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Is an anti-universe possible?

  1. Sep 6, 2013 #1
    Is an "anti-universe" possible?

    By anti-universe, I mean a universe where anti-matter dominates over matter and the direction of time is reversed. My understanding is that one interpretation of antiparticles is that they are the same as regular particles going backwards through time.

    If a universe contained predominately anti-particles, would time run in reverse?

    A related question: Is it possible that an anti-universe was created from the same big bang that created our universe? The lack of antimatter in our universe may be a result of antimatter going into the anti-universe at the big bang.

    Time for the anti-universe would be reversed and logically the second law of thermodynamics would also operate in reverse. It has been about 14 billion years since the big bang. The anti-universe would have been at a similar state to our present universe 14 billion years before the big bang.

    I have not seen any speculation in this area. Has anyone looked into the theoretical possibility of an anti-universe?
  2. jcsd
  3. Sep 6, 2013 #2


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    This is just not true. Antimatter follows the same rules for time as everything else. Otherwise I'm sure we'd see some very, very odd results when working with antimatter in the real world.

    Consider that single antimatter particles decay in predictable rates just like normal matter. Does that sound like time going in reverse to you?

    No. What possible reason would time have for running backwards?

    Philosophical implications aside, I don't see how that could happen since we have antimatter in our own universe that we know to behave like normal particles. We don't see them running backwards down our particle colliders or any other nonsense.

    Let's not talk about "before the big bang". That currently is beyond science and will attract crackpots.
  4. Sep 6, 2013 #3
    I want to try and further expound on this topic. Drakkith is correct that antimatter does obey the same laws that regular matter obeys, which includes temporal movement. Now we do know that according to the math there isn't a real understanding as to why we experience time in only one direction. The science is that time is equal going either backwards or forwards, and particles would treat any time arrow as the same.

    Now someone might point out entropy, which I'm familiar with. I won't debate that, but overall the topic is still not completely understood. But there are other things to this. Scientists think there might be antimatter systems out in the universe: stars, planets, even entire galaxies all created with antimatter in the same ways that matter creates its systems. It's not far fetched to think that there might be antimatter universe(s) and that the antimatter we experience in our own universe might be those particles jumping back and forth, in which case, matter might do the same in that antimatter universe.

    But for any antimatter system to form, it would still need to obey the the second law of thermodynamics, the aspect of creation.
  5. Sep 6, 2013 #4
    According to Feynman's interpretation, antimatter is essentially the same as conventional matter only it is moving backwards in time. Thus an electron-positron creation is really an positron moving backwards in time, interacting with a photon, and then moving forwards in time so that the particle and antiparticle exist at the same time.

    For details see:

  6. Sep 6, 2013 #5
    Welcome to PF, Bill.in.PA!

    Well, what you are doing is actually basically taking an old computational trick, interpreting it as fact and extrapolating it to cosmology. Such things can get messy :biggrin:.

    Why would it? ?ti lduow yhW
    I've never seen time run in reverse, except in movies :smile:.

    Or the lack of antimatter may be the result of something completely different.

    I do personally not know any good, reliable scientific source that discusses along these lines. And as you hopefully understand, there is very much speculation in your post. Please note that the PF Global Guidelines states

    "Generally, in the forums we do not allow the following:
    Personal theories or speculations that go beyond or counter to generally-accepted science."

    EDIT: I just noticed Drakkith managed to sneak in a reply while I was writing :).
    Last edited: Sep 6, 2013
  7. Sep 6, 2013 #6
    Where did you get "really" from, who told you that? An electron-positron creation is really an electron-positron creation, and it is causal.
  8. Sep 6, 2013 #7


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    I am not aware of any reputable scientists that believe this. Such objects would interact with the interstellar/intergalactic medium and readily annihilate, emitting gamma radiation that would would be able to detect. It also does not follow with the currently accepted theory of baryogenesis. What little antimatter existed 13 billion years ago was simply too spread out to ever form anything larger than simple molecules at best.

    I disagree. I think that's a huge stretch. Not only do we have zero evidence for the existence of anything other than our own universe, you'd still need a method for them to "jump" from one universe to the other. This is more sci-fi than science.

    Yes, and I'd guess that is not because he actually believes them to be moving backwards in time, but that it makes the equations/diagrams easier to work with.
  9. Sep 6, 2013 #8
    Don't get how that answers the OP's question. But I am just a n00b in this topic...A cocktail party philosopher as Feynman would put it.
    As for difference between antimatter and matter its not reversal of time its the reversal of properties such as charge, baryon and lepton numbers. All properties like mass and time dependence is symmetric with their matter counterparts.

    As for reversal of time in Hawking's lecture Does the arrow of time reverse? He says he once entertained that time would reverse when [and if- a big if as far as I understand] the universe left its expanding stage and entered into a collapsing one. Here he says "People in this world would live their lives backward. They would die before they were born..." but then he goes on to say how his colleague Don Page pointed out that contraction did not imply reversal and his student Raymond Laflamme proved that Hawking's assumption was wrong and contraction would not lead to decrease in entropy but entropy would go on increasing. And Hawking gracefully concedes that he was wrong.
  10. Sep 6, 2013 #9
    Much of the development of physics has been related to making the equations easier to work with.

