A local star


At this month’s meeting of the Wanstead Historical Society, Dr John Fisher will give a presentation about James Bradley (1692–1762), a local unsung hero of science who proved the Earth orbits the sun from observations made in Wanstead

After I married my wife in her home village of Sherborne, in the Windrush Valley in the Cotswolds, I soon learned that James Bradley, the third Astronomer Royal, had been raised there, attending Westwood’s Grammar School in nearby Northleach, as did my wife. After buying our house near Wanstead Flats, we discovered Bradley had also lived in Wanstead for many years after leaving Sherborne, being the nephew of James Pound, the rector of Wanstead. This amazing coincidence led me to seek Bradley’s biography, but since a memoir had been published by Stephen Peter Rigaud in 1832, nothing of real note had been written since.

I decided to write a biography of Bradley myself. However, my only acquaintance with the history of science was as an undergraduate of the Open University, so I wrote to an academic in Cambridge. I was met with kindness and support and was helped by some of the country’s leading historians of science. My years of research at Cambridge University Library and the Bodleian Library in Oxford led to working for a Master’s degree at Imperial College, followed by a doctorate on Bradley’s work.

After many years of work, I realised the remarkable achievements of Bradley at Greenwich, Oxford and initially at Wanstead had never been fully recognised. He is one of the great unsung heroes of science. In his own lifetime, he was recognised as the finest astronomer on Earth. After his death in 1762, the then director of the Paris Observatory asserted that Bradley’s discoveries of the aberration of light and of the nutation of the Earth’s axis were the most important astronomical discoveries of the 18th century.

It is easy to understand why Bradley’s achievements have not been widely acknowledged, for his discoveries demand some understanding of astronomical technicalities, but the consequences of his discoveries made in Wanstead in a modest dwelling on the site of the present Co-op were far-reaching. The first, the aberration of light, made in 1728, was the first universally accepted observational evidence of the motion of the Earth. 

Ask most people with any interest in the subject at all who first proved that the Earth revolved around the sun and the answers usually swing between Copernicus and Galileo. In truth, both men conjectured that the Earth moved, and indeed Galileo was put on trial by the Holy Inquisition for asserting it. By the following century, most astronomers believed the Earth revolved around the sun but no one was able to prove it. It was Bradley, working with his suspended telescope at his aunt’s house in Wanstead, who discovered the phenomenon that established once and for all that the Earth did indeed move.

The aberration of light is difficult to explain without using technicalities. Over the years, I have used the expedient of an umbrella to show people how aberration works. Imagine rain falling vertically on a windless day. You hold your umbrella directly over your head. However, if you walk, you will have to tilt your umbrella forward. The faster you move, the greater the tilt. As the Earth moves around the sun, light from the stars is likewise ‘slanted’, just in the same way as rainfall appears to be slanted as you walk into the rain. What Bradley discovered is that every object in the sky is shifted in the direction the Earth moves as it travels around the sun.

Bradley’s discovery of the nutation of the Earth’s axis was even more remarkable. As the moon revolves around the Earth, the plane of its orbit is tilted five degrees from the plane of the Earth’s equator. The Earth is slightly oblate, wider at the equator than across the poles. The moon tugs at the Earth’s equator causing the Earth to wobble. The technical term to describe this wobble is nutation. It is a tiny movement, yet remarkably, Bradley observed it for 20 years before publishing his discovery paper in 1748. It established the accuracy of Newton’s universal law of gravitation with a degree of precision previously undreamed of.

I intend that my talk for the Wanstead Historical Society won’t blind people with science. I will attempt to tell the story of how the third son of an obscure steward on a Cotswold estate (now owned by the National Trust) became the most celebrated astronomer in Europe. Wanstead should be mightily proud of its connections with this man.

Dr John Fisher’s presentation for the Wanstead Historical Society will take place at Wanstead Library on 7 November from 8pm (visitors: £3). Call 07949 026 212

Author: Editor