What If?

The webcomic xkcd draws strange hypothetical questions from its readers, and Randall Munroe answers them with real science. One asks what would happen if someone tried to hit a baseball thrown at 90 percent of light speed; another asks how long humanity would survive a robot apocalypse. To find out, Munroe runs computer simulations, works through differential equations, reads declassified military research memos and talks to nuclear reactor operators. Most of the several dozen chapters take on a single question, with stick-figure comics and footnotes alongside. The selection mixes entries from his What If? blog with nineteen new ones, plus a few unanswered questions from his inbox. A sequel, What If? 2, followed later.

Bill Gates featured it in his 2015 beach reading post, noting that it delivers exactly what its subtitle promises, with reader questions spanning physics, chemistry and biology. It also appears among the books Fabrice Grinda recommends in a profile on how he reads almost 100 books a year.