Jeremiah Horrocks and the transit of Venus

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Anyone getting up early at the crack of dawn this morning in Lancashire to observe the transit of Venus would have been disappointed. The sky was covered by a blanket of white cloud that obscured the sun. Luckily this wasn’t the case at 3:00 pm on 4 December 1639 (24 November  according to the Julian calendar that was then in use) as it was on this date that Jeremiah Horrocks observed this rare astronomical event from the garden of a house in Much Hoole, a village just south of Preston.

Jeremiah Horrocks, was probably born in Toxteth, then a hamlet just outside Liverpool, but today part of the inner city, in 1619. He was obviously a bright lad as at only thirteen he entered Emmanuel College, Cambridge as a “sizar” ( a poor scholar). In those days Universities were establishments for training men for the clergy, but while he was there Horrocks studied astronomy. Apparently he was the only person at Cambridge at that time to accept Copernicus’  heliocentric theory – i.e. that the the planets, including the Earth, orbit the sun.

In 1635 he returned to Toxteth and using Kepler’s Laws of Planetary Motion, worked out that the Moon had an eliptical orbit.

The transit of Venus is where the planet passes between the Earth and the sun, and (if you’re lucky!) can be seen as a dark dot passing across the face of the sun. Pairs of transits occur eight years apart separated by long gaps of 121.5 years and 105.5 years. It was Horrocks who worked out that they occurred in pairs.

File:Venus transit 2012 animation.gif

Animation of simulated transit in equatorial coordinates. Picture source: Wikipedia

Unfortunately, Horrocks died on January 3rd 1641 at the early age of 22. I wonder what he would have achieved if he’d lived longer.

There’s a memorial plaque to Horrocks in Westminster Abbey and two stained glass windows in St.Michael’s Church, Much Hoole. And recently a memorial was erected at the Pier Head in Liverpool. This monument, by Andy Plant, is in the form of a telescope pointing to the Sun and Venus. I snapped it during a recent visit to Liverpool. The photo isn’t that great – I took it with the camera on my mobile phone and it was a grey, overcast day. There’s a better picture on the artist’s website

According to Andy Plant’s website:

The sculpture has a working hand powered mechanical orrery, the position of Venus has been replaced by a copper angel version of Jeremiah and as his wings flap he orbits the other planets. Inside the large telescope there is a video animation of the life of Jeremiah by Tim Hunkin.

Horrocks was also a poet and there’s an extract from one of his poems, describing the long wait until people would be able to see the next transit of Venus, inscribed on the base of the sculpture.

Thy return posterity shall witness;

Years must roll away,

But then at length the splendid sight

Again shall greet our distant children’s eyes

Unfortunately the cloud shielded this splendid sight from our eyes this morning!