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Time in the past

  1. Jun 11, 2006 #1
    I read in Bob Berman's book, Strange Universe, that astronomers found out from observing distant stars, that time in the past went slower, or something. Can you give me a link to an article (from some more... trustful source), please?
     
  2. jcsd
  3. Jun 11, 2006 #2

    Garth

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    Time always passes at one 'second per second'.

    What your source meant, or should have meant, was that a clock, or other process, is observed to go more slowly in the past when compared with the observation of a nearby clock in the present.

    This time dilation is the result of the signals from the distant clock traversing the curvature of space-time caused by the gravitational field of the universe as a whole. It is normally attributed to a relativistic doppler effect in the expanding uiverse - i.e. cosmological red shift.

    Garth
     
  4. Jun 12, 2006 #3
    Although I interpreted the question differently, probably inncorectly, and probably don't fully understand the answer either, I was under the impression that recent research indicates that the universe is not only expanding but also accelerating in its expansion, thus I am curious how you think this would affect realative time from, for example, ten thousand years ago to the present (though I realize the original question was talking about far more distant time periods). Does not an atomic clock approaching the speed of light, relative to one on earth, measure time as slower. Doesn't this mean that entire galaxies accelerating away from each other are going to 'travel through time' (for lack of a better term) slower than those same galaxies ten thousand years ago?
     
  5. Jun 12, 2006 #4

    Garth

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    Whether the universe is accelerating or not in its expansion is irrelevant. Only over time would you notice the difference.

    A difference has been noticed in the apparent magnitudes of distant Type Ia supernovae over the time since they went supernova.

    They are fainter than originally predicted, which means they are further away (for a set z) than originally predicted, which means the universe has expanded faster than originally predicted.

    Its expansion must therefore have accelerated, or, possibly, there is some other expalnation such as early SN are intrinsically fainter than later ones, or the faintness is due to a space-curvature effect rather than an expansion effect.
    Think about what you have said. How would a clock "measure time as slower", or distant galaxies "'travel through time' slower"?

    At what rate does time pass, at what rate does anything "travel through time"?

    As I said in my earlier post, the only way that such statements make any sense at all, except at the tautological rate of "one second per second", is when one clock (say, in this case, a distant clock) is observed and compared with another one (a laboratory clock). Such time dilation is observed from afar. The dilation is an artifact of the curvature of the intervening space-time (i.e. the expansion of space).

    Garth
     
    Last edited: Jun 12, 2006
  6. Jun 27, 2006 #5
    I am glad to see that you agree on that SNe results can be:
    ... due to a space-curvature effect rather than an expansion effect.

    and also on that:
    The dilation is an artifact of the curvature of the intervening space-time (i.e. the expansion of space).

    Juan
     
  7. Jun 27, 2006 #6

    Garth

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    Yes. Of course the physical process being observed in the distant past might actually be going slower than in the nearby laboratory...

    For atomic processes such as the emission and absorption of spectral lines this might be caused by fundamental particle masses, c, [itex]\alpha[/itex] or h varying over cosmological time.

    This creates a degeneracy in our ability to interpret cosmological observations.

    However if these 'constants' should vary then there would be other, often dramatic, consequences and these would be noticed in other observations.

    It is therefore important to have a consistent and concordant theory by which the cosmological data can be interpreted.

    GR is one such theory, except in the respect that it requires Inflation, and therefore a Higgs or Inflaton particle, a DM particle(s) and DE to make it work.

    The unsatisfactory aspect of this is these cosmological entities have not been identified in laboratory experiments (yet).

    Until they are we ought to remain humble about our understanding of the universe-at-large. "Cosmologists are often in error but never in doubt".

    Garth
     
    Last edited: Jun 28, 2006
  8. Jun 27, 2006 #7
    I think you all are missing the point! Time did go slower in the past. Yes, time passes a second per second, but a year is a lot less than it used to be! When I was 5 years old, it seemed like a lifetime to get to my sixth birthday. Now at 70 years old each year goes by very quickly!

