James Moriarty (?-1891) was one of the greatest of the many astronomer-mathematicians who flourished in the nineteenth century, however among the general public his scientific accomplishments are forgotten. Mention his name and most people will think of the dark rumours about his personal life and the lurid circumstances of his death.


We do not know much about Moriarty’s family other than he had at least two brothers (confusingly one of them was also called James). The young Moriarty received an excellent education and demonstrated a phenomenal aptitude for pure mathematics. It was in this field that he initially made his name. By the time he was twenty-one he had written A Treatise on the Binomial Theorem, one of the two works he is remembered for today. His theories as expounded in this paper were more accepted in continental Europe than in his homeland, but it still earned him the chair in mathematics at one of the smaller universities with the generous salary of £700 per annum (John F. Bowyer’s biographical sketch of Moriarty  makes a compelling argument that this was Queen’s College, Cork). It seemed that a most brilliant career lay before the young professor.

However it was not to be. He was dogged by spiteful gossip about his private life, including allegations of dishonesty. Possibly these rumours were spread by jealous colleagues, envious of his early success. Eventually he was forced to resign his post and take a relatively mundane position as a mathematics tutor to army officers in London.

Moriarty was apparently an enthusiastic and gifted teacher. There is an account of him responding to a question on eclipses from a member of the public with a spontaneous demonstration with a globe and lantern which “made it all clear in a minute”. If only there had been a planetarium in Victorian England to use such a talent! During this time as an instructor to the military he befriended the celebrated soldier and big-game hunter Colonel Sebastian Moran (possibly introduced by Moriarty’s brother James, who also held the rank of colonel). This pairing of a mild-mannered intellectual and bon vivant seems to make an unlikely duo, but Moran proved a true friend, staying loyal to the professor through the difficult days ahead and beyond.



Moriarty’s thoughts on his fall from grace are not known but about this time his interests moved from pure mathematics to celestial mechanics. There is no evidence that Moriarty was an astronomical observer, rather he was a leading theorist. The mechanics of the Solar System was a major field of study at this time. In the early 1800s, the great German astronomer and mathematician Carl Friedrich Gauss (1777-1855) spent eight years calculating the orbits of the newly-discovered asteroids Ceres and Pallas. Later, in 1867 Daniel Kirkwood (1814-95) had explained anomalies in the distribution of minor planets as a result of the gravitational influence of Jupiter. Astronomers today still talk of the Kirkwood Gaps. Possibly building on the work of Gauss and Kirkwood, Moriarty focused his formidable intellect on the small bodies of the Solar System. His masterpiece on the topic is, of course, On the Dynamics of an Asteroid, a book “which ascends to such rarefied heights of pure mathematics that it is said that there was no man in the scientific press capable of criticizing it”.


image of lutetia

A Dynamic Asteroid: Lutetia as seen by the Rosetta probe. The asteroid 5048 Moriarty is named after the professor. (image credit: ESA)


This book is still respected today; in fact by 2005 it had been cited in 263 scientific papers. Yet it is one of those important historical documents that is often referenced while remaining infuriatingly elusive (Al-Hazred’s Necronomicon is the other classic example). You will not find Moriarty’s Dynamics in Armagh Planetarium’s library for example. Hence it is unclear which particular asteroid’s trajectory he analyzed, or whether his conclusions could be generalized to all asteroids and comets. In these days of concern over the potential threat from Near Earth Objects, a review of Moriarty’s magnum opus for any possible data to aid homeworld security would seem timely. If you have a copy please let me know!

Never one to seek the public spotlight, the self-effacing Moriarty was unknown to the public; content to make his great intellectual voyages in private. Yet in his middle age his quiet life was disturbed by a renewal of the scandalous rumours of his youth. Anonymous allegations of criminality led to a police investigation into the professor which found no irregularities. Despite this the accusations continued, so seeking relief from this ordeal Moriarty set off on a holiday to Switzerland.  In an article published in the Strand Magazine in December 1893 he was described at this time as being extremely tall and thin, with a domed forehead and sunken eyes. “He was clean-shaven, pale, and ascetic-looking… His shoulders were rounded from much study…”. Included on Moriarty’s tour itinerary was a visit to the Reichenbach Falls, a famed beauty spot.

There on 4 May 1891 he fell to his death when he was brutally attacked by a fellow Englishman. Moriarty’s assailant was a well-known and apparently unhinged drug addict who had developed an unhealthy fascination with the distinguished scholar and followed him across Europe with the intention of killing him. Psychotic stalkers of celebrities are clearly not just a modern phenomenon. After faking his own death and spending several years on the run, the killer (who was the brother of a senior government official) finally returned to London and confessed his crime – yet was never prosecuted! Cynics would say that his friendship with senior policemen no doubt also helped him retain his freedom.

Professor Moriarty is best-remembered for his tragic end – and his caricature as a scheming villain. Perhaps it is time that this pioneer of minor planet studies was remembered for his scientific achievements instead.

(Article by Colin Johnston, Science Communicator)




Murgatroyd · January 3, 2012 at 12:23

Isaac Asimov wrote a short piece in which he speculated about the content of Professor Moriarty’s treatise (which he, too, had been unable to locate). He pointed out that there could have been little theoretical novelty in Moriarty’s analysis. As you’ve noted, the general and specific mathematical cases had been explored rather thoroughly by such luminaries as Gauss, Kirkwood, Poincare, and Newcomb; relativistic effects that would have complicated the Newtonian N-body dynamical analysis were unknown in the Nineteenth Century. Asimov concluded that, as you note, Moriarty must have been referring to one particular asteroid, and directed his speculations toward a consideration of characteristics that would have made it noteworthy. If Asimov was correct, On the Dynamics of an Asteroid must be a very interesting treatise indeed.

Alas, I wasn’t able to find Asimov’s piece on the Web, but this site discusses “The Ultimate Crime” in slightly greater detail:


The same page also links to short discussions of two other speculations about the paper’s content.

It’s a shame that in the age of the Internet many older, classic scientific papers such as Moriarty’s are essentially unknown to modern readers; some university students seem to be unaware that any science was conducted before 1980 or so, because the relevant literature isn’t available on the Web. And it truly is frustrating that Dover Publications doesn’t have Moriarty’s book in its catalog …

If someone out there has a copy of this classic treatise, please consider allowing the good people at Project Gutenberg to prepare a digitized version of it!

    admin · January 3, 2012 at 13:48

    Thanks for the info, I was completely unaware of Asimov’s contribution to piecing together Moriarty’s background!

Barbara Krzewicki · December 27, 2011 at 07:30

So sad. Nicolaus Copernicus, Galileo Galilei, Giordano Bruno, James Moriarty . . . it seems that great men of science are too often persecuted. To think what Professor Moriarty might have accomplished if his life had not been prematurely by a crazed third-rate violinist who fancied himself some sort of detective.

    Barbara Krzewicki · December 27, 2011 at 07:38

    Forgive me. This article rendered me so distraught at the untimely death of Professor Moriarty that I left out a word. The second sentence should have read: To think what Professor Moriarty might have accomplished if his life had not been prematurely ended by a crazed third-rate violinist who fancied himself some sort of detective.

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