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FAWS comments on Best career models for doing research? - Less Wrong
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I'm surprised that noone has asked Roko where he got these numbers from.
Wikipedia says that there are about 80 billion galaxies in the "observable universe", so that part is pretty straightforward. Though there's still the question of why all of them are being counted, when most of them probably aren't reachable with slower-than-light travel.
But I still haven't found any explanation for the "25 galaxies per second". Is this the rate at which the galaxies burn out? Or the rate at which something else causes them to be unreachable? Is it the number of galaxies, multiplied by the distance to the edge of the observable universe, divided by the speed of light?
calculating...
Wikipedia says that the comoving distance from Earth to the edge of the observable universe is about 14 billion parsecs (46 billion light-years short scale, i.e. 4.6 × 10^10 light years) in any direction.
Google Calculator says 80 billion galaxies / 46 billion light years = 1.73 galaxies per year, or 5.48 × 10^-8 galaxies per second
so no, that's not it.
If I'm going to allow my mind to be blown by this number, I would like to know where the number came from.
Hmm, by the second wikipedia link there is no basis for the 80 billion galaxies since only a relatively small fraction of the observable universe (4.2%?) is reachable if limited by the speed of light, and if not the whole universe is probably at least 10^23 times larger (by volume or by radius?).