent on amateur contributions) is in seeking transient phenomena on Solar system bodies. Spotting comet impacts on Jupiter is becoming a frequent event. MEteorites hitting the Moon too. Martian dust storms hasve been recognised since the 1880s or so (with people straining their eyes to the point of seeing canals). Venus too exhibits subtle variations, as recorded here with contributions from the Hellenic Amateur Astronomy Association, Astronomical Society of Australia, Union of Italian Amateur Astronomers, Kagarlyk Kiev Region Ukraine, AstroCampania Association Italy, British Astronomical Association, Asociación Astronómica del Campo de Gibraltar Spain, Private Astronomical Observatory Messina Italy, Agrupación Astronómica de la Safor Spain, Portuguese Association of Amateur Astronomers, Astronomy Society of NSW Australia and Astroqueyras, France. They did the shivering in the rain, hoping for a break in the clouds ; the professionals just processed and collated their data.
That Venus has clouds is in every elementary school textbook. That the clouds exhibit variations in the UV (ultraviolet) and IR) is less well known. But with appropriate filtering and non-eyeball observation, you can see variation in the clouds, and if you coordinate with other observatories you can see the clouds move. We do the same on Earth, but we can see the clouds with the naked eye.
The structure of Venus's clouds is more complex than on Earth (then again, Venus has about 90 times the amount of atmosphere ... so, less than surprising). This study is about middle-level clouds about 50-56km above the surface, which can be seen in the near IR (less thean 1µm - accessable to amateurs with the right imager). Following a serendipitous observation of a gap in the clouds in March 2020, a call went out to amateur astronomers which uncovered suitable imagery from OCtober 2019 until the feature disapperaed at the end of April 2020. The data are available on a JAXA (Japanese Space Agency) website, if you particularly fancy downloading 25=plus GB of imagery.
During the observation campaign the CD (Cloud Discontinuity) rotated around the planet several times, taking about 5 days each time (Venus is a very slow rotator itself - and retrograde too! - taking 243 days to rotate on it's axis). The detailed structure and wind speed structure (3 to 4 times hurricane force, in Beaufort terms) varied with time and each apparition, with dark stripes and turbulent patches appearing from time to time. Evidently, when (if?) the Musk Terrraforming Company is floated on the stock market, they're going to have to include weather forecasting on their to-do list.
Fun, but not immediately useful. The surface topology may be visible in it's effects on the clouds, particularly the deep layer, but to what effect?
Alternative ideas in cosmology
https://arxiv.org/pdf/2202.12897.pdf
A week rarely goes past without someone bleating that their "ELectric Universe", "Plasma Universe", or (less insanely) MOdified Newtonian Dynamics (MOND - a way of getting observed gravitational rotation profiles without Dark Matter) favourite alternative model of the universe doesn't get considered by "big science". There's then often a somewhat paranoid diatribe against the university system that doesn't pay them (the author, normally) to sit on their arses and complain about the injustice of their lives on blogs. OK, I'm being a bit harsh - but there is a lot of that going on.
Of course, people who actually read the journals know that alternative ideas are proposed all the time. But they generally don't attract many people to work in that particular idea, for whatever idea. It is a market place of ideas, and success requires knowing what is likely to generate new ideas, and attract funding and students. That is where the "I have a new Theory of Everything crowd fall down - they can't attract people to follow and develop their ideas, and test them, and (for most hypotheses) find them wanting and discard them.
What do they consider an "alternative" theory? Well, they start from Λ-CDM - the so-called "Standard Model" of cosmology which is "dominated by gravity (Friedmann equations derived from general relativity) with a finite lifetime, large scale homogeneity, expansion and a hot initial state, together with other elements necessary to avoid certain inconsistencies with observations (inflation, non-baryonic dark matter, dark energy, etc.)" (their phrasing). They first consider a variety of "minor variations" on Λ-CDM with "different considerations on CP violation, inflation, number of neutrino species, quark-hadron phase transition, baryonic or non-baryonic dark-matter, dark energy, nucleosynthesis scenarios, large-scale structure formation scenarios; or major variations like a inhomogeneous universe, Cold Big Bang, varying physical constants or gravity law, zero-active mass, Milne, and cyclical models." (again, their words - that I only understand some of them is a justification of sorts for the whole work). Then they move out to more extreme models, such as static universes, "tired light" (I recognise that one from the wingnut branch of Young Earth Creationism) and other very peculiar cosmologies. Whether they get to counting elephants on turtles ... [SPOILER ALERT : elephants = turtles = 0]. For those on the further extents of theoretical work, the critical thing is to try to get your theory as well developed as possible, and try to get it published into the literature. You might manage that through posting a log, but if you can foster a relationship with a published cosmologist, you should be ale to get the credentials to get your work published if it is of publishable quality. In my (limited) experience of shuc theorising, that bit about "forming a relationship" is the difficult bit.
A lot of models are briefly described - and that in itself is a useful contribution - in several groups. After each grouping, I'll summarise issues.
Minor variations with respect to the standard model
| Antimatter and CP violation |
| Inflation |
| Dark energy variations |
| Scenarios without non-baryonic cold dark matter with standard gravity |
| Nucleosynthesis variations |
| Large–scale structure formation variations |
- The antimatter problem is that we have more matter than antimatter - at least locally. But all our experiments produce equal amounts of matter and antimatter - the CP problem. One or other, or both of these must have been wrong (at least at some point in time) so ... yes there are plenty of reasons to try to find a way between this Scylla ans Charybdis.
