Light always travels at a speed of 299,792,458 meters per second. But if you're in motion too, you're going to perceive it as traveling even faster -- which isn't possible! In this second installment of a three-part series on space-time, CERN scientists Andrew Pontzen and Tom Whyntie use a space-time diagram to analyze the sometimes confounding ...

In the first two lessons of this series on space-time, we've dealt with objects moving at constant speeds, with straight world lines, in space-time. But what happens when you throw gravity into the mix? In this third and final lesson, CERN scientists Andrew Pontzen and Tom Whyntie explore what gravity means for space-time — or rather, what space...