Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

The Big Rip - new evidence for it?

  1. May 13, 2016 #1
    Bulk viscosity is a factor now claimed to support the big rip scenario. Its nearly a year old, but an intriguing story nonetheless, as detailed in the guardian:

    https://www.theguardian.com/science...ang-but-with-a-big-rip-how-the-world-will-end

    and for any with access, physical review online:

    http://journals.aps.org/prd/abstract/10.1103/PhysRevD.91.043532

    being both a sci-fi fan and (almost predictably) a layman on, I am not well versed in the technical details. But I'm interested in subjects like this. Anybody knowledgeable enough to give any summations on whether this is just a rogue theory or a new, better one that fits the evidence?
     
  2. jcsd
  3. May 13, 2016 #2

    phinds

    User Avatar
    Gold Member
    2016 Award

    I got as far as checking the Guardian's report and it has some very seriously incorrect statements so I stopped. Could be just the reporter's lack of understanding and the science behind it may not reflect his ignorance.
     
  4. May 13, 2016 #3
    The article didn't suggest to me any new evidence.
    'Big rip' always has been a possible scenario as have re-collapse and heat death.
    It depends on what 'dark energy' is and how it behaves in the future, nobody can honestly claim that they know.
    What does seem to be the case empirically though is that the rate of expansion has varied in the past, so it's possible that it might change again.
     
    Last edited: May 13, 2016
  5. May 13, 2016 #4
    Thanks for the replies. I am not well versed in the subject. The big rip scenario makes me rather depressed about the future [if only the universe cared]. Could one of the previous posters, or perhaps someone else who agrees with them, summarize why this 'new' theory is not actually good evidence for the big rip?
     
  6. May 13, 2016 #5

    PeterDonis

    User Avatar
    2016 Award

    Staff: Mentor

    A new theory, by itself, isn't evidence for anything. The only way to get actual new evidence is to make new observations or run new experiments. If the new theory makes significantly different predictions from the current ones about some new observation or experiment that you can make, then you can test it. But I don't see anything about that in the article.
     
  7. May 13, 2016 #6
    The article says the new theory: "refines current models by finding a more consistent way to account for a property called bulk viscosity, a measure of a fluid’s ability to expand or contract. In this case, the fluid is the universe itself" The scientists involved claim that there new theory explains the data more effectively. Its far from flawless but still, wouldn't it be considered new evidence? And, what other evidence/s, against the big rip theory, would it have to go up against?
     
  8. May 13, 2016 #7

    PeterDonis

    User Avatar
    2016 Award

    Staff: Mentor

    No, just a new theory that purports to explain existing evidence "more effectively". Developing such things is part of science, but it's not the "evidence" part.

    It's not a matter of evidence "against" the big rip vs. other models. All of the models in this category are huge extrapolations beyond our current evidence. It's more a question of which extrapolation "feels right" in the subjective opinion of various cosmologists.
     
  9. May 13, 2016 #8

    PeterDonis

    User Avatar
    2016 Award

    Staff: Mentor

  10. May 13, 2016 #9

    George Jones

    User Avatar
    Staff Emeritus
    Science Advisor
    Gold Member

  11. May 14, 2016 #10

    phinds

    User Avatar
    Gold Member
    2016 Award

    Indeed. A very thoughtful discussion of the intersection of actual science and pop-science reporting, with, I think, the exception that he was overly generous towards the media.
     
  12. May 14, 2016 #11
    The main alternatives aren't great either, but then this about trillions of years in the future.
     
  13. May 14, 2016 #12
    Ok, we're making progress. :)

    It would be fair to say that the guardian article exagerates the new 'evidence' for the big rip, correct?
    While were at it, is there a consensus, most popular view, on the ultimate fate of the universe, and if so, why is said theory believed to make the most sense?
     
  14. May 14, 2016 #13

    phinds

    User Avatar
    Gold Member
    2016 Award

    yes
    Continued expansion leading to heat death, because that fits the current model and there is currently no evidence to the contrary.
     
