The term was coined in 1938 by 9-year-old Milton Sirotta (1929–1981), nephew of American mathematician Edward Kasner. Kasner popularized the concept in his book Mathematics and the Imagination (1940).
Other names for googol include ten duotrigintillion on the short scale, ten thousand sexdecillion on the long scale, or ten sexdecilliard on the Peletier long scale.
A googol has no particular significance in mathematics, but is useful when comparing with other very large quantities such as the number of subatomic particles in the visible universe or the number of possible chess games. Edward Kasner used it to illustrate the difference between an unimaginably large number and infinity, and in this role it is sometimes used in teaching mathematics.
A googol is of the same order of magnitude as the factorial of 70 (70! being approximately 1.198 googol).
A googolplex is ten raised to the power of one googol: it is a large number. In the documentary Cosmos, astronomer and broadcast personality Carl Sagan estimated that writing a googolplex in base-10 numerals (i.e., 1 followed by a googol of zeroes) would be physically impossible, since doing so would require more space than the known universe provides.
Deskarati says – By the way, the picture at the top shows the point that Charles Ingram cheated his way to a £1,000,000 on the game show ‘Who wants to be a millionaire?’ – cough!