Horrocks Bollocks!

The HISTSCI_HULK was gently easing his way into Monday morning, occasionally glancing over my shoulder at my Twitter stream, when a link posted in my notifications by the Aussie AnthropoidTM, John Wilkins, caught his eye. Before I could stop him, I knew no good could come of it, he had clicked on the link and as he read the linked article from The Observer, the steam started coming out of his ears. 

Romanticised Victorian painting of Horrocks making the first observation of the transit of Venus in 1639. No contemporary portraits of Horrocks survive Source: Wikimedia Commons

The article is titled The forgotten maths genius who laid the foundations for Isaac Newton and is about the early seventeenth-century, English astronomer Jeremiah Horrocks, whom I honoured with a blog post back in 2009. The article is occasioned by the fact that somebody has written a stage play about him entitled simply, Horrox, presented as part of the Cambridge Festival 2023.

The lede to the article is:

A new play explores the short life of Jeremiah Horrocks, whose astonishing discoveries ‘changed the way we see the universe’

This is total hyper-bollocks as old Hulky is fond of screaming, when he gets really worked up. Horrocks made some important contributions to the development of astronomy in the early seventeenth century but none of them ‘changed the way we see the universe’.

The opening paragraph is OK…

On a cloudy afternoon in England in 1639, 20-year-old Jeremiah Horrocks became the first person to accurately predict the transit of Venus and measure the distance from the Earth to the sun.

But in the next paragraph the whole think develops into a major trainwreck of astronomical proportions:

His work proved, for the first time, that Earth is not at the centre of the universe, but revolves around the sun, refuting contemporary religious beliefs and laying the foundations for Isaac Newton’s groundbreaking work on gravity.

His work did nothing of the sort, but the claim gets repeated as a direct quote from the author of the play David Sears, a couple of paragraphs further on:

Now, a new play, Horrox, will attempt to reassert Horrocks’s rightful place in history as a British genius who, according to the playwright David Sear, “changed the way we see the universe”.

“We had no idea of the scale of the universe until Jeremiah Horrocks,” said Sear. “He was the first person to prove that the Earth was not the centre of creation, destroying key precepts of Christian teachings and the primacy of a literal interpretation of the Bible in the process.”

By the time poor old Hulky got this far in the article he was incandescent.

Sears is obviously under the mistaken impression that Horrocks’ observation of the transit of Venus was the first proof that Venus orbits the Sun and that this is a proof of the heliocentric model of the cosmos. Neither of these statements are true, as regular readers of the Renaissance Mathematicus will already know. 

Telescopic observations of the phases of Venus by Thomas Harriot, Simon Marius, Galileo, and the Jesuit astronomers of the Collegio Romano, all made around 1611, so twenty-eight years before Horrocks observed the transit, had proven that Venus orbits the Sun and not the Earth. This is, however, totally consistent not only with a heliocentric model, but also with a geoheliocentric model, in which several or all the other planets orbit the Sun, which in turn orbits the Earth. 

Sears also gets Horrocks’ determination of the astronomical unit (AU), distance between the Earth and the Sun, wrong. He says:

“The only way you could measure the distance to the sun at the time was by getting an object to fix on, between the Earth and the sun, and then triangulating through,” said Sear.

I’m not going to go through the method in detail that Horrocks used, it occupies several pages of Albert van Helden’s excellent Measuring the UniverseCosmic Dimensions from Aristarchus to Halley (University of Chicago Press, 1985), which I recommend if you want all the grisly details, but Horrocks did not use triangulation as claimed here by Sears but a highly speculative method based on the diameters of the planets (he had measured the diameter of Venus during the transit) and a theory of Kepler’s that the diameters of the planets was proportional to their distance from the Sun. Using this highly dubious calculation he arrived at a figure of 59 million miles, much bigger than previous determinations but still well short of the actual value of 93 million miles.

We now get some more hyper-bollocks from Sears:

In 1687, Newton acknowledged the importance of Horrocks’s observations in his Principia: “Newton wouldn’t have been able to complete his work on gravity, if Horrocks hadn’t done these observations at the time he did,” said Sear. “Newton relied on this earlier work.”