Lifetime of the proton theorising falls into this group too. We don't see proton decay, and people have looked, for decades.
-Inflation is a solution to the isotropy problem - a.k.a. the horizon problem. Which it does - but it makes people uncomfortable. A thousand variations on inflationary theory are mentioned - leading to the charge that it is too flexible a theory. On the other hand, that also means this is a very active area of research.
- "Dark Energy" - the Λ in Λ-CDM - is another thing that makes people uncomfortable, and has generated a number of alternatives. A lot of these challenge the assumption that we are "Copernican" observers, with an isotropic universe about us. If there is a net movement of galaxies extending across our line of site that might indeed produce the semblence of dark energy's acceleration. A change in supernova properties with time (or metallicity) might also produce the same effect. Again, this is a significant area of research. Whether it's an alternative theory or testing the assumptions of the Λ-CDM model is a two-whisky problem. Time-variable cosmological parameters also fall into this category, at least sometimes.
- "Scenarios without non-baryonic cold dark matter with standard gravity" is a bit of a mouthful covering a range of models for the galaxy-mangling effects of dark matter, but using some variant of regular matter. Unfortunately most such forms of matter, being electromagnetically active, also have consequences on the Cosmic Microwave Background Radiation (CMBR) which ... is a major problem from an observational point of view.
- Nucleosynthesis variations don't normally mess with the half-life of the neutron (that's too well known), but the number of neutrino species is a parameter that people try to play with, as well as attempts at examining non-uniform distributions of protons versus neutrons.
- Most universe-history models have small structures (galaxiaes) forming and coalescing to form larger structures (clusters, walls, voids). But some theories postulate the formation of large structures (of dark or normal matter) first, then smaller and smaller strutures. This produces a fair number of modelling experiments, and the inter-galactic distribution of dark matter is amenable to expermental probing via gravitational lensing.
Major variations with respect to the standard model
| Inhomogeneous universe |
| Cold Big Bang |
| Variations or oscillations of physical constants |
| Modifications of the gravity law |
| Other Friedmann-Lemáıtre-Robertson-Walker (FLRW) solutions |
| Cyclical universes |
- Inhomogenous universes fall into two groups :
| Those where the mass within a region of radius R does not follow R3 but follows a lower (normally - but I'd have to check that - less than 3) dimensionality implying a fractal distribution of matter. |
| Those where rate of time varies with the mass distribution - normally running slower in high-mass regions and slower in low mass regions, which differences then accentuate. At some point that's going to have drastic effects, à la "Big Rip" |
- The "Cold Big Bang" is referred to the 1960s. Very little more is said about it - it has major observational comflicts such as the CMBR, the Hubble relation ... Wikipedia adds a little, asserting that the initial state of the universes was a very high entropy state, not the Λ-CDM model's low entropy state. Regardless, the heating necessary to go from a cold big bang, wherever it came from, would leave signs on the acoustic patterning of the CMBR, which are just not seen.
- Several models look at varying one or other of the fundamental constants. The speed of light, Planck's contstant, the fine structure constant and various others have been proposed. Variations in the force of gravity form their own group.
- A whole class of theories fiddle with gravity - either varying the gravitational constant (with time, or with place) or varying the gravitational law. The best known of thse is the MOND family, which typically have F=/=ma for certain ranges of a. Some successes have been claimed for this group of theories, but disputed because of difficulties with such data sets. A lot of other "different gravity" theories go under obfuscating names : Einstein-ether theory, bimetric or general higher-order theories, Hoˇrava-Lifschitz gravity, Galileons, Ghost Condensates, including Kaluza-Klein, Randall-Sundrum, Dvali-Gabadadze-Porrati model 4D gravity on a brane in 5D Minkowski space, Weyl conformal gravity. Some of these are very busy fields, judging from their appearences on Arxiv.
- The "FLRW metric" is "an exact solution of Einstein's field equations of general relativity; it describes a homogeneous, isotropic, expanding (or otherwise, contracting) universe that is path-connected, but not necessarily simply connected" [WIKI], which adds up to "General Relativity- plus". Other relations that cover the same distance- speed- momentum- time territory are available, and are used. One discussed reange of alternatives is the "Zero-active mass condition", which notes that the present day deceleration of the Hubble flow (because of gravity) ia approximately matched by the acceleration due to dark energy, so the net effect is not far from if the universe had no effective mass, and the Hubble flow were not decelerating (due to gravity) or accelerating (due to dark energy). This is achieved by (if I've got this right) scaling distance differently at different times. Which is an interesting interpretation, indeed.
- A different way of replacing "FLRW" is "Milne Cosmology," which does various things with the FLRW metric, but specifically includes a requirement for density = 0. Which is clearly wrong (I'm here, you're there, and there is something between us including a web server). So I don't know why people go any further with it.
- The "cyclical universes" include the ones popular in SF, and to give a sort of answer to "what happened before the Big Bang?" questions. Typically they have a smooth "Big Bang" (so they don't need an inflation phase). Obviously they also need to have no dark energy (or insufficient dark energy to prevent re-collapse of a universe.
