The Ultimate Challenge: The Exploration and Colonisation of Extrasolar Planets

At the end of the twenty-first century, humanity will have explored out to our solar-system’s boundaries, beyond which many have speculated for centuries about what may exist there. Plato and Aristotle, who dominated the cosmology of the ancient Greeks and Romans, considered the universe to be composed of the five planets visible to the naked eye, plus Earth and the Moon. What lay beyond was left to metaphysical speculation. However, Democritus claimed that countless stars composed the Milky Way and that they appeared as points of light due to their vast distances from Earth. Lucretius thought the universe to be infinite and populated by an infinite number of stars. The Catholic Church adopted Aristotle’s mechanistic ideas (ipse dixit…), which dominated the following centuries.