So look, what we're doing, what we're in the middle of is three classes interrupted by a holiday on November 11th, three classes looking at the period from the early 1640s. You can do it from when Horrocks died in 1641, from when Galileo died in January of 1642, or from the publication of Torricelli's work on projectiles in 44, and the publication the same year of Descartes' Principia.

The way I put it up here is between the two Principias, and that's probably as good as any. As I've said last time, leading off these three classes there's a completely standard view of how Newton's Principia came into being. Namely, take Kepler's so-called laws and Galileo's mechanics. Put them together with him responding to things he disliked in Descartes' Principia, and you have Newton's Principia.

And it makes it sound like nothing happened between 1645 and when Newton started work on what became the Principia in very late 1679, early 1680. And nothing really could be further from the truth. Just an enormous amount happens between 1644 and 1679. I think the best way to think of it is science becomes professionalized.

It becomes a profession to be a practicing scientist, in many cases outside the academy, as you'll be hearing tonight. And there just wasn't anything like that before. There was not a profession of being an empirical scientist. The last time I didn't adequately drive home that feature, because we were looking at mechanics over those years.

And while other people were important to mechanics in the 35 years I am talking about, from Newton's point of view Huygens was so dominant in influence, that what anybody else did was essentially of secondary concern. Huygens was just a dominant factor in the Principia. This time however it's gonna be dramatic, the community.

So there are 27 names up here. I'm gonna run through them very briefly. Most of them, not all of them are important in the history of astronomy. John Wallace is a little bit in astronomy but not a major figure. He's a mathematician who you'll see next week had a huge influence on Newton's development of the calculus.

And of course he wrote that book on mechanics. Seth Ward was Professor of Astronomy at Oxford in the early 1650s. You already know who Jeremiah Horrocks was. Vincent Wing is a mathematical astronomer. Nicholas Mercator happened to produce a very, very important book in mathematical astronomy that I'll be featuring part of tonight.

He's also a major mathematician and is one of the reasons Newton actually tried to publish his work on the calculus, for fear that Mercator would beat him to everything. Thomas Street, published a book in 1661, and I'll talk about it at length tonight. It's the book from which Newton first learned astronomy.

And it's nice it's in English. Robert Boyle of course best known for chemistry and for being the spearhead behind the formation of the Royal Society. He never did any work in astronomy that I know of. Christopher Wren became the Professor of Astronomy at Oxford when Seth Ward left the chair.

I don't, when did Ward die? Ward did not die, but he left the chair. And Wren inherited it and stayed there until he won the contract for rebuilding Saint Paul's. And then from there on in his life he was primarily an architect. Though, in 1683 was president of the Royal Society, so he was attending Royal Society meetings and still very actively involved, but he had other things on his mind.

Robert Hook, you'll hear about a good deal tonight. He's done some things in astronomy, but he was curator of experiments in the Royal Society. James Gregory was primarily a mathematician, nothing on astronomy. Newton, of course, you know. Flamsteed was the first royal astronomer of England. And Halley, you'll notice how much younger he is than everybody else?

When he was 19 or 20, he was already a major figure in astronomy. He was a real prodigy in all of this. And of course, he's the editor of the first edition of the Principia, quite important person. So that's, I think that's 12 names up there. Let's do the ones below.

Borelli was one of the founding members of the Accademia of Experiment, Cimento in Florence that was formed after Galileo died, committed to experiment. Viviani, another major member. Borelli's up here because in the 1660s, he produced a small book, monograph, on the motion of the satellites of Jupiter. Looking at it from a physics standpoint, trying to combine the Cartesian vortex picture with a magnetic picture of motion in and out along a radius producing an ellipse.

And it's a book that Newton not only read, he annotated extensively, and in the back pages, he has a whole bunch of writing on the Borelli. So, Borelli's something he read and was important. Hevelius was Polish, he's gonna be important for a lot of reasons. But by the late 1660s, he published the compendium on the history of comets.

He went back and collected information as best he could. It's a gigantic book, comet after comet. And he was the authority on comets. Picard was an astronomer in France. He did many things, his name will be showing up several times today. He's one of the co-inventors of the screw micrometer in telescopes.

Mariotte was the experimenter at the Royal Academy. I don't know that he ever did anything in astronomy as such, but he was Hook's counterpart in Paris designing experiments all the time and producing some significant work in mechanics. Ozoo worked with Picard. The two of them worked together before they became academicians and continued afterwards.

Pascal died as you can see even before the Royal Society was formed. He was primarily a mathematician though he showed up on work on pneumatics when we were looked at Descartes. Cassini's gonna be a major figure tonight. He lived quite a long time, 87 years. And from roughly the early 1650s until he died he was the leading observational astronomer in the world for reasons that will come out tonight.

Huygens you already now. Richer was one of Cassini's assistants at the Royal Observatory in France. Campani ground the lenses that Cassini used in his telescopes, they were the best lens in the world. And gave Cassini and Campani a quality of telescope that everybody else envied, because they couldn't match them.

And they basically had control of those lenses. Campani actually worked out of Rome. De La Hire was another assistant to Cassini at the Royal Observatory. Roemer became an assistant when he was brought back from Denmark. In a story I will tell you that Liebniz is the other figure up there who did nothing in astronomy until after Newton's Principia.

But all of these people, during this period between the two Principias, became very major figures. And to a remarkable extent, they were in communication with one another and in many instances knew one another personally. And this is the tip of the iceberg. Almost everybody up there is professional scientist.

That is, they ended up not having academic positions, or if they had academic positions, they were also fellows of the Royal Society. All the academicians in Paris had the liberty of not teaching, just doing research all the time, under the King's funding. So the vast majority of the people at the bottom were professional scientists.

All right, with that as background, what I'm going to do is move through these years starting in the 1640s. And this is an unusual class. First of all, it's got a god-awful lot of slides. Because part of the reason for that is I'm just gonna give a kind of panoramic picture of what happened between 1645 and 1679.

Some of it very striking, others perhaps a little less striking. The one book that I'll pass around, it's an interesting little book. Gassendi put out a little book on, and this is a later edition, on the Copernican and the Tychonic systems, and the problems of distinguishing between them.

The original came out in 1647. It's of course in Latin. But what makes it interesting is when Newton was asked by Richard Mentley in the early 1690s what did he need to read in order to read the Principia, this was the basic astronomy book that Newton recommended. This and Mercator's book were the two astronomy books Descartes' Geometry in the second Van Schooten edition, which is, Darcartes' a little tiny fraction of.

And Huygens's is Horologium Oscillatorium are the featured books. You'll see that later. You'll see that beginning in next term, what he thinks people should read to prepare to read the Principia. But strikingly, the Gassendi is in there. Even though it's fairly elementary, it's sort of stating a problem at the time.