Philosophy 167: Class 4 - Part 5 - Kepler's Biography: Comments on His Life and His Publications.

Smith, George E. (George Edwin), 1938-


  • Synopsis: A brief biographical sketch of Kepler.

    Opening line: "Okay, this is the rest of his life. He lived to be, it turns out, 58 years old."

    Duration: 12:49 minutes.

    Segment: Class 4, Part 5.
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Okay, this is the rest of his life. He lived to be, it turns out, 58 years old. He was in his 59th year, that's a question of which month. Essentially 20 more years during which time, he produced a large number of books. I'm gonna go through them in a moment.
The culmination of all of this was fulfilling the promise that he had made to Tycho, that Tycho had made to Rudolph to put out a set of tables. Which is in 1627, as you can see the Rudolphine table is printed in, I can't read it, but you have it in front of you.
After which he doesn't do a whole lot. He dies. He just gets sick while at a meeting and dies on the spot. I don't know that anybody knows why, whether it was bad pneumonia or what. But once he got the Rudolphine tables out, he did more work, as I'm about to show you.
But, it was almost as if he had it done as much as it's humanly possible to do, working from Tycho's data. From there on, you were gonna have to weigh better data, and he knew perfectly well that was coming with the telescope. But it didn't arrive until 80 years later.
Okay? Even when Newton was writing telescopic observations of longitude and latitude, were no better than Tycho's. Because they didn't have the proper correction for parallax and atmospheric refraction. Okay, so they were stuck. They had greater precision looking through the telescope. But the greater precision did nothing for them if they had to do corrections, and the corrections were swamping out the precision.
So it's a long time coming. I mean, the next tables, after the Rudolphine tables. There are lots of subsequent tables. The next table's to really represent telescopic observations are in the 1740s. Two sits by concenie and posthumously from Allie. It's a long way away. All right just this list of books.
I've told you a little about mysterium cosmographicum earlier, and we'll look at it right after this slide. It's what got Kepler started thinking he could solve the profound problems of astronomy. The 1602 book on astrology was, you may not accept this. It was an attempt to persuade Rudolphine that the money he was putting in to all of this was worth having.
Rudolph took astrology quite seriously. This is not the first person in astronomy who thought astrology was totally garbage, but nevertheless wrote on it because that's a way to get funding, okay. Then you already know about the astronomical part of astronomy, that 1604 book ,The nova. The new star now called a Nova that burst on the scene, the Nova of 1604, he and Galileo both wrote about.
I'm not gonna bother you with what Kepler wrote, but you will see some of what Galileo wrote. Then of course Astronomia Nova delayed four years after it had been written because of controversy over releasing the observations. Then in 1610 Galileo, you'll read it next week, Galileo publishes Starry Messenger.
And I'll start the advertisement for it now. I hope everybody in this course, auditors and everybody, reads Starry Messenger. The easiest way to describe it is, no book like that has ever been written before and probably has ever been written since. And there's some question whether we're capable, any longer, of writing it.
What it did was to suddenly show that what people thought they knew, was a minuscule fraction of what there was in the world that they had never seen before, and it astounded everybody. Nobody remotely anticipated the number of stars. Nobody remotely anticipated Milky Way consisted of thousands of individual stars and I can go on and on.
You'll read it for yourself. So the book was an amazing book. My usual way of telling this story as I keep telling you for 13 years, Bernard Cohen and I would have lunch every Friday, while working on the new translation of the Principia. And I once said to him, well the same effect would be produced today if we suddenly discovered intelligent life elsewhere in the universe.
He said, but we've anticipated that possibility. They hadn't anticipated any of these possibilities. Okay so, that book came out and almost immediately Kepler wrote a short monograph supporting it. Followed by a, let's see, the first one is the conversation with the Sidereal Messenger, and the second one is a narration on the satellites of Jupiter, which again, no one knew existed.
Actually, somebody may have known they existed because the human eye at most extreme, can actually, probably pick up those satellites. But it's 1 in 10 million people that have that kind of visual acuity. It's way out there. The 10 million I'm pulling out, but it's a very rare acuity.
Ted Williams, somebody like that. The Dioptrice is a very important work. It's the only work of Kepler's that Newton owned a copy of. It does some of the, it repeats some of the work from the early optics like describing in great detail how the eye works. It also gives the first complete theory of how telescopes work.
