| Sir Edward Sabine | |
|---|---|
| Born | 14 October 1788 Dublin |
| Died | 26 June 1883 (aged 94) East Sheen |
| Nationality | Irish |
| Fields | Astronomy, ornithology |
General Sir Edward Sabine KCB FRS (14 October 1788 – 26 June 1883) was an Irish astronomer, geophysicist, ornithologist and explorer.
Two branches of Sabine's work in particular deserve very high credit: Determination of the length of the seconds pendulum, a simple pendulum whose time period on the surface of the Earth is two seconds, that is, one second in each direction; and extensive researches connected with the Earth's magnetic field. He led the effort to establish a system of magnetic observatories in various parts of British territory all over the globe and a great part of his life was devoted to their direction, and to the reduction and discussion of their observations.
While the majority of his research bears on one or other of the subjects just mentioned, other research deals with such widely different topics as the birds of Greenland (Sabine's Gull is named for him), ocean temperatures, the Gulf Stream, barometric measurement of heights, arc of the meridian, glacial transport of rocks, the volcanoes of the Hawaiian Islands, and various points of meteorology.
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He was born in Dublin to Joseph Sabine, member of a prominent Anglo-Irish family whose connections with the country can be traced back to the seventeenth century. His mother died when he was just one month old. His elder brother was naturalist Joseph Sabine.
He was educated at Marlow and at the Royal Military Academy, Woolwich. In 1803 he obtained a commission in the Royal Artillery as a 2nd lieutenant, becoming a captain ten years later. He attained the rank of major-general in 1859.
Sabine was stationed in Gibraltar during the Peninsular War, but it was in the War of 1812 against the United States that he had his first taste of combat. In May 1813, while making for Canada, the English packet-ship Manchester was attacked by an American privateer. In the ensuing battle Sabine, who was the Manchester's astronomer, reportedly handled a gun "to good effect."
In Canada Sabine commanded the batteries at the siege of Fort Erie. After a short spell of military service in Quebec, he returned to England and devoted the remainder of his long life to the more peaceful pursuits of astronomy, terrestrial magnetism and physical geography.
Sabine was elected a Fellow of the Royal Society in April 1818,[1] and it was thanks to the society's recommendations that he was invited to take part that year in Captain John Ross's first Arctic expedition. As the expedition's appointed astronomer, Sabine was told to assist Ross "in making such observations as may tend to the improvement of geography and navigation, and the advancement of science in general."
Although the principal purpose of the voyage was to find the Northwest Passage, several objects of scientific curiosity were deemed worthy of investigation, such as the location of the Earth's north magnetic pole and the behaviour of pendulums in high latitudes.
The expedition failed to discover the Northwest Passage and ended in controversy. When Ross found his progress through Lancaster Sound blocked by sea ice, he turned around and headed back to Britain, much to the annoyance of the other members of the expedition. Both Sabine and Ross's second-in-command William Edward Parry doubted the very existence of the so-called Croker Mountains, which it seems only Ross saw.
Objecting to Ross's precipitate retreat, Sabine later recalled his "very visible mortification at having come away from a place which I considered as the most interesting in the world for magnetic observations, and where my expectations had been raised to the highest pitch, without having had an opportunity of making them."
To make matters worse, a very public row broke out between the two men when they arrived home. Sabine objected when Ross claimed the credit for certain magnetic observations. He also accused Ross of stealing magnetic measurements without giving him due credit, and of refusing to allow him enough time on the expedition to take accurate readings.
The results of Sabine's magnetic researches were published in the Philosophical Transactions of the Royal Society. Although he viewed his work as confirming and extending the discoveries of earlier "magnetic collectors," he stressed the need for the multiplication and repetition of observations. Sabine was a diligent and careful scientist. He generally avoided theoretical discussion in his writings, believing that a true understanding of terrestrial magnetism would only be arrived at after exhaustive observations had been made on a global scale.
The following year (1819) both Sabines returned to the Arctic as members of Lieutenant William Edward Parry's expedition in search of the Northwest Passage.
The Admiralty once again instructed the participants to gather such scientific data as "must prove most valuable and interesting to the science of our country." They were to pay particular attention to magnetic measurements, especially the possible interactions between magnetic needles, atmospheric electricity and the aurora borealis. They were also to attempt to establish the location of the Earth's North Magnetic Pole, then believed to lie somewhere along the western shore of Baffin Bay.
