7 JANUARY 1610
Galileo discovers Jupiter's largest moons
The astronomer finds evidence that Earth is not the centre of the universe
During the winter of 1609–10, the Florentine astronomer Galileo Galilei was peering into the night sky using a homemade telescope in Padua. The polymath had managed to drastically increase the instrument’s magnifying capability, bringing distant celestial objects into sharper focus. On 7 January he pointed it towards Jupiter and spotted something strange. Around the blurry disc of the remote giant planet, he observed three points of light arrayed in a line which he initially postulated to be stars. Galileo turned his telescope to the same spot night after night, noting that the lights appeared to move in the ‘wrong’ direction. On 13 January, a fourth star had appeared.
Gradually, it
