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Space Science

Could Dark Matter Be Explained by an Anti-Universe Running Backwards in Time? (livescience.com) 104

Posted by EditorDavid from the extraordinary-claims dept.
"A wild new theory suggests there may be another 'anti-universe,' running backward in time prior to the Big Bang," writes Live Science, citing a new paper recently accepted for publication in the journal Annals of Physics. The idea assumes that the early universe was small, hot and dense — and so uniform that time looks symmetric going backward and forward. If true, the new theory means that dark matter isn't so mysterious; it's just a new flavor of a ghostly particle called a neutrino that can only exist in this kind of universe.

And the theory implies there would be no need for a period of "inflation" that rapidly expanded the size of the young cosmos soon after the Big Bang. If true, then future experiments to hunt for gravitational waves, or to pin down the mass of neutrinos, could answer once and for all whether this mirror anti-universe exists....

Physicists have identified a set of fundamental symmetries in nature.... We live in an expanding universe. This universe is filled with lots of particles doing lots of interesting things, and the evolution of the universe moves forward in time. If we extend the concept of CPT [charge/parity/time] symmetry to our entire cosmos, then our view of the universe can't be the entire picture. Instead, there must be more. To preserve the CPT symmetry throughout the cosmos, there must be a mirror-image cosmos that balances out our own. This cosmos would have all opposite charges than we have, be flipped in the mirror, and run backward in time. Our universe is just one of a twin. Taken together, the two universes obey CPT symmetry.

The study researchers next asked what the consequences of such a universe would be. They found many wonderful things. For one, a CPT-respecting universe naturally expands and fills itself with particles, without the need for a long-theorized period of rapid expansion known as inflation. While there's a lot of evidence that an event like inflation occurred, the theoretical picture of that event is incredibly fuzzy. It's so fuzzy that there is plenty of room for proposals of viable alternatives....

We would never have access to our twin, the CPT-mirror universe, because it exists "behind" our Big Bang, before the beginning of our cosmos.
The theory ultimately just extends the symmetry of CPT, argues the article, "from applying to just the 'actors' of the universe (forces and fields) to the 'stage' itself, the entire physical object of the universe."

Thanks to long-time Slashdot reader fahrbot-bot for sharing the story!
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Could Dark Matter Be Explained by an Anti-Universe Running Backwards in Time? More

Could Dark Matter Be Explained by an Anti-Universe Running Backwards in Time?

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  • It's that this won't end well for any of us.

    • We could be the ones running backward in time as there would be no definition of what positive time meant. It would be an arbitrary sign convention. It would also be irrelevant since this has nothing to do with causality. That's preserved in either reference frame. Nor is this some time travel loop hole.

      • Re: (Score:1)

        by Jimekai ( 938123 )
        I was a cowboy with Asperger's Syndrome designing an accounting system from scratch and was using IBM's binary coded decimal (BCD) to store numbers. The two digits per byte storage ended with a D or a C. I took that to stand for Debit or Credit and the entire system was made consistent so it didn't matter that it the sign didn't mean that at all and no one ever knew six months into live production when I reversed the whole thing.

      • Re: (Score:2)

        by bjwest ( 14070 )

        We could be the ones running backward in time as there would be no definition of what positive time meant. It would be an arbitrary sign convention.

        Backwards in time, to us, is the reverse of our direction in time. To people in the other universe, we're the ones going backwards, but to us, they're the ones going backwards.

    • Re: (Score:3)

      by Gherald ( 682277 )

      But "Counterpart" has taught me that it can lead to a compelling drama series with 100% on rotten tomatoes, free on Amazon Prime ;)

  • Our universe is an anti-universe running backwards in time! That's why I get out of bed every day in the evening and slowly forget what happened to me over the day, until I finally get back in bed in the morning.

  • It sounds like there is no way to test this idea, and that it is broad enough to endlessly adapt to fit whatever circumstance presents itself.

    Sabine Hossenfelder argues that we should stop being such romantics about beauty and symmetry, and get back to experimentation and rigor for science.

    • And that person is dead wrong. You do both. One because science and rigor are brutally important. And two because by nature humans like to understand the universe beyond what we can measure. One way to do that is to philosophize about how the universe works and see if we can come up with any mathematical models that might support it. The theory of special relativity wouldn't exist under Hossenfelder's nonsense.

