Philosophy 167: Class 11 - Part 5 - Thomas Streete: Astronomia Carolina, Tables, and Another New Method for Calculating Orbits.
Smith, George E. (George Edwin), 1938-
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1661 is the publication of Thomas Street's Astronomia Carolina. The Carolina is Charles II. Remember, Charles I was beheaded. Cromwell, in 1648, Cromwell until he died was the protectorate, and his rather incompetent son tried to take over. It all collapsed. They invited Charles II to come back and assume the throne in a totally bloodless revolution.
So it's dedicated to Charles, Astronomia Carolina, but it's totally in English. And as I say, this is the book from which Newton seems to have initially learned Mathematical Astronomy, from reading Street. Again, I don't have that hard-bound, I have it only in xerox printout. I'm gonna give you one long passage from it, but let me tell you a little about it first.
This book does an unusual thing. It decides that we should use the three-halves power rule and a period to determine the lengths of the major axes. Who had proposed that? Horrocks. Street had read Horrocks. He told people he had read Horrocks, and Horrocks had proposed that, and he didn't.
So this book brought Horrocks suddenly to the existence before the eyes of major figures. Huygens was in London the year this book appeared. He bought a copy of the book. He then obtained a manuscript copy, he ended up with two copies, one for himself and one I'll tell you about in a moment, of Horrocks' Transit of Venus from the 1637, 39, whichever year it was, that little book.
He sent one of the copies of the manuscript to Hevelius in Poland. Hevelius publishes it along with his own manuscript on the recent transit of Mercury. So suddenly Horrocks is published. With everything that he had achieved out before the public in 1662, thanks to Huygens being so impressed by this that he got it out.
So this book had major effects quite independent of its own content, simply by calling attention to Horrocks when Horrocks was virtually unknown. We don't know how Street discovered Horrocks' papers. At least I don't know and I don't know anybody, Street's a slightly mysterious person in some respects. Since this is 1665, I'm assuming this is a reprint that I work from, because I know perfectly well the books in 1661, and full tables come out in 1664.
I first read this book right when I was beginning to teach this course. I spent summer in London and read the book in the British Library, and this page really stood out to me. I've chosen not to type it out, I realize it's hard to read. But it's so striking, I wanted you to see a direct reproduction.
So I'm gonna read it out as best I can from looking at it here. I'm gonna start with the first full paragraph. The old supposition of solid orbs to support and carry the planets I count scarce worth the mention. The earth we see hath no such orb and nature with all.
I can't quite read it. I probably am better off just reading off of here. I know where I'm best off, cuz I can read it off the handout where I don't have to struggle with either my eyesight or the imperfect focus. Nature itself with all observations to the true motions of secondary planets and of comets, plainly demonstrating the impossibility of any such thing, solid orbs.
Next, nor shall I hear mention any of those many and gross absurdities which will necessarily follow in all such systems as a tribute to the sun or first stars any of the earth's natural motion. So much for the dichotic system. That's an argument I will not mention. Okay.
But further to clear the truth from all seeming contradictions, whereas we see that all corporeal substances appertaining to this, our earthly globe, do proportionally to their quantities, as proportion of their quantities of matter, tend downward towards the earth's center. Let us observe that this comes to pass by the natural magnetic power of the earth attracting its parts, a property common to every one of the planets, whereby, according to the Creator's will, they become compact bodies and do something their constant form.
The sun also and fixed stars, though of a different principle, having the like retentive faculty. And that the air, the clouds, a bird flying, a stone falling from any height, an arrow or bullet shot or driven any way, and all things else within the sphere of the earth's activity, whether otherwise moved or not, do naturally and exactly follow her annual and diurnal motion.
So that we, the earth's inhabitants, cannot possibly perceive or be made sensible thereof any other way than by such real demonstrations as are here given. We shall exemplify this in the planets Jupiter and Saturn, whose attendance at a far larger distance do not only keep their constant revolutions about them, but together with them about the sun.
The light both our moon about the earth and both about the sun, so that by the impulse and universal consent of nature, whether accidental motions be annexed or not, all things so near the earth do precisely keep the same motion with it. Now, Newton read this when he was very young, first in university.
And of course, it's suggesting the moon is held in orbit by some magnetic power toward the earth that also is responsible for the earth holding together as a solid body. You'll see, next week, Newton actually starts testing whether the centrifugal force of the moon matches surface gravity, as measured by Huygens.
So it's gonna be picking up on this very idea, but now with the value, now being able to actually measure the force required to keep the moon in its orbit and see if it goes as an exact inverse square to the surface of the earth. But I take that passage in Street to be very significant statement about the possibility of what we now think of as a gravity-like force holding the moon in orbit.
And that's not an everyday thought at the time. Remember, we're still in a world where gravity is a terrestrial phenomenon, and celestial phenomenon have a different physics, except from Descartes, so things are going on here. The reference in here to the natural magnetic power, starting in the 1640s, Wilkins, a name that was up on that first chart and I'll come back to in a moment, started pushing the idea of an analogy between magnetism and gravity.
And it came to be known as the magnetic philosophy, and people like Christopher Wren and Hooke were adopting it. Obviously Street was too. Exactly what they meant by this is unclear, but the analogy between gravity and magnetism is not a small thing. The tables that Street produced, they're in 1664.
They're not in the 1661 publication. They came out separately. The quote a few years later is they are the exactest of them all. I esteem Mr. Street's numbers the exactest of any extant. That's 1669 by Flamsteed. So the tables are very successful. This is a Curtis Wilson comparison of all the people I'm preoccupied with except Mercator, we'll come to him in a moment.
But the two winged volumes, Boulleaux and Street, they compare to what Simon Newcomb says the value should be for the eccentricity of the aphelion and then the mean distance. And you will notice, Street's values for the mean distance are spectacularly good because, of course, he's the only one using the three-halves power rule.
Street ends up adopting the same construction as Boulleaux in place of the area rule, but attributes it to a friend of his who obviously learned it from Boulleaux and didn't tell Street, by the way, I got this from somebody else. So he attributes it, I think it's Robert Anderson is the person he attributes it to.
But Street's tables last well into the 18th century. They turn out to have been, on the whole, the best tables that anybody was able to do.