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1639 transit of Venus
The first known observations and recording of a transit of Venus were made in 1639 by the English astronomers Jeremiah Horrocks and his friend and correspondent William Crabtree. The pair made their observations independently on 4 December that year (24 November under the Julian calendar then used in England); Horrocks from Carr House, then in the village of Much Hoole, Lancashire, and Crabtree from his home in Broughton, near Manchester.
The friends, followers of the new astronomy of Johannes Kepler, were self-taught mathematical astronomers who had worked methodically to correct and improve Kepler's Rudolphine tables by observation and measurement. In 1639, Horrocks was the only astronomer to realise that a transit of Venus was imminent; others became aware of it only after the event when Horrocks's report of it was circulated. Although the friends both died within five years of making their observations, their ground-breaking work was influential in establishing the size of the Solar System; for this and their other achievements Horrocks and Crabtree, along with their correspondent William Gascoigne, are considered to be the founding fathers of British research astronomy.
By the 17th century, two developments allowed for the transits of planets across the face of the Sun to be predicted and observed: the telescope and the new astronomy of Johannes Kepler, which assumed elliptical, rather than circular, planetary orbits.
In 1627, Kepler published his Rudolphine Tables. Two years later he published extracts from the tables in his pamphlet De raris mirisque Anni 1631 Phaenomenis which included an admonitio ad astronomos (warning to astronomers) concerning a transit of Mercury in 1631 and transits of Venus in 1631 and 1761. The Mercury transit occurred as predicted and was observed by Johann Baptist Cysat in Innsbruck, Johannes Remus Quietanus in Rouffach and Pierre Gassendi in Paris, vindicating the Keplerian approach. But their observations threw into question previous theories about the Solar System, as Mercury was shown to be much smaller than expected.
Although Kepler's calculations indicated that the 1631 transit of Venus would best be visible from the American continent, he was not fully confident of his prediction, and advised that European astronomers should be prepared to observe the event. Gassendi and others in Europe watched for it but, as predicted, the Sun was below the horizon during the transit. According to modern calculations, observers in much of Italy and along the eastern Mediterranean should have been able to view the last stage of the transit, but no such observations were recorded. Kepler had predicted a near miss for a Venus transit in 1639 and, as the next full transit was not expected for another 121 years, Gassendi and the other astronomers concentrated their efforts in other areas.
Jeremiah Horrocks (1618 – 3 January 1641) was born in Lower Lodge, Toxteth Park – now part of Liverpool but at that time a separate town. His father James was a watchmaker, and his mother Mary Aspinwall was from a notable Toxteth Park family. Several members of the Aspinwall family were also in the watchmaking trade, and it is said that a watchmaker uncle first interested Jeremiah in astronomy. Jeremiah joined Emmanuel College on 11 May 1632 and matriculated as a member of the University of Cambridge on 5 July 1632 as a sizar, which meant he did not have the means to fully support himself and was given specific duties to compensate for a reduction in fees. At Cambridge, he would have studied the arts, classical languages, a little geometry, and some traditional astronomy, but not the latest work by Galileo, Tycho Brahe and Kepler. He used his spare time to teach himself the more demanding mathematical astronomy and familiarise himself with the latest thinking. Horrocks read most of the astronomical treatises of his day, identified their weaknesses, and was suggesting new lines of research by the age of 17. In 1635, he left Cambridge without formally graduating, presumably owing to the cost of the graduation ceremony.
After leaving Cambridge, Horrocks returned to his home in Lancashire and began collecting books and instruments in order to pursue his main interest, the study of astronomy. In the summer of 1639, he left home and moved about 18 miles (29 km) along the coast to the village of Much Hoole. This was probably to become tutor to the children of the Stones family, prosperous haberdashers who lived at Carr House, within the Bank Hall Estate, Bretherton.
Horrocks was the first to demonstrate that the Moon moved in an elliptical path around the Earth. He also wrote a treatise on Keplerian astronomy and began to explore mathematically the properties of the force that became known as gravity. Decades later, Isaac Newton acknowledged Horrocks's work in relation to the Moon in Newton's Principia.
