August 4 – Happy Birthday, William Rowan Hamilton

nPostednon August 4, 2015

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nTonthis day, mathematicians pay homage to today’s famous birthday,nWilliam Rowan Hamilton, by walking from Dunsink Observatory to BroomnBridge, in Dublin, Ireland. n

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nAndnthere they reach the spot where Hamilton was struck by a brilliantnthought.

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nThis is where he carved an equation into the side of thenbridge with his pen knife. This equation is the most famous ofnHamilton’s mathematical contributions: an equation for quaternions. n
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nActually,nmathematicians and other tourists cannot see even a remnant ofnHamilton’s equation carving, but there is a stone plaque under thenbridge to commemorate the discovery of quaternions .

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nYounare probably wondering what quaternions are. They are a number systemnthat doesn’t work the same way as our more familiar number system.n(To give an example of a difference, multiplication isn’tncommutative. You know how, in our familiar number system, 3 time 6nequals 6 time 3? Well, in quaternions, that kind of turn-aroundndoesn’t always work.)

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nItnseems like a theoretical, pure-mathematical number system would havenno practical applications, but in actual fact, quaternions are usednin 3-D computer graphics, crystal analysis, and other modernnscientific applications.

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nHamilton,nborn on this date in 1805, was more than just a mathematician – henwas also a physicist and an astronomer. He made importantncontributions to mechanics, optics, and