John Mitchell

From around 1650 CE, a vital era in human advancement, known as the Enlightenment, unfolded over approximately 150 years. While its characteristics varied across regions and countries, in Europe and North America, this period witnessed the flourishing of ideas that now underpin many aspects of modern society. Central to this movement were the principles of reason and logic, a newfound emphasis on individualism and democracy, and a profound belief in the power of human ingenuity. Although poverty remained widespread, and many struggled for survival, a sense of optimism permeated the intellectual circles of natural philosophers.

The Scientific Method had taken hold, emphasising enquiry, observation, and experimentation, leading to insights through evidence and hypothesis. Pivotal characters such as Huygens, Leibniz, and Isaac Newton emerged, celebrated to this day as giants. These figures, among many, make well-earned appearances in Jimbo’s Assumption. Please take a look.

Invisible now, like the dark stars he predicted, but a great man.

Enlightenment science

Such was the vibrancy that talents who might previously have sought a career in the Church were attracted by the challenges of science. One exceptional scholar who straddled both worlds was John Michell, an original scientist and a respected clergyman, a rector. Creativity and probity, however, have not prevented us from forgetting Michell.

Magnetism and inverse squares

A man with a voracious appetite for physics, he contributed to geology, magnetism, astronomy, and gravitation. His endeavours extended from the practical to the abstract. A manual, written for instrument-makers and perhaps used by seafarers, described the manufacture of magnets. Among the first to infer that the inverse square law, a common phenomenon in nature, also applies to a magnetic field.

Stars and dark stars

In considering the cosmos, Michell pioneered the application of statistics, a then-nascent mathematical field, to astronomy. He found that stellar pairs or even groups occur more frequently than would be expected, implying a non-random distribution. This likely inspired his contemporary and fellow astronomer, William Herschel, to embark on his study of binary star systems, heavenly bodies held in a mutual gravitational embrace. Once again, the inverse square law.

His astronomical contemplations not only included musings on the distances to nearby stars, anticipating Friedrich Bessel’s 19th century breakthrough, but, astonishingly, to predicting the presence of black holes or ‘dark stars’, nearly two centuries before scientists confirmed their existence. In 1783 CE, his arguments were presented to the Royal Society. A diameter > 500 times greater than the Sun would be necessary for such a body to prevent light escaping, he calculated. Prescient ideas.

Earthquakes and waves

Our time is almost consumed, but, besides the celestial, Michell’s imagination also extended to the very ground beneath his feet. An early seismologist, he performed a mathematical analysis to estimate the epicentre of the Lisbon earthquake of 1755 CE, introducing the idea that the impulse propagated through the planet’s crust as a wave. Perhaps also the originator of the insight that submarine earthquakes can generate tsunamis.

Weighing Earth

Finally, and most extraordinarily, he devised a means of calculating Earth’s density and therefore its mass. He designed a torsion balance for the research but sadly did not live to see it realised. His approach was adopted by Henry Cavendish, an accomplished English physicist, who successfully pursued the investigation, while crediting Michell. The exploits of the wealthy yet reclusive Cavendish are described in Jimbo’s Assumption.

Overlooked polymath

What of the heroic John Michell, a polymath, brilliant but overlooked? As the American Physical Society poignantly observed, Michell was “so far ahead of his scientific contemporaries that his ideas languished in obscurity, until they were re-invented more than a century later”. Invisible now, like the dark stars he predicted, but a great man.