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Thread: Problem with approaching light speed

  1. #1
    Join Date
    Oct 2008
    Posts
    235

    Problem with approaching light speed

    I understand one of the problems with flying near light speed is that a collision with a small object (even a speck of dust?) might destroy your spaceship. Hence I'm envisioning a forward shield (or multilayered shields) that might absorb those impacts. My question then is about relativistic length contraction - which I understand works in the direction of travel. So even if you had a shield a kilometer ahead of you with lots of crumple zones, would relativistic length contraction, near light speed, eliminate its benefit, so that any impacts would essentially be 'in your face' anyway? Thanks

  2. #2
    Join Date
    Jul 2005
    Posts
    18,371
    No, because length contraction does not occur in the rest frame of your spacecraft. So your shield would retain its shape and size, as far as the crew of the spacecraft were concerned. It would be the oncoming particles and dust that would be length contracted, according to observers moving with the spacecraft.

    Grant Hutchison

  3. #3
    Join Date
    Oct 2005
    Posts
    26,932
    And keep in mind that in the rest frame of the rocket, you want a high acceleration so you're going to have a very considerable artificial gravity. That would present a problem over a kilometer of distance, so you'd better insert propulsion systems throughout the shield to offset those gravitational stresses or the whole thing will indeed end up "in your face"! But that's not relativity. It does however mean that there's no particular reason to regard the shield as part of the same spacecraft, it would have to essentially be a series of independently propelled objects designed to sacrifice themselves when targets are encountered.

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