What If?

XKCD is one of my favorite comics. The artist, Randall Munroe, started answering absurd and fun questions using physics and math in a weekly What if? feature. Now, some of those have been collected and printed upon dead tree carcasses that you can purchase in a virtual store and have delivered to your place of residence. How droll.

He also gave a TED Talk on what would happen if a baseball were thrown at 90% of the speed of light, which I think was his first What if? feature. Well worth listening to or reading, if you like science at all.