In my unaccountably popular The Mathematics of Monkeys and Shakespeare, my final computation was based on a figure of seventeen billion (2^34 to be precise) galaxies, each containing seventeen billion habitable planets, each of which was inhabited by seventeen billion monkeys all typing away furiously for seventeen billion years. At the time, I knew that seventeen billion years was in the right ballpark with regards to the currently popular scientific view of the age of the universe, but the number of planets and galaxies was pretty arbitrary. As it happens, however, the number of planets may be in the right ballpark too.

The computations are hugely speculative, and I would sooner call it "para-scientific guesstimation" than "a scientific theory", but for what it's worth, these astronomers reckon that the number of earth-like planets in our galaxy is greater than one billion, and maybe as high as thirty billion. How about that? My own, personal, invented-it-for-my-own-convenience figure is smack-bang in the middle of the range. I'll therefore leave that part of my monkey scenario completely unrevised.

If we grant that seventeen billion monkeys is a reasonable population size for an earth-like planet, the only figure that still needs checking is the seventeen billion galaxies figure. This, too, is probably in the right ballpark, although according to this site, one hundred billion is also a popular figure. That would be somewhere between 2^36 and 2^37, as opposed to my 2^34 figure.

So, in summary, my mostly-made-up figures turned out to be pretty reasonable, although the number of galaxies figure may be a bit lower than most astronomers would like. If you want to readjust my final probability calculation to compensate for extra galaxies, then I suggest that multiplying the final answer by about ten will suffice, and the impact of that multiplication is basically too small to notice. This still assumes that our galaxy is average-sized, which it may not be, but it's also probably fair to say that our galaxy is above-average in terms of its capacity for earth-like planets.

But all this tweaking and twiddling with numbers is somewhat pointless. The original figures were meant to give an idea of how much brute-force monkey-power you could throw at a small problem like that and still not generate a result. Anyone who thinks that tweaking for a few more galaxies here or a few more monkeys there is going to help has missed the point.