Scott Aaronson on computational complexity and the anthropic principle

I just read some notes from an entertaining talk (one that’s surprisignly accessible, even if you’re neither a computer scientist nor a string theorist) that Scott Aaronson recently gave at Stanford, and came across this gem:

But what could NP-hardness possibly have to do with the Anthropic Principle? Well, when I talked before about computational complexity, I forgot to tell you that there’s at least one foolproof way to solve NP-complete problems in polynomial time. The method is this: first guess a solution at random, say by measuring electron spins. Then, if the solution is wrong, kill yourself! If you accept the many-worlds interpretation of quantum mechanics, then there’s certainly some branch of the wavefunction where you guessed right, and that’s the only branch where you’re around to ask whether you guessed right! It’s a wonder more people don’t try this.