Wanstead: good with science

The first universally accepted observational evidence of the motion of the Earth was made in WansteadThe first universally accepted observational evidence of the motion of the Earth was made in Wanstead

Most people walk past the Co-op in Wanstead and barely give it a second glance, yet on that site there once stood a modest house in which a series of observations were made which transformed the worldview of modern science. Dr John Fisher, curator of an astronomy exhibition currently on show at The Temple in Wanstead Park, outlines the work of a local unsung hero of science.

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 that 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 much 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 at the Bodleian Library in Oxford led to working for a master's degree at Imperial College, followed by a doctorate on the work of Bradley.

After many years of work I realised that 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 that 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 that 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.

Astronomer James BradleyAstronomer James BradleyThe 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, every star travelling in an annual ellipse. Stars shift their position by up to 40 seconds of arc a year.

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 8 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 amounting to less than a second of arc a year. Yet remarkably, Bradley observed it for twenty 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.

In his work in Wanstead, Bradley established the truth of the Copernican theory which Galileo had been placed on trial for supporting. He firmly established the truth of Newton's physics within the limits of what could be observed at that time. Bradley's lectures on experimental philosophy at Oxford are the finest on Newtonian science during the 18th century. I am presently working on these lectures together with a notebook written by one of his students in 1754. Whilst Bradley worked at Wanstead and taught in Oxford he also reformed and re-equipped the Royal Observatory and made the finest series of observations of the entire century.

The Wanstead Astronomers exhibition is free to attend and runs until 9 January 2012 at The Temple in Wanstead Park from 10am to 3pm on Saturdays, Sundays and bank holidays. For more information, call the Epping Forest Visitor Centre on 020 8508 0028. To find out more about astronomy in general, the North East London Astronomical Society meet at Wanstead House on the third Sunday of every month, call 020 8550 6549 for details.

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