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Given expansion, finally each particle will have only 1 neighbor

  1. Mar 29, 2013 #1
    If the universe expands to the point that each particle has only one neighbor that can communicate given the speed of light, what happens when each particle loses contact with it's last "friend?" i say time stops, space collapses. Conservation can occur because no particles communicate. What do you say?
     
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  3. Mar 30, 2013 #2

    Drakkith

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    Why would time stop? And what does "space collapses" even mean in a scientific sense?
     
  4. Mar 30, 2013 #3

    Chronos

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    In a universe without mass [ie, no gravity], time and space would appear to be meaningless. Of course, this is not probable in our immediate future [as in the next trillion or so years].
     
  5. Mar 30, 2013 #4

    marcus

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    That's a big "IF" isn't it?

    Your scenario is not what professional cosmologists are ordinarily talking about when "accelerating expansion" and "dark energy" is discussed.

    The usual cosmic model, with "accelerating expansion", does not have expansion ever get enough to pull the Milky Way galaxy apart. It does not even get strong enough to prevent the Andromeda galaxy to continue moving in and eventually merging with our galaxy.

    Pop-sci journalism over-dramatizes. What you are talking about is so unrealistic that it is not awfully interesting to contemplate.
     
  6. Mar 31, 2013 #5
    Thanks Marcus for your kind and prompt response. Are you suggesting that consensus says the density of matter approaches a constant asymptotically locally even with eternally accelerating expansion?

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    If a galaxy sized sphere is immune from accelerating expansion, where is the edge of "the sphere of immunity" i assume it would have to be smaller than a void, because voids exist, but bigger than a single galaxy based on argument-by-authority (authority being you). Has consensus determined whether the magnitude of this sphere of influence is variable with time eternal?

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    You think my question is uninteresting. Perhaps i can redeem it somewhat by sounding more like a modern cosmologist: "Assume an expanding universe with only two particles in it. How will those particles interact?" A seemingly simple question, simply framed. The question interests me because i'm curious about time, space, expansion, universe. What's not to like?

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    i haven't read the pop-sci you refer to, perhaps you can source some of it? Pop-sci i've read only mentions expansion tearing individual particles asunder, not isolation. Maybe pop-sci shares scientific consensus and isolation is just plain uninteresting to everyone but me. But then my favorite quote in Gravitation was on page 50 where, it might have been Wheeler quipped that one couldn't tell if space was pushing you down or gravity was pulling you down. i read it right after it came out. i'd thought the same thing since i was 10. Consensus however is still that gravitons somehow come out of earth and pull stuff down, even given Casimir and dark energy. "Uninteresting" is my middle name.
     
  7. Mar 31, 2013 #6

    marcus

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    I believe I was not kind or prompt enough. Sorry about the curtness.

    You might like an article by Lawrence Krauss "the return of the static universe". It envisages the distant future assuming the standard LCDM model.

    The Milky Way, having merged with some of its neighbor galaxies, persists indefinitely.

    We get the same misunderstanding of "accelerated expansion" over and over again.

    It doesn't mean that the growth speed of separations of a given size (like one megaparsec) will increase. In fact for one megaparsec the growth speed is now 70 km/s and is slated to go down to around 60 km/s in the very long run.

    So any structure which has adjusted to the present mild expansion (like our galaxy has) will have an EASIER TIME IN THE FUTURE HOLDING TOGETHER.

    When they say "accelerated expansion" this refers to something different: consider two objects which are stationary with respect to CMB (the background of ancient light). Assume they are not part of any bound structure like a galaxy or cluster of galaxies, and that they are drifting apart at the standard rate which is currently 1/146 of one percent per million years.

    THEN THEIR SEPARATION WILL INCREASE EXPONENTIALLY. Because as they get farther apart, since it grows at roughly a constant percentage rate (or only very slowly declining percent rate) the separation has to grow exponentially like money in a bank savings account. As the base amount increases the yearly increment increases. So that is the acceleration.

    the growth speed associated with a separation of a FIXED SIZE actually is DECREASING, but despite that if you track a given separation between two stationary observers over a long period of time you will see the separation increasing faster as it gets bigger (like the bank account).