Others; the outer fringes
| Quasi-Steady State Cosmology |
| Plasma Cosmology |
| Universe as a Hypersphere |
- The Steady State cosmology has an intimate relationship to the Big Bang, thank you Fred Hoyle. (He invented the term "Big Bang", as a slur.) They postulated the creation ex nihilo of about 10-24 baryons/cc/s, doing away with the early hot phase, probably any beginning (at least any obvious beginning) and any obvious end state, but retaining isotropy, expansion and homogeneity (in both space and time). But the CMBR pretty much shot the SS in the back of the head. Hoyle (and others) tried resurrecting the theory in the 1990s with an oscillating expansion rate (never going into contractino, but sometimes expanding faster, sometimes less fast). Lots of problems remain with the Steady State theory though, and it doesn't get much activity now.
- Plasma cosmology suffered from the attentions of Internet Kooks, and still does, but it's origins are in the works of several Nobel laureates, so at least the maths is well done. It's central postualte is that the electromagnetic forces of a universe-dominating plasma produces fields at least as strong as the gravitational field. With a factor of 1020 or more between the strengths of electromagnetic and graviational fields for a dilute plasma, fairly low levels of net charge difference would lead to significant forces. Bolted-on amendments give answers of a sort for the CMBR.
- Plasma cosmology "posits that our universe is a hypersphere of a higher-dimensionality geometrical entity; that is, a set of points at a constant distance from its centre, constituting a manifold with one dimension less than that of the ambient space." Whatever the fuck that means. Variations on this class use different numbers of dimensions, and ascribe the to diffferent properties of the universe, for example : "More recent is the hypothesis of the existence of five combined spacetime dimensions. By making some peculiar assignments between coordinates and physical distances and time, a hyperspherical symmetry is made apparent by assigning the hypersphere radius to proper time and distances on the hypersphere to usual 3-dimensional distances in a Euclidean universe" Which sounds quite weird, but almost sounds sort of credible. Again. they're not dead theories, but they're not popular.
Static Models and non-cosmological redshifts
| Cosmological models motivated by tired-light redshifts | 7 varieties! Waste of time. |
| Other non-cosmological redshifts and other static models | A mere 2 varieties! |
| Plausibility of static models | Just to offend those who don't wish to be judged! |
Static models deny the existence of a Hubble flow. That's problematic, by the Feynmann Test - if it disagrees with experment, it's wrong.
"Tired light" models - these first came to my attention, dragged out like dead puppets by Young Earth Creationists (YECs) desperate to be important in the universe. Do they have any redeeming characteristics at all.
A tired-light scenario assumes that the photon loses energy owing to some proposed photon–matter process, photon–photon interactions, or some dissipative property of the photon.
Zwicky went down this path from about 1929 to the mid-50s. Unfortunately, a photon that interacts in flight to lose energy, and does so in a distance-of-flight related way, would also exchange some momentum (vector) in that interaction. Therefore, the line of flight would be modified. And distant objects would be lurred. Which they're not. QED (Feynmann). The YECs were wasting their time.
- Curvature Cosmology - I don't get this at all. I'ts a single-author idea.
- Plasma-Redshift - weird. Another single-person counter-factual.
- Subquantum Kinetics ... "works as if intergalactic space were on average endowed with a negative gravitational mass density." Another single-author counterfactual.
- Scale Expanding Cosmos - "A universe is proposed in which not only space expands (therefore, it is not properly a static = non-expanding model) but time also expands: the relationship between space and time could remain constant during the cosmological expansion and all cosmological locations in time and space could be equivalent, if the metrics of both space and time expand." Sounds slightly less kooky than some of the others, but "why?" One significant outcome might be that "The scale expansion could be eternal, which would eliminate the creation event", and for many people that is a desirable outcome.
- Dichotomous cosmology - "Contrary to general relativity, here there is a dichotomy between light and matter dynamics: the luminous portion of the Universe is expanding at a constant rate as in the de Sitter cosmology in a flat Universe, whereas the matter component is static" Well that's wild. One author. No follow on.
- Wave System Cosmology - Another deeply weird one. "The universe is a pure system of waves with mass density and tension parameters proportional to the local intensity of the modes of the waves." One author, no follow-up.
- Eternal Universe - "Based on the existence of a negative pressure in a cosmic fluid derived from general relativity (not very different from the role that the cosmological constant has acquired nowadays", but these postulated properties (the universe is static, infinite, without an instant of creation, and without expansion) is in contradiction to Olber's Paradox, despite the assertion that "Olbers’ paradox is solved by means of absorption in clouds of dust.". One author, no follow-on.
Other non-cosmological redshifts
"Self Creation Cosmology (SCC)" gets a one paragraph description - "In SCC, energy is conserved but energy–momentum is not. Particle masses increase with gravitational potential energy and, as a consequence, cosmological redshift is caused by a secular, exponential increase of particle masses. The universe is static and eternal in its Jordan frame and linearly expanding in its Einstein frame." Whatever that means. But there is a sort-of testable outcome : "Furthermore, as the scalar field adapts the cosmological equations, these require the universe to have an overall density of only one third of the critical density while remaining spatially flat." That's interesting because the optical density (matter content) is lower than that, but only by a factor of 5 or so. By cosmology's standards, that a pretty good agreement.
"Cellular Cosmology" gets a paragraph too, but I can't make out much from that.
