When I was a kid, probably six or seven years old, I remember picking up a book someone had left at my grandmother's house and flipping through it. It was a book about Earth and the solar system. I stopped on a page with a drawing of a large, red circle in a sky over a dim, lifeless wasteland. This was meant to portray Earth billions of years from now, when our sun has become a red giant.

Well, perhaps it wasn't Earth. When the sun's core burns off its hydrogen, it will contract under the weight of gravity causing the outer layers to heat up and expand. And as that happens, the sun will get bigger until the radius of the red giant sun will be just beyond the Earth's orbit. Earth will be vaporized. So maybe it was meant to be the surface of Mars or Jupiter.

Sitting there on my grandmother's couch was the first time I had really thought of such things - the Earth ceasing to be. Whether through the natural life-cycle of the sun or an asteroid obliterating us, our world will end.

Of course, I knew "billions" meant a lot of zeroes...many, many years from now, but that wasn't the point. This world I lived in would one day be no more. It was a new thought for me, and a depressing one even at that age. What was there to be done? I knew I wouldn't be around to see what would happen, but I wondered what might become of the human race by then. Where will we go? How will we evolve? Will there even be humans billions of years from now? Even a million years from now?

---

Where do we go from here? There's something in the sky, shining in the light, spinning and far away --David Bowie, Earthling "Looking For Satellites" (1997)