Now we're going to talk about one of a problem that has fascinated humans since we were cave dwellers. No, not how to make a decent club to thump our neighbors with, but what we always do in our more contemplative moods, look up at the sky at night, and wonder about all those little tiny lights up there.
The more we looked and looked the more that emerged. We pretty soon discovered that some of those lights up there were different than others. We call those planets. We started trying to see if we could predict where they were going to be. It was a big problem for thousands of years to figure out what those darned planets were doing.
It seems easy today since we know the answer. But if you didn't know the earth was spinning, while rotating about the sun, the motion of the planets would seem pretty darned complex. People got really keen on finding the answers to where the planets would be. Lots of religions are based on these things. So surprise surprise, people became a little hot headed and started calling each other heretics and such nasty things. All over these silly spots of light in the sky.
Eventually technology progressed to the time of Tycho Brahe, where he convinced the king of Denmark, in the sixteenth century to help him set up a big observatory to make accurate observations of the positions of the planets. He hoped to use this data to predict eclipses and the like, things that most humans thought would portend various unsavory events.
His disciple Johannes Kepler, spent a couple of decades analyzing the data and trying to make sense out of it all. The problem is that he seemed by present day standards to be a bit of a lune-tune, and quite literally. He had this notion that the planets were singing tunes as they merrily spun around the sun.
Galileo himself being a musician wasn't very impressed by Kepler's tunes and didn't take the man all that seriously. But buried in some long rambling treatise, are Kepler's three laws that have stood the test of time, and provoked Newton to give serious consideration to this problem.