Galileo’s Daughter, Part 2: The Genius of Galileo

In part 1 of my review of the excellent book Galileo’s Daughter, I concentrated on how the author treats the confrontation between Galileo and the Roman Catholic church. In this part of the review, I want to focus on how the book treats other aspects of Galileo’s life.

The book shares all sorts of interesting things regarding Galileo about which I was completely unaware. For example, did you know that you can see a preserved part of his body if you wish? Indeed, the middle finger of his right hand is inside a glass egg at the Museum of the History of Science in Florence. My wife and I spent a day in Florence, but there are so many amazing things to see, we never got to the Museum of the History of Science. As a result, we never got to see Galileo’s finger.

I also learned that Galileo did not like academic garb. At that time in history, if you were a teacher at a university, you were expected to wear your academic robes at all times while you were working. When Galileo got his first teaching post at the University of Pisa, however, he:

deemed official doctoral dress a pretentious nuisance, and he derided the toga in a three-hundred-line verse spoof that enjoyed wide readership… (p. 19)

Now this is a man after my own heart. I hate it when university professors try to set themselves apart by any pretentious means. Not only did Galileo hate that as well, he actually wrote a snarky poem about it!

While little facts like these are interesting, there were two things I read in this book that I had never heard before, and they clearly show that Galileo was nothing short of a true genius!

The first thing deals with the sunspots Galileo discovered. I knew he had discovered sunspots, of course, and I knew he used them in support of the Copernican theory that the sun was at the center of the universe. However, I always thought he used them as an example of how Aristotle was wrong. Aristotle believed that the sun was a perfect sphere, and that there were no blemishes on it. Galileo demonstrated Aristotle to be wrong about the sun, and I thought that was the force of Galileo’s argument. Essentially, I thought he said, “See – Aristotle was wrong about the nature of the sun, so he could be wrong about where the sun is!”

That’s not the case at all. Indeed, what Galileo learned from sunspots is that the earth must be orbiting the sun on a yearly basis. Now think about that for a moment. Galileo used the properties of the sun’s surface to learn something about the earth’s motion! Isn’t that amazing? How did he do it? Well, he observed sunspots a lot, and he found that they appear to travel across the surface of the sun. He found that two days out of every year (the winter and summer solstices), the sunspots appeared to travel in a straight line across the sun. The rest of the year, they traveled on what appeared to be arcs. However, for six months out of the year, the arcs seem to curve downward on the face of the sun, and for the other six months, they seemed to curve upward.

This was enough to tell Galileo that the earth orbits the sun! After all, if the sun orbited the earth each day (as it must in an earth-centered universe where the earth is not allowed to rotate), the apparent paths of sunspots should vary daily, not yearly. Instead, they followed a very regular, yearly pattern. This supported the idea that the earth orbited the sun each year, and it played havoc with Ptolemy’s earth-centered view of the universe. As the author says:

More serious and scientific followers of Ptolemy, however, would have to spiral the Sun through the most complex gyrations imaginable, in order to save these newly recognized appearances in a geocentric and geostationary system. (p. 170)

Now I find it amazing that Galielo could use sunspots to determine that the earth orbits the sun once a year, but the second thing I learned really knocked my socks off!

After being rebuked by the Roman Catholic church, Galileo still did scientific research. He just didn’t do much related to the heavens. Instead, he did a lot of investigation about motion. He really thought understanding motion was the key to understanding creation, so he did lots of experiment related to motion. Now as a nuclear chemist, I study motion quite a bit, and one thing you need to have in order to study motion with any real detail is a good way of measuring time. Without a good measure of time, you cannot learn anything about velocity and acceleration, which are key to understanding motion.

While Galileo was alive, however, there was no really good way to keep track of time. I had never thought about that. The pendulum clock (like a grandfather clock) had been invented, but it was no more accurate than a sundial. Indeed, clocks were regularly adjusted based on what the sundial outside showed! So how does someone studying motion measure time when the best clock is no better than a sundial? Amazingly enough, Galileo weighed time in his experiments.

When he wanted to time how long it took an object to move a set distance, he used what was essentially a container of water with a hole in it. When water was added to the container, it would drip from the hole at a constant rate. So when Galileo wanted to “start the watch,” he would put a dry bowl beneath the hole. The bowl would then collect the water that was dripping from the hole. When Galileo wanted to “stop the watch,” he would take the bowl out from under the hole. Then, to measure the elapsed time, he simply weighed the water!

Now of course, Galileo wasn’t really measuring time this way. He couldn’t say that a certain weight meant a certain number of seconds. However, he could say that the weight of water was proportional to the time elapsed. So suppose a ball rolled down a ramp in a span of time that produced 10 ounces of water in the bowl. Suppose the ramp was adjusted, and the ball rolled down in a span of time that produced only 5 ounces of water in the bowl. From those weights, Galileo could determine that the average velocity of the ball was twice as fast in the second experiment as compared to the first experiment.

Now that’s the work of a real genius! He didn’t have a good enough clock, so he made something that would function as a clock. Since what he measured wasn’t exactly what he wanted to measure, he worked in ratios to make all of his conclusions. It’s no wonder Galileo changed the face of science so dramatically. Both his grand theories and his mundane measurements demonstrate his true genius!