back to article 'It's back to the drawing board...' Innocent axions found not guilty of dark matter crimes

Physicists have ruled out the existence of axions once considered possible dark matter candidates. Dark matter has scientists stumped. It is widely believed that about 27 per cent of the universe is dark matter: mysterious globs of undetectable stuff that nobody really understands. Astronomers can observe its effects, and …

  1. This post has been deleted by its author

    1. Anonymous Coward
      Anonymous Coward

      Re: Phlogiston

      I don't think you are being fair here - axions are a /possibility/ allowed for by existing theoretical models, models which generally work very well indeed. So it's hardly unreasonable to suspect axions might exist, and go looking for them.

      1. Voyna i Mor Silver badge

        Re: Phlogiston

        I deleted my post because I thought it had been misunderstood. I was a bit cryptic.

        The similarities between phlogiston and axions that I saw were these:

        Phlogiston fitted in with the Standard Model of the day, in which the primary entities of chemistry were the metal oxides, and metals were believed to be oxides + something else, which was called phlogiston.

        Because early experiments were not precise, experiments on burning metals usually led to loss of "calx" (oxide) leaving early chemists to think there was a weight loss when metals burned.

        Greater precision of experimental method, however, led to the discovery that when metals burnt they gained mass. To explain this additional mass and keep the phlogiston hypothesis, it was argued for a while that phlogiston had negative mass. But around this time there was a revolutionary new paradigm in which the primary substances were the metals, and the calxes were metal + oxide.

        Science, in fact, did its job with the information available and the paradigm changed when experiments improved.

        In the axion case we have the problem that the universe seems to have too little matter to explain its gravitational forces. Axions fitted into the theoretical framework and there was no experimental evidence to disprove their existence.

        Then better experiments demonstrated that axions don't seem to exist.

        In both cases there was a great deal of publication, and physicists clinging to their ideas.

        I was just interested in the parallel, that's all. If the downvoters thought I was describing axions as some sort of pseudo-science, I suggest that they go and read some history of science. I think the history of phlogiston is instructive - especially if you agree with Kuhn.

        1. cream wobbly

          Re: Phlogiston

          Completely agree. It seems like "dark matter" is elusive because it's not there, but that doesn't make it a bad model to explain the universe. The only problem is that people are trying to explain the universe in terms of something for which only its non-existence has been shown. Phlogiston-as-cautionary-tale is very much a valid take, here. Emperor's New Clothes is another. Not that we know they don't exist, just that *so far* we cannot be sure.

        2. Paul Kinsler

          @Voyna / Re: Phlogiston

          I think the reason your post was so widely read in a negative way was because of the wording. Now you've deleted it I can't be as specific as I'd like about your wording - but I'd noticed at the time that how it read (what it implied) differed markedly from a studiously neutral interpretation of the actual words. As a result, I can offer this commentary:

          First, you mentioned "phlogiston", which (however reasonable it may have seemed at its historical time) is now pretty much regarded as an exemplar of infamously wrong hypotheses, and that infamy then transferred itself (unfairly) to axions because you seemed to clearly be comparing (not contrasting) the two. Second, you mentioned experiments in a way which also emphasized the comparison, but again, the somewhat toxic reputation of the phlostigon hypothesis dominated; and so that transfer of reputation *seemed* to be your point. Lastly, axions have a status as possible objects existing within wider mathematically based theory, whereas phlostigon didn't, and this difference rather undermined your (apparent) argument.

        3. handleoclast Silver badge

          Re: Phlogiston

          +Voyna i Mor

          I'd go further in poking fun at it.

          In the later stages, phlogiston had both positive and negative mass, for reasons, in order to account for observed behaviour (burn this and it gets heavier but burn that and it gets lighter).

          It seems reasonable that a new boson, named phlogiston (it ends in "on" so it;'s a boson) can be responsible for both dark matter puling the universe together and dark energy pulling the universe apart.

          Simples.

    2. Paul Kinsler

      Re: Phlogiston / an hypothesis... was falisifeied.

      I think maybe quite a lot of science involves a hypothesis, followed by experimental tests, which quite possibly give a negative result.

      1. Jack of Shadows Silver badge

        Re: Phlogiston / an hypothesis... was falisifeied.

        One of the major problems with how science is done today across all the fields is that we need people conducting repeat experiments so we can assess the accuracy of the initial experiment. Unfortunately, this doesn't bring grant money when it should. Without the verifiable component, we end up with questionable research such as functional magnetic resonance imaging. That was a thang for quite a while before someone actually went and tried to replicate the experiments.