Neither Horrocks’ observations of the transit of Venus nor his determination of the AU appear anywhere in Newton’s Principia. There are a couple of very brief references to the solar parallax value of Flamsteed and Horrocks, which Newton originally rejected but then latter adopted. Beyond this Horrocks’ main contribution to Newton’s work was his model for the Moon’s orbit around the Earth, which Sears nowhere mentions. Kepler, perhaps wisely, had not included the Moon’s orbit in his elliptical model of heliocentricity. Horrocks was the first to adopt an elliptical orbit for the Moon, which Newton briefly acknowledges in passing. Newton, in his failed attempts to make the Moon fit his model of universal gravity, used Flamsteed’s values for the lunar apogees, which he states are, “adapted to the hypothesis of Horrocks.”  These are literally the only references to Horrocks in the whole of the Principia. This doesn’t quite seem to fit Sears’ grandiose claims. 

Sears really piles on the pathos when it comes to the posthumous publication of Horrocks’ Venus in sole visa (Venus seen on the Sun).

Despite this, Horrocks’s great treatise on the transit of Venus was nearly lost for ever. Only a Latin manuscript survived the ravages of the civil war and the Great Fire of London. Passed from one astronomer to another for 20 years after Horrocks’s death, it would not be published until 1662, in an appendage to a Polish astronomer’s work.

Firstly, I strongly suspect that there were several copies of Horrocks manuscript made by Nos Kepleri the group of English supporters of the Keplerian model of the cosmos founded by Horrocks. It was John Wallis, who was a contemporary of Horrocks’ at university, who sent a copy of the manuscript to that Polish astronomer, who was none other than Johannes Hevelius, Europe’s most prominent astronomer, meaning Horrocks’ text got maximum exposure. Those who have been paying attention and remember their school history lessons will have noticed that Hevelius published Venus in sole visa in 1662, whereas the Great Fire of London was first four years later in 1666. It should also be noted that the Royal Society published Horrocks’ Opera Posthuma edited by William Crabtree and John Flamsteed in 1673.

Sears now tries his hand at a bit of biography:

Horrox, which will run in Cambridge’s ADC theatre from 28 March to 1 April as part of the   Cambridge Festival, begins in 1632 as Horrocks makes his way to university in the city on foot. Sear said: “At the age of 14 or 15 – no one’s quite sure – he walked to Cambridge from Lancashire, to study the stars.”

The son of a watchmaker, who was largely self-taught, Horrocks worked as a sizar while studying at Cambridge, serving his fellow students and even emptying their bedpans to pay his way. “He begged and borrowed books from the various Cambridge colleges, and left without a degree, probably because he’d run out of things to read,” said Sear. 

The Aspinwalls, Horrocks maternal grandparent, with whom his father worked, were very successful and wealthy watchmakers, so it is very unlikely that Jeremiah walked from his home in Toxteth Park to Cambridge. Both the Aspinwalls and the Horrocks were highly educated and not self-taught. They were also very strict Puritans, which would have explained why he was a sizar at Cambridge. Puritan ethics dictating that if you wanted a university education you worked for it and didn’t get it served up on a plate. Horrocks is known to have enquired about the latest and best book on astronomy, which would explain Sears’ “begged and borrowed books.” It is not known why he left university without a degree.

Sears makes a last attempt in this article for the most hyper-bollocking statement possible:

At his age, understanding the maths he did, making these amazing observations on rudimentary telescopes and then drawing conclusions that overturned established religious and scientific beliefs about the nature of the universe – he was a genius and 400 years ahead of his time.”

Jeremiah Horrocks was an intelligent and astute astronomer, but he did not overturn any “established religious and scientific beliefs about the nature of the universe,” and I fail to see how he was in anyway “400 years ahead of his time.”

The pain continues. On the webpage for the play Horrox. Here Sears writes:

The arc of his life is shown in parallel with that of his main inspiration, Johannes Kepler, the Copernican astronomer- mathematician who measured the movement of the planets. Kepler, called a heretic by the world, served three Holy Roman Emperors and a Duke (and wasn’t paid for his labours by any of them).

Kepler had his religious differences with the Lutheran Church because of his liberal ecumenical views but he wasn’t called a heretic by anybody. Whilst Kepler, at times, had difficulties getting the monies due to him from the Imperial treasury, to say that “wasn’t paid for his labours by any of them” is a crass exaggeration. 

Sears delivers up a splendid example of how not to do the history of science. He appears to have gathered a small collection of half facts that he doesn’t really understand and woven a third-rate fairy story out of them. Apparently, the Observer doesn’t believe in fact checking and appears to believe that its readers will swallow any old garbage.