what if? is a blog hosted on the xkcd.com domain and written by Randall Munroe with entries posted every Tuesday. As per the site's tagline, the purpose of the site is "answering your hypothetical questions with physics, every Tuesday". On the blog, Randall uses his degree in physics and strong scientific background to discuss hypothetical physics questions apparently submitted by readers.
Unlike other sites which answer readers' questions, what if? typically takes the question beyond the original scope likely intended by the reader and takes it to some extreme for humorous effect. For example, in the first article, he discusses what would happen if a baseball were pitched at 90% of the speed of light. After effectively describing what would occur as a nuclear explosion, leveling the stadium and the surrounding mile radius, he concludes with the note "A careful reading of official Major League Baseball Rule 6.08(b) suggests that in this situation, the batter would be considered 'hit by pitch', and would be eligible to advance to first base."
The questions Randall tackles range from realistic possibilities (e.g. the probability of achieving a perfect SAT score by guessing) to completely fictional questions (e.g. How much Force power can Yoda output?). In his explanations, Randall, often uses diagrams in an xkcd style. Regardless of the context, Randall tends to take the questions extremely literally and responds seriously to them, even if they are whimsical (such as the Yoda question). This is clear from his response to the question of what would happen if everybody on Earth stood together and jumped at the same time. After acknowledging that the question has been answered elsewhere, he recaps the result, but then focuses more intently on the unasked resulting issue of the aftermath of everyone on Earth being magically transported to one location as they all try to return home.