My favourite non-fiction book

What if? is an incredible book. It is hilariously funny. I read the whole thing in a few days, engrossed in it throughout. With calculations, big numbers and ...

Well, it is just incredible. The author also has a webpage (with everything that is in the book available for free):

(click here to see it).

Here is a question from the book (click on the text to see the answer):

What would happen if you tried to hit a baseball pitched at 90% the speed of light?