    It is possible to work out celestial mechanics with the earth as the frame of reference, but the equations get really ugly because the earth far from an intertial frame. A breakthrough occurred when people realized that using the sun as the frame of reference greatly simplified the equations since it much closer to being an intertial frame.

    My question is if the convention for the direction of time for antiparticles in the Feynman Diagram would imply that a universe that is filled with antimatter instead of matter would follow a similar convention on the direction of time. If so, then such a universe could behave in essentially the same way as the conventional universe, only with time operating in the opposite direction.
  11. Sep 6, 2013 #10
  12. Sep 6, 2013 #11


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    The connection between the temporal direction of matter and antimatter is illogical. Were that true, could you not make a case that positive and negative electrical charges travel in opposite temporal directions? That is pretty obviously silly.
  13. Sep 6, 2013 #12


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    No, it does not imply that an antimatter universe would have time reversal. It's just a convention used in the diagrams, not something you can apply to the universe.

    Note that, at least according to wiki, antimatter is thought of AS IF it were traveling backwards in time, not that it actually does.
  14. Sep 6, 2013 #13
    Drakkith said nothing at all about that. Please do not put words in other people's mouths. We are NOT talking about string theory/M-theory here, we are talking about some kind of undefined, unknown no-name hypothesis. I would advise new posters to stop this wild train of speculation, and start to listen. And probably calm down, too. :wink:
  15. Sep 6, 2013 #14
    Can you provide a link or reference for this statement?

    If antiparticles exhibit the same decay rate as the corresponding conventional particles, it would confirm that they are behaving with the same direction of time.
  16. Sep 6, 2013 #15


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    I've never even heard of that and I can almost guarantee you that a large object composed entirely of antimatter would be an extremely interesting find for the very reason that it is practically an impossibility in the standard model.

    While there may be some minor amount of debate, to my knowledge it is generally accepted that antimatter behaves just like normal matter in regards to gravity. We don't know for sure, as we don't have enough antimatter to reliably test it, but we have no reason to believe it does.

    We only discuss mainstream theories here on PF. If someone asks or says something that goes against a mainstream theory they will be corrected.

    No, that is entirely not true. String theory/M theory has a very good mathematical backbone, they just have no evidence to tell them whether they are right or wrong yet. This is completely different from what you said.

    Use the following tags to quote a section of someone's post.
    (quote) (/quote) Replace the parentheses with brackets.
  17. Sep 6, 2013 #16
    I never said he said anything. I actually asked a question. I did no such thing as to say "Drakkith you said this..." in which that person never said. I only used what I used as an example to relate that because you don't have evidence for something doesn't mean it can't be a theory or is or isn't correct. No way of proving multi-universes which String/M theory describe, but this is considers credible. He said what I was saying had no evidence and that it was a stretch. I used an example to say it wasn't a stretch. I probably should have been more clear on that, but I was under the assumption that some people could make that connection.

    I know I'm not on any wild train of speculation. I'm not saying anything is or isn't...I'm saying the idea has been around, and I've even said that what I'm saying could just be an idea at best. I'm pretty calm. I understand how to handle myself in a discussion manner. Please give me that kind of courtesy, and not feel you need to moderate something that needed no moderation.
  18. Sep 6, 2013 #17


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    A quick reference:

    The mean lifetime of the (positive) muon is 2.1969811±0.0000022 µs.[1] The equality of the muon and antimuon lifetimes has been established to better than one part in 10^4.

    Note that the positive muon is the antiparticle of the negative (normal) muon.
  19. Sep 6, 2013 #18
    Excellent. I'm not a moderator, I was just trying to be helpful. What I was trying to say was that this discussion should be about the original post #1. String theory and M-theory is irrelevant, since the OP has not said anything about it.
  20. Sep 6, 2013 #19
    You've never heard of Flatlander? That's a little surprising, if that was what you referring to when you said "I've never even heard of that". I'm totally with you on how extreme of a find that would be. I'm trying to find the article I read that anti-star might be out there.

    I'm with you on that. antimatter is said to have the same properties of matter, but I know I read that the thought might be that it reacts the same way with gravity, or that it creates gravity of the same magnitudes, but it creates it just slightly different in that antimatter and regular matter can repel each other.

    Ok. I'll keep that in mind. Although that seems kind of limiting. It's only recent that people are starting to think of Time as being multiple dimensions and not just one. There was even an offer I found to Physicist in which that was a category to work in, and it proposed the question of multiple temporal dimensions.
  21. Sep 6, 2013 #20
    Totally understandable. Like I mentioned I just used it as an example. I didn't want to derail the original topic. And oddly enough, this conversation we are having is doing it just as well, haha
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