    You cannot convince me that time is not relative to ones age!
     
  9. Jun 28, 2006 #8

    Garth

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    Concur.

    'A healthy life really isn't any longer, it just seems that way.' :biggrin:

    Garth
     
  10. Jun 28, 2006 #9

    selfAdjoint

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    Gee, all this agreement and once again I'm an outlier. My last (72nd) birthday seems eons ago now, and the days are really NOT hurrying on to my next one in August. As I think and remember things (maybe edited of course) my course through this year has been psychologically not so different from that through my sixth year.

    Part of the reason could be that my older granddaughter is now coming up on her seventh birthday, in September, and her new sister, born last Winter Solstice, is traversing her very first year, and those are my "relational/emotional" clocks.
     
  11. Jun 29, 2006 #10
    Garth,

    I am not suggesting that fundamental constants are changing along cosmic time.

    As yourself, there is an important number of researchers that are concerned about problems with inflation and Dark Energy in the framework of standard cosmological model.

    My proposal refers to a simple way to avoid the need of inflation and DE,
    which is based in a slight negative curvature of space-time, resulting in a constant or slightly increasing H. Its main consequence would be that Universe was eternal in the past, even if always expanding and becoming colder...

    If there was no Big Bang, there is no need of creation of mass, energy, space and time (violating first principle of thermodinamics), nor singularity problem.

    Juan
     
    Last edited: Jun 29, 2006
  12. Jun 29, 2006 #11

    Garth

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    Okay
    And unidentified non-baryonic DM as well.
    Is your proposal just a 'hand waving' idea or a well developed theory? Actually I'm closer in agreement with you than you think! (SCC)

    Yes negative curvature could do the trick, but your model would have to be internally consistent as well as being concordant with observations.
    This sounds similar to the Steady State theory (SST), in which
    R(t) [itex]\propto[/itex] Exp(Ht), but SST had k = 0 not k = -1. Its problem was to explain BBN and CMB, would your model fare any better?

    Garth
     
    Last edited: Jun 29, 2006
  13. Jul 5, 2006 #12
    Yes, my model is internally consistent.

    The Nucleosynthesis and the Cosmic Microwave Background are esentially explained in the same way than in the Standard Model, since both universes were in fact denser and hotter in the past. The basic difference is the time elapsed since the conditions were adequate for primordial nucleosynthesis and recombination, which in the discussed model are much longer than in Standard model.
     
  14. Jul 5, 2006 #13

    Garth

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    Has it been published, if so where and what is the theory's name?

    If not would you like to post it to the Independent Research Forum? (noting all that Forum's guidelines in the process)

    Or is it elsewhere on the web/arXiv?
    So although you say there was no BB, am I correct in saying that nevertheless, for cosmological nucleosynthesis to have taken place, the universe must have gone through a period of compact volume and high temperature and pressure?

    Garth
     
  15. Jul 6, 2006 #14
    The model has not been published yet.
    What and where is the Independent Research Forum?

    Well, the universe must have gone through a period of high temperature and density, but not of compact volume, since this volume has always been infinite.

    Juan
     
  16. Jul 6, 2006 #15

    Garth

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    here, but make sure you read the "Rules for submission to this Forum" first.
    How do you then obtain the high temperature, pressure and in particular density to generate nucleosynthesis?

    Garth
     
  17. Jul 11, 2006 #16
    Going backwards in time you can reach whetever temperature and density you need, but the time elapsed until now is much larger than in standard model.
     
  18. Jul 11, 2006 #17
    Going backwards in time, one can get whenever temperature and density needed for nucleosynthesis. The only difference is that time elepsed since then is much larger than in standard model.

    Juan
     
  19. Jul 17, 2006 #18
    Going backwards in time, as in standard model, but the time elapsed since primordial nucleosynthesis is much larger than usually believed.
     
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