There are 10^23 to 10^24 neurons on the planet. The human brain has around 86 billion neurons. World population * human neurons = 10^~10*11^~10 = 10^~21 (slightly less, but let’s round up).
This means the human population can “safely” increase by at least two more orders of magnitude to 1 to 10 trillion, so the ~100 billion that I posit for the Age of Malthusian Industrialism is safe.
1. Perhaps more complicated brains are harder to simulate in principle (e.g. costs of simulating them increases at a faster than linear rate relative to the number of neurons).
2. The Age of Malthusian Industrialism is only temporary. The gears of natural selection will get grinding again, average IQ will rise again, technology will recover, and so will carrying capacity. And unlike today, those high IQ people will be genotypic breeders.
So that’s potentially only around 10-100 planets we can settle assuming we plop down 100 billion on each.
And we might be in danger in our planet merely reaches the trillion person mark (Coruscant/Holy Terra).
3. If we mind upload and turn into ems, the simulators may be forced to shut us down real quick. Just our one planet may be far more than sufficient.
10^24? At least for slow ems. Faster ems take proportionally more resources.
— Robin Hanson (@robinhanson) December 19, 2017
At any rate, interstellar expansion with ems sure is a dicey proposition, seeing as we don’t know how much more room there is down in the basement.