Michio Kaku, professor of theoretical physics at City University of New York, has a pretty mindblowing article in the latest issue of Cosmos on how super-advanced civilizations across the universe might be able to harness the power of stars and galaxies and survive indefinitely. Using the basic laws of physics as a guide, he posits that there are three levels of advanced civilizations possible based on how they harness their energy: I, II, and III. The bad news: we're not even a I. He generously calls us a 0.7 civilization. Bummer.
While we're stuck burning fossil fuels for energy, a type I civilization would be able to harness all of the energy of their planet in a balance. "Global pollution is a mortal threat for a Type 0 civilization, but not a Type I civilization, which has lived for several millennia as a global force and necessarily achieved ecological balance with its home planet."
A type II civ would harness the energy of a star such as our sun, perhaps by building a huge sphere around it. A type III would harness the power of entire galaxies, controlling the life and death of stars at will.
Perhaps the only serious threat to a Type II civilisation would be a nearby supernova explosion, whose sudden eruption could scorch their planet in a withering blast of X-rays, destroying all life. Thus, perhaps the most interesting civilisation is a Type III civilisation, for it is truly immortal. It has exhausted the power of a single star, and has reached out to other star systems. No natural catastrophe known to science has the capacity to destroy a Type III civilisation.
Faced with a neighbouring supernova, it would have several alternatives, for example altering the evolution of a dying red giant star which is about to explode, or leaving this particular star system and terraforming a nearby planetary system.
If you're at all interested in astronomy, extraterrestrial life, or thinking about the universe millions of years in the future, you'll love this article. It's one of the most fascinating reads on the subject I've read. Go, go now! [Cosmos]