Cowell, Philip Herbert

(b. Calcutta, India, 7 August 1870; d. Aldeburgh, Suffolk, England, 6 June 1949)

dynamical astronomy.

The second son of Herbert Cowell, barrister, and of the former Alice Garrett, third daughter of Newson Garrett of Aldeburgh, Cowell had a wide cultural background. After showing unusual mathematical ability at Eton, he went to Trinity College, Cambridge, with an entrance scholarship. He graduated as senior wrangler in 1892 and was awarded the Isaac Newton Studentship in 1894, in which year he was elected fellow of Trinity. In 1896 Cowell was appointed chief assistant at the Royal Observatory at Greenwich, and in 1910 he became superintendent of the Nautical Almanac.

Because of the large perturbations by the sun and the extreme complexity of those by the planets, the development of a theory of the motion of the moon is extremely difficult. Cowell, using powerful mathematical and computational techniques, made important contributions to three distinct aspects: the theoretical development of the motion of the node of the orbit; the analysis of observations, from which he deduced the essential correctness, but inadequacy, of the current theories; and the determination of the secular acceleration of the mean longitude from a study of the records of ancient eclipses. For this work he was elected a fellow of the Royal Society in 1906.

Cowell’s name is perpetuated in “Cowell’s method” of step-by-step numerical integration for the solution of the relatively simple differential equations in rectangular coordinates defining the motions of bodies under their mutual gravitational attraction. He first applied the method to the newly discovered eighth satellite of Jupiter; then, with A. C. D. Crommelin, he used it brilliantly to predict the return of Halley’s comet in 1910.

Cowell did not realize his full potential. Neither of his posts provided him with the scope for theoretical research that a Cambridge professorship, which eluded him, would have done; in later years he was frustrated and devoted himself more and more to other pursuits.

BIBLIOGRAPHY

Some fifty of Cowell’s research papers are published in Monthly Notices of the Royal Astronomical Society, 64–70 (1903–1910). The “Investigation of the Motion of Halley’s Comet From 1759 to 1910” is an appendix to Greenwich Observations for 1909.

An obituary is Edmund T. Whittaker, in Obituary Notices of Fellows of the Royal Society of London, 7 (1949), 375–384.

D. H. Sadler