What Good Is a Telescope? Part 2

Yesterday we left off with the geocentric view of our universe (with Earth at the center and everything else orbiting it), as propounded by The Church. Since this model could help predict the future positions of the planets, this meant power.
But of course, this couldn't last forever; absolute power and all that. The guy who changed everything forever was Galileo, and he did it with a telescope.
Galileo was an Italian scientist who became a student of Copernicanism upon reading works of Nicolaus Copernicus, an astronomer who died 21 years before Galileo was born. Copernicus maintained that the sun, not the earth, was the center of the universe (I'm using the term 'universe' as it would have been described at that time, not in our time). This model explained retrograde motion more clearly and simply that the geocentric model did, and thus provided more accurate predictions.
In the early 17th century, Galileo heard of a device called a spyglass and adapted a similar device to study the heavens. It was a simple device, a tube with a concave lens at one end and a convex lens at the other. It wasn't like a telescope you would use today; in fact, its power and quality were probably a bit less than a decent pair of binoculars today. To his credit, Galileo made vast improvements in the design of telescopes, eventually grinding his own mirrors and thereby drastically bettering his view of the universe.
Once he applied this new technology to the study of the stars, Galileo stumbled upon a cosmic quandry that would resolve the geocentric/heliocentric debate: the phases of Venus. If the geocentric view were to be correct, Galileo would never see Venus as more than a crescent in his telescope; if the heliocentric view were correct, Venus would grow from crescent to nearly full as viewed from the earth. Below are two animations demonstrating what each of these models would look like respectively.


Ptolemy's Model


Copernicus' Model

You guessed it; as Galileo studied Venus' phases through his telescope, he saw not just a crescent Venus but as time passed, all the way to a gibbous Venus in his field of view. And as quick as that, thousands of years worth of cosmological thinking were made obsolete.
You probably know the rest of the story. I won't go into details, but The Church wasn't particularly gracious about this new information (remember, astronomical knowledge = power); nor was Galileo gracious in his response. Nonetheless, the Scientific Revolution had begun and our understanding of the universe changed forever.
One last note: if you would like to listen to a fascinating account of all this, I highly recommend you give my fellow former planetarian Davin Flateau a listen. His podcast (part 365 Days of Astronomy podcast series) is available here. It's definitely worth nine minutes of your time. And the theme song is awesome!

Check back tomorrow for the exciting conclusion of our telescope tale.