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1639 transit of Venus
The first known observations and recording of a transit of Venus were made in 1639 by the English astronomers Jeremiah Horrocks and his friend and correspondent William Crabtree. The pair made their observations independently on 4 December that year (24 November under the Julian calendar then used in England); Horrocks from Carr House, then in the village of Much Hoole, Lancashire, and Crabtree from his home in Broughton, near Manchester.
The friends, followers of the new astronomy of Johannes Kepler, were self-taught mathematical astronomers who had worked methodically to correct and improve Kepler's Rudolphine tables by observation and measurement. In 1639, Horrocks was the only astronomer to realise that a transit of Venus was imminent; others became aware of it only after the event when Horrocks's report of it was circulated. Although the friends both died within five years of making their observations, their ground-breaking work was influential in establishing the size of the Solar System; for this and their other achievements Horrocks and Crabtree, along with their correspondent William Gascoigne, are considered to be the founding fathers of British research astronomy.
By the 17th century, two developments allowed for the transits of planets across the face of the Sun to be predicted and observed: the telescope and the new astronomy of Johannes Kepler, which assumed elliptical, rather than circular, planetary orbits.
In 1627, Kepler published his Rudolphine Tables. Two years later he published extracts from the tables in his pamphlet De raris mirisque Anni 1631 Phaenomenis which included an admonitio ad astronomos (warning to astronomers) concerning a transit of Mercury in 1631 and transits of Venus in 1631 and 1761. The Mercury transit occurred as predicted and was observed by Johann Baptist Cysat in Innsbruck, Johannes Remus Quietanus in Rouffach and Pierre Gassendi in Paris, vindicating the Keplerian approach. But their observations threw into question previous theories about the Solar System, as Mercury was shown to be much smaller than expected.
Although Kepler's calculations indicated that the 1631 transit of Venus would best be visible from the American continent, he was not fully confident of his prediction, and advised that European astronomers should be prepared to observe the event. Gassendi and others in Europe watched for it but, as predicted, the Sun was below the horizon during the transit. According to modern calculations, observers in much of Italy and along the eastern Mediterranean should have been able to view the last stage of the transit, but no such observations were recorded. Kepler had predicted a near miss for a Venus transit in 1639 and, as the next full transit was not expected for another 121 years, Gassendi and the other astronomers concentrated their efforts in other areas.
Jeremiah Horrocks (1618 – 3 January 1641) was born in Lower Lodge, Toxteth Park – now part of Liverpool but at that time a separate town. His father James was a watchmaker, and his mother Mary Aspinwall was from a notable Toxteth Park family. Several members of the Aspinwall family were also in the watchmaking trade, and it is said that a watchmaker uncle first interested Jeremiah in astronomy. Jeremiah joined Emmanuel College on 11 May 1632 and matriculated as a member of the University of Cambridge on 5 July 1632 as a sizar, which meant he did not have the means to fully support himself and was given specific duties to compensate for a reduction in fees. At Cambridge, he would have studied the arts, classical languages, a little geometry, and some traditional astronomy, but not the latest work by Galileo, Tycho Brahe and Kepler. He used his spare time to teach himself the more demanding mathematical astronomy and familiarise himself with the latest thinking. Horrocks read most of the astronomical treatises of his day, identified their weaknesses, and was suggesting new lines of research by the age of 17. In 1635, he left Cambridge without formally graduating, presumably owing to the cost of the graduation ceremony.
After leaving Cambridge, Horrocks returned to his home in Lancashire and began collecting books and instruments in order to pursue his main interest, the study of astronomy. In the summer of 1639, he left home and moved about 18 miles (29 km) along the coast to the village of Much Hoole. This was probably to become tutor to the children of the Stones family, prosperous haberdashers who lived at Carr House, within the Bank Hall Estate, Bretherton.
Horrocks was the first to demonstrate that the Moon moved in an elliptical path around the Earth. He also wrote a treatise on Keplerian astronomy and began to explore mathematically the properties of the force that became known as gravity. Decades later, Isaac Newton acknowledged Horrocks's work in relation to the Moon in Newton's Principia.
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