Several grounds for considering the plausibility of a model are discussed. Trying to get around a Dopper interpretation of the Hubble relation generates a lot of twisting and turning, cosmological constants, varying constants of physics, and gravities of finite range. Fiddling with the geometry of space is popular too, producing unusual geometries. Olbers Paradox is also mentioned as a constraint, requiring more special pleading, particularly for infinite duration universes.
Plausibility of static models
While static models are definitely not very popular, they're not impossible. Einstein's attempt at a static universe (with a cosmological constant to work against collapse) being a case in point (and the cosmological constant being a case in point of the difficulty of getting such models to match the observed universe). Finite-range gravity and variable fundamental constants are other routes to stabilizing such universes. When contemplating universes of infinite duration, Olber's Paradox requires some special treatment to avoid contradiction.
Themes in Cosmology
Moving on from the listing area. This is a listing of places where there are major variations in cosmology, and where there is experimental/ observational evidence to the contrary, the proponant really needs to have an explanation of "why".
Themes - Classification according to characteristics.
| Gravity, forces |
| Expansion |
| Age of the universe |
| Redshift |
| Dark elements |
| CMBR origin |
| Light Element Nucleosynthesis |
| Homogeneity at large-scale |
| Galaxy formation |
Gravity and forces - Most models use a GR-like gravity, but some go further. A lot further. How the Cellular Cosmology generates a gravity is really obscure. Well, obscure compared to the geodesic property of space-time generating it's gravity.
Expansion is accepted by most models. Those that don't have to fiddle with space, clocks (or light speed - same thing) and the like to explain the Hubble relation.
Age of the universe As mentioned above, infinite universes have a problem with Olber's Paradox. It may be an old problem, but it's still a problem. Most universes accept a finite age, and the cyclical universe dodges the question.
Redshift - most models accept a recession origin for the redshift, but a few take the bull by the horns and have a non-recession red shift, such as the varios "tired light" scenarios, Plasma Cosmology, and however Cellular Cosmology generates it's red shift at cell boundaries.
Dark elements are sometimes explicit (dark matter, dark energy in λ-CDM, the C-field creating matter in Hoyle et al's, and sometimes more cryptic (Plasma Cosmology requires strong inter-galactic magnetic fields - which aren't detected). Dark here, dark there, dark everywhere!
CMBR origin The signal from z ≅ 1100 is simple in λ-CDM. Static models, on the other hand either have to come up with some novel mechanism such as thermalisation of radiation by dust (which process hasn't been observed), or they just ignore the problem.
Light Element Nucleosynthesis Again, this happens naturally with a hot big bang, but cold big bang, QSSC etc don't have a simple mechanism and rely on stellar nucleosynthesis - which is in arguable contradiction to the composition of gas clouds in distant galaxies, which are still about 25% He. "In the version of hypersphere universe by Netchitailo, it is produced in the dark cores of Macro-objects." which sounds like pure guff to me.
Homogeneity at large-scale That's given in the design of most scenarios, but not all. Some variable gravity scenarios do have inhomogeneity, but that is in contradiction to observation. Cue the Feynmann criterion.
Galaxy formation is controlled by gravity in most cosmologies, but not Plasma Cosmology, which calls for otherwise unseen electromagnetic forces. Feynmann's criterion, again.
General problems of the alternative models
There is a general problem of "development", with λ-CDM simply having had more work done in it's arena than others. In the spirit of generosity and exploration, theories which haven't had a particular observation explored, generally aren't discounted for that under development, but it is a problem for them. Bluntly, such theories need to attract more workers to develop them better, or they are never going to improve. But there isn't a mechanism to propel people towards unpopular fields of study. There is an erroneous link in the paper (to http://www.astro.ucla.edu/∼wright/errors.htm ; a typographical tilde has replaced the ASCII tilde). The correct link is titled "Errors in some popular attacks on the Big Bang", and includes the damning disclaimer that "For each theory debunked here there are a hundred more that are totally crazy, but I don't have the time or the inclination to debunk all of them." That is one of the more generaous treatments of some of these theories.
Another quote : "A solution to Olbers’ paradox by dust absorption in a universe of no defined extent, for instance, is not clear. One may wonder, if energy does not disappear, whether the absorbing element (dust) should be heated and re-emit, and, if the energy disappears how that can be consistent with known physical laws. This problem has no easy solution." And the problem does need a solution! Literally, in some of these universes the night sky should be the brightness and intensit of the surface of a star.
Time is another issue. A universe without a definite start - or even, no start - can have time to generate heavy elements without the need for a very early population of stars ("Population III") postulated by other universes, but not observed in ours. Most of these universes come into strong internal contradictions, or postualte "dark" elements to fix these problems.
The CMBR is another problem for many cosmologies. "Nonetheless, all proposals to explain a CMBR produced in the intergalactic medium — even assuming that a perfect black body shape can be produced — have the problem that the integration along the line of sight gives a superposition of many layers of black body radiations, each with a different redshift, giving in total something different from a black body". People seem to think that black body radiation is in some way fractal, and adding multiple BBs would produce another BB with a different characteristic temperature. Not so. (I suspect people get confused by the way that they have the same shape when plotted on log-log axes.)
Although the QSSC is one of the best developed of alternative cosmologies, it has a snake at it's bosom: "The very idea of continuous creation of matter also necessitates some very exotic physics, and has no empirical support" Feynmann would have something very rude to say about this. With bongo drum accompaniment.
