[Above: It looks unimpressive, but this image (taken 90 years ago this week) proved for the first time that there was something outside the confines of what was then to believed to be the full extent of the Universe – the Milky Way. Edwin Hubble (pictured) excitedly crossed out his previous annotation of ‘N’, for nova, and replaced it with a triumphant ‘VAR!’, for variable.]
AT THE START OF THE 20TH CENTURY, astronomers thought they knew what the Universe was all about. It was an island of light, afloat alone in the dark, infinite sea of existence. Measuring about 100,000 light years across, it contained about 100 million stars – a fixed, unchanging and eternal raft of stars sometimes called the Milky Way.
Then, on October 4, 1923, from a dark mountainside in California, a discovery was made that would redraw the map of the cosmos – starting astronomy down a path that no one could have imagined or predicted, and that would eventually lead the way back 13.8 billion years to the birth of the Universe itself.