      • No. Special relativity was very specific, and also accounted for existing evidence clearly, and was also further testable. It was solid Science. The problem isnâ(TM)t theory. The problem is more like- making up fairy tales that can not really be tested.

        • You probably don't know then, that Einstein's work back then often came about after, his wife at the time, and his Italian electrical engineer buddy (and maybe other friends) would sit around a table in a coffee house in Bern, and talk about the universe in esoteric terms. Discussing ideas almost in a flight of fancy until they would come upon an idea that made sense in his head. E.g. riding a beam of light. And those would form the kernel of his real work ideas. Einstein would have been the first to tell y

          • Re: (Score:1)

            by shoor ( 33382 )

            There's the Special Theory and the General Theory. The eclipse of 1919 was used to test a prediction of the General Theory, that light would be influenced by gravity. But, from what I understand, Einstein knew he had gotten his General Theory right when it predicted the known and observed orbit of Mercury more accurately than Newton's Gravitational Theory did. That part though, was an explanation of an already observed phenomenon. The prediction of gravity influencing light was a new phenomenon that ha

    • It sounds like there is no way to test this idea, and that it is broad enough to endlessly adapt to fit whatever circumstance presents itself.

      From TFA: "If true, then future experiments to hunt for gravitational waves, or to pin down the mass of neutrinos, could answer once and for all whether this mirror anti-universe exists."

    • Re: (Score:1)

      by Jimekai ( 938123 )
      Build a bridge to prophesy by pinging those traveling the other way... Two electrons walk into a bar talking shit about when there was once only two holographic electrons moving back through time in a brand new reality, interfering with each other, and leaving traces in time that come back to exponentially repeat the process. Each was now an entangling copy of the original pair, somehow now lost in time, then spawning further copies with dark matter components fuzzily bleeding off at the split position and

    • Re: (Score:3)

      by jd ( 1658 )

      There are ways to test the theory. As noted in the article, gravitational waves and the mass of the neutrino will tell us. There's also the fact that if dark matter is a result of a mirror universe, then you won't be able to find it and will indeed be able to prove that it isn't physically present even though it is having a physical effect.

      So no. This is the same problem I've seen over and over, with people looking at a few keywords, deciding they know everything and ignoring everything that's actually said

    • It sounds like there is no way to test this idea, ...

      From TFA:

      But that doesn't mean we can't test this idea.

      The researchers found a few observational consequences of this idea. For one, they predict that the three known left-handed neutrino species should all be Majorana particles, which means that they are their own antiparticles (in contrast to normal particles like the electron, which have antimatter counterparts called the positrons). As of now, physicists aren't sure if neutrinos have this property or not.

      Additionally, they predict that one of the neutrino species should be massless. Currently, physicists can only place upper limits on the neutrino masses. If physicists can ever conclusively measure the neutrino masses, and one of them is indeed massless, that would greatly bolster the idea of a CPT-symmetric universe.

    • Re: (Score:2)

      by fermion ( 181285 )
      There is only one particle. It presents differently depending on how we measure it. It appears to many particles as it is traveling back and forth in time. The longer the universe exists, the more oscillations it makes, the bigger the universe is. The only thing that seriously contradicts this theory is thermodynamics. Thermodynamics is just a compilation of observations.
  • I have had this nagging feeling that time has been going backwards since around 2016.
  • Because of its reversed thermodynamic arrow of time, things can only get better.

  • Because of the way cause and effect work - we could BE that universe, and wouldn't be able to tell.

    See - our memories would still be formed at some point, and would have to have been formed, in order to lead back to the past - and in having those memories, we'd still be living the same life as if time were running the other way.

    Our lives would be the same.

    Reminds me a lot of debates on philosophical zombies. Time being an illusion is a bit like souls being real or not - it's all context that might or might

    • Re: (Score:2)

      by jd ( 1658 )

      Our lives would be but the mass of the neutrino wouldn't. That is dictated by such parameters. Now, you might be ok with a universe where the evidence is utterly inconsistent with the model used to describe it, but you can't seriously expect the rest of us to be.

