In checking out the numbers from the immediately preceding post, I looked up “sextillion” on wikipedia just to make sure it’s 10E21 (it is, in the US/Canadian/modern British system). There are, it turns out, a whole lot of named very large numbers.

We’ve all heard of a googol… 1E100, or a one followed by a hundred zeroes. Most readers of this blog will, I’m sure, have heard of a googolplex, which is ten to the power of a googol… one followed by a googol zeroes. Carl Sagan pointed out that a piece of paper with a googolplex written out in full on it would not fit within the visible universe.

There are other very large numbers between a googol and a googolplex that might be of interest. Doubtful they’d be of much actual *use,* of course, since most of these numbers are so much larger than any realistic physical phenomenon that they’d never be useful for describing anything real. As an example: the smallest possible distance would seem to the the Planck length. This is 1.6e6E-35 meters. (A good description of the size of the Planck length is this: if a 0.1mm circle was blown up to the size of the observable universe, the Planck length from that original dot would be scaled up to, wait for it, about 0.1mm.) Well, one light year is 9,460,730,472,580,800 meters. So one light year is about 5.85E50 Planck lengths. If the visible universe is 13.8 billion light years in radius (current best estimate), that’s 8.08E60 Planck lengths. A sphere that size would have a volume of 2.21E183 cubic Planck lengths.

No calculation that has any practical meaning for the universe as it currently stands would seem to ever be likely to come anywhere near needing numbers much bigger than 1E183. And yet, being humans, we’ve named numbers we’ll never have any use for. The number of Planck lengths in the visible universe, as it turns out, is easily expressible in Sexagintillions.

Names of large numbers