Like Ross, Parry did not find the passage, but he did set a new record for the "furthest west," which stood for several decades.
In order to alleviate the tedium of the long Arctic winter, Sabine produced a weekly newspaper for the amusement of the crew. Known as the North Georgia Gazette and Winter Chronicle, it ran for twenty-one issues. Due to public demand, it was actually published on their return to Britain – much to Sabine's surprise.
During this expedition, which lasted from May 1819 to November 1820, Sabine noted that changes in magnetic intensity had taken place since his previous visit. He attributed such changes to either a fluctuation in the Earth's magnetic intensity or the shifting positions of the terrestrial magnetic poles.
For his work in the Arctic Sabine received the Copley Medal from the Royal Society in 1821.
Sabine next turned his attention to the science of geodesy, which had already engaged his attention during the first of his Arctic voyages, and in particular the determination of the length of the seconds pendulum.
By measuring the length of a seconds pendulum in different latitudes, one can calculate the "oblateness" of the Earth - i.e. the degree to which the "figure of the Earth" departs from perfect sphericity. Attempts to do this had been made in the eighteenth century, but it was not until Sabine's lifetime that precision instruments were available to allow sufficiently accurate measurements to be made.
Sabine threw himself into the task with his usual diligence. Between 1821 and 1823 he travelled halfway around the world with his pendulums and carried out innumerable measurements on the intertropical coasts of Africa and the Americas. He also returned to the Arctic, journeying up the eastern coast of Greenland with Captain D Clavering on Parry's old ship the Griper. Observations were made at Little Pendulum Island, in latitude 74° 30', and among the snows of Spitsbergen. Sabine even had an island named in his honour during this expedition.
The results of his research were published in 1825. They represented the most accurate assessment of the figure of the earth that had ever been made. Not content to rest on his laurels, Sabine conducted further pendulum experiments throughout the 1820s, determining the relative lengths of the second's pendulum in Paris, London, Greenwich, and Altona.
Sabine was also drawn into the famous "longitude problem," which was one of the great controversies of the age. Determining one's longitude remained the primary navigational concern at that time. Sabine hoped to devise a simple method of achieving this by measuring minute variations in the Earth's magnetic field. In the eighteenth century Sir Edmund Halley and William Whiston (Newton’s successor as Lucasian professor at Cambridge) had theorized that one could calculate both the latitude and longitude of any position on the surface of the earth by measuring the magnetic dip of a compass needle.
But the extraordinarily accurate chronometers of John Harrison were generally available from the 1820s on, rendering the whole question immaterial. By the time Sabine became interested in the problem, it had already been solved, and in 1828 the British government abolished the Board of Longitude. As it happened, secular changes in the Earth's magnetic field meant that Halley and Whiston's method would never have been practicable.
But Sabine did make one notable contribution to the longitude problem. In 1825 he and fellow-astronomer Sir John Herschel collaborated with a French government commission to determine the precise difference of longitude between the observatories of Paris and Greenwich. By means of rocket-signals the difference was found to be 9' 21.6" – an error of less than one arcsecond.
In 1827 The Duke of Wellington granted Sabine general leave of absence from the army on the understanding "that he was usefully employed in scientific pursuits." But his leave did not last very long. Political agitation in Ireland necessitated an increased military presence in the country, and in 1830 Sabine was recalled to military duty. He remained in his native land for the next seven years, but he did not allow his new military duties to interrupt his scientific endeavours. He continued his pendulum investigations and in 1834 commenced a systematic magnetic survey of Ireland – the first of its kind in what was then the United Kingdom. It was extended to Scotland in 1836, and to England the following year.
On the abolition of the Board of Longitude in 1828, it was arranged that three scientific advisers to the Admiralty should be nominated from the council of the Royal Society. Sabine, Michael Faraday, and Thomas Young were chosen. Sabine's appointment was violently attacked by Charles Babbage, the father of the computer, (largely on account of his associations with the Royal Society, whose scientific credentials Babbage did not recognise) in a pamphlet entitled Reflections on the Decline of Science in England, and on Some of its Causes. Sabine, however, refused to be drawn into the controversy.
During these decades the Royal Navy and Royal Society devoted so much energy to the problems of magnetic variation that magnetism came to be seen as an eminently "British" science. There was intense interest in figuring out what many called "the great remaining physical mystery since Newton's work on gravitation." By the beginning of the nineteenth century, it was widely recognized that the Earth's magnetic field was continually changing over time in a complicated way that interfered with compass readings. It was a mystery which some scientists believed might be associated with weather patterns.
