There is not enough space in the universe to write down the number googolplex. But can you write down a googol?
There are numbers so ridiculously huge that there just is not enough space in the universe to write them down. What's even more amazing, is that these astronomically large numbers are actually of utmost importance, and even crucial, for understanding the world.
The two largest meaningful numbers are the googol (which has since become world famous in the form of Google) and the googolplex. The googol got its name from a nine year old nephew of mathematician Edward Kasner. He asked his nephews for any ideas they might have to name a really big number, and that is what nine year old Milton Sirotta came up with.
Kasner decided that 10^100—or, the number one followed by one hundred zeroes—would henceforth be known as a googol. Young Milton suggested an even larger number, the googolplex. He said it must be a number 1 followed by as many zeroes as could be written down before one gets tired.
Kasner felt it needed a better definition. It would be 10^googol, or 1 followed by a googol of zeroes. Therefore, a googolplex is 10^10^100. Carl Sagan once pointed out that it would physically impossible to write down all the zeroes in a googolplex, because there simply isn't enough room in the universe!