My conclusions
For what is mostly a listing, my interpretations are hampered by the fact that I don't often understand either the maths or physics at quite a high level. However the exercise has been useful. I now recognise the context of a large number of other phrases I see in use on the cosmology channels of arXiv. Contrary to the claims of the wingnut fringe, there is a lot of work being done in directions away from the direct line of λ-CDM. A lot of this is on the minor variants (different FLRM interpretations, for example), but that is what you would expect for a main theory with a lot of experimental evidence.
For example, previously I wouldn't have recognised "arXiv 2203.00413 (gr-qc) Flat LRW Universe in logarithmic symmetric teleparallel gravity with observational constraints" as being a study of an alternative cosmology, but it is. It's not very alternative, but I've got a better framework to position it in now.
Unprecedented change in the position of four radio sources
https://arxiv.org/pdf/2202.13119.pdf
If we are looking at a star, the angular size of the object is (almost always ; see Betelgeuse above) below the resolution of our images. So if you see a motion, you're safe in concluding that the object is moving across the field of view. This is the procedure which Bessel used in 1838 to determine a distance to 61 Cygni. It is also used to characterise galactic stars in general and to determine which may be closest. The fastest-moving star on the plane of the sky is Barnard's Star (GJ699), moving a little over 10 arcsec/year. When you get to extragalactic objects though, you wouldn't be expecting to see measurable movement though. So, seeing aparrent movement of some 55mas (0.055 as, to compare to Barnard's Star) in a radio source, 3c48 was unexpected to say the least. Further, examination of the data showed the RA didn't change significantly, but the DEC did, arguing against gross errors of measurement.
The data was inspected in more detail, with re-mapping of the source regions. Then it ecame clear that the shape of the extended source had changed, the source including a seemingly (because of relativistic redshift beaming) superluuminal jet from the compact body postulated in the core of the source.
Three other seemingly rapidly-moving radio sources were examined (CTA 21, 1144+352, 1328+254) and also showed similar shape changes i nthe structure of their jet lobes.
An interesting bit of science as it is done. "Oh, that's odd" ; [looks more closely] ; "Oh, that's what's going on."
Do Atoms Age
https://arxiv.org/pdf/2203.00195.pdf
Now that is a very simple, and therefore interesting, question.
Abstract : Time evolution generically entangles a quantum state with environmental degrees of freedom. The resulting increase in entropy changes the properties of that quantum system leading to “aging”. It is interesting to ask if this familiar property also applies to simple, single particle quantum systems such as the decay of a radioactive particle. We propose a test of such aging in an ion clock setup where we probe for temporal changes to the energies of the electronic state of an ion containing a radioactive nucleus. Such effects are absent in standard quantum mechanics and this test is thus a potent null test for violations of quantum mechanics. As a proof of principle, we show that these effects exist in causal non-linear modifications of quantum mechanics.
Hmmm, so basically, it doesn't seem as if they do know of such a measure, but if we did find one it wouldn't be with conventional QM. A backwards way of looking at it, but also a reason to continue to look for such situations. They're looking for changes in single particles, so that implies "single particles which don't interact with the outside world", which would disrupt the system.
Hitting a New Low: The Unique 28 h Cessation of Accretion in the TESS Light Curve of YY Dra (DO Dra)
https://arxiv.org/pdf/2203.00221.pdf
Compact bodies tend to accrete anything in the neighbourhood (subject to Keplerian rules), and they're messy eaters. But if there's (temporarily) nothing around to eat ... the lights go out. All very predictable - except that the process is essentially stochastic, so from this distance you can't predict it (pulsar brightness has been proposed as a source of widely distributed high-quality cryptographic randomness), but it's going to happen sometimes. And it did.
"there is a day-long, flat-bottomed low state at the beginning of 2020 during which the only periodic signal is ellipsoidal variation and there is no appreciable flickering" This relates to .... [ SOMETHING ELSE RECENT, twin SMBHs, orbiting each other, quiet periods allow the sinusoidal signal to come through the noise.]
Maybe later.
The Asteroid-Comet Continuum
https://arxiv.org/pdf/2203.01397.pdf
Sorry, but any "build a stellar sytstem model has small, medium and large (non-stellar) bodies in a continuum of sizes. Baseball round the head time - yes, it's a continuum.
Jupiter’s inhomogeneous envelope
https://arxiv.org/pdf/2203.01866.pdf
Building a solar system isn't easy (see above). We're still trying to work out how the Solar system was built. We still don't know, but "what does Jupiter contain?" is a good question, important for constraining models of the assembly of the Solar system. We know that other planetary systems have different trajectories (q.v. "hot Jupiters"), but for the foreseeable future the Solar system is going to remain the best studied member of the class.
