ABSTRACT
When NASA sent the Pioneer 10 space probe to explore the solar system in 1972, they placed on board a metal plate, engraved with various pictures and signs. On one part of the plate was a diagram of a hydrogen atom, while on another was a diagram of the relative sizes of the planets in our solar system, indicating the planet from which Pioneer 10 came. The largest picture on the plate was a line drawing of a naked man and a naked woman, with the man’s right hand raised in greeting. The idea behind this was that when Pioneer 10 eventually left the solar system it would pursue an aimless journey through space, perhaps to be discovered in millions of years time by some alien life form. And perhaps these aliens would be intelligent, and would be able to understand the diagrams, recognise the extent of our scientifi c knowledge, and come to realise that our intentions towards them, whoever they may be, are peaceful.
