I invited my brother to join me and some friends for the preview screening of Sunshine, which happens to be taking place on his birthday. He declined the invitation, and this was his reason why:
Gah, this one, I’ve heard about it…
Sol’s power output is roughly equivalent to 100 billion thermonuclear warheads detonating every second (or 10 trillion nuclear warheads of the type dropped on Hiroshima). Asking me to suspend my disbelief that anything we could possibly send would make any iota of difference is impossible.
Besides, as Sol starts to die, it’s not going to get colder, it’s going to get hotter, and bigger… a LOT hotter and bigger… ending up as a red giant. Imagine a grain of sand (representing Sol as it is now) ballooning up into something the size of a beach ball. Sol’s outer corona will extend even past Terra (but won’t quite make it to Mars), however this outer layer is so tenuous that Terra will continue to orbit Sol’s core for several thousand years, slowly losing momentum due to friction with the corona, and getting hotter and hotter until all but the most heaviest elements have boiled away leaving behind the iron core. Terra’s iron core will continue to spiral in towards Sol’s core, encountering thicker and hotter layers of the corona is it falls, until finally in just a few more thousand years the iron core itself boils away, and that’s the end of our planet.
The red giant phase won’t last long though, not long enough to get life going on any of Jupiter’s now-temperate moons anyway… violent stellar winds powered by x-rays and UV light will blow from Sol’s core, eventually dispersing the corona into interstellar space to form a planetary nebula, leaving behind a Terra-sized (but much denser and heavier) white dwarf with light so feeble it wouldn’t even support life on Mercury, if Mercury hadn’t first been vaporised by the red giant phase…
Of course, that’s a few billion years in the future… closer to our own timeframe, Terra’s interior will cool to the point that convection stops about 800 million years from now, its magnetic field will all but disappear, exposing our atmosphere to the stellar wind, and just another few hundred million years after that Terra will have virtually no atmosphere or water (this is what happened to Mars 2 billion years ago, being smaller its interior cooled more quickly). It’s an interesting coincidence that advanced life has appeared here within that narrow window of opportunity between snowball Earth and desert Earth…
For some reason I am reminded of this scene from Annie Hall:
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