  • It's one of those things in physics that is more about imaginative philosophy within the constraints of the evidence. It's interesting to contemplate, but does lead to confusion when people presume these specific theories are specifically prescriptive about what the evidence suggests rather than wild speculation that is merely possible within the confines of our current understanding.

    • Re: (Score:3)

      by crow ( 16139 )

      It does several things: It presents a new model that addresses something that wasn't explained before. It provides a model with simpler and more consistent math. It addresses a long-standing conundrum about missing antimatter. And it suggests some tests that might help verify it.

      So assuming the math really does work out, this could provide a model that better explains everything we've observed, which would make it the standard model until someone comes up with one that explains things even better.

      It may

    • Re: (Score:3)

      by jd ( 1658 )

      It's a simpler description (meeting William of Occam's constraint) and is falsifiable. One thing it is not is philosophy.

      • Re: (Score:2)

        by Junta ( 36770 )

        As a mathematical principle, sure. However when it gets a bit specific about conjuring up a picture of a mirror universe, it gets closer to philosophy.

        Much in the same way the 'many worlds' interepretation of quantum behavior is more a philosophical imagination of what our current understanding of the physics permits. If I recall correctly Heisenberg himself tried to be clear he's just giving math that works, and any further speculation on implications of why the math is the way it is is not something a bit

  • So from the summary, this explains why we don't see equal amounts of matter and antimatter in the universe (though I've wondered if there might be antimatter galaxies and we just don't know it). It also explains the early hyperinflation of the universe (it wasn't just printing money to buy more space). But there's nothing in the summary to say anything about dark matter.

    • If there were antimatter galaxies, given the truly massive number of galaxy mergers including our own having merged many times already, we would see catastrophic releases of energy. But we don’t. Not a single one in the visible universe.

      • Re: (Score:2)

        by crow ( 16139 )

        My thought was that maybe the antimatter galaxies were all went in one direction, and matter in the other. (And that's pretty much exactly what this theory is, only in the time dimension.) And my understanding is that much of the universe is beyond the observable universe, as it's more than 13 billion or so light years away, so we can never observe it, so even if there were any galaxies colliding between the two sets, they could all be past the observable boundary.

        But my Ph.D. in physics was from reading

        • Galaxies are connected by hot gas known as intergalactic filaments, without colliding. The space between galaxies is never empty -- it's effectively empty to us because it's so much emptier than galactic space, but if it contained antimatter then the string of explosions would make it noticeable very quickly.

          Also, the observable universe is 93 billion light years -- not 13 billion, which is the age of the universe. It's true that we can't observe what's beyond that, but all indications lead to the belief th

  • ...says, "No."

  • Didn't Sakharov suggest this back in the '80s? (Score:4, Interesting)

    by parker9 ( 60593 ) on Saturday March 19, 2022 @01:51PM (#62372257) Homepage

    Roughly, shortly after the Big Bang, CP violations had to occur for matter to outbalance anti-matter. He then pointed out he could get CP symmetry back by extending time (T symmetry) to before the Big Bang and doing the opposite CP violation leading to global CP symmetry. He then had a second universe running backwards. This appears to be what the article is saying. Our universe is dominated by matter while the other one would be dominated by anti-matter. This would also persevere CPT symmetry (the one symmetry that has never been seen to be violated).

    Can't quite wrap my head around time before the Big Bang, I must admit. I'm sure my anti-me can't quite see time after the Big Bang either, so ...

    • "space and time and thought... aren't the separate things they appear to be?"

    • I'm sure my anti-me can't quite see time after the Big Bang either, so ...

      Likely just tongue in cheek but just because the other universe has opposite symmetry breaking in physics does not mean every macroscopic thing has an identical but property switched copy. Rather, symmetry of physical law is broken in a way that is the opposite of ours so the result of both together is mirror symmetrical. Further, time viewed by us or within a universe is simply possibility diffusion, both universes would “start” with the hot dense state and proceed toward heat death if observ

    • Re: (Score:2)

      by juancn ( 596002 )
      It sounds a bit like the Big Bounce [wikipedia.org] theory. Although with a single universe made of (mostly) antimatter.
  • Most people will come into existence from dust or fire and come out of the ground to great ceremony(not yet conscious). You wake up, most likely in a bed, knowing everything you will ever know then slowly lose it throughout your life. But you will become more youthful. You shove your children back into your wife's vagina. Sex means semin goes back into you, but also cleans up a lot of womens faces. You produce a lot of food and liquid from your mouth, but first from your toilet putting shit and piss in

  • Or are beards generally considered anti-shave?

