xkcd's What If?

What would happen if the Earth and all terrestrial objects suddenly stopped spinning, but the atmosphere retained its velocity?

What would happen if you tried to hit a baseball pitched at 90% the speed of light?

Stopping rain from falling on something with an umbrella is boring. What if you tried to stop rain with a laser that targeted and vaporized each incoming droplet before it could come within ten feet of the ground?

How long could a nuclear submarine last in orbit?

What if I took a swim in a typical spent nuclear fuel pool? Would I need to dive to actually experience a fatal amount of radiation? How long could I safely stay at the surface?

What would happen if everyone on earth stood as close to each other as they could, jumped, and landed on the ground all at the same instant?

If all the lightning that occurs worldwide on any given day all struck the same place at once, what would happen to that place?