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Slowing of Time

  1. Feb 9, 2010 #1
    An article in Wired concerning a new atomic clock has as part of its lead sentence "The new timekeeper could one day ... detect the slowing of time predicted by Einstein’s theory of general relativity."

    See
    http://www.wired.com/wiredscience/2010/02/quantum-logic-atomic-clock/#ixzz0f1IPhJLR
    for the full article.

    Is that statement true? Does Einstein's GR theory predict a slowing of time, and by consequence, a time that initially was faster at the birth of the universe at the Big Bang?
     
  2. jcsd
  3. Feb 9, 2010 #2

    HallsofIvy

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    Because there is no such thing as "absolute" time, it makes no sense to talk about time slowing. We can only talk about the time flow in one frame relative to the time flow in another. My thought was that they were talking about the slowing of time on, say, a satellite or fast moving airplane, relative to a clock on the ground. "Wired" just may not be aware that that's already been done!
     
  4. Feb 9, 2010 #3
    Depending on what is meant, the GPS system frequently takes into account the slowing of time...otherwise positions would be way off rather quickly....
     
  5. Feb 9, 2010 #4

    JesseM

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    Looking at the article, I think it was just a weird way of expressing the speculation that certain "constants" of nature, such as the fine structure constant, might actually vary with time. I don't know the details of how these speculations are supposed to be tested, so I don't know why high-precision clocks would be needed...
     
  6. Feb 9, 2010 #5
    The atomic clock in the Wired article is based on the photon energy in UV lasers. We already know that the photon changes energy in gravitational fields, as shown in the famous Pound Rebka Mossbauer Effect experiment at Harvard. A photon falling in a gravitational field is blueshifted. See

    http://en.wikipedia.org/wiki/Pound–Rebka_experiment

    So how could the atomic clock detect Einstein's predicted slowing of time, unless there is an absolute clock?


    Bob S
     
  7. Feb 9, 2010 #6

    ZapperZ

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    When you have something THAT accurate, with that kind of an error budget, then simply putting one clock on the top shelf of a cabinet can make a difference.

    Read the Perspective article by Daniel Kleppner in the 28 March 2008 issue of Science. In reviewing another experiment on a more accurate clock, he pointed out this:

    When you can have the ability to detect such difference at the terrestrial level, then not only do you have to be extra careful in using such clocks, but it also opens a whole new avenue of testing something which could not have been tested that easily before in a reasonable-sized setup.

    Zz.
     
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