Suppose you're traveling on a space ship at 9/10 the speed of light (.9c). You have a high-powered rifle that shoots bullets at the same speed. Suppose you shoot the bullet perpendicular to your direction of travel.

It appears that the bullet would travel at a 45-degree angle (northeast, if the ship is traveling north and the bullet is shot eastward), at about 1.2728c which is faster than light. Why is this wrong, and what would the actual speed and direction be?

Relative to the ship, the bullet will travel at .9c perpendicular to the direction its traveling. Relative to the Earth (assuming the ship is traveling at .9c relative the the Earth) the bullet would appear to be traveling somewhere between .9c and c. But it would appear to be traveling much slower relative to the ship from the point of view of the Earth.

Posted by Danny on 2005-01-17 22:36:31