Thomas Harriot: A Telescopic Astronomer Before Galileo

In a paper to be published in Astronomy and Geophysics, the journal of the Royal Astronomical Society (RAS), historian Dr Allan Chapman of the University of Oxford explains how Harriot not only preceded Galileo but went on to make maps of the Moon’s surface that would not be bettered for decades.

Harriot lived from 1560 to 1621. He studied at St Mary’s Hall (now part of Oriel College), Oxford, achieving his BA in 1580 before becoming a mathematical teacher and companion to the explorer Sir Walter Raleigh. In the early 1590s Raleigh fell from royal favour and was imprisoned in the Tower of London.

From this time Harriot was passed to the patronage of Henry Percy, the Ninth Earl of Northumberland who was himself imprisoned as one of the Gunpowder Plotters in 1605 but continued to support Harriot in his residence at Sion (now Syon) Park, in what is now west London. Harriot became a leading force in mathematics, working on algebraic theory and corresponding with scientists in the UK and across Europe.

By 1609, Harriot had acquired his first ‘Dutch trunke’ (telescope). He turned it towards the Moon on 26 July, becoming the first astronomer to draw an astronomical object through a telescope. The crude lunar sketch shows a rough outline of the lunar terminator (the line marking the division between night and day on the Moon, as seen from the Earth) and includes a handful of features like the dark areas Mare Crisium, Mare Tranquilitatis and Mare Foecunditatis.

Harriot went on to produce further maps from 1610 to 1613. Not all of these are dated, but they show an increasing level of detail. By 1613 he had created two maps of the whole Moon, with many identifiable features such as lunar craters that crucially are depicted in their correct relative positions. The earliest telescopes of the kind used by Harriot (and Galileo) had a narrow field of view, meaning that only a small portion of the Moon could be seen at any one time and making this work all the more impressive. No better maps would be published for several decades.

Despite his innovative work, Harriot remains relatively unknown. Unlike Galileo, he did not publish his drawings. Dr Chapman attributes this to his comfortable position as a ‘well-maintained philosopher to a great and wealthy nobleman’ with a generous salary (somewhere between £120 and £600 per annum or by way of comparison several times the level of the Warden of Wadham College, Oxford). Harriot had comfortable housing and a specially provided observing chamber on top of Sion House, all of which contrasted with Galileo’s financial pressures.

Dr Chapman believes that the time has come to give Harriot the credit he deserves. “Thomas Harriot is an unsung hero of science. His drawings mark the beginning of the era of modern astronomy we now live in, where telescopes large and small give us extraordinary information about the Universe we inhabit.”

Professor Andy Fabian, President of the Royal Astronomical Society, agrees. “As an astrophysicist of the 21st century, I can only look back and marvel at the work of 17th century astronomers like Thomas Harriot. The world is right to celebrate Galileo in the International Year of Astronomy – but Harriot shouldn’t be forgotten!”