In the process showing that the kind of telescope Galileo was using was seriously limited, and proposing a new telescope that inverts the image in the way the eye does. That has ever since been called the Keplerian telescope, and, it's the telescope that took over. Within by 1630, the Galilean telescope was never used for anything but spyglasses at sea and binoculars, things like that where you don't want the image inverted.
So that work is a really major work in the history of both telescopy and optics. Then what do we get? The stereometria. These are the methods that Kepler introduced in Astronomia Nova to approximate what we now call calculus. Remember he broke it into 361 degree triangles around the circle?
Those methods which originate from, he picked the idea from Archimedes. He used those methods for much more effectively than had been used classically. This book describes how to use those methods. They, of course, we would call them finite difference methods, now. They disappeared from need to use them after Newton and Leibniz independently developed the calculus.
Then Harmonices Mundi, the Harmonies of the World, I'll pass that around, 1618. As Gingrich likes to say, and he says it around me, he knows it irritates me, that it was surely Kepler's favorite book. And when you see, you'll see in a moment why it irritates me. The epitome of Copernican astronomy, obviously, that's a play on the Regiomontanus title, the Epitome of the Almagest.
He's putting, it came out in three segments, that's the 18 to 21, books one through three, which are really elementary spherical astronomy. How to do spherical triangles, all the things that are utterly standard. There's the first three books, they were in 1618. I think actually precede Harmonices Mundi by a few months.
Then the books four and five, the ones you were assigned, part you got excerpts for tonight, they came out as a second volume. And then a third volume on the individual orbits and comparisons with Ptolemy with one of the questions being have things changed over 1500 years is book seven.
That work became very widely circulated. After 1631 when people decided that Kepler was right about the ellipse. All of the sudden the Epitome went through several new editions. Of course, Kepler was dead so he didn't live to see any of this. But all of a sudden the Epitome became a very widely read book.
Newton I don't know read it I just can't tell, he definitely didn't own a copy of it. Then the comet of 1619, no it's actually the comet of 1618, the book is 1619. He adopts a Tycho like view. Comet's are out there in space. Galileo rips into him saying, no no, comets are an atmospheric phenomenon.
They're sublunary. All you people who say they're out there celestial are just dead wrong. We'll see that next week. Not only could Galileo be wrong, he could be incredibly outspoken and insistent that he's right when he's dead wrong. And it did not make him popular among people. In 1621, he reissues Mysterium Cosmographicum now knowing things about ellipses, area rule, etc.
So he thinks it's largely a clean up of the earlier one, saying he can do better now than he did the first time, cuz he knows more. Then the Rudolphine Tables in 1627. As they say, that is the book that most serious astronomer over the next century owned a copy of.
Newton did not, but Newton was not a serious astronomer. In that sense, he would turn to others. But the person that he turned to, John Flamsteed, was the first royal astronomer of Britain, very much had that copy and used it all the time. So, it's a major work not translated.
I'll go to the last one first and then come back to the next to last one. The Somnium, I'll pass that around. It's a piece late in life, where he presents it as a dream. But the dream is what would it be like in a dream to fly to the moon and look at all the celestial realm from the moon?
How would it differ from looking from the earth? And he works it out and describes it. So it's almost a tale for children, except it's pretty serious, as such. The one before that is what's call Ephemerides. What they did, and he started doing this earlier, is put out each year a set of predictions on salient events during the year.
The one for that he put out for 1630 was very important because it announced that in 1631 both Mercury and Venus were going to be transiting across the face of the sun. That's an extremely valuable thing to be able to see because you know exactly what the longitude is of Mercury when it's clearly visible as a spot along the sun.
If you know where the sun is, you know where Mercury is and you know where Venus is. Another way to say this to try to drive the point home. I trust you all know about the famous 43 arc seconds per century that led to the first evidence for Einstein's theory of gravity.
Led to it because he wouldn't publish a theory of gravity until he could reproduce those 43 arc seconds. That date is all from transits. You can't get that accurate without transits at that time. So he predicted the transit. Nobody had ever observed a transit and that's gonna be a big thing next week, his successful prediction of that.
It is, simply put, that's what swung everybody to ellipses. He predicted the transit almost to a matter of minutes everybody else predicted it to within a few days. And since Mercury is so elliptical the attitude was okay, Kepler shown us Mercury's elliptical, all the others must be elliptical too.
And that's almost the sole reasoning. Once you grant Mercury's elliptical why stop there? Okay, so that's a very important work.