4 ms·

Question: In the year 2200, if a 10 year old child were to travel to the planet at a speed of 0.9999c, then were to immediately turn around and travel back to

by palish 15y ago

Question: In the year 2200, if a 10 year old child were to travel to the planet at a speed of 0.9999c, then were to immediately turn around and travel back to Earth, they would be approximately 50 years old. However, what year would they arrive back on Earth? Assumptions: - no acceleration or deceleration time. - the planet is exactly 20 light years away. - the velocity of the ship remains exactly 0.9999c while in transport. (The answer is not 2240. It's much greater. My question is, how much greater?)

svrocks 15y ago
5028
- deleted 15y ago
  [deleted]
DavidSJ 15y ago
I think you've got it reversed. From Earth's perspective, it would take exactly 40 years, but the child would age very little.
forensic 15y ago
http://www.wolframalpha.com/input/?i=time+dilation+traveling+at++.9999c+&a=*FS-_**RelativisticTimeDilationFormula.t-.*RelativisticTimeDilationFormula.to--&f2=40+years&x=7&y=11&f=RelativisticTimeDilationFormula.to_40+years http://www.wolframalpha.com/input/?i=time+dilation+traveling... 2828 years + 2200 = 5028 A.D. says wolfram alpha
- palish 15y ago
  Fascinating. 40 years at 0.90000c = 91.76 years 40 years at 0.99000c = 283.55 years 40 years at 0.99900c = 894.65 years 40 years at 0.99990c = 2828.00 years 40 years at 0.99999c = 8944.00 years
  - Confusion 15y ago
    With the caveat that nobody will be traveling at 0.99999c for 40 years. You'd be really really far away by then.
    - splat 15y ago
      Well, you'd still be less than 10,000 light-years away. That's still well within the galaxy.
btilly 15y ago
Your problem statement is wrong. The child is traveling 40 light years at 0.9999c, which takes about 40 years + 35 hours. However the child won't arrive back 50, the child will not yet be 11. See http://www.wolframalpha.com/input/?i=time+dilation+traveling+at++.9999c+&a=*FS-_**RelativisticTimeDilationFormula.to-.*RelativisticTimeDilationFormula.t--&f2=40+y&x=6&y=5&f=RelativisticTimeDilationFormula.t_40+y http://www.wolframalpha.com/input/?i=time+dilation+traveling... for the exact age. See http://en.wikipedia.org/wiki/Twin_paradox http://en.wikipedia.org/wiki/Twin_paradox for more on this, including an explanation of why your belief about the age of the traveler is wrong.
- palish 15y ago
  How can this be? If the child were moving at 0.9999c (which is less than 1.0000c) and the planet is 20 light-years away, then how could it take less than 20 years for the child to reach it? Let alone ~0.5 years? EDIT: Here's an explanation from a friend: light always travels at c even if you're already moving close to c but it's impossible for anything to travel faster than c so if you're traveling at .9999c the passage of time must be scaled for the traveler to make light on the ship appear to move at c even though it's only moving at 1-.9999c That's... awesome.
  - Confusion 15y ago
    If the planet is 20 light years away, you're saying we could reach it in less than a year if we attain a velocity of 0.9999c? Yes. In the reference frame of the traveler, very little time passes. However, when he returns, people on earth will have aged more than 40 years. This is also why particles traveling at c cannot possibly decay: no time passes for them. A photon is everywhere at once, from its own point if view.
    - aik 15y ago
      Amazing. I hope to some day wake up and have a deep conceptual understanding of the relationship between velocity and time in relation to the various bodies at play. I also hope to have an understanding of what it means for a photon to be everywhere at once, from its own point of view. In the end, I guess I just want to understand the universe just a bit more than I do.
deleted 15y ago
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by palish 15y ago

svrocks 15y ago

5028

deleted 15y ago
[deleted]

DavidSJ 15y ago

I think you've got it reversed. From Earth's perspective, it would take exactly 40 years, but the child would age very little.

forensic 15y ago

http://www.wolframalpha.com/input/?i=time+dilation+traveling+at++.9999c+&a=*FS-_**RelativisticTimeDilationFormula.t-.*RelativisticTimeDilationFormula.to--&f2=40+years&x=7&y=11&f=RelativisticTimeDilationFormula.to_40+years http://www.wolframalpha.com/input/?i=time+dilation+traveling... 2828 years + 2200 = 5028 A.D. says wolfram alpha

palish 15y ago
Fascinating. 40 years at 0.90000c = 91.76 years 40 years at 0.99000c = 283.55 years 40 years at 0.99900c = 894.65 years 40 years at 0.99990c = 2828.00 years 40 years at 0.99999c = 8944.00 years
- Confusion 15y ago
  With the caveat that nobody will be traveling at 0.99999c for 40 years. You'd be really really far away by then.
  - splat 15y ago
    Well, you'd still be less than 10,000 light-years away. That's still well within the galaxy.

btilly 15y ago

Your problem statement is wrong. The child is traveling 40 light years at 0.9999c, which takes about 40 years + 35 hours. However the child won't arrive back 50, the child will not yet be 11. See http://www.wolframalpha.com/input/?i=time+dilation+traveling+at++.9999c+&a=*FS-_**RelativisticTimeDilationFormula.to-.*RelativisticTimeDilationFormula.t--&f2=40+y&x=6&y=5&f=RelativisticTimeDilationFormula.t_40+y http://www.wolframalpha.com/input/?i=time+dilation+traveling... for the exact age. See http://en.wikipedia.org/wiki/Twin_paradox http://en.wikipedia.org/wiki/Twin_paradox for more on this, including an explanation of why your belief about the age of the traveler is wrong.

palish 15y ago
How can this be? If the child were moving at 0.9999c (which is less than 1.0000c) and the planet is 20 light-years away, then how could it take less than 20 years for the child to reach it? Let alone ~0.5 years? EDIT: Here's an explanation from a friend: light always travels at c even if you're already moving close to c but it's impossible for anything to travel faster than c so if you're traveling at .9999c the passage of time must be scaled for the traveler to make light on the ship appear to move at c even though it's only moving at 1-.9999c That's... awesome.
- Confusion 15y ago
  If the planet is 20 light years away, you're saying we could reach it in less than a year if we attain a velocity of 0.9999c? Yes. In the reference frame of the traveler, very little time passes. However, when he returns, people on earth will have aged more than 40 years. This is also why particles traveling at c cannot possibly decay: no time passes for them. A photon is everywhere at once, from its own point if view.
  - aik 15y ago
    Amazing. I hope to some day wake up and have a deep conceptual understanding of the relationship between velocity and time in relation to the various bodies at play. I also hope to have an understanding of what it means for a photon to be everywhere at once, from its own point of view. In the end, I guess I just want to understand the universe just a bit more than I do.

deleted 15y ago

[deleted]