From Martin Welbank, Cambridge, UK
A book you review, Out of This World and Into the Next, suggests the sun’s eventual wrathful death makes it wise to get our butts to Mars. We should be able to persist on Earth for the next billion years or so before solar changes get too bad. For perspective, a billion years ago, we were little more than sea-dwelling sponges. To imagine what we may evolve into a billion years from now is as meaningless as those sponges trying to imagine us. By the time the sun makes things difficult for life here, we probably won’t even have butts(17 May, p 26).
