A googol is a famous large number equal to 10100. The mathematician Edward Kasner was the first person to use it, in his book Mathematics and the Imagination, which he co-wrote with James R. Newman in 1940. However, the person who named it was neither Kasner, nor Newman, but Kasner’s 9-year-old nephew Milton Sirotta. Kasner asked Milton to think of a name for “1 with a hundred zeros after it.” Milton replied, “Googol.” The name stuck.
Just how big is a googol? Here’s what it looks like written out:
A googol is much larger than the number of grains of sand on Earth or the number of known stars in the sky. In fact, it is estimated that there are between 1072 and 1087 particles in the entire known universe, which is much smaller than a googol.
Edward Kasner invented another number that is even larger than a googol. A googolplex is 10(10100) or 10googol. It would be written as 1 followed by a googol zeros. This number is so large that you cannot even write down all the zeros. If you tried to write down all the zeros of a googolplex in a book like this one, the book would be larger than the entire universe!