If I was on a spaceship traveling almost at the speed of light, my time would slow down relative to the time for a stationary external observer.

My question is, since we measure distances between stars in "light years", those years are relative to the external observer.

The person on the space ship moving almost at the speed of light, would it take 1 year of their time to travel 1 light year, or would they feel like the trip took no time at all because their time slowed down so much relative to the external observer. Who was viewing their ship traveling almost at the speed of light, but who's time was running so much faster than the individuals on the ship.

(yes I know it is impossible to travel at the speed of light, if you would like make it 99.99999999% the speed of light)

  • 5
    $\begingroup$ This question does not show any research effort. $\endgroup$ Feb 29, 2016 at 19:56
  • $\begingroup$ Time doesn't slow down. What changes is the rate at which an observer moving relative to you will perceive your clock. Matter can't move at the speed of light, so one can't make instantaneous space trips that way. If you want to go that fast, you have to go as light, which is probably easier to do, anyway. $\endgroup$
    – CuriousOne
    Feb 29, 2016 at 20:44
  • $\begingroup$ The traveler does not observe faster then light travel because of length contraction. The closer he gets to the speed of light the less the distance he observes between himself and his destination. So he will arrive very quickly at 99.99999999% the speed of light and will also observe traveling a very small distance. $\endgroup$
    – trampster
    Mar 23, 2017 at 22:33

1 Answer 1


The time for the traveler would take very little time. The closer to the speed of light they travel, the shorter the time for the journey. For a stationary observer, like on earth, if the star was 1 light year away, it would appear that the trip travel time for the traveler would be very close to one year, but a little longer than that for speeds less than the speed of light. Using your 99.99999999% of speed of light value, the traveler would experience a total time for the trip of about 446.3 seconds, or 7.44 minutes. For the stationary observer it comes to 1.0000000001 years.


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