    Anyway in future according to standard LCDM model our galaxy will be bigger and have more stars than it does today. You might Google "krauss return static universe" and see if you like his description of the distant future.
     
  8. Mar 31, 2013 #7
    thx Marcus; your kindness to an old man will not go unpunished.
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  9. Mar 31, 2013 #8
    oh man! Krauss is so funny! He should write for Analogue if he hasn't already. All he needs is a good storyline. The young aspiring grad student in the year Goog. It's impossible to find the cosmologic truth according to Krauss, yet this idiotic young upstart has somehow stumbled onto the truth, by faith! He's a mystic! Character drives plot. Paradox drives character. There are only two cosmologists in the known universe, and he is second fiddle. But his girlfriend, well, really she likes the other cosmologist too. And she wants a man who can come up with new ideas! HOO HAW!

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    Good one Marcus!

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    Apart from the bleak future of professional cosmology, according to Klauss, i assume that the voids will get voider, and even the most attenuated clusters will somehow settle into a homeostatic world where i can confidently invest in a condo which will not be wrenched apart beyond the warranty period.

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    i dont want to be the Scalia in the punch bowl here but, but the question of the decay of matter by several means still comes up. Even black holes evaporate. Will all matter be reduced to photons, electrons, and neutrinos, or not? If so, i can't imagine these last fundamental particles hanging around each other in some yuppie galaxy...unless...could it be...dark matter?

    eww!

    Time to run for popcorn! i hate the mushy stuff!
     
  10. Mar 31, 2013 #9
    ROFLMAO. This has to be one of the more entertaining responses
    I have come across. Well done!!!!
     
  11. Mar 31, 2013 #10

    marcus

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    That's the message. About the future lack of observational evidence of an expanding universe. and about the milky way not getting dissolved by expansion.

    As I recall he does NOT go into future miseries like the stars dying, and the other things you mentioned. It is a paper about the future of observational cosmology, not about the overall future of life and all.

    It's something people speculate about. I find it hard to keep my attention on the conditions of life in far future, which speculation has engaged some famous brilliant people, like Freeman Dyson.
    Tastes differ, my favorite thing about the distant future is that the cosmological constant becomes manifest as the Hubble distance and the Cosmological Event Horizon. Both these distances, which are currently different, converge to the same 17.6 billion lightyear value.
    I like mathematical beauty and I'm basically easy to please. This important constant Lambda which is now obscure and hidden in the data on "acceleration of expansion", i.e. has to be painstakingly dug out of data on the dimness of a certain type of Supernova, will then stand revealed like Botticelli Venus in a glorious naked obvious way.
    One over the square root of Lambda is the distance 17.6 Gly. And two of the most basic distances in astronomy will equal that, to three decimal place accuracy, some 50 billion years from now. You can see how my taste runs.
     
  12. Apr 2, 2013 #11
    Ah taste!
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    i mostly just have moods. When my wife is gone i imagine the crushing relativistic vapor pressure of solitude, doesn't matter how the particle got there. Time stops, space collapses. Find here the vast wheat-fields of lonliness currently harvested by Facebook and such.
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    When cracking eggs, it's "which came first, space/time, or mass/energy?"
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    When i'm trying to sing and whistle simultaneously, i wonder if the universe is one big super-position and what happens when it collapses, or is it continually collapsing?
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    Cleaning out the closet, i'll curse gravity and claim it's a fraud; there are only 3 forces! All hail Casimir!
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    When i add cubes, my version of counting sheep, i wonder if Fermat's conjecture says something about space. That the avg closest approximation of splitting a perfect n-cube into two more perfect n-cubes, might be a transcendental number connected to entropy, as a result of the nature of mathematical space.
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    And when i soap my mirrors, i'm all like, "Time is an illusion dude!"
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