[MBlume]

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.

[CamperBob2]

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.

[ars]

> 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]

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.