There are several chief results:
| Conclusion (from abstract) | My comments |
| We also find that uncertainties in the equation of state (EoS) are crucial when determining the amount of heavy elements in Jupiter’s interior. | Well, actually that's imediately obvious when you first start trying to work out how conditions change with distance from surface. We learned about ideal gasses in secondary school, but most people forget the caveat we were given that "ideal gasses do not exist". Yeah, they don't. You need an EoS. Which are not easy to construct ab initio, or to measure at mid-Jupiter conditions. Particularly when you don't have a good handle on the chemical composition. |
| Our models put an upper limit to the inner compact core of Jupiter of 7 M⊕, independently on the structure model (with or without dilute core) and the equation of state considered. | That's a bit lower than "traditional" (last decade or two) levels, which have estimated it at 10 to 30 M⊕, but the exact numbers are very much dependent on how the "heavy" elements are distributed within the planet, from "everything at the centre", to "evenly distributed, below the visible clouds". |
| Furthermore, we robustly demonstrate that Jupiter’s envelope is inhomogenous, with a heavy-element enrichment in the interior relative to the outer envelope. | Again, since the end point models haven't been made to work, generally people get that ; what the distribution is, remains a question. |
The study combined three different EoS for the H2 component, two EoS for the He component, one for the silicates and one for the H2O component. We have a reasonably well constrained temperature for the temperature at the 1bar level (166K from the Galileo death-plunge ; between 165 and 170K from various interpretations of the Voyager radio-occultation data), about which point a range of values are examined.
A Star-sized Impact-produced Dust Clump in the Terrestrial Zone of the HD 166191 System
https://arxiv.org/pdf/2203.02366.pdf
Most astrophysics descriptions of star formation have them forming within molecular clouds of gas and dust, andalmost always i nthe close proximity of other stars. The continuing use of studies of "extinct" (short-lived) isotopic systems as clocks to study the first few millions of years of the Solar system is enerally ascribed to the proto-Solar structure being pepperd with deris from a nearby supernova, and many models (and no small number of popular science descriptions) rather depends on this proximity.
Therefore, one should see the results of star-star (or proto-star - proto-star) interactions sometimes on the sky. Which we do already, with things like "blue stragglers" in globular clusters (probably the result of two small, old stars meeting and merging, to produce an abnormally bright and blue star in a cluster of generally older stars ; note that brightness (luminosity) has a steeper-than-linear relationship with mass. (My astronomy workbook has luminosity as mass^(2.3 - 4.0) with an overall exponent of close to 3.0.). Similarly, we should see the results of "hierarchical" impacts (impacts of similarly sized bodies together) in the dust+gas discs surrounding young stars.
This report descries a star which has a brief (5-10 years) period with a lot of IR excess and a temporary dimming, which are interpreted as something hitting the system Oor possibly two planets colliding, producing a lot of warm dust and gas in a cloud of around 0.6AU diameter. ("Diameter" assuming the particles are on circular Keplerian orbits.)
Observations from 2015 to 2020 (when the Spitzer spacecraft stopped working) showed an approximate 2-fold increase in IR brightness between mid-2018 and early 2019. The optical brightness did not change significantly over this period. A "giant impact" of two bodies of approsximately Ceres- or Vesta- size. Early during the "rise" phase of the change, which was partly sampled during one of the 39-day long periods each half-year when the spacecraft could observe the system, there was a brief decrease of the "colour temperature" of the system. In combination, these observations suggest the sudden production of a large amounts of cool dust from a compact body (planetesimal), which dust then warms as it disperses from the source.
Our models suggest we should see these things. Some people who don't like being unexceptional (typically god-squaddies) don't like these models, and sieze on a low number of such observations as evidence that we are exceptional. Well, here's another case suggesting that we are, indeed, inhabitants of an unexceptional stellar system.
Dielectric properties and stratigraphy of regolith in the lunar South Pole-Aitken basin: Observations from the Lunar Penetrating Radar
https://arxiv.org/pdf/2203.02840.pdf
The Chang'e-4 Lunar Rover was landed on the far side of the Moon in 2019 and operated until September 2020. During it's traverse across the floor of the Von Karman crater, it carried a Ground-Penetrating Radar (GPR) system which could read some of the mineralogy and structure of the regolith below the rover. The rover trail wasn't straight, but tended generally WNW for about 550m from the landing point. On this traverse, some 15000 radar soundings were taken, which this paper presents to give an approximate distance-depth cross-section, presented here as figures 2 (raw, up to 600ns/ section), 7 (migrated, up to ca 45m depth) and 8 (interpreted, up to 45m depth).
Unsurprisingly, the contrasts between one layer of regolith and the next aren't great. Density is a bigger contrast than mineralogy, with a bulk density varying from 1.49 to 2.07 g/cm3 (as determined from "reflection hyperbolae" from boulders suspended in the regolith. Assuming a mineral grain density of 3.6 g/cm3, mid-range for olivine, that corresponds to 58 to 42 % porosity. Uniform spheres have a porosity of 37% in a close packing, so these reduced densities imply non-spherical grains which are less than perfectly packed. The lowest densities are nearest the surface, which isn't incompatible with the compaction one would expect. If some of the grains are not spherical (cows in a vacuum, or olivine grains, also in a vacuum), like many fragments of impact glass retrieved from the Apollo samples, one would also get those reduced packing efficiencies.
Figure 8 - the "interpretation" of the migrated section - shows there to be a small crater, about 120m across and 10m deep below it's rim, (their measures on the full print out give 128m across and 13m deep, but it's hard to be that precise on the print resolution versions). which is compatible with a small impact crater. This crater cuts across 2 (possibly 3) of the sub-surface layers, but contains it's own fill unit elow the surface layer of unstructured material (with the lower density as noted above).
A nice bit of work. "Radar Robin" would like it - or would have, before he retired.
Assessment of Microbial Habitability Across Solar System Targets
Hmmm, well everyone (and their dogs, and cats) are happy that there is a non-zero chance of microbes (as reciognised on Earth, today) surviving trips to other places, and surviving the trip, and living on afterwards. Small, but non-zero chances.
