There’s a gratifyingly long, though slightly wacky, comment thread on the NY Times Room for Debate discussion I contributed to, about the prospects for manned space flight.

The justifications being offered for government-funded manned space flight are all familiar. The weirdest, I always think, is the one saying: “We might do something terrible to the Earth. Then we’ll have to go live on some other planet. We must prepare!”

Even I am not that pessimistic. We might indeed do something terrible to the Earth. I am, however, unable to imagine what we might do that would make our planet anything like as inhospitable to life as the most hospitable extraterrestrial location we know of.

This also applies to things Ma Nature might do. At which point during the last, oh, 3 billion years was the Earth’s surface less hospitable to life than the current surfaces of Mars, Venus, or the Moon? The Ice Ages were rough, no doubt; but on Mars, it’s Ice Age every day of the week, with surface atmospheric pressure less than 1 percent of Earth’s. And that’s not even air.

The locations we don’t currently know of — Earthlike planets in other star systems — are so far beyond our present technological reach, a thousand years’ delay here or there really makes no difference.