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Time dilation in space travel

  1. Nov 17, 2006 #1

    DaveC426913

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    Many short story ideas I have involve space travel. I'm looking at the Lorentz transform formula and scratching my head.

    Is there a relatively straightforward way to use the time dilation formulae and calculate subjective travel times for space travel?

    Presume a spaceship accelerates at a=1g for the first half of its trip, and a=-1g for the second half, to stop at its destination. If the distance to its destination is d light years, how long does the trip take subjectively and how long does the trip take from stationary observer's PoV?

    OK, now what if I change a to, say, 2g?
     
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  3. Nov 17, 2006 #2

    selfAdjoint

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    Two novels based on the time dilation formula are To The Stars by L. Ron Hubbard (a lush coming-of-age operetta), and Tau Zero by Poul Anderson (a sensawunda barn burner).
     
  4. Nov 17, 2006 #3

    robphy

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  5. Nov 17, 2006 #4

    DaveC426913

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    That's great, thanks.

    OK, so for a trip to, say, Vega, which is 27 ly distant, it would take 6.6 years ship's time.

    But how long does that take Earth-time? I guess the only way to know is to come back. So a round trip, with a stopover at Vega would take 13.2 years ship-time. How much time has passed on Earth?

    Oh wait. I see. That's covered. It takes 28 Earth years one-way. So, the round trip takes 56. Thus, upon reaching home, people on Earth will be older than astronauts by (56-6.6) 49.4 years.

    And this holds true regardless of how long their stopover is. So, they fly to Vega, build their colony, and then in 20 years, they come back for supplies or shift-change. The Earth they come back to is 49.4 years older than they are.
     
  6. Nov 17, 2006 #5

    DaveC426913

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    Is there a graphical way of representing this? Light cone stuff?

    My next step is to time events of multiple spacecraft in the story, so I understand sequence of events. (such as, if you accelerate at 2g instead of 1g, how much earlier do you arrive?)
     
  7. Nov 17, 2006 #6

    robphy

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  8. Nov 17, 2006 #7

    DaveC426913

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    Cool.
    10char
     
  9. Nov 18, 2006 #8
    Contarary to many explanations offered on these forums and in the literature, there is no need to return to earth to explain the difference in time - When the spaceship arrives at Vega, the clock at Vega will read the same as a clock on earth (since earth and Vega are in the same inertial frame at all times during the one way journey). The spaceship clock will have logged less time than all of the clocks in the earth-Vega frame, and the difference is easily deteminable when the spaceship docks on Vega. If the traveler decides to return, under the same rates of acceleration and velocity, the time difference is simply doubled.
     
  10. Nov 18, 2006 #9

    DaveC426913

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    Well yes, I deliberately doubled the trip, but not out of a misguided necessity. My intent was to avoid any additional complexity in terms of non-simultaneity of events between Earth and Vega. While you're on Vega, how do you know for sure what time it is on Earth?
     
  11. Nov 19, 2006 #10
    i googled "oh my god particle". and the first hit is a paper about this cosmic partical that was detected.
    travelling at almost the speed of light, so fast in fact that it would arrive just a few millimeters behind the photons that were emitted at the same time.

    one section of this article, has a chart of the Time Dilation experienced by this high speed particle.

    it show that this particle would travel a distance of 2000 lightyears but due to its speed, its would make that trip in 3.5 minutes, (IN ITS frame of reference).

    so you are looking through a telescope at an object 2000 yl away, and you say "what does it look like NOW??".

    its 1pm Nov 19, 2006, you just into your spaceship, that travels at just under the speed of light, and you travel to that object 2000 ly away.

    your watch now reads 1:03:30, and 3.5 minutes have elapsed since you viewed this object that YOU ARE NOW AT.

    you turn your space ship around, and point towards earth, and flash your headlights. at the same time, you get on your faster than light space phone and ring up earth.

    you ask them to look out at the object, and to see if they can see you.
    they reply Yes, we can see you flashing your headlights.

    you ask the person on earth what year it is, and they say, the time is 1:04year 4006.

    only 3.5 minutes are elapsed for the traveller, and 2000 years for the people who stayed on earth.

    to me that puts into question about when an event actually occures, because if this high speed particle was an atomic clock, and you times how land ago that event occued, its would say that an event that occured 2000 yl distance, happend 3.5 minutes ago,

    and if you asked the photon how long ago that event occured, its would say "just then". or NO time. and therefore for the phone no distance either.

    (is a photon just a sub-atomic particla with a zero half life, as soon as it experiences "TIME", its decays ?? )

    sorry for long post, and for not really asking anything, my question is this correct. or way off track.

    but the "oh my god particle" article is a good read


    http://www.fourmilab.ch/documents/ohmygodpart.html
     
  12. Nov 19, 2006 #11

    DaveC426913

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    That's one seriously fast - and heavy - proton.
     
  13. Jun 3, 2011 #12
    "OK, so for a trip to, say, Vega, which is 27 ly distant, it would take 6.6 years ship's time.
    But how long does that take Earth-time? I guess the only way to know is to come back. So a round trip, with a stopover at Vega would take 13.2 years ship-time. How much time has passed on Earth?
    Oh wait. I see. That's covered. It takes 28 Earth years one-way. So, the round trip takes 56. Thus, upon reaching home, people on Earth will be older than astronauts by (56-6.6) 49.4 years.
    And this holds true regardless of how long their stopover is. So, they fly to Vega, build their colony, and then in 20 years, they come back for supplies or shift-change. The Earth they come back to is 49.4 years older than they are."



    That doesn't sound right. Wouldn't it be 49.4 years elapsed on earth plus stopover time, since you aren't travelling while stopped.
     
  14. Jun 3, 2011 #13

    Ryan_m_b

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    I've always wanted to try and make a well programmed spreadsheet where I can plug in the distance and the acceleration and it would give me the time on the clock, I've always failed :(

    EDIT: Oops, didn't realise how dead this thread was. Apologies for the necropost.
     
  15. Jun 4, 2011 #14
    Dave, please see link to the very new and exciting explanation of time dilation:

    <crackpot link deleted>

    Time Dilation – Explained. Description of the experiment verifying the interpretation of time dilation of the Theory of Relativity
     
    Last edited by a moderator: Jun 4, 2011
  16. Jun 4, 2011 #15

    DaveC426913

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    There are lots of relativity calculators online that will do this.

    Not a chance am I opening an unknown .doc file. Save it as a PDF and I'll look at it.
     
    Last edited by a moderator: Jun 4, 2011
  17. Jun 4, 2011 #16

    Ryan_m_b

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    Really? I've never found any. All I've managed to find are calculators that give the time dilation factor and once found a journey time calculator for continuous thrust. What I want is something where I can plug in distance, acceleration and if there is a midway turnover (to decelerate/intercept) and get back the total time as measured by the ship and by an observer who is relatively at rest.
     
  18. Jun 4, 2011 #17

    DaveC426913

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    Try this one:
    http://www.orionsarm.com/fm_store/RTTCalc.htm
     
  19. Oct 17, 2011 #18
    This one is kind of cool too. Although you won't see the math behind the calculations.
    Space Math.
     
  20. Oct 17, 2011 #19
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