What's the most mind-blowing fact you heard/read in your life?

f\left ( x \right )=e^{x} \to {f}'\left ( x \right )=e^{x}

That people used to believe the world was flat. Then I went to college and got my mind blown AGAIN when I learned that this "fact" was actually a blatant lie.

Logic paradoxes always did (and still do) blow my mind:

1: The farther out in space you look, the farther back in time you are seeing. If you could look back all the way to the big bang, you would be looking (billions of miles away) at the inside of a universe about the size of a grape fruit (or whenever super-inflation was supposed to start).

2. You cannot move. In order to move between A and B, you must first move half way between the two. etc.

3. Some people "invest" in the lotto.

Most recently I found out that the Russian Salyut 3 space station (whos missions were to take 3" resolution pictures of the US) had a cannon mounted on the bottom of it. Not only was there a machine gun in space, but it was fired too.

Related: Dock Ellis pitched a no-hitter while on LSD http://en.wikipedia.org/wiki/Dock_Ellis#June_12.2C_1970_no-h...