Light travels at a speed of approximately 186,000 miles per second:
186,000 miles is over seven times the circumference of the earth. On a
clear, moonless night a faint patch of light can be seen in the constellation
Andromeda. This is the Andromeda nebula. It is a galaxy of about a
hundred thousand million stars, each of them a sun like our own. Its light
takes some two million years to reach us. It is the farthest object visible to
the naked eye. Yet by comparison with other galaxies it is a close neighbour.
Who can fail to be moved by the sheer scale of it all? Who can deny
the humbling and awesome effect of contemplating those vast, silent
reaches?
It is the same when we think about the past. Imagine that the fivethousand-
million-year history of the earth were condensed into a decade.
Then dinosaurs died out between two and three months ago; about a
fortnight ago proconsul apes appeared; nine hours ago humans were
beginning to make tools; approximately two minutes ago Jesus Christ
was born; and three seconds ago the atom bomb was exploded.