The English Copernicans: the Moving Earth in England 1558 to 1660 Dr Allan Chapman

The Almagest which apparently means “The Great Book” or “The Great Syntax” was actually a collection of thirteen separate books written in ancient Greek in around 170 AD, it was the first ever large scale attempt to objectively record humanity’s knowledge about the cosmos of which it was a part. It defined, introduced and established the concep

ts and terminology that have defined astronomy in the 21st century. Terms such as the ecliptic, parallax, zodiac, magnitude, retrograde, equinoxes were first explained 2000 years ago amongst those 13 books. It also established that the planets and the stars move in concentric spheres centred on the Earth. The Earth according to Ptolemy did not move.

Allan’s presentation focused on the activities of a handful of British scientist who understood, explored and popularised the work of

Nicolas Copernicus. Copernicus died in 1543 and for the next hundred years there was a “mini” renaissance in northern Europe through which his ideas conclusively replaced those of Ptolemy and through the early days of colonialisation, spread to the “new” world.

Observations of the motions of Mercury and Venus from Earth were easy to understand. The outer planet however, Mars, Jupiter and Saturn (Uranus, Neptune and Pluto had yet to Discovered) displayed an odd looping behaviour where they would appear to go back on their trajectory and repeat this habit systematically. Mars would do it twice a year, Jupiter 12 and Saturn nearly 30. This looping back or retrograde motion could be completely understood if the Sun was in the centre and not the Earth. Copernicus, through intense mathematics explained that the retrograde behaviour was simply the Earth overtaking the outer planets in its smaller swifter orbit.

The firs English Copernican was a Welshman from Tenby - Robert Recorde. They have a saying in Wales that without him we would not be able to add up, he invented the “=” sign. He was warmed to Copernicus’s ideas as an influential mathematician spread Copernicus’s ideas throughout England. The same year that Copernicus died, 1543 was the year his book - On the Revolutions of the Heavenly Spheres was first printed in the German city of Nuremberg and although still highly technical, his ideas gained even wider appeal.

In 1576 Thomas Digges produced a supplement to a book, Perpetual Almanac, that his late father Leonard had published. This included a short simplif ied version of Copernicus’s ideas and it was in English. In contrast with the title “A Perfit Description of the Caelestiall Orbes according to the most aunciente doctrine of the Pythagoreans, latelye revived by Copernicus and by Geometricall Demonstrations approved” the content were succinct free of complex mathematics. This supplement was also remarkable for its depiction of an infinite universe with the Sun at the centre and the stars stretching away in to the corner of the image.

In the absence of his father, Thomas Digges was brought up under the guardianship of John Dee 1527-1608. Although a respected astronomer, navigator and mathematician he dabbled in magic but still considered as a Copernican. Others also involved (the English Copernicans) in the promulgation of the Copernican ideas included Walter Raleigh 1554 – 1618, Robert Hooke 1635-1703, John Wilkins. (1614-1672), Christopher Wren 1632-1723 , Johannes Kepler (1571 – 1630) and Thomas Harriot 1560-1621. By the end of this remarkable period the Earth had moved not only from the centre of the Solar System but it now truly moved – around the sun and turned on its axis once a day.
Just as the mince pies were running out on January 6th 2007, Allan was on the way back to the north to address members and visitors of Macclesfield Astronomical Society

on the subject of Robert Hooke at Jodrell Bank.