What if? By xkcd

Describing itself as a series of “Serious Scientific Answers to Absurd Hypothetical Questions”, the What-If articles by xkcd are a collection of responses in both written and comic form to user-submitted questions such as “what if all the rain fell to earth as one giant raindrop?” and “what happens when a baseball is pitched at 90% of the speed of light?”. Fascinating (and hillarious) stuff!