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Why Do You Travel Into The Future As You Approach The Speed Of Light?

  1. May 15, 2006 #1
    Time appears to pass more slowly for faster-moving bodies. In other words the faster you travel, the slower time will move for you.

    When you reach the speed of light time stops. If you travel faster than the speed of light it is assumed you can go back in time.

    All these natural explanations of time seems harmonically sound..........until you get to how you can go into the future.

    Why does time speed up as a approach the speed of light? Doesn't the violate the "Time appears to pass more slowly for faster-moving bodies" principle. Time going slower as you go faster seems to logically make more sense. Time all of a sudden speeding up instead of slowing down as you approach the speed of light (as will as some other aspects of time dilation) do not logically make much sense.

    Instead, it would be more logical to go forward in time with negative speed (t). However we all know that you cannot go at a negative speed, and in this alternative way you cannot go forward in time. This alternative law of nature is similar to the fact that you can't go over the speed of light and therefore you cannot go back in time.
  2. jcsd
  3. May 15, 2006 #2
    You misinterpeted that: 1) Time doesn't move faster for you when you speed up time goes slower but for everthing that's moving slower then you are time goes faster.
  4. May 16, 2006 #3


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    What he said.
  5. May 16, 2006 #4


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    This is a good opportunity to seek volunteers to write an FAQ for our forum that tackles this misconception about time dilation. Any volunteers?


  6. May 16, 2006 #5


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    You don't need to "approach the speed of light" to travel into the future! You are doing it right now sitting at your desk. As others have pointed out, time slows for an observer moving at high speed relative to others, not speeds up.

    I'm not sure what you could mean by " However we all know that you cannot go at a negative speed". "Speed" is by definition (in the strict physical sense) non-negative but you certainly can have a negative velocity.
  7. May 16, 2006 #6
    I volunteer to write a piece that debunks the "reciprocal time dilation" (aka Dingle's folly).
  8. May 16, 2006 #7
    By traveling into the future I don't mean traveling at normal speed. If you go closer to the speed of light you go very quickly into the future if you are the one going close to the speed of light. This however contradicts the fact that time passes slower as you go faster? Should time go even slower if you approach the speed of light? If so why would you nearly "warp" to the future as you approach the speed of light?

    By negative speed I mean.....say......-10 KPH. It isn't possible, but it would make more sense to travel quickly into the future by going at negative speeds than approaching the speed of light.
  9. May 16, 2006 #8
    I think it goes like this. since you are going slower in time. but that's in your reference frame.therefore , for other observers. Time will be normal. So you will have aged less because time for you is slower but time for other people is the same.

    So it'd be... say for example 3 years for you but for example it's been 5 years to people on earth. which indirectly means you have gone to the future.

    Hope I got it right there.
  10. May 16, 2006 #9


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    Let me make a few suggestions:

    1) take a look at

    http://www.onestick.com/relativity/" [Broken]

    to get a better idea on what time dilation due to velocity actually means. The main point you appear to be missing is that if A moves relative to B, A thinks that B's clocks run slow, while B also thinks that A's clocks run slow.

    Your next question will undoubtedly be about the twin paradox, but I suppose that can't be helped.

    2) Forget about travelling "at the speed of light" or "faster than the speed of light". This is not possible within the bounds of relativity. Asking questions about impossible conditions is an almost-surefire way to confuse yourself.

    Do yourself a favor, and attempt to actually understand relativity, and avoid questions about travelling "at lightspeed" and "faster than light" until you do understand relativity.

    In this vein, realize that if you accelerate at a constant rate (say 1 Earth gravity) your velocity will always increase, but you will never, ever, no matter how long you accelerate, reach the velocity of light.

    BTW, the mathematical formula for your velocity after accelerating by your wristwatch for a time T is

    v = c*tanh(AT/c)

    Then tanh function approaches 1 as its argument reaches infinity, but never reaches 1


    tanh(1) = .762
    tanh(2) = .964
    tanh(5) = .99991
    tanh(10) = .999999995

    Last edited by a moderator: May 2, 2017
  11. May 16, 2006 #10


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    Nope. Your time always flows normally, whoever you are, as long as you are inertial (not accelerated). Your instruments show you other people's time flows slower than that. Other people measure your time as slower than theirs, too. All of this time comparison is relative, and the transformations are symmetric; what you see happening to their lengths and times is just what they see happening to yours.
  12. May 16, 2006 #11


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    from the '70s there's a pop song by the Steve Miller Band that goes: "Time keeps on slippin', slippin', slippin' into the future...."

    i guess we're all time traveling into the future at a rate of 1 minute per minute.

    now, if you can spend the entire gross domestic product of the U.S. for a few years, maybe you can build yourself a really fast spaceship with all of the life support systems you need to live for a few years and take about 8 years to fly to Alpha Centauri and back at 0.999 c. it'll seem like about 8 years to you, but when you get back, it will be about 179 years later here. so that would be time-traveling into the future at a rate of 22 minutes per minute.

    rots o' ruck.
  13. May 16, 2006 #12


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    Er, You've got that a little wrong. It would take a little over 8 years Earth time, and about 4 1/3 months for you.
  14. May 20, 2006 #13
    for the question of travelling into future, i think it is convinience to refer to the twink paradox.
  15. May 20, 2006 #14


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    "Twink" paradox? They have to be THAT young?


  16. May 20, 2006 #15
    what mean by THAT young?
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