        I don't want to think at all about my primary "science," economics.

  2. Chris Miller

    27 per cent of the universe is dark matter

    That's on the assumption that 2/3 of the universe is constituted by the even more mysterious 'dark energy'. If dark matter exists (i.e. if our current understanding of gravity is correct) there must be about four times as much of it as ordinary matter.

    1. Doctor Syntax Silver badge

      Re: 27 per cent of the universe is dark matter

      "If dark matter exists (i.e. if our current understanding of gravity is correct) there must be about four times as much of it as ordinary matter."

      And given that dark and ordinary matter interact via gravity then surely gravity should cause them to clump together. I should weigh even more than I do given that some dark matter should have attached itself to me.

      1. Isn't it obvious?
        Alien

        Re: ...some dark matter should have attached itself to me

        Thetans! You've cracked it; dark matter is Thetans!!

      2. Voyna i Mor Silver badge

        Re: 27 per cent of the universe is dark matter

        "And given that dark and ordinary matter interact via gravity then surely gravity should cause them to clump together. "

        The thing is that in the absence of the EM field, dark matter has only one way of losing momentum: through actual collisions which result in the formation of new particles. As gravity is such a weak force, it doesn't result in enough attraction between particles to produce many collisions. So we would expect dark matter to cluster only very slowly indeed around even galaxies, because it takes such a long time to slow down enough for gravitational capture.

  3. Uncle Slacky Silver badge
    Boffin

    The invisible and the nonexistent...

    ...look very much alike.

    1. Francis Boyle Silver badge

      Well,

      that's the problem.

  4. Teiwaz Silver badge
    Coat

    Axions were not axioms after all...

    ...Hey I'm not an academic...

    I don't so much have a 'field of expertise' as a marshy bit at the bottom of the garden.

    1. breakfast

      Re: Axions were not axioms after all...

      I mean, they certainly sounded logical.

  5. Mage Silver badge
    Alien

    Dark Matter

    Dark Matter and Dark Energy are both fudges to make observations match what we think we know.

    A solar system follows the rules. Further away stuff has a much longer orbital period. A spiral galaxy ought to be the same. Instead the outer bits rotate nearly at same rate, as if it's a giant solid disc (like how a record or floppy spins). This seems to contravene Kepler's laws (originally Newtonian stuff) as well as Einstein's stuff.

    Also the rate of expansion of the observable universe seems wrong (viewing galaxies), considering mass and energy.

    Dark Energy and Dark Matter make the the macro scale of the Galaxies (our own and others) and the observed universe fit the known "laws" and physics.

    So one solution is finding out what Dark Energy and Dark Matter are, the other possibility is that on a Macro scale something else is happening. Adding an extra non-inverse square law term to "gravity" doesn't seem to work well and what is the theory anyway?

    The observations of the expansion have been revised, due to interstellar dust and gas reducing photon/EM energy and thus making red shift seem larger than it should be. More dust and gas has been found in the galaxy, but not enough to account for the lack of difference in orbital period of outer and inner parts of spiral arms.

    It's a really interesting detective story with both space observation (I look forward to James Web) and lab tests including LHC.

    1. find users who cut cat tail

      Re: Dark Matter

      > Adding an extra non-inverse square law term to "gravity" doesn't seem to work well and what is the theory anyway?

      Of course people have been trying [something like] this [because we really talk general relativity here], with various corrections, but not with much success -- so, pretty much like anything else that we have tried so far.

      One of the main problems is that you cannot say ‘We just change this equation and that fixes it. Done.’ -- you can do this in bogus science but not in actual science. In an actual theory the equation is connected to a bazillion other laws or observations we still consider correct, either it follows from them or they follow from it, it is not used to calculate just the one thing you want to come out differently but also other things... So you have to be careful and are quite restricted in what you can change and how.

      1. Mage Silver badge

        Re: bazillion other laws or observations we still consider correct

        Actually a good test of a theory is not just does it fit, but does it predict something we can test or observe.

        Quantum Theory and Relativity did make predictions. Actually some semiconductor devices, lasers and atomic clocks used Quantum theory, otherwise we might not have invented/discovered them.

        The orbit of Mercury didn't seem to match Kepler laws / Newtonian predictions, but Relativity added the solution (it's closest to sun). It also later transpired the axial revolutions were not tidally locked as the moon is to us, but a more complex resonance.

