55 From the earth: Greetings

Recent developments in astronomy have made it possible to detect planets in our own Milky Way and in other galaxies.

This is a major achievement because, in relative terms, planets are very small and do not emit light.

Finding planets is proving hard enough, but finding life on them will prove infinitely more difficult.

The first question to answer is whether a planet can actually support life.

In our own solar system, for example, Venus is far too hot and Mars is far too cold to support life.

Only the Earth provides ideal conditions, and even here it has taken more than four billion years for plant and animal life to evolve.