To solve this mystery once and for all, a number of physicists recommended that a magnetic survey of the entire globe be carried out. Sabine was one of the instigators of this "Magnetic Crusade," urging the government to establish magnetic observatories throughout the empire. He also recruited many disciples to the cause – most notably James Clark Ross, a nephew of Sir John's, the German explorer Alexander von Humboldt and the astronomer royal, George Airy.
A committee, of which Sabine was a prominent member, was established to work out the details. Suitable locations for the observatories were selected in both hemispheres and representations were made to despatch an expedition to the Southern Ocean to carry out a magnetic survey of the Antarctic. In the spring of 1839, the government approved the scheme. Observatories were to be established at Toronto, St. Helena, Cape Town, Tasmania and at stations to be determined by the East India Company, while other nations were invited to co-operate. Sabine was appointed to superintend the entire operation.
Most of these observatories were of limited size and were dismantled as soon as the initial survey was complete, but the one founded by Sabine at Toronto in 1840 is still in existence. Originally housed in a modest building at the newly established University of Toronto, it was called the Toronto Magnetic and Meteorological Observatory. It was the first scientific institution in the country.
The birthplace of Canadian astronomy was a simple log building held together with copper nails and brass fastenings. Non-magnetic materials were used to avoid the problem of "local attraction." A second room was built to house a telescope, which was used to make accurate time readings based on the movement of the Sun and stars. The modern stone observatory was erected in 1855.
In those days, there was no way to take continuous readings: everything had to be done by hand. Thousands of painstaking observations were taken by the staff – sometimes as frequently as every five minutes! These observations were all carefully scrutinised by Sabine back in Britain.
In 1852, Sabine recognized from the Toronto records that magnetic variations could be divided into a regular diurnal cycle and an irregular portion. The irregularity correlated very closely with fluctuations in the number of sunspots, whose cyclic nature had been discovered in 1844 by the German amateur astronomer Heinrich Schwabe. Sabine was the first to recognize that solar disturbances affected the Earth's magnetic environment. On 6 April 1852 he announced that the Sun's 11-year sunspot cycle was "absolutely identical" to the Earth's 11-year geomagnetic cycle.
The following year, Sabine also made a similar correlation with the Moon, establishing that that celestial body too had an influence on the Earth's magnetic field. He concluded that the Moon must have a significant magnetic field of its own to cause such an effect. But for once he was mistaken: the effect is actually the result of gravitational tides in the ionosphere. (Nevertheless, a crater on the Moon has been named in his honour.)
Throughout the 1840s and 1850s, Sabine continued to superintend the operation of magnetic observatories throughout the British Empire. The result was Sabine's magnum opus: as complete a magnetic survey of the globe as was then humanly possible.
Throughout his long life Edward Sabine received numerous decorations for his contributions to science. In 1849 the Royal Society awarded him one of its gold medals for his work on terrestrial magnetism. Sabine was president of the society from 1861 until his resignation ten years later. He was a member of the Royal Commission of 1868-1869 for standardizing weights and measures. Both Oxford and Cambridge bestowed honorary doctorates on him. He was a fellow of the Linnean and the Royal Astronomical Societies, a foreign member of the Royal Swedish Academy of Sciences (from 1867) and president of the British Association for the Advancement of Science.
He was knighted in 1869, becoming a Knight Commander of the Order of the Bath. He retired from the army on full pay in 1877, by which time he had achieved the rank of General.
In 1879 Sabine's wife, Elizabeth Leeves, died. An accomplished woman in her own right, she had assisted her husband in his scientific endeavours for more than half a century. Her four-volume translation of Alexander von Humboldt’s monumental textbook of geophysics Kosmos, was published 1849-1858.
Sir Edward Sabine died at East Sheen, Surrey, on 26 June 1883 and was buried in the family vault at Tewin, Hertfordshire. He was 94.
The Californian Gray Pine (Pinus sabineana) is named after him, as is Sabine's Gull (Larus sabini).
A crater on the Moon is named in his honor. Sabine Crater lies directly adjacent to the landing site of the first manned mission to Luna, by the crew of Apollo XI in July 1969, in the southern Mare Tranquillitatis region.
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