[kmcgivney]

OK, so I'm wondering how fast would the quarter have to travel to actually shrink to the size of a dime, based on special relativity?

[kragen]

The FitzGerald contraction would only shrink it in one dimension.

[Leon]

What would happen if the quarter was rotated on its disk at relativistic speeds?

[Leon]

http://math.ucr.edu/home/baez/physics/Relativity/SR/rigid_di...

http://en.wikipedia.org/wiki/Ehrenfest_paradox

Which is the best I could find for the question of shortening a quarter to the size of a dime using relativity.

[TrevorJ]

The best "What if?"s always come from science geeks, I swear.