Spacetime versus Spacespace

t

0

rapidity

-3

This Demonstration shows a spacetime and a spacespace configuration of light cones. Two space stations, at distance 10 from each other, begin emitting regular transmissions at

t=-5

. At

t=0

, a meeting is arranged halfway between the two space stations, so that representatives from many inertial reference frames can watch the first signals arrive together. Such a momentous event leads to a decision to make this the origin of all their reference frames:

(t,x)=(0,0)

.