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

Will there be matter at the end of the universe?

  1. Aug 25, 2011 #1

    phinds

    User Avatar
    Gold Member
    2016 Award

    I was watching Brian Cox on TV last night and he was talking about the heat death of the universe and made the statement that in the far future (he was talking the FFFFFAAAAARRRR future ... out there when even super-massive black holes have evaporated) there would be NO matter left and only radiation tending towards absolute zero. He did not say anything about why normal matter would disappear (or if he did, I missed it).

    First, is that a correct statement and second, if it is then am I correct in assuming that this will happen because super-low-probability quantum events of particles spontaneously converting to radiation will ALWAYS, given enough time, happen ?

    Thanks
     
  2. jcsd
  3. Aug 25, 2011 #2

    BillSaltLake

    User Avatar
    Gold Member

    If protons (that is, protons not swallowed by black holes) decay, the only stable matter that results will be positrons. These will be essentially equal in number density to the (stable) electrons. If they all meet and annihilate, only energy will be left, but it's certainly possible that some electrons and some positrons remain indefinitely.
     
  4. Aug 25, 2011 #3
    Just as an additional note to this; Increasing expansion will mean that any positrons/electrons left will exist within their own OU, with all matter "moving" due to expansion - away from everything else >c. Matter/energy interactions will eventually cease as a thermal equilibrium across the U is reached.

    At lease thats how I see it and its not a terribly happy ending!
     
  5. Aug 25, 2011 #4

    phinds

    User Avatar
    Gold Member
    2016 Award

    yes, I agree w/ all that both of you have said, and this DOES contradict what Cox said. He said no matter at all. It was an unambiguous statement which I found puzzling.
     
  6. Aug 25, 2011 #5

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    Under Caldwell's big rip hypothesis [see: http://arxiv.org/abs/astro-ph/0302506] [Broken] all matter will be destroyed a finite time in the future - possibly as soon as a mere 22 billion years from now. Waiting for all the supermassive black holes to radiate away would be quite boring by comparison - which would take many, many trillions of years.
     
    Last edited by a moderator: May 5, 2017
  7. Aug 25, 2011 #6

    phinds

    User Avatar
    Gold Member
    2016 Award

    Interesting, thanks. Do you have any sense of how likely/unlikely this hypothesis is to be correct?

    If this is NOT the explanation, do I have it right that it would likely be essentially "quantum evaporation" overy a huge period of time?
     
    Last edited by a moderator: May 5, 2017
  8. Aug 25, 2011 #7

    Ryan_m_b

    User Avatar

    Staff: Mentor

    To be fair Cox has to present a very complex field to layman, not only that but he's restricted by being able only to give one explanation that has to be presented to a myriad of people with different backgrounds, educations, beliefs and intelligences.
     
  9. Aug 25, 2011 #8

    phinds

    User Avatar
    Gold Member
    2016 Award

    Oh, I take all that into account, which is why I didn't just take his word for it. It still seems to me that he is either right or wrong and if wrong then he should avoid such a straightforward statement of mis-information.
     
  10. Aug 25, 2011 #9

    Drakkith

    User Avatar

    Staff: Mentor

    So you'd rather him confuse most people or present things in such a complicated way that they can't understand him?
     
  11. Aug 25, 2011 #10

    phinds

    User Avatar
    Gold Member
    2016 Award

    I don't believe it has to be one or the other.
     
  12. Aug 25, 2011 #11

    Drakkith

    User Avatar

    Staff: Mentor

    Things aren't black and white. You have to compromise between getting the overall concept across to the largest possible audience and making it accurate enough to still be "correct". If people wanted to hear a detailed explanation that truly explains the subject they can either read a bunch of books or go to college.
     
  13. Aug 25, 2011 #12

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    The low timeline [22 billion years] appears unlikely, a trillion years, however, looks very realistic. The 100,000 billion years + for black hole evaporation is unrealistic, IMO.
     
  14. Aug 26, 2011 #13
    it will take a lot longer than a few trillion years for super massive blackholes to evaporate
     
  15. Aug 26, 2011 #14
    I think the largest detected super massive black hole will take 1 google years to evaporate. The idea that all matter will decay is also the heart of Penrose CCC idea. I think Cox should have emphasised that this is just one view of the far future universe, its not a matter of fact and I think it wouldnt be too confusing to present the idea with the caveat of its provisonality. Not just state it as a blunt fact ,which it isnt. Overall I think Cox does a great job of popularising science but in this show I think he overstepped what is known. We dont even know for sure that dark energy is a constant.
     
  16. Aug 26, 2011 #15
    I agree with Skydive Phil, to be fair to Cox he does a very good job and in honesty it was the Wonders of the Solar System series that inspired my interest in cosmology!

    Would have been nice to see the other theoretical "end" of the universe scenarios in the Wonders of the Universe show, but he has limited time and the show has to entertain as well as inform.

    Just so you all know the series/episode this discussion is around: Wonders of the Universe Episode 1: The arrow of time. (I am pretty sure this is still on I-player)
     
  17. Aug 26, 2011 #16

    phinds

    User Avatar
    Gold Member
    2016 Award

    I'm not sure how the discussion of relatively short time durations came into play here. I did not say anything about what COX said about the time all this would takes, I use the slightly less precise term "FFFFFAAAAARRRR future"

    If you want to know what he DID say, as best I can remember it he said he was talking about "a trillion, trillion, trillion, trillion, trillion, trillion years". I may be off by one in the number of trillions. but you can, perhaps, see why I'm puzzled why Chronos, for example, thought that I had said COX mentioned several different MUCH shorter times, none of which were in my post.
     
  18. Aug 27, 2011 #17

    Chronos

    User Avatar
    Science Advisor
    Gold Member

    You are confused, phinds, I never asserted Cox said anything of the kind. I was speaking of the Caldwell hypothesis [big rip].
     
  19. Aug 27, 2011 #18

    phinds

    User Avatar
    Gold Member
    2016 Award

    Well, since your statements were directly below a quote from ME, I don't see why you would think I should have interpreted it differently. At any rate, I'm glad you cleared that up.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Will there be matter at the end of the universe?
  1. The end of the universe (Replies: 22)

Loading...