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Do you want proof that something can move faster than light?

Set up a laser on a shaft that rotates 3600 rpm. On a night when there is a cloud layer with a ceiling of 1000 feet rotate the laser a full 180 degrees. The spot from the laser, on the cloud base, will travel from horizon to horizon at a speed greater than than that of light. This a mathematical certainty. Explain why this possible and no laws of nature are violated.

6 Antworten

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  • Anonym
    vor 1 Jahrzehnt
    Beste Antwort

    The spot isn't a "thing." From one moment to the next, it is a different photon striking a different cloud droplet. No photon and no cloud droplet travel at faster than c in this example.

    I could also set up a movie marquee, you know the kind, with light bulbs turning on and off in the right order to make it appear as if a ball of light was moving quickly around the sign. I could pre-program the marquee to make the light-ball appear to go faster than c, and that would be completely legal because it's a different light bulb each time; it only appears that a ball of light is moving around the marquee when in fact there is no motion at all. That's exactly the same situation as yours.

  • Anonym
    vor 1 Jahrzehnt

    Yes it is possible. I wouldn't call it (or anything in physics really) a mathematical certainty, but sure it works.

    What law of nature do you suppose is being violated? I don't recall learning about a speed limit for laser spots.

  • Anonym
    vor 1 Jahrzehnt

    Yes it is possible. I wouldn't call it (or anything in physics really) a mathematical certainty, but sure it works.

    What law of nature do you suppose is being violated? I don't recall learning about a speed limit for laser spots.

  • Anonym
    vor 1 Jahrzehnt

    Yes it is possible. I wouldn't call it (or anything in physics really) a mathematical certainty, but sure it works.

    What law of nature do you suppose is being violated? I don't recall learning about a speed limit for laser spots.

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  • vor 1 Jahrzehnt

    The "spot" doesn't exist as a single moving object--and the pictures in a motion picture aren't really moving either.

    Each bit of the "spot" is the reflection of a _different_ bit of light from a different part of the cloud. Those events aren't related by anything moving between them. In fact, all that the relativity limit says about this is that it is impossible for an observer to move along with the "spot".

    Quelle(n): _Spacetime Physics_, Taylor and Wheeler
  • vor 1 Jahrzehnt

    Imagine your laser is a machine gun that fires bullets at 1000 m/s. The bullet you fire east is NOT the same bullet that impacts west.

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