Maddy was not consumed by the immediate pressures of the here and now. She had been provided with a fatal indulgence: time to think. - Charles Sheffield

It was the age-old conundrum: How do I know that the ‘me’ who wakes after a night’s sleep is the same ‘me’ who went to bed? I don’t. I merely employ it as a working assumption, for lack of anything better.

Where orbits are wildly varying, life has no chance to develop. Changes are too extreme. Temperatures melt tin, then solidify nitrogen. If it is once established, life is persistent; it can adapt to many extremes. But there is a fragility in the original creation that calls for a long period of tightly-controlled variations.

It is not clear to me whether the insouciance of youth will be the doom of humanity or its salvation. I prefer to think the latter, but I have my doubts.