Friday (Isaac) Newton blogging (Thursday edition): “The Coffee House” meeting

I don’t think I’ve got this precise to the day, but I can’t let the month pass without tipping my hat to Sir Christopher Wren, Robert Hooke, and the incomparable Edmund Halley. It was in January, 1684 that three men met for refreshment and conversation after one of the Royal Society’s weekly meetings.

They may have done so to put a little rigor into an evening that could have been truly scattered. Neal Stephenson caught the flavor of early Royal Society meetings perfectly in the first volume of his Baroque Cycle. His account is taken from life: if you look at the early volume’s of the Society’s pleadings (JSTOR has ’em all online, if you have access to that resource) you’ll find articles like “An Accompt of the improvement of Optick Glasses” and Robert Hooke’s own telescopic observation “A Spot in one of the Belts of Jupiter” jostling for space with “An Account of a very odd Monstrous Calf” or “Of an Hungarian Bolus of the same Effect with the Bolus Armenus.” (All of these from meetings in 1665.)

So it may well have been either boredom with yet more deformed animals, or exhilaration at some deep observational challenge that got three of the real intellects in the Society going that January night.Wren asked the question that got the fireworks going. How, he asked, did the force of gravity vary as the distance between objects changed? Could it be an inverse square relationship, as he and others had speculated, but failed to demonstrate? (I.e. — did the force of gravitational attraction between two bodies vary inversely with the square of the distance between them?)

This was, of course, the fundamental cosmological problem of the day. The geometry of the solar system was basically understood — laid out by Johannes Kepler and his three descriptive laws of the planets’ orbital motion. But how the planets held to the paths they traced — that no one knew, though Wren and his listeners recognized that the ill-understood phenomenon of gravity must have something to do with problem.

Wren himself and Halley too both confessed they could not demonstrate that an inverse square law actually held in the real world, but Hooke claimed that he had already completed a proof of the idea. Pressed to reveal it, he declined, declaring he would hold it back for a time so that “others triing and failing, might know how to value it.”

To coax out the truth, Wren offered a prize — a book worth 40 shillings (a week’s stipend for Newton at that moment, as it happened) — to Hooke (or anyone else) if he could actually do what he claimed he could within two months. Nothing came.

Then, in August, Edmund Halley made his way to Cambridge for his famous chat with Isaac Newton. In the middle of the conversation, seemingly as an aside, he asked Newton, “what he thought the Curve would be that would be described by the Planets supposing the force of attraction towards the Sun to be reciprocal to the square of their distance from it?”

An ellipse, Newton answered, without pause for thought.

How did he know?

“I have calculated it.”

Newton probably had, unlike the similarly confident Hooke, though he didn’t produce the calculation on the spot. In November, though, he sent Halley a more in depth analysis of the problem, a nine page manuscript “on the motion of bodies in orbit.” Halley immediately recognized that this wasn’t merely the resolution of a bet, but the outline of a whole new science. He urged — almost demanded — that Newton fill out the account…

…and hence, with considerable labor yet to come and a great debt owed to Halley as the project’s midwife, was born Newton’s Principia — and with it, much of what we think of as modern science.

I do not usually toast with coffee, preferring stronger stuff. But it is time to titrate some caffeine into my system, so, in remembrance of that argument in the coffee house, I will shortly lift my mug of Peet’s brew — not to Isaac Newton, this time, deserving of his honors as he certainly is — but to those other three men, who at the crucial moment asked the crucial question, which ultimately found its way to the right man.

So, in this three hundred and twenty first fourth January since Sir Christopher Wren offered his prize, here’s to Wren, Robert Hooke, and above all, to Edmund Halley.

PS: in case anyone was wondering, the name of this blog is indeed an homage to Newton, the subject of my forthcoming book. (Jan-Feb, 2009, at last count.)

Update: arithmetical error corrected above, proving that I shouldn’t do mental arithmetic while in a state of mild caffeine withdrawal. Dependency is an ugly thing.

Image: Robert Hooke’s microscope from Micrographia, 1665. Source: Wikipedia Commons.

Explore posts in the same categories: astronomy, History, History of Science, Isaac Newton, Newtoniana, Science Fiction

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3 Comments on “Friday (Isaac) Newton blogging (Thursday edition): “The Coffee House” meeting”


  1. Great blog. Do we know how much of Newton’s mathematical proof was worked out before and after Halley’s question to him in August 1684?

    • Tom Says:

      Not for certain, no. There is some speculation that Newton had worked it out ahead of time, discovered an error as Halley pressed him for an answer, and redid the proof in the late summer/early fall of 1684. But while that’s plausible, it’s not a certain rendering of historical fact.


  2. Nice story Tom. Do you know the source of it?


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