Posted by **Darren** on Tuesday, May 3, 2011 at 12:35am.

At what speed must one frame of reference be moving relative to another for the two frames to disagree about lengths by 1%? Express your result as a fraction of the speed of light.

At what speed must one frame of reference be moving relative to another for the two frames to disagree about time intervals by 1%? Express your result as a fraction of the speed of light.