The relativistic baseball JUL 11 2012
XKCD is answering "hypothetical questions with physics" once a week and the first installment is just flat-out delightful: What would happen if you tried to hit a baseball pitched at 90% the speed of light?
The ideas of aerodynamics don't apply here. Normally, air would flow around anything moving through it. But the air molecules in front of this ball don't have time to be jostled out of the way. The ball smacks into them hard that the atoms in the air molecules actually fuse with the atoms in the ball's surface. Each collision releases a burst of gamma rays and scattered particles.
These gamma rays and debris expand outward in a bubble centered on the pitcher's mound. They start to tear apart the molecules in the air, ripping the electrons from the nuclei and turning the air in the stadium into an expanding bubble of incandescent plasma. The wall of this bubble approaches the batter at about the speed of light-only slightly ahead of the ball itself.
All science writing should (and probably could!) be this entertaining. (via @delfuego)