Thomas Hornsby facts for kids
Thomas Hornsby was an important British astronomer and mathematician. He was born in Durham in 1733 and passed away in Oxford on April 11, 1810. He made many important observations of the sky and helped set up a famous observatory.
Contents
Life and Discoveries
Early Career at Oxford
Thomas Hornsby became a Fellow at Corpus Christi College, Oxford in 1760. This was an important step in his academic journey.
From 1763, he held a very important position at Oxford University: the Savilian Chair of Astronomy. This meant he was the main astronomy professor there. In the same year, he also became the Sedleian Professor of Natural Philosophy.
Watching Venus Cross the Sun
Hornsby was very keen on observing the transit of Venus. This is a rare event where the planet Venus passes directly in front of the Sun. From Earth, Venus looks like a small black dot moving across the Sun's bright surface.
In 1761, he watched the transit of Venus from Shirburn Castle in Oxfordshire. This castle was the home of the Earl of Macclesfield, George Parker, 2nd Earl of Macclesfield. The Earl was also a famous astronomer who had his own observatory there.
On April 1, 1764, Hornsby also observed a partial solar eclipse. This is when the Moon blocks part of the Sun.
Planning for the 1769 Transit
Observing the 1761 transit was difficult because of bad weather around the world. In 1766, Hornsby told the Royal Society that they needed to prepare much better for the next transit in 1769.
He wrote about the "cone of visibility." This showed the best places on Earth to see the transit clearly. His work helped astronomers plan their observation spots carefully.
Hornsby himself watched the 1769 transit from the Tower of the Five Orders in Oxford. This tower is part of the entrance to the famous Bodleian Library.
Calculating Earth's Distance to the Sun
Hornsby published several important papers in a science magazine called Philosophical Transactions. He compared the 1761 and 1769 transits of Venus. He also suggested good viewing spots, even in the Pacific Ocean.
Using the information from the 1769 transit, he calculated the average distance from Earth to the Sun. In 1771, he announced this distance was about 93,726,900 English miles.
Today, we know the distance is about 92,955,000 miles. Hornsby's calculation was incredibly close, differing by less than one percent! This was amazing, especially considering the tools astronomers had back then.
Building the Radcliffe Observatory
Hornsby played a key role in setting up the Radcliffe Observatory in Oxford. This happened in 1772. He became the first Radcliffe Observer in the same year.
Later, in 1782, he was again appointed Sedleian Professor of Natural Philosophy. In 1783, he also became the librarian for the Radcliffe Science Library. In 1788, he was made an honorary member of the American Academy of Arts and Sciences.
His Unseen Observations
Thomas Hornsby made tens of thousands of astronomical observations. However, these were not published during his lifetime. They were finally published in 1932. In 1935, they were given to Corpus Christi College, Oxford.
His notes included how the Earth's tilt changes over time. He also measured the movement of the star Arcturus. Both of his measurements were very close to what modern science has found.
A Crater on the Moon
To honor his contributions, a crater on the Moon is named after him. It is called Hornsby.
Sources
- Thomas Harriot's manuscripts
- History of transit observing
- Stephen Johnston, "Blast from the Past: Measurement and morals in the early Transits of Venus," Museum of the History of Science, University of Oxford, at http://www.physics.ox.ac.uk/phystat05/Talks/johnston.ppt (accessed July 2006)
- Kentish Gazette 24 April 1810
- Oxford Dictionary of National Biography