        1. cream wobbly

          Re: bazillion other laws or observations we still consider correct

          By which you mean, these ain't fudges; they were just written as unknowns which became known later.

          Dark matter and dark energy are unknowns. Axions might turn out to be the phlogistons of our age, but right now, we don't know. That's kinda what "unknown" means.

  6. michael cadoux

    Modified Newtonian Dynamics

    There may indeed be Dark Matter, but the only reason to invoke it is to explain observed galactic/stellar rotations that aren't consistent with Newton's inverse-square law. Why are the various MOND theories so unfashionable?

    Surely very slight tweaking of low-acceleration gravitation on cosmological scales is more in accordance with Occam's Razor, all the more so as gravity is far harder to measure experimentally than subatomic phenomena, which can give staggering accuracy .e.g. clocks accurate to a few seconds over the lifetime of the universe.

    1. Cuddles Silver badge

      Re: Modified Newtonian Dynamics

      "There may indeed be Dark Matter, but the only reason to invoke it is to explain observed galactic/stellar rotations that aren't consistent with Newton's inverse-square law."

      Complete nonsense. There are wide variety of independent observations which all lead to the same conclusion that there is some matter we can't see. Even Wikipedia lists 10 separate lines of evidence, and that's far from the whole story. I really don't understand why people constantly insist on bringing up this idea that there's only a single weak piece of evidence to support dark matter, when just a few seconds with Google or Wiki proves the claim wrong.

      "Why are the various MOND theories so unfashionable?"

      Because they don't work. Occam's razor gets brought up in cases like this all the time, but it's simply irrelevant. Occam's razor says that, all else being equal, you should tend to prefer the theory with fewer assumptions. People tend to forget that first part, but it's by far the most important - most of the time, all else is not equal. MOND and dark matter (and various other theories) do not make the same predictions. In the case of MOND, the predictions it makes do not match actual observations. Occam's razor is therefore utterly irrelevant; we're not picking between two indistinguishable theories that lead to the same results from different assumption, we're picking between a theory that doesn't work and one that mostly does, although obviously none are perfect which is why people are still working it.

      "gravity is far harder to measure experimentally than subatomic phenomena, which can give staggering accuracy .e.g. clocks accurate to a few seconds over the lifetime of the universe."

      Ah yes, those amazingly accurate caesium fountain clocks that certainly don't involve any understanding of the gravitational field they use in order to function. Incidentally, said clocks have an accuracy on the order of a second in 100 million years, so you're off by a few orders of magnitude there.

      1. Doctor Syntax Silver badge

        Re: Modified Newtonian Dynamics

        "There are wide variety of independent observations which all lead to the same conclusion that there is some matter we can't see."

        But don't these all add up to much the same thing - observations failing to confirm one theoretical prediction or another?

        There also seem to be a variety of independent experiments that have failed to identify what it might be. At the very least there ought to be some consideration that the observations are falsifying the hypothesis or hypotheses on which the predictions are based. Or is it going to be a case of science advancing one obituary at a time?

      2. Mage Silver badge

        Re: MOND theories so unfashionable?

        Because the don't actually match observations and they are not theories, just fudged equations claiming gravity varies with distance other than Inverse Square Law. It's more likely that dark matter and dark energy exist. However there may be something else we haven't thought of.

        The MOND theories do not meet an Occam's razor criteria as they are a complication with no explanation.

        1. Captain DaFt

          Re: MOND theories so unfashionable?

          It's more likely that dark matter and dark energy exist.

          Well, something exists that exhibits what we observe.

          IMHO, right now we're at the 'Luminiferous aether' stage, where we're postulating a cause, but in reality the actual cause may be something entirely different that'll look damned obvious to boffins once some bright spark stumbles across it.

      3. handleoclast Silver badge
        Coat

        Re: Modified Newtonian Dynamics

        Ah yes, those amazingly accurate caesium fountain clocks

        What has always puzzled me when people make claims that caesium fountain clocks are amazingly accurate is how they know? Surely you'd have to measure them against an even more accurate clock to know that they're accurate.

        It's Friday and I'm reaching for my phone with the GPS receiver in the pocket. If there are at least 4 satellites in view it's a very accurate clock. So people claim.

