Newton's 1702 Lunar Theory
The Hollow Earth of Edmond Halley
Isaac Newton left an ultra-dense Moon circling the Earth. To Edmond Halley, there was only one logical explanation: a hollow Earth. It is sometimes claimed that Halley's prediction of a periodically-returning comet, made in the autumn of 1895, was the first deduction drawn from the new gravity theory of the Principia. Thus, 'Halley's prediction of the comet's return was the first prediction based on Newton's theory of gravitation' (Edmond Halley- A commemoration' QJRAS, 1993, 34,143). This view is mistaken, as the first deduction to be drawn from the Principia was in 1691, when Halley proposed to the Royal Society that the Earth was hollow.
He drew this conclusion from the Principia's values
for lunar density:
Implicit in Halley's argument we may note is the notion of matter having uniform density, whereby he reached his conclusion that four-ninths of Earth was empty. Within this hollow Earth was another sphere, Halley explained, inhabited and illuminated, which the force of gravity would keep from bumping into the outer sphere. His bold hypothesis could also explain how the four magnetic poles of the Earth were wandering about, by the slow rotation of this inner sphere against the outer sphere.
In 1716 a magnificent aurora borealis was visible over much of northern Europe (signifying the conclusion of the 'Maunder Minimum', a period when a dormant Sun was virtually devoid of sunspots, for over sixty years, believed to correspond to a mini-ice-age in the late seventeenth century when the Thames froze solid). The Royal Society required Halley's opinion, and he gave an explanation in terms of the non-spherical shape of the Earth, as described in the Principia. There was an illuminated vapour inside the hollow Earth which would occasionally 'transude through and penetrate the Cortex of the Earth.' This vapour tended to emerge from the polar regions, as the crust was thinner there.
Halley's essay on the subject was popular and frequently reprinted. In 1717 a theological treatise by William Whiston (Astronomical Principles of Religion) incorportated Halley's arguments, differing only in that it found scriptural corroboration, as Halley had not, for the lower regions of the hollow Earth being inhabited. When, in later years, Halley had his portrait painted as the Astronomer Royal in 1736, he had himself depicted with a diagram showing the multiple shells of his hollow Earth.
Sources: Kollerstrom, 1985, 1991,1992 (NB, The above material is not contained in my Doctoral thesis).
The contents of this page remain the copyrighted, intellectual property of Nicholas Kollerstrom. Details. rev: May 1998