If you fell in a hole connecting opposite sides of the Earth, you'd reach
the other side in about 42 minutes.

Let's say you could drill a hole through the Earth. Theoretically, how long
would it take to jump into the hole, fall through the Earth, and come out
the other side? This question has been a staple of introductory physics
classes since the answer -- 42 minutes and 12 seconds -- was first
calculated in 1966. In 2015, however, physicist Alexander Klotz of McGill
University in Montreal came up with a slightly faster calculation.