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Objects near the speed of light

  1. Jan 16, 2007 #1

    i'm new to this and maybe this has been covered but-

    Imagine an object moving at almost the speed of light, is on a collision course with earth. To observers on earth the ship seems to be motionless, due to it's speed being extremely close to c.

    Eventually the ship is going to be very close to earth, lets say, that to an earth observer it seems to be hovering about 1m from the earths surface.

    What would happen to someone or something which touched this ship?
    Would they be instantly propelled into the ships frame of reference or would they be able come and go as they please?

    I hope that made some sort of sense.... any thoughts would be much appreciated...

  2. jcsd
  3. Jan 16, 2007 #2
    That is incorrect.
  4. Jan 16, 2007 #3
    incorrect how? could you please direct me to something which will explain how an observer on earth would see the ship.

    i came to believe that it was a consequence of time dialation
  5. Jan 16, 2007 #4
    Imagine a stopped clock being thrown at you: they won't see the occupants moving very quickly inside the ship, but they will see the entire ship (and everything inside) approaching at nearly the speed of light. It will hit the earth very quickly (with little notice).
  6. Jan 16, 2007 #5
    i don't understand what your trying to say...
    are you saying that the observers on earth would see the ship approaching at nearly the speed of light and not time dialted to a point where it appears motionless?

    i forgot to mention that the ship is moving at nearly the speed of light relative to the observers of the earth
  7. Jan 16, 2007 #6


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    That is correct, it won't. As Cesium frog said, time will 'slow down' for the people inside the ship, but will be running at 'normal' time for you. Time will appear dilated for the crew but not for you.
    Last edited: Jan 16, 2007
  8. Jan 16, 2007 #7
    okay, so what would be the relationship between my time and the time in the ship? in other words if i could see a clock in the ship at what speed is it running and vice versa?

    i'm trying to make sense of the time dialtion formula in special relativity that i found on wikipedia, maybethat was my first mistake?
  9. Jan 16, 2007 #8


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    Okay, say someone on this ship (travelling towards you at v m/s) was bouncing a ball. Another crew member timed the interval between two bounces. This would be the proper time interval ([itex]\Delta t_{0}[/itex]). Now, if you timed the same interval on earth you would measure the time interval as [itex]\Delta t[/itex], such that;

    [tex]\Delta t = \gamma \Delta t_{0} = \frac{\Delta t_{0}}{\sqrt{1-\beta^2}}\hspace{1cm}\beta = \frac{v}{c}<1[/tex]
  10. Jan 16, 2007 #9
    running very slowly, but nonetheless moving towards you very quickly.
  11. Jan 16, 2007 #10
    i think that is where i was getting confused... i thought that since the clock was running slowly then the whole ship would seem to be moving slowly.....

    thank you both for clearing that up....

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