It looks like Randall Munroe of XKCD fame has a new project: "what if?". Every Tuesday he answer a hypothetical question with an illustrated essay. The first question tackled is "what would happen if you tried to hit a baseball pitched at 90% the speed of light?".
Suppose you’re watching from a hilltop outside the city. The first thing you see is a blinding light, far outshining the sun. This gradually fades over the course of a few seconds, and a growing fireball rises into a mushroom cloud. Then, with a great roar, the blast wave arrives, tearing up trees and shredding houses.
Everything within roughly a mile of the park is leveled, and a firestorm engulfs the surrounding city. The baseball diamond is now a sizable crater, centered a few hundred feet behind the former location of the backstop.
A careful reading of official Major League Baseball Rule 6.08(b) suggests that in this situation, the batter would be considered "hit by pitch", and would be eligible to advance to first base.
I am looking forward to the future questions/answers.