      4. michael cadoux

        Re: Modified Newtonian Dynamics

        Not cesium, I was referring to strontium (optical lattice) clocks, accurate to within 1 second over 15 billion years. This has even shows relativistic differences comparing 2 clocks in the same room, one a few centimetres higher than the other.

        1. handleoclast Silver badge

          Re: Modified Newtonian Dynamics

          @michael cadoux

          Same question. How do you know they're accurate?

          You can demonstrate precision. You can even demonstrate they show relativistic effects (probably, unless they're sensitive to air pressure). Accuracy? Nope. Because to determine accuracy you have to compare them to a known standard or to a reference of greater or equal accuracy.

          1. PatuTessa

            Re: Modified Newtonian Dynamics

            This problem exists with all measuring devices. We have no absolute yardsticks anywhere. Clocks are compared against each other. If they pass consistency checks, they become the standard of time, which is now defined in terms of atomic transition frequencies. The exact transition chosen is updated as the technology improves. That is all we can know.

          2. Axman

            You can demonstrate precision... Accuracy? Nope

            precision

            prɪˈsɪʒ(ə)n

            noun

            the quality, condition, or fact of being exact and ACCURATE.

            synonyms: exactness, exactitude, accuracy, accurateness, correctness, preciseness, clarity, clearness, distinctness; faithfulness, fidelity; care, carefulness, meticulousness, scrupulousness, punctiliousness, particularity, methodicalness, perfection, rigour, rigorousness, nicety

  7. sitta_europea

    In my view galaxies aren't in the steady state, and any theory which attempts to describe them as such is bound to fail.

    The stuff in the galaxies is just going down the plughole. That is, the black hole in the middle.

    Simple. No need to postulate imaginary stuff that we can't see that isn't there.

    Somebody ought to do the maths, and share the Nobel Prize with me. :)

    1. Anonymous Coward
      Boffin

      Actually that's how its done, postulating possibilities from the observable and predictable and looking for the debris or evidence.

  8. Doctor Syntax Silver badge

    "At some point during the genesis of the universe, there would have been equal amounts of matter and antimatter, and they should have annihilated one another."

    We live on a planet that clearly consists of matter. I don't think anybody has suggested that odd bits of the solar system that come crashing into us are antimatter either so it looks as if the rest of the solar system is matter and probably the rest of the galaxy as well. But if one looks at other galaxies is there any way of determining that they're all matter other than assuming uniformity? Is there any basis for knowing that half the galaxies we see aren't entirely anti-matter?

    1. Mage Silver badge
      Mushroom

      matter and antimatter, and they should have annihilated one another

      Another great as yet unsolved mystery. Seemingly unrelated to universe expansion/Red Shift and also to the strange rotational behaviour of all the galaxies (spiral?) we have been able to measure. Andromeda is only the nearest spiral galaxy. Some other galaxies are closer than the diameter of our own galaxy, a staggering 100 ly approx. Note the "dark" bits between the visible arms have a mind boggling number of stars. The numbers are all really not comprehensible.

      "Is there any basis for knowing that half the galaxies we see aren't entirely anti-matter?"

      Possibly Cosmic Radiation? (Wikipedia says so)

      There are other issues too with Antimatter and the birth of the universe.

      "There is considerable speculation as to why the observable universe is composed almost entirely of ordinary matter, as opposed to an equal mixture of matter and antimatter."

      Anyway, if the Enterprise Star Trek was real, it would be like making batteries, badly. The only way to get the Antimatter would be a scary automated Fusion powered factory at a gas giant.

      Antimatter / Matter fuel pods are essentially insane batteries that make the worst made and managed Li poly batteries look really safe. I won't travel on such a vessel. Icon for likely fate of such a vessel the first time its OS crashes. It's a worse idea than a car with a fuel tank of nitroglycerine as fuel on a pot holed road with no shocks.

    2. Cuddles Silver badge

      "But if one looks at other galaxies is there any way of determining that they're all matter other than assuming uniformity? Is there any basis for knowing that half the galaxies we see aren't entirely anti-matter?"

      There's no easy way to tell the difference just by looking at them. However, if some parts of the universe are matter and some are anti-matter, then there must be regions where they meet each other. Even if the interface is way out in inter-galactic space, there's still enough (anti)matter around that we should see the annihilation radiation produced. It does get harder to see as you make the regions bigger, but we've more or less narrowed it down to them not being smaller than the observable universe, which unfortunately makes it unfalsifiable - there could be a big pile of antimatter just over the horizon, but since we can never see it it's not particularly interesting to speculate about.

