The Great Moon Hoax, as it has become known, was published in the New York Sun over several days in the summer of 1835. It claimed to describe what the astronomer John Herschel had seen through his telescope from the Cape of Good Hope. It was read and, apparently, believed by tens of thousands of people across the US and Europe.

The New York Sun was a penny newspaper with a circulation of 15,000, and rising. It usually carried local news and human-interest stories alongside fiction, poems and humour. A piece that announced “Great Astronomical Discoveries Lately Made by Sir John Herschel, LL.D. F.R.S. &c. At the Cape of Good Hope [From Supplement to the Edinburgh Journal of Science]” was uncommon but clearly intriguing.

It began by admitting that this was “an unusual addition to our journal” but promised it was worth reading, for there had been

recent discoveries in Astronomy which will build an imperishable monument to the age in which we live, and confer upon the present generation of the human race a proud distinction through all future time.

The first article gave little more away, simply describing Herschel’s telescope. Over the following days, however, the articles included increasingly lavish descriptions of planets, the lunar landscape, “several new specimens of animals” and, ultimately, in the last paragraph of the 6th and final part, the bat-like “Vespertilio-homo”, which appeared “scarcely less lovely than the general representations of angels by the more imaginative schools of painters.”

You can read the lot online here. Two things stand out. The first is the sheer length and density of the ornate prose. Second is the fact that there is a good deal of plausible detail.

Those who knew something of scientific matters would be aware that not only was there a Sir John Herschel FRS but also that he was then at the Cape of Good Hope, observing with a large telescope. There was an Edinburgh Journal of Science too, although it had recently folded. Names of real instrument makers, opticians and astronomers were dropped, the optics of the telescope were described with convincing technical language, and what could be more likely than that the inventor consulted the Board of Longitude? (Except that it, too, had shut down.)

There has been much discussion (e.g. here, here, here and here) about the purposes of this elaborate fiction. It has been seen as prefiguring newspaper circulation wars, as demonstrating the gullibility of the public, as early science fiction (along with Edgar Allen Poe, who wrote not dissimilar newspaper pieces), and as a critique of popular science writing.

What seems certain is that many did, at least initially, believe these were genuine observations. Harriet Martineau, who was then in America, mentioned the “sensation” surrounding the story, adding “it was some time before many persons, except professors of natural philosophy, thought of doubting its truth”.

The Sun itself did nothing to disabuse them, which seems strange if the story was intended as a hoax. The point a hoax is usually to convince and then confess, revealing the foolishness of readers and the skill of the hoaxer. Yet when the writer was outed by a rival newspaper, he repeatedly denied authorship.

All becomes clear when we learn that the story was intended as satire rather than hoax. Richard Adams Locke, an apparently well-educated recent British immigrant who wrote for the Sun, eventually came clean in a letter to another newspaper (although this did not end speculation). It was, he said, “an abortive satire”; he was “self-hoaxed” because his mimicry was too accurate to be spotted as parody.

Locke’s target was the widespread and uncritical belief in extra-terrestrial life among men of science. In particular, he took aim at Thomas Dick, a Scottish minister, teacher and author, whose faith in the existence of other worlds appeared throughout his writings. Suffused with natural theology, this books were achieving enormous popularity.

It was this popularity that undid Locke’s satire. People were well prepared to hear that men had been found on the Moon, and the heightened style was familiar to readers of Dick’s bestselling Christian Philosopher (1823). This presented astronomy as standing “in an intimate relation to religion”, and described how the sun “gradually ascends the vault of heaven”, the moon “presents a round full-enlightened face”, stars are “twinkling orbs”, and the mind is “elevate[d] … to the contemplation of an Invisible Power”. Much of it was, indeed, beyond parody.

But Dick was not merely popular. Many men of science shared his views on extra-terrestrial life, from John Herschel’s father William to David Brewster, who endorsed his book. Dick himself published in the Memoirs of the Royal Astronomical Society, of which he was later made a fellow. His was the approved rhetoric of much popular science of the period; the equivalent to the millions of light years, awe and wonder in popular astronomy today.

Not everyone likes “awe” now, and Locke did not like sweeping rhetoric and speculation then. Some see the Hoax as a case of science versus religion, but this is too simple. Quite obviously Dick saw himself as standing for religion and science, while Locke, although probably a political radical, disliked the “crude speculation and cant” because it was dangerous to “rational religion” as well as “inductive science”.

For years Locke stayed quiet about his failed satire because it signally failed to alleviate that danger. Herschel himself took the story as “innocent” and an “amusement”, but his friend Augustus De Morgan told him in 1842 that it still had currency. Meanwhile, Thomas Dick’s books remained immensely popular and influential throughout the century on both sides of the Atlantic.