If you were watching a friend (or better still, an enemy!) who has fallen as far as the event horizon of a black hole, what would you measure as his heartbeat (apart from effects caused by his adrenaline level)?

Question

Quizplus · Accepted Answer

An observer at a safe distance watching someone who has fallen into a black hole would see their motion slow down and eventually stop at the event horizon due to time dilation. From the perspective of the outside observer, time runs slower closer to the black hole due to the intense gravitational field. Therefore, the person's heartbeat would appear to slow down and eventually stop completely at the event horizon, causing it to appear as if their heart had stopped.

If You Were Watching a Friend (Or Better Still, an Enemy!)