      Fortunately, that's not a particularly likely outcome. In fact, we already have a bit of a handle on the matter-antimatter problem, since we've observed reactions and decays in which they don't behave identically. So far the differences aren't enough to explain the whole problem, but the fact that we've found them at all is extremely significant - we've gone from having no idea how there could be different amounts of matter and antimatter to simply trying to explain the exact ratio.

  9. Al Pha

    If the Universe is infinite, Star Trek exists.

    1. Mike Moyle Silver badge

      I try not to think about what a truly infinite universe means, because the concept of an infinite number of J.J. Abramses terrifies me.

    2. Claptrap314 Bronze badge
      Happy

      Types of infinity

      It is a common error to conflate "the universe is infinite" with "there is an infinite amount of matter & energy in the universe" with "the average density of matter & energy over large enough scales is roughly equal infinitely many times". With "there are an infinite number of locally identical spaces in existence." A implies B implies C implies D.

      To see what I mean, consider a universe where the total mass/energy out to a distance of 10 bly was X, but the total mass/energy from 10 bly - 20 bly was X/2, the total from 20 bly - 40 bly was X/4, etc. In this case, the majority of the universe is already in advanced heat death--no reason to expect infinite anything that matters to physics. So A > B.

      My intuition says B > C strongly, but I'm having difficulty with a demonstration.

      C > D is trickier, but you can see this by thinking about it in terms of entropy. You can have an infinite number of high-entropy states, which do not support life on "earth", and only a finite number of low-entropy states, which do.

      To my knowledge, astrophysicists appear to talk in terms of the diameter of the universe being a single-digit multiple of the diameter of the observable universe. Which is a long, LONG ways from being infinite.

  10. Daedalus Silver badge

    It's worse than it looks

    Axions were proposed as a way of fixing a problem with the theory of the strong nuclear force. Since the strong force holds everything together, proving that axions don't exist might mean that suddenly all matter will cease to

  11. Anonymous Coward
    Anonymous Coward

    This is one of the most crappily written science articles I've read since the last time I glanced at New Scientist.

    Please, send this intern back to The Sun.

  12. TrumpSlurp the Troll Silver badge
    Coat

    Dark Matter Fudge - revolutionary new slimming product.

    The greatest scientific minds agree that Dark Matter is essentially a fudge.

    They also agree that it is inherently indetectable. Therefore it won't register on the bathroom scales.

    So eat as much as you like and you will not gain any weight. It may look as if the wrapper is empty, but trust me and the Greatest Scientists In The World! Buy one, get two free (included in the original wrapper).

    .

    .

    -> Off to Shoreditch with some free samples.

  13. Captain Boing
    Megaphone

    Don't make stuff up so your sums work...

    It seems there is a correlation between the shrinking estimates for dark matter ratio versus the increasing ratio of observed conventional matter based on new discovery: Galaxies existing in huge bubbles of hydrogen (https://www.theregister.co.uk/2015/05/09/hubble_andromeda_galaxy_gas_halo/), vast webs of hydrogen connecting galactic clumps (http://www.iflscience.com/space/astronomers-directly-image-filament-%E2%80%9Ccosmic-web%E2%80%9D-first-time/).

    I never accepted the premise of dark matter "our sums don't add up so we'll invent something to make them". I have every expectation dark matter, as it is conventionally envisaged, will wither to nought as our discoveries, quite literally, fill the void. In the past tow or three years we have discovered extra hydrogen that amounts to a quarter of the mass of the universe that was unknown five years ago... Science will answer everything but it takes a while.

    As with all good science, I will be delighted to be proved wrong with the discover of the dark matter particle(s) - and let's face it, we have barely scratched the surface and are infinitesimally distant from the Planck Mass.

  14. michael cadoux

    More ordinary matter found - dark, not Dark

    So, semi-undetectable filaments connecting galaxies. Also recently more dwarf galaxies than previously detected. I'm sure there will be more such discoveries of dark non-Dark Matter, hence the "need" for DM - or the size of MOND adjustments - will correspondingly shrink.

    https://www.newscientist.com/article/2149742-half-the-universes-missing-matter-has-just-been-finally-found/

POST COMMENT House rules

Not a member of The Register? Create a new account here.

  • Enter your comment

  • Add an icon

Anonymous cowards cannot choose their icon

Biting the hand that feeds IT © 1998–2019