Speed of push

  1. Can a push, be faster than light?
    If I was to hold a stick that stretched out to the moon, and pushed it. Could I push the moon instantly?
    Seeing as that the stick could defy physics etc and I had enough strength to make an impact on the moon.
  2. jcsd
  3. I feel like it's possible. I push one end, the other end needs to move to make room for the stick pushing right?
  4. Even though the 'poke' is 'travelling' faster than light, as long as the stick is travelling slower than light, you're okay. If you had a million billion trillion km long stick that you pushed 1mm in 1/100th of a second, nothing would actually be going faster than light. The same idea applies with a laser pointer on the moon. If you flick the dot back and forth really fast on earth, the dot appears to move faster than light.
  5. But the push would have to react instantly. How can one end of the stick move, while the end doesn't?
    Has to be faster than light
  6. A.T.

    A.T. 6,462
    Science Advisor
    Gold Member

    It is not. The impulse is traveling at the speed of sound within the rod, which is slower than light. The impulse carries information so it cannot travel faster than light.

    No, it is completely different.

    It doesn't just appear, it is moving faster than light. But the dot carries no information across the surface, so it can move at any speed.
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