James Gregory was a Scottish mathematician and astronomer. He was born near Aberdeen, Scotland in November 1638. He was the youngest son of John Gregory, a minister, and Janet Anderson. As a child he was introduced to geometry by his mother. After his father's death in 1651, his oldest brother, David, sent him to Aberdeen for grammar school, and eventually he would later attend Marischal College there. Encouraged by his brother, who was also mathematics fanatic, James dedicated himself to studying mathematical optics and astronomy.
In 1662, looking for more scientific opportunities, he decided to travel to London. There in London he would publish Optica promota a year later. In this book, he describes the first practical reflecting telescope, which was one of his big contributions to astronomy. Now called the Gregorian telescope, it was revolutionary because it used a combination of mirrors and lenses which made it more effective than previous telescopes using just lenses or just mirrors. Not actually able to built the telescope himself he tried to hire Reive, the leading optician, to build it for him. Unsatisfied, he gave up on the idea of building it. It would successfully be built ten years later by Hooke, who heard of Reive’s failed attempt. Optica promota would eventually earn him some influential friends including Robert Moray, interim president of the Royal Society in 1660.
Continuing to gain scientific knowledge, Gregory then traveled to Italy to study geometry, mechanics, and astronomy under Stefano degli Angeli in Padua. There he would publish two more works, Vera circuli et hyperbolae quadratura (1667) and Geometriae pars universalis (1668). Geometriae pars universalis is really the first attempt to write a text-book on what we would eventually call calculus. After publishing these he returned to London, where he was elected to the Royal Society despite implications from Huygens that Gregory had stole his results and published them in Vera criculi et hyperbolai quadratura as his own. Gregory then published Exercitaiones Geometricai to rebut Huygens.
In late 1668, Gregory presented some of his papers to the Society on various topics including astronomy, gravitation, and mechanics. Most likely with Moray’s influence in the society, Charles II was persuaded to make the Regius Chair of Mathematics so Gregory could continue his mathematical research. He was nominated to this new chair of mathematics at St. Andrews in Scotland. During that time he married a young widow, Mary Burnet, in 1669. They would have two daughters and a son.
Around 1671, Gregory discovered Taylor’s theorem. His friend Collins wrote to Gregory saying that Newton has found a similar result. Remembering his dispute with Huygens, Gregory wanted to wait until Newton published his results first to avoid another dispute. He decided to not go any further with this work out of respect for Isaac Newton.
At St. Andrews, the upper room of the library had a clear view to the south which was a great place for Gregory to put up his telescope. In 1674, he worked with colleagues in Paris to make simultaneous observations of an eclipse of the moon. With this, he was able to find out the longitude for the first time even though he had already started to work on an observatory. In 1673, the university permitted him to purchase instruments for the observatory on the condition that he would have to organize collections for funds to build it himself. He would leave St. Andrews a year later and go to Edinburgh due to the prejudice he felt against him at the university.
In Edinburgh, Gregory would become the first person to hold the Chair of Mathematics there. However, this would be short lived because he would pass away one year later. His death was very sudden. One night when he was observing the moons of Jupiter to his students with his telescope, he suffered a stroke and became blind. He would die a few days later at only the age of 36.
Over time we can finally see just how brilliant he was. He anticipated Newton in discovering the interpolation formula and the general binomial theorem. He discovered Taylor expansions more than 40 years before Taylor discovered it himself. He had solved Kepler’s famous problem of how to divide a semi circle by a straight line through a given point of the diameter in a given ratio. He gave one of the earliest examples of a comparison test for convergence, which would essentially be Cauchy’s ratio test. And he also gave a definition of the integral which was pretty much the same definition Riemann would give later. James Gregory was indeed a great man of science.
Works Cited
"Gregory (More Correctly Gregorie), James." Complete Dictionary of Scientific Biography. Vol. 5. Detroit: Charles Scribner's Sons, 2008. 524-530. Gale Virtual Reference Library. Web. 30 Sept. 2010.
O'Connor, J. J., and E. F. Roberston. "James Gregory." MacTutor History of Mathematics. JOC/EFR, Sept. 2000. Web. 30 Sept. 2010. <http://www-history.mcs.st-and.ac.uk/Biographies/Gregory.html>.
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