One of the most common misconceptions people have about astronomy is that Galileo invented the telescope. We know he didn't; it had been around for years before he used one. What he did do was make one himself that was a big improvement over what had been done previously, and was among the first to turn it to the skies.
But that last part is important: he was among the first. He wasn't the first person to use the telescope to look at astronomical objects, and he wasn't even the first to document what he saw!
|The first telescopic map of the Moon ever made, by Thomas Harriot in July, 1609.
Credit Lord Egremont and the RAS.
The image above is the first known drawing of the Moon made using a telescope. It was done by Thomas Harriot in July 1609, many months before Galileo published his own drawings. It's crude, to be sure, but it shows that Galileo was not the first to set eyes on the Moon using the new instrument. Harriot was a mathematician and astronomer, and apparently beat Galileo in observing the skies by many months. The whole story is detailed by astronomical historian Allan Chapman at the University of Oxford. He wrote an article on this that will be published in the February edition of Astronomy and Geophysics. He gives evidence, from letters sent by Harriot to friends, that at least some of these drawings were made before Galileo's.
Not to downplay what Galileo did! He was a pioneer in astronomy, and his careful observations are one of the reasons we remember him today, and are celebrating the International Year of Astronomy this year. But what you have to understand that one reason we celebrate Galileo's contributions is because Galileo was very good at self-promotion. He published his drawings, while Harriot did not.
Of course, Galileo's self-image is what got him into so much trouble later in life. He went way out of his way to insult the Pope and the Church, and was pretty much a huge jerk about it. The Church at the time was not exactly the picture of acceptance and tolerance, but I think even Mahatma Gandhi would have poked Galileo in the eye after being around him for a few minutes. Obviously, self-promotion has its place. But you have to remember others did good work, too.
|A map of the entire Moon's face made by Harriot.
Credit Lord Egremont and the RAS.
This map made above is pretty amazing. It was made by Harriot around 1613, around the time he suddenly (and for unknown reasons) stopped observing the sky. I've spent my fair share of time eyeballing the Moon, and this is a pretty decent map, certainly way better than I could do, even with the far-superior optics in my own telescope. Harriot independently discovered sunspots, and observed Jupiter's moons (though after Galileo discovered and announced them; to his credit Harriot timed carefully the motions of the moons, and his observations have been confirmed).
As far as his stopping observing, it's possible that with the crude instruments available to him, Harriot had pushed the state-of-the-art as far as he could. Galileo's superior telescope let him do more, but I think we need to remember Thomas Harriot during this celebratory year. If you happen to peer through a telescope at the Moon, or Saturn, or some other celestial object this year, take a moment to remember those people who, four centuries earlier, were doing it for the very first time, and try to imagine what it must have been like to see a whole new world -- a new Universe -- open up in front of them.