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Time theories?

  1. Apr 8, 2015 #1
    I'm new to Astrophysics but some scientists say that all time is happening at one time. How is this possible if the universe is still expanding
  2. jcsd
  3. Apr 8, 2015 #2


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    What scientists? Do you have a credible source for this claim?
  4. Apr 8, 2015 #3


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    The statement "all time is happening at one time" doesn't seem to make any sense. As Chronos asked, please post a reference.
  5. Apr 8, 2015 #4
    Are you referring to imaginary time? All imaginary time occurs in the present. If you think of regular time, where you can move forward into the future, or backward into the past, then imaginary time would allow you to move left or right through time, but only in the present.
  6. Apr 8, 2015 #5


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    What does "left or right through time" mean ?
  7. Apr 8, 2015 #6
    That is if you consider time as every "NOW" slice; then the PAST, PRESENT and FUTURE exists at any moment. Someone who is, suppose 1 million light years away, just suppose, and is moving towards us / away from us, then THEIR "NOW" slice will be directed at our PAST or FUTURE. Therefore from this you can conclude theoretically that every slice of time is in a "NOW" slice and that the PAST and FUTURE is just an illusion which works within space-time, and everything is in "NOW" or PRESENT state, and including PAST and FUTURE that we believe.
  8. Apr 8, 2015 #7
    Something like Interstellar? I admit, I'm equally confused.
  9. Apr 8, 2015 #8


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    I haven't seen Interstellar, and I don't take my physics from movies so that doesn't clear things up.
  10. Apr 8, 2015 #9
    I think "left or right" as in past and future?
  11. Apr 8, 2015 #10


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    No, that's forwards and backwards. I don't think "left and right" has any meaning regarding time, which is why I asked glitch what he means
  12. Apr 8, 2015 #11
    Yeah, I was just saying that "left" and "right" in time doesn't make much sense to me either (I wasn't asking you to borrow flawed sci-fi physics:P ).
  13. Apr 8, 2015 #12


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    OK, gotcha.
  14. Apr 8, 2015 #13


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    That's not quite right, as there are some constraints on what events can be placed in a space-like surface of simultaneity (what you're calling a "NOW slice"). There are many ways of slicing spacetime up so that unrelated events that are simultaneous to one observer but not another (google for "Einstein train relativity of simultaneity" to see how people moving at different speeds relative to one another have different NOWs) but no way of slicing it up so that an effect can ever precede a cause. If you google or search this forum for phrases like "light cone", "timelike", "spacelike", you'll find much good stuff.
  15. Apr 8, 2015 #14
    Think of it as moving through different dimensions of time. It is also not a concept from any science fiction movie, but rather based upon Special Relativity and quantum mechanics.

    Imaginary Time - Wikipedia

    Wikipedia's example describes imaginary time as moving left into the past or right into the future, with imaginary time being up and down (the opposite of what I described), but the point of both our examples is that imaginary time moves perpendicular to regular time and is rooted in the present.
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