8 ms·

Relativity says that you can't construct a rigid beam 25 million miles long.

• MBlume 14y ago
  I think that's going a little too far. If you can construct a "rigid beam" five feet long, I see no way that relativity countermands a "rigid beam" 25 million miles long. It's just that "rigid" doesn't mean what grandparent thinks it means -- info still travels through the beam via pressure waves.
  • ars 14y ago
    > If you can construct a "rigid beam" five feet long Except you can't. A existence of sound traveling through the beam proves without a doubt that the beam is not rigid.
    • jlgreco 14y ago
      Exactly, you can only construct beams at any scale that seem rigid at some scale. A 2 foot long piece of re-bar looks pretty rigid, until you look closer.
  • CamperBob2 14y ago
    The pressure waves are ultimately manifestations of the exclusion principle, expressed through forces that are constrained to travel at or below c. So yes, relativity dictates that you can't create a rigid beam 25 molecules long, much less 25 million miles long. There can be no such thing as a perfectly rigid beam of any length.