Category Archives: Astronony

Christopher Wren


We all know Wren as an architect but at the age of just 25 he was appointed professor of astronomy at Gresham College.

He studied mathematics, mechanics, medicine, meteorology and microscopy. He was a member of parliament who served three terms in the House of Commons and, despite being born a sickly child in the 1600s lived to the age of 90.

It is, however, as an architect that we best know him. in 1669, three years after the Great Fire, King Charles II appointed him Surveyor of Works and charged him with rebuilding the City.

Rebuild it, he did. Aside from other buildings, he rebuilt 52 City of London churches including St Paul’s cathedral.

He was assisted by architect and polymath Robert Hooke and worked alongside architect Nicholas Hawksmoor.

He laid the groundwork for the formation of the Royal Society of which he was later president.

Robert Hooke


Hooke was a scientist engaged in a number of disciplines. He formulated Hooke’s Law relating to elastic properties of materials.

Hooke became curator of experiments for the Royal Society in 1662.

Three years later, in 1665, he was appointed Professor of Geometry at Gresham College.

Hooke was a pioneer in the development of the microscope and also wrote papers on gravity which are respected to this day.

As an architect he was chief assistant to Christopher Wren when rebuilding the City of London after the Great Fire of 1666.

Like Wren, Hooke was an astronomer and determined to prove that the earth rotated around the sun. This led to a failed experiment involving the star Gamma Draconis.

Gamma Draconis

Many of you will know the tower called The Monument. You may not know that its design was inspired by an object 150 light years away.

The Monument commemorated the Great Fire of 1666 and was built by Christopher Wren. The architect, however, was not Wren but his assistant Robert Hooke who had a particular plan for the building.

Like Wren he was also an astronomer. At this time some scientists still believed that the sun rotated around the earth. Hooke was determined to prove that the opposite was true.

A star called Gamma Draconis passes over the City every night and Hooke reasoned that by taking observations of the star at different times of the year he could prove that the earth went around the sun.

To do this he needed a telescope around 200’ long and, obviously somewhere to put it. The tower, therefore, was also an observatory.

Hooke’s astronomy was perfect, his calculations were flawless, the telescope was built with absolute precision and positioned perfectly within the building.

He had, however, failed to take two factors into consideration. His observations could involve fractions of a millimetre but every time a vehicle rolled down nearby Fish Street Hill, the tower vibrated slightly and upset his readings. Also, surprisingly for an architect, he’d failed to consider that a 200’ tall building would sway in the wind!


How would Hooke’s experiment have worked? He was using something called parallax.

Here’s an example. Stand at the end of a room and choose something, say a picture, on the opposite wall. Take 3 paces left and you’ll be looking at the picture from a certain angle. Take 6 paces right and the angle changes. This is parallex.

He theorised that if the earth went around the sun then in, say, June it would be one side of the sun and in December on the other. and there would be quite a long way between the two.

If he took observations of Gamma Draconis in June and then again in December and the star was shown to be at a different angle (albeit a tiny one) then this would prove that the earth was indeed circling the sun.