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Is there a name for this equation?

  1. Sep 14, 2009 #1

    Is there a name for the equation that calculates how fast someone has to travel to move forward in time, say for example, a day? Infact, does such an equation even exist? i ask this becoz i hear in different videos how astronauts have traveled into the future.. even if its just milliseconds. How do they calculate this?
  2. jcsd
  3. Sep 14, 2009 #2


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    Science Advisor

    For both special relativity and general relativity there are effects as you described. The SR effect is called the Lorentz transformation. The GR effect (gravitational) is probably what you have heard about.
  4. Sep 14, 2009 #3


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    Gold Member

    Suggestion: Use Wikipedia and search for "Twin Paradox"
  5. Sep 14, 2009 #4


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    Staff: Mentor

    Or "time dilation".
  6. Sep 15, 2009 #5
    Thanks guys. i wish i had taken up this field in uni instead of IT :(
  7. Sep 16, 2009 #6
    I understood time travel as "the farther you move into space the more you are going back to past". Please explain me how can some body get into future???
  8. Sep 16, 2009 #7
    Erm, I dont know who said that. Moving into space wont send you anywhere in time.

    I know exactly what you are getting confused about though.

    When you 'look' further into space you are seeing the past. That is becus the light is only just reaching us.

    So for example we are seengin the sun as it was 8 minutes ago. as its 8 light minutes away. We see a star 1 light year away, we are seeing the light emitted from that star 1 year ago. If we travelled to the star we shouldnt have gone back in time. When we look at something a billion light years away, we are seeing stuff that happened a billion years ago, as that light is only just coming to us.

    So futher away you go, further you are loooking into the past.
  9. Sep 16, 2009 #8


    Staff: Mentor

    Wait a while.
  10. Sep 16, 2009 #9

    Ah! But is it technically the future when you get there?
  11. Sep 16, 2009 #10


    Staff: Mentor

    Just as much as any other possible mechanism of getting to the future.
  12. Sep 16, 2009 #11
    That is what i read and understood! But what about future? Is that some kind of travel in the direction of expansion of the universe (a real weird guess although i believe its towards every direction!!!)
  13. Sep 16, 2009 #12
    You didnt read/understand the other bit did you.

    Far away isnt in the past. IF you could magic yourself there, you would still be in the present. The fact that light takes time to travel doesnt affect the time period of the region of space it came from.

    If you were 5 billion light years from earth, and had good enouhg eyesight, you could see its formation. That doesnt mean we are currently sitting 5 billion years in the past, or that you would be 5 billion years in the future.

    Therefore no direction of travel will take you in any direction of time.

    No you cant travel to the past.
    No you cant travel to the future.
    No you cant see the future as it hasnt happened yet.

    The only reason we can see the past is that it takes light time to travel from its source to the destination.
  14. Sep 16, 2009 #13
    Thanks Chris, you are right! I am reading about Time Dilation now and hopefully in the next 24 hours, i will have some 10^x questions! I am very poor in relativity theories and need some help!!!
  15. Sep 16, 2009 #14


    Staff: Mentor

    Yes, you can. In fact, you can't stop travelling to the future.
  16. Sep 16, 2009 #15
    As I said before, when you arrive there it is no longer the future.

    Within the context of this discussion, pertaining to acutally travelling to a time that hasnt happened yet without the pesky business of waiting for it to happen. No you cannt travel into the future.

    The 'future' is a moving target that is always out of reach, much like an abstract view of 'tomorrow'.

    Now we can nail down and say as of 00:00 hours, we will be both in tomorrow and the future. But by the time we get to 00:00 we will consder it to be the present and and tomrrow will be (EDIT:) friday (god i dont even know what day of the week it is).

    Now there is a semantic argument to bend your head round.
    Last edited: Sep 16, 2009
  17. Sep 16, 2009 #16


    Staff: Mentor

    In your definition the future is not a set of events, but a direction in spacetime. In which case you still travel to the future, just like you can travel to the east. Anyway, as you say, it is a purely semantic argument and therefore boring.
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