Remembering Galileos contribution in the International Year of Astronomy
Galileos first instrument magnified objects about eight times their original size,said Owen Gingerich,eminent astronomer and sometime historian. He first looked at the moon. The ancient philosophers had seen the moon,sun,planets and stars as immaculate objects that circled the corrupt,filthy Earth,which was like the Dumpster of creation. But Galileo saw that the moon,far from being a perfect,crystalline sphere,had surface features. It had mountains and craters. It was a world.
With improved telescopes Galileo saw the phases of Venus,sunspots and then,most dramatically,four moons orbiting Jupiter. When he aimed his instrument at the Milky Way,he saw that it was full of many,many stars (the latest count is about 100 billion).
Galileo didnt invent the telescopehistory gives credit to the Dutchman Hans Lipperhey,among othersand he may not even have been the first person to look at the night sky with one. An Englishman,Thomas Harriott,looked at the moon in the summer of 1609 and made some drawings of what he saw. But Galileo published his findings. Most important,he grasped the powerful philosophical implications of what he saw.
Galileos observations validated the theory of Nicolaus Copernicus,who had died in 1543. The Copernican model featured the bewildering notion that Earth,which is seemingly stationary,is in fact spinning. And it declared that Earth isnt the centre of the universe. The Vatican prohibited Galileo from teaching the Copernican model,but he hammered away,and ultimately faced charges of heresy.
Though spared a death sentence,he was forced to renounce his teachings and spent the remainder of his life under house arrest.
Galileo had the ultimate ally in the universe itself,which revealed new wonders with each incremental improvement of the telescope.