Going through some of the old xkcd what-ifs. I love the writer's sense of humor.
"Everyone fires 500-terawatt lasers at the moon. The moon leaves." is one of the best alt-texts I've seen, ever. (this was after an extensive discussion of what would happen if everyone fired indestructible 500-terawatt lasers at the moon, including talk of laser ablation propulsion and the definition of a planet)