The mathematician discovers how the ancient Babylonians used their bodies to count to 60 (which gave us 60 minutes in the hour), how the number zero was only discovered in the seventh century by Indian mathematicians contemplating the void, why in China going into the red meant your numbers had gone negative, and why numbers might be our best language for communicating with alien life. But for millennia, contemplating infinity has sent even the greatest minds into a spin. Then at the end of the 19th century mathematicians discovered a way to think about infinity that revealed it is a number that we can count. They also found that there are an infinite number of infinities, some bigger than others…