  • As long as the neutrinos aren't mutating... (Score:3)

    by Petersko ( 564140 ) on Saturday March 19, 2022 @02:16PM (#62372315)

    ... we'll be fine.

  • Additionally, they predict that one of the neutrino species should be massless. Currently, physicists can only place upper limits on the neutrino masses. If physicists can ever conclusively measure the neutrino masses, and one of them is indeed massless, that would greatly bolster the idea of a CPT-symmetric universe.

    Much like with gravitational waves that have been verified to be light speed with high precision, we just need a far off source and a good detector to measure the time of flight to answer the question. Perhaps a “nearby” supernova could be utilized.

  • Is it just ever decreasing entropy or what? Just sounds like gobbledygook made up on a slow news day

    • Re: (Score:2)

      by noodler ( 724788 )

      No, it's just like normal entropy but the whole timeline goes in the opposite direction to ours. So from the big bang onward these timelines were separated. But i don't know how that explains dark matter.

      • What do you mean by “whole timeline goes in the opposite direction to ours”
        How exactly would it be different?

        • Re: (Score:2)

          by noodler ( 724788 )

          Imagine that time is on an axis. Imagine time 0 (zero) is at the big bang and that our universe evolves along the positive side of the axis.
          Then there is another universe which also started at time 0, but which moves in the negative direction along the time axis.
          It evolves similarly to ours but in the other direction compared to our universe.
          And from that universes perspective time just moves normally and the anti-matter is just the normal form of matter and behaves like our matter.

      • Comment removed based on user account deletion
  • Dark Matter theories have been falsified so many times, maybe it's best to try a completely new approach? https://www.wired.co.uk/articl... [wired.co.uk]

  • ...your dog, wife, and pickup come back to you.

  • If it's a perfect mirror, then it's not really "in a different place", just a different viewpoint or projection of our universe. We would just be saying it's in a different "place" or "time" because English isn't powerful enough to describe it well. It's more like a giant mirror than a different "area".

  • the research, hypothesis', theories and proposals are very much appreciated :D

  • Hi everyone

    For many years now, Jean-Pierre Petit, a French scientist retired from CNRS France work on a model named 'Janus cosmological model'.

    Most of his work is in french, but you have an english resume of his model in english in this video https://www.youtube.com/watch?... [youtube.com]

    But then check all his 29 videos (and more) with english subtitles on Janus cosmological model starting with historical fact about evolution of science up to his consideration of a new (and more precise) evaluation of schwarzschild equa

  • ... cyclic conformal cosmology is a lot cooler. Grants limited access via CMB as well.

  • ...so what should the Protagonist [imdb.com] do, knowing this?

  • They end up in a dimension where time goes backwards and Rimmer and the Cat get jobs as performers since they go in the opposite direction.

  • What if an exact copy of our universe is indeed running in reverse in parallel with our own? But it is entangled on a quantum level with our own and that's why we have this dark matter that we can't account for? And indeed, in this "reverse" universe they have the same dark matter that originates from our own?

    This may violate some kind of quantum physics. I don't know. I'm a graphic designer and a science fiction nerd so I'm not qualified to have an expert opinion. What if this can explain some deja vu that

  • ...just slightly below the one that says that the dark matter is what the monkeys that might fly out of my butt are made of.

  • It seems more logical to propose that the universe maybe revolves in some way, like any planet or galaxy (or every other conceivable object within it), and simply has a light side and a dark side that faces away from the metaphorical light source, and that our side is currently on the daytime side, perhaps even locked to the light side like our moon always faces us so that we only see one side unless we find ways to explore the other side of it.

  • Leave it to astrophysics theorists to complicate an already complicated issue. There is zero proof of any other universe much less a multiverse. You have to solve that problem first I think.

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