These authors try to develop a systematic analysis. It's a useful idea, but it gets practically an extra free parameter for every inhalation. Definitely needs more work to make it workable. It's also something that sticks to the "known unknowns" part of the field (not that you can really do anything else).
Potentially useful, but complex.
New satellites of figure-eight orbit computed
with high precision
https://arxiv.org/pdf/2203.02793.pdf
This is a new numeric approach to computing possible stale orbits in a Newtonian 3-body problem.
The 3-body problem has notoriously no analytic solution, but that doesn't preclude finding solutions by numberical searches. The typical situation examined is of three identical bodies moving in each other's gravitational fields. If you examine a case with differing body masses, then you collapse rapidly towards a single main mass with "light" "test particles" moving in the main particle's gravitational field with neglegible influence from the field of the other "light" "test particle" (that is what "light" "test particle" means!), or to a case of two large particles orbited by a single "light" "test particle". The situation is held in a plane defined by the three bodies, and since they comprise the entire universe of the model, there's nothing to generate an out-of-plane force, so it stays like that.
The "figure-of-eight" orbits referred to here are a class where, if you set up a rotating frame of reference centred on the centre of mass of the system, oriented how? There is a lot of crossing of the "zero point" in the plots, so there must be some offset between the plot and the points involved, or they'd have the system collapsing by collision. Clearly there's something going on in the presentation of these results that I don't understand.
Is it worth pursuing, tracking down the references? I don't really think so, for me. It's a numerical method, about a non-physical situation. Good improvements in computational efficiency no doubt, and that'll play back into things like collision modelling. Very useful. But definitely not my field.
Can a particle moves zigzag in time?
https://arxiv.org/pdf/2203.04200.pdf
Everyone has heard of Wheeler's electron? Right? Physicist, author of some of the classic texts on gravity and GR that informed generations of physicists. I see that Wiki calls it the "one-electron universe". Seems a good enough name for it. Wheeler's (half-joking?) suggestion was that the universe only contains one electron, which zig-zags backwards and forwards in time (at what sort of clock cycle?), showing as an electron when travelling in one direction, and as a positron in the other direction. Nice idea - how does it describe what happens when a positron annihilates with an electron? And how does it explain the preponderance of electrons over positrons today? Well, quibles aside ... the question of whether a particle can zigzag in time does seem fairly fundamental to the model. Hence this paper.
The "arrow of time" still pervades fundamental physics, sometimes appearing as the "arrow of causality", sometimes as the arrow of thermodynamics.
OK, it's a complex question. The problem is that the authors claim that zigzag trajectories are possible ... but don't lead to results that can be measured. Even in theory. Very big "Hmmmm", indeed.
It looks like this is going to be dense. I can get this though : "In this paper, we consider the third question, “why can a particle zigzag in space but not in time?”. But ... then it gets beyond me. "The transition amplitude kernel has a well-known formal form" - does it really? Nope, totally beyond me. The English is a bit strained, which doesn't help, but I don't think the original russian would be much of an improvement - the problem is in the maths. And the physics.
On the fate of quantum black holes
https://arxiv.org/pdf/2203.04238.pdf
I remember discussing this question on CIS:SciMath, way back about the millennium. As the mass-energy of a BH decreases, the curvature of spacetime at the event horizon increases, and so the energy of the (mean) particle of "Hawkins' Hair" also increases. At some point, the (mean) particle emitted by such a decaying BH will contain as much mass energy as the BH itself. And thwen what happens?
I never did get a confident answer from the physicists (and mathematicians) there. Quite a brush-off, IIRC, even. Which probalby marks it as an interestingly difficult question. Lets see what these people have to say.
The endpoint of the process of Hawking evaporation remains unknown—it is expected that a theory of quantum gravity will answer this question by resolving the singularity and providing dynamics past the classically singular region.
Question dodgers!
A construct called "loop quantum gravity (LQG)" is "a non-perturbative attempt to quantize general relativity using (stuff that falls under the non-FLRW "alternative cosmologies discussed above. It's not a hopeless situation : "Solving the full quantum dynamics in LQG currently remains out of reach, but there is a substantial body of work on symmetry-reduced models, including applications to homogeneous cosmological space-times known as loop quantum cosmology (LQC)"
I'm not sure how to classify this in terms of the families of cosmologies discussed above. I hadn't particularly picked up on this assertion : "In LQC, these methods have successfully led to the resolution of the big-bang singularity in classical general relativity, replacing it with a non-singular bounce in homogeneous cosmological space-times" - but maybe I've just classified all the "Big Bounce" models as dodging the singularity for reasons of dodging the singularity.
One partial success of these approaches is that "In the second category are works that use coordinates in spherical symmetry where the radial coordinate remains spacelike throughout the entire space-time, making it is possible to treat the interior and exterior of the black hole on an equal footing for quantization." I.E. a lot of other tools can be used to study the interior of the black hole. That's good, I think.
Then they go further "It has the advantage that the correct classical limit is recovered where the space-time curvature is small compared to the Planck scale." Which I think is talking about the situations where I'm asking about the release of high-mass-energy particles from a severelt "bent" event horizon. I may have stumbled on a quite important question.
"A generic feature of these works is that, as in cosmology, the singularity is resolved and matter bounces when space-time curvature reaches the Planck scale." That is, indeed a level of scale that I'd suspected would be important.
