Our outer solar system (beyond Neptune) holds a great deal of promise for the future of humanity, and for life in general. It is vast, with hundreds possibly thousands of dwarf planets, and countless smaller objects. Many of these are icy, so securing water will not be a problem. Technologies will allow us to harness solar energy, and other power sources such as nuclear fusion could be powered using Helium-3 mined from the atmospheres of the planets Uranus and Neptune.
In this track then, I imagine humanity living out there, so far from the Sun. With our Earth-centric viewpoint, it would appear to be desolate and lonely. But it might also be beautiful and majestic. Well before the end of this millennium the majority of humans will most likely NOT be living on Earth, but out there. Trillions of people, not just a handful of billions. They will take life from Earth with them, and together we can adapt to our new environment. Will they remain recognisably human? Possibly...I hope so.
"Humanity will not remain on the Earth forever, but in the pursuit of light and space will at first timidly penetrate beyond the limits of the atmosphere, and then will conquer all the space around the Sun."
Konstantin Tsiolkovsky, 1911.
"There is no law of physics or biology that forbids cheap travel and settlement all over the solar system and beyond."
Freeman Dyson, 2000
