The Great Meteor of 1783

Sep 8, 2021 0 comments

On the night of 18 August 1783, four gentlemen and their two lady companions were on the terrace of the Windsor Castle, enjoying the warm summer night after a fulfilling and sumptuous dinner, when their casual conversation was cut short by a descending light in the horizon. As the spectators turned their attention towards the bluish colored apparition, they saw the light streak across the north western sky, gradually increasing in brightness. And even as they watched, the light broke up into a band of smaller lights forming a fiery procession with the smaller bodies trailing a brighter leading nucleus. For some thirty seconds the flaming band silently trailed across the sky before extinguishing in the south eastern quarter of the heavens. The remarkable spectacle left our six companions enthralled and dumb-struck, for they had never witnessed such a sight before.

The Great Meteor of 1783

The Meteor of August 18, 1783, as seen from the East Angle of the North Terrace, Windsor Castle. Painting by Paul Sandby

Amongst the group of people on the terrace of Windsor Castle was Italian natural philosopher Tiberius Cavallo, who published a description of the celestial event:

Some flashes of lambent light, much like the aurora borealis, were first observed on the northern part of the heavens, which were soon perceived to proceed from a roundish luminous body, whose apparent diameter equaled half that of the moon, and almost stationary in the same point of the heavens [...] This ball at first appeared of a faint bluish light, perhaps from appearing just kindled, or from its appearing through the haziness; but it gradually increased its light, and soon began to move, at first ascending above the horizon in an oblique direction towards the east. Its course in this direction was very short, perhaps of five or six degrees; after which it directed its course towards the east [...] Its light was prodigious. Every object appeared very distinct; the whole face of the country, in that beautiful prospect before the terrace, being instantly illuminated. At this moment the body of the meteor appeared of an oblong form, but it presently acquired a tail, and soon after parted into several smaller bodies, each having a tail, and all moving in the same direction, and at a small distance from each other, and very little behind the principle body, the size of which was gradually reduced after the division. In this form the whole meteor moved as far as the S.E. by E. where the light decreasing rather abruptly, the whole disappeared.

The meteor Cavallo described is believed to have entered Earth's atmosphere over the North Sea, before passing over the east coast of Scotland and England and the English Channel. After travelling across the atmosphere over south-western France or northern Italy, for around a thousand miles, it broke up into a series of smaller bodies and each fragment traveled across the sky in the same path. This is known as a meteor procession, and while meteors are extremely common occurrence, meter processions are not, and only a handful of examples of these have been recorded in history. Of course, the rare meteoric phenomenon of 1783 ranks among the brightest and most spectacular of such objects ever recorded.

The 1783 meteor is particularly interesting to historians of science for at least two reasons. First, its appearance prompted a detailed investigation by British scientist Charles Blagden, where he attempted to estimate the meteor’s size, altitude, and speed—one of the first such empirical investigation conducted on the phenomenon of meteorites which was not much understood at that time. The second reason why this meteor is of interest is because of the great number of etchings, engravings and water color pictures that were produced of it. These pictures are the first detailed and generally accurate representations of such a phenomenon.

The Great Meteor of 1783

The meteor of 1783 by Henry Robinson.

The spectacular event occurred at a time when many people in Scotland and England were awake and active (the bolide appeared between 9:15 PM and 9:30 PM), leading to many and varied eye-witness accounts and observations. Blagden assembled many of these detailed eye-witness accounts and attempted to unravel the mysteries of the meteoric phenomenon that baffled many scientists before him.

The first attempt to scientifically explain meteors was made by Aristotle. According to the Greek philosopher and polymath, the Sun's heat gives off two kinds of vapors or exhalations from the Earth's surface. One is hot and
dry, and the other cold and moist. The cold vapors rise upwards and form clouds, while the hot vapors rise to
the very top of the Earth's atmosphere, where, under the right conditions, ignite to give rise to the fiery meteoric phenomena. This assertion remained unchallenged for nearly two thousand years, until John Pringle, in 1759, suggested that meteors might be extraterrestrial.

Blagden rejected both the Aristotelian hypothesis (as outlined by Edmund Halley in his 1719 paper) and Pringle’s assertion of extraterrestrial origin. Of the former, he notes:

Dr Halley gives no just explanation of the nature of these vapours, nor of the manner in which they can be raised, ... , nor does he account for the regular arrangement in a straight and equable line of such prodigious extent, or for their continuing to bum in such rarefied air. Indeed it is very difficult to conceive, how vapours could be prevented, in those regions where there is in a manner no pressure, from spreading out on all sides in consequence of their natural elasticity., ... Besides, it is to be expected, that such trains would sometimes take fire in the middle, and so present the phenomenon of two meteors at the same time, receding from one another in a direct line

Blagden also rejects the extraterrestrial hypothesis. He writes:

Most observers describe the meteors, not as looking like solid bodies, but rather like a fine luminous matter, perpetually changing its shape and appearance ... I think whoever carefully peruses the various accounts of fireballs, ... , will perceive that these phenomena do not correspond with the idea of a solid nucleus

Blagden’s rejection is based on account that meteors cannot be solid bodies, otherwise fragments of it would have fallen every now and then to the ground. Interestingly, it was only twenty years later that E. Biot, while investigating falling stones in L'Aigle, France, concluded that stones, in fact, do fall from the sky. Some forty years after the great meteor swooped over Great Britain, the general consensus among astronomers had shifted towards the extraterrestrial hypothesis of meteor origin. The conclusive proof came after the observation of the Leonid meteor storm in 1833. The vast number of witnesses across Northern America and the sheer number of meteors streaking across the sky gave astronomers plenty of opportunities to study the nature and origin of the celestial phenomenon. By 1863, astronomers knew enough about meteors and meteor showers to correctly predict the arrival of the next meteor storm.

# Martin Beech, The Great Meteor of 18th August 1783, Journal of the British Astronomical Association
# Tiberius Cavallo, Description of a meteor, observed Aug. 18, 1783, Royal Society


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