Another interpretation of Hawking radiation has been popular in the SF world for a long time, and these ideas of white holes are also still in play in cosmologies. "It may also be possible to understand the bounce generated by quantum gravity effects as a transition from a black hole to a white hole, with potential observational consequences."
The paper then starts going foar over my head, but I do see one result worth noting "After evolutions spanning two orders of magnitude in data mass M , we find that this lifetime is T ∼ M^2/(Planck Mass, mPl). " "Data Mass" is an interesting concept too, as well as that lifetime estimate. It seems to have escaped Wiki, but I'll have to look deeper on that.
Six more sections of maths lose me completely. But I think I've got some significant points out of that.
Yet another star in the Albireo system
https://arxiv.org/pdf/2203.04222.pdf
Yeah, I fucked up. There's a famous quadruple-star system that has considerable colour contrasts, even in a small telescope. It's not Albireo. I can't remember which star I'm thinking of. But yeah, another star is multiply multiple ; film at 11.
Terrestrial volcanic eruptions and their association with solar activity
https://arxiv.org/pdf/2203.03637.pdf
People have ben trying to predict volcanic eruptions and earthquakes since ... probably 5 minutes after the first hominid felt an EQ and had the nous to think "WTF was that?" [more traceably, 1910 (Reid, Harry Fielding (1910), "Volume II. The Mechanics of the Earthquake.", The California Earthquake of April 18, 1906: Report of the State Earthquake Investigation Commission, Washington, D. C.: Carnegie institution of Washington.) and 1935 (Wood, H. O.; Gutenberg, B. , "Earthquake prediction", Science, 82 (2123): 219–320, doi:10.1126/science.82.2123.219, PMID 17818812.] Unsurprisingly, that followed the 1906 San Francisco earthquake and the increasing spread and reliability of the instrumental record of earthquakes.
To say that "Earthquake Prediction" (and it's cousin, volcano prediction) is a branch of science covered with illustrious success and unalloyed glory would be a bit optimistic. To claim that it has any successes at all is a bit optimistic. But people still hope that there is some successful combination of measurements which they can take which would lead to a usable prediction (in terms of magnitude, location and timing. The timing element is what distinguishes a prediction from a forecast, which is not so restricting on the timing.)
Unsurprisingly (particularly since a major US earthquake would mean a lot of dollar damage, and even dead white people - when the highest likelihood of the first million-casualty earthquake is going to be along the Himalayan Front. But that'll only kill poor brown people, so that's not as important as a bit of property damage in California), there are quite a lot of people really keen that a successful method is found. Ditto for volcanic eruptions, but that's more of an Indonesian (poor, brown, non-English-speaking) and Japanese (rich, brown, non-English, and not even using the Latin writing system) obsession than American, and so considerably less vociferously pursued. Such intense desire does not however mean that there is such a system, today, or possible. (Why do I doubt that it is possible? The wallrocks of the faults involved are inhomogeneous ; the faults are inhomogeneous vertically, horizontally and in terms of confining pressure ; the necessary information is on the centimetre to metre scale, but the technology for measuring what is happening kilometres into the ground can give accuracies to the scale of tens of metres (that hasn't changed much in the last 30 years that I've been drilling oil wells, needing that improved precision ; of course, once you've got a well in place and logged, you can take a lot of the uncertainties out of the particular solution for that fault, but that's not a scaleable solution). You're not going to get the information you need to buld a reasonably accurate model of the fault plane.) Volcanos are even more complex, and their plumbing systems are even harder to image than a single fault plane.
One consequence of this ... is "desperation" too strong a word? ... to find a workable predictino method is that people are looking everywhere to find something that correlates with, and leads, earthquakes. A couple of years back there was a probably successful claim of correlating the ocurrence of volcanic eruptions with the phase of the Moon. Which ... well the phase of the Moon does exert considerable gravitational forces on the Earth, so that isn't so terrribly surprising. But it is a weak relationship.
This paper continues the process of data mining, but to my mind less convincingly. Here they see a small, positive correlation between the strength of the geomagnetic field and the occurrence of earthquakes. But to get the answer they are looking for from the analysis they have to be careful to align the cycles of the solar magnetic field "just so" - whereas surely a correlation should come out, without needing a careful alignment.
In the end, the authors sum up the predicament of the field thus : "there are no viable mechanisms yet proposed for the explanation of any correlation between volcanic activity on the Earth and solar activity." I don't see any estimation of the forces that the geomagnetic field can exert on the near-surface rocks of the Earth from it's (varying) interaction with the Solar field, and how to feed that back into triggering earthquakes and volcanic eruptions.
Without that sort of mechanical force estimate, there remains "no viable mechanisms", as the authors say. So just from that, I doubt that there is a meaningful mechanism for this correlation. I'm also quite suspicious of how they derive their estimates for the Solar magnetic field strength from before the instrumental record. There's a suspicious "geomagnetic jerk" that they bring in to associate with the 1859 Carrington event, which is probalby significant in "improving" their statistical results.
It's an interesting idea, but I remain decidedly unconvinced. Attempts to reconstruct magnetic field strengths before the instrumental record seem particularly dubious to me - there are so many confounding effects. But as the instrumental record extends (at a rate of 1 year per year) one would hope that the signal to noise ratio improves. If there is a signal.