  15. May 14, 2016 #14
    Thank you; I am getting less depressed about the big rip so far :D Even in light of this new 'theory', what overall is the specific reason/s for heat death being the most likely possibility?

    Also, though this might be a bit off-topic, the youtubian enlightenment revalates that Michio Kaku is enthusiastic about travel to another universe being possible for a very advanced civilization, such as humanity might be in the future (wish I could find all the videos, but has a lot to do with negative energy, wormholes and the like). What would others here say about that? Just wishful thinking, or plausible, even if far out humankind's current range?
     
  16. May 14, 2016 #15

    phinds

    User Avatar
    Gold Member
    2016 Award

    Exactly what I said. Continued accelerating expansion.

    Also, though this might be a bit off-topic, the youtubian enlightenment revalates that Michio Kaku is enthusiastic about travel to another universe being possible for a very advanced civilization, such as humanity might be in the future (wish I could find all the videos, but has a lot to do with negative energy, wormholes and the like). What would others here say about that? Just wishful thinking, or plausible, even if far out humankind's current range?[/QUOTE]Kaku has been widely, and in my view deservedly, panned here for some time now due to his going way too far in his attempts to popularize science. He is not to be taken seriously.
     
  17. May 14, 2016 #16

    Bandersnatch

    User Avatar
    Science Advisor

    In the currently-favoured model of evolution of the universe, the difference between big rip and heat death depends on whether dark energy is in the form of a cosmological constant, or something that varies in time (e.g. 'quintessence'). Dark energy being the thing responsible for accelerated expansion. In both cases expansion accelerates, but in the latter case the growing (if it's growing) dark energy influence leads to gradual overcoming of local gravitational, and later intermolecular an nuclear forces (i.e., 'ripping' everything apart).

    To distinguish between the two, we have to rely on observations of rates of recession of distant objects. We try to fit the models to these observations, and decide which is a better match.

    As far as I'm aware of the developments in the field, there is no sufficient evidence that dark energy varies with time, but the observations relied upon are still imprecise enough to permit both explanations in principle. The steadily increasing precision of observations narrow down the possibilities towards constancy (read: the model with the cosmological constant remains a good-fit to the data), so if the dark energy is to vary, it would do so slowly.
     
  18. May 14, 2016 #17

    phinds

    User Avatar
    Gold Member
    2016 Award

  19. May 14, 2016 #18
    Phinds, why is the continued accelerated expansion not evidence for a big rip? If it keeps expanding faster, isn't that more consistent with the big rip than the big freeze?

    Bandersnatch. So you're saying that evidence shows dark energy does not vary over time, and, this is evidence for the big freeze, correct? And, are there any specific projects, or technologies that, given current rates of progress, will significantly increase our precise knowledge on this issue, such as new computers, sattelites, measurement devices, etc. ?
     
  20. May 14, 2016 #19

    phinds

    User Avatar
    Gold Member
    2016 Award

    No, there is so far no evidence at all that gravitationally bound systems such as galactic clusters will be affected by it and that would be necessary for the big rip.

    Really, I think you would be better served by reading some basic cosmology than asking random questions on an internet forum. Once you've got some basics under your belt things will make more sense and many of your questions will evaporate. Of course, there will be new ones to take their place.
     
  21. May 14, 2016 #20
    I appreciate your enduring my uninformed curiosity:smile:. Having little exposure to formal education on the issue, I'm not sure what sources to start with. Any particular book titles, or even links to webpages, written with layperson comprehensibility included would be a good start, with the caveat that i can get some reasonable measure of enlightenment on scientific appraisal of the big rip specifically. It is the one that, by far, has my curiosity piqued.

    Just so we're clear--and rest assured this will be last randomly-blurted inquiry--gravitationally bound systems, such as galactic clusters, are *not* being affected by the accelerated expansion of the universe, as would be necessary for the big rip, correct?
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: The Big Rip - new evidence for it?
  1. Big Rip red sky? (Replies: 6)

  2. Big Crunch or Big Rip? (Replies: 14)

  3. Big Rip theory (Replies: 10)

Loading...