Making the first observation of
the transit of Venus in 1639
Lower Lodge, Otterspool,
Toxteth Park,Liverpool, UK
Toxteth Park, Liverpool, UK
|Alma mater||University of Cambridge|
|Known for||Transit of
Jeremiah Horrocks (1618 – 3 January 1641), sometimes given as Jeremiah Horrox (the Latinised version that he used on the Emmanuel College register and in his Latin manuscripts), was an English astronomer who was the only person to predict, and one of only two people to observe and record, the transit of Venus of 1639.
Horrocks was born in Lower Lodge, in Toxteth Park, Liverpool, Merseyside. His father was a small farmer; his uncle was a watchmaker; he was relatively poor during his entire brief life. He joined Emmanuel College on 11 May 1632 and matriculated as a member of the University of Cambridge on 5 July 1632 as a sizar. In 1635 he left without formally graduating, presumably due to the cost of continuing his studies. The traditional view is that he supported himself financially by holding a curacy in Much Hoole, near Preston in Lancashire, but there is little evidence for this. According to local tradition in Much Hoole, he lived at Carr House, within the Bank Hall Estate, Bretherton. Carr House was a substantial property owned by the Stones family who were prosperous farmers and merchants, and Horrocks was a tutor for the Stones children. He may have been a Calvinist and, through his connection with Emmanuel College, a Puritan, although there is little evidence of his religious convictions.
At Cambridge, he became familiar with the works of Johannes Kepler, Tycho Brahe, and others. Horrocks read most of the astronomical treatises of his day, found the weaknesses in them and was suggesting new lines of research by the age of seventeen. He was the first to demonstrate that the Moon moved in an elliptical path around the Earth, he wrote a treatise on Keplerian astronomy and began to explore mathematically the properties of the force that later became known as gravity. Sir Isaac Newton acknowledged Horrocks's work as the bridge which connected him with Copernicus, Galileo, Brahe and Kepler. Horrocks was convinced that Lansberg's tables were inaccurate when Kepler predicted that a near-miss of a transit of Venus would occur in 1639. Horrocks believed that the transit would indeed occur, having made his own observations of Venus for years.
Horrocks focused the image of the Sun through a simple telescope onto a piece of card, (see helioscope) where the image could be safely observed. From his location in Much Hoole, he calculated that the transit was to begin at approximately 3:00 pm on 24 November 1639 (Julian calendar, or 4 December in the Gregorian calendar). The weather was cloudy, but he first observed the tiny black shadow of Venus crossing the Sun on the card at about 3:15 pm, and observed for half an hour until sunset. The 1639 transit was also observed by his friend and correspondent, William Crabtree, from his home in Broughton.
Horrocks' observations allowed him to make a well-informed guess as to the size of Venus (previously thought to be larger and closer to Earth), as well as to make an estimate of the distance between the Earth and the Sun. His figure of 59 million miles (95 million kilometres, 0.63 AU) was far from the 93 million miles (150 million kilometers) that it is known to be today but it was a more accurate figure than any suggested up to that time.
A treatise by Horrocks, Venus in sub sole visa (Venus in transit across the Sun) was published by Johannes Hevelius at his own expense in 1662. This paper, which caused great excitement when revealed to members of the Royal Society 20 years after it was written, contained much evidence of Horrocks' enthusiastic and romantic nature, including humorous comments and passages of original poetry. When speaking of the century separating Venusian transits, he rhapsodised,
Horrocks also put his energies into the highly complex task of determining the Moon's orbit. He correctly hypothesised that the orbit was elliptical rather than circular, and he anticipated Isaac Newton in suggesting an influence on the orbit from the sun as well as the earth. In the final months of his life he also made detailed study of tides, in an attempt to explain the nature of lunar causation of tidal movements.
Horrocks returned to Toxteth Park sometime in the summer of 1640 and died suddenly and from unknown causes on 3 January 1641, aged only 22. As expressed by Crabtree, "What an incalculable loss!"
The lunar crater Horrocks is named for him.
JEREMIAH HORROCKS (1619-1641), English astronomer, was born in 1619 at Toxteth Park, near Liverpool. His family was poor, and the register of Emmanuel College, Cambridge, testifies to his entry as sizar on the r8th of May 1632. Isolated in his scientific tastes, and painfully straitened in means, he pursued amid innumerable difficulties his purpose of self-education. His university career lasted three years, and on its termination he became a tutor at Toxteth, devoting to astronomical observations his brief intervals of leisure. In 1636 he met with a congenial spirit in William Crabtree, a draper of Broughton, near Manchester; and encouraged by his advice he exchanged the guidance of Philipp von Lansberg, a pretentious but inaccurate Belgian astronomer, for that of Kepler. He now set himself to the revision of the Rudolphine Tables (published by Kepler in 1627), and in the progress of his task became convinced that a transit of Venus overlooked by Kepler would nevertheless occur on the 24th of November (O.S.) 1639. He was at this time curate of Hoole, near Preston, having recently taken orders in the Church of England, although, according to the received accounts, he had not attained the canonical age. The 24th of November falling on a Sunday, his clerical duties threatened fatally to clash with his astronomical observations; he was, however, released just in time to witness the punctual verification of his forecast, and carefully noted the progress of the phenomenon during half an hour before sunset (3.15 to 3.45). This transit of Venus is remarkable as the first ever observed, that of 1631 predicted by Kepler having been invisible in western Europe. Notwithstanding the rude character of the apparatus at his disposal, Horrocks was enabled by his observation of it to introduce some important corrections into the elements of the planet's, orbit, and to reduce to its exact value the received estimate of its apparent diameter.
After a year spent at Hoole, he returned to Toxteth, and there, on the eve of a long-promised visit to his friend Crabtree, he died, on the 3rd of January 1641, when only in his twentysecond year. To the inventive activity of the discoverer he had already united the patient skill of the observer and the practical sagacity of the experimentalist. Before he was twenty he had afforded a specimen of his powers by an important contribution to the lunar theory. He first brought the revolutions of our satellite within the domain of Kepler's laws, pointing out that her apparent irregularities could be completely accounted for by supposing her to move in an ellipse with a variable eccentricity and directly rotatory major axis, of which the earth occupied one focus. These precise conditions were afterwards demonstrated by Newton to follow necessarily from the law of gravitation.
In his speculations as to the physical cause of the celestial motions, his mind, though not wholly emancipated from the tyranny of gratuitous assumptions, was working steadily towards the light. He clearly perceived the significant analogy between terrestrial gravity and the force exerted in the solar system, and by the ingenious device of a circular pendulum illustrated the composite character of the planetary movements. He also reduced the solar parallax to 14" (less than a quarter of Kepler's estimate), corrected the sun's semi-diameter to 15' 45", recommended decimal notation, and was the first to make tidal observations.
Only a remnant of the papers left by Horrocks was preserved by the care of William Crabtree. After his death (which occurred soon after that of his friend) these were purchased by Dr Worthington, of Cambridge; and from his hands the treatise Venus in sole visa passed into those of Hevelius, and was published by him in 1662 with his own observations on a transit of Mercury. The remaining fragments were, under the directions of the Royal Society, reduced by Dr Wallis to a compact form, with the heading Astronomia Kepleriana defensa et promota, and published with numerous extracts from the letters of Horrocks to Crabtree, and a sketch of the author's life, in a volume entitled Jeremiae Horroccii opera posthuma (London, 1672). A memoir of his life by the Rev. Arundell Blount Whatton, prefixed to a translation of the Venus in sole visa, appeared at London in 1859.
For additional particulars, see J. E. Bailey's Palatine Note-Book, ii. 253, iii. 17; Bailey's " Writings of Horrocks and Crabtree " (from Notes and Queries, Dec. 2, 1882); Notes and Queries, 3rd series, vol. v., 5th series, vols. ii., iv.; Martin's Biographia philosophica, p. 271 (1764); R. Brickel, Transits of Venus, 1639-1874 (Preston, 1874); Astronomical Register, xii. 293; Hevelii, Mercurius in sole visus, pp. 116-140; S. Rigaud's Correspondence of Scientific Men; Th. Birch, History of the Royal Society, i. 386, 395, 47 0; Sir E. Sherburne's Sphere of M. Manilius, p. 92 (1675); Sir J. A. Picton's Memorials of Liverpool, ii. 561; M. Gregson's Fragments relative to the Duchy of Lancaster, p. 166 (1817); Liverpool Repository, i. 570 (1826); Phil. Trans. Abridged, ii. 12 (1809); C. Hutton's Phil. and Math. Dictionary (1815); Penny Cyclopaedia (De Morgan); Nature, viii. 117, 137; J. B. J. Delambre, Hist. de l'astronomie moderne, ii. 495; Hist. de l'astronomie au X VIII e siecle, pp. 28, 61, 74; W. Whewell, Hist. of the Inductive Sciences, i. 331; R. Grant, Hist. of Physical Astronomy, pp. 420, 545; J. Madler, Geschichte der Himmelskunde, i. 275; M. Marie, Hist. des Sciences, iv. 168, vi. 90; J. C. Houzeau, Bibl. Astr. ii. 167. (A. M. C.)