3 ms·
I think it's possible (although not a foregone conclusion) that in fact much of the filter is from what he terms 'discrete' events. That is, having the right so
by donaldc 17y ago
I think it's possible (although not a foregone conclusion) that in fact much of the filter is from what he terms 'discrete' events. That is, having the right sort of sun, the right-sized planet at the ideal distance from this sun, with a substantial moon to act as a gyroscope, active tectonics to recycle elements that would otherwise get locked up, etc.
I've not, for example, seen any conclusive estimates on how likely it is that an otherwise earth-like planet would get a moon to act as a stabilizer for axial tilt (which itself is probably important for complex life).
- donaldc 17y agoAlso, his assumption that life could spread at nearly the speed of light may be overly optimistic. If, by contrast, one assumes that light can spread at only 1/10th the speed of light, and that the earliest star-faring life could have arisen was a billion years ago (due to as the time needed for a second-generation yellow star to brighten enough to keep an earth-like planet warm after its conversion to an oxygen/nitrogen atmosphere), then one only needs to explain why star-faring life has not yet arisen in relatively nearby galaxies, rather than why it has not yet arisen anywhere in the visible universe. This is a much less daunting hurdle.