Black holes

Black holes are well understood by physicists, but I’ve read too many oversimplified, confusing, and seemingly-contradictory descriptions of them. Over time, I’ve settled on my preferred mental model of a black hole, one that usually helps me to work out the right answers to questions that non-physicists have about black holes. (An example of such…… Continue reading Black holes

How long does it take to fall through a ball of ice?

Planet FrictionlessIceball has a straight, narrow tunnel connecting two points on its surface. How long does it take to slide through the tunnel? Simplifying assumptions As with most story problems, we have to make some simplifying assumptions. But I think they’re fairly reasonable. We assume the faller starts out motionless, at one end of the…… Continue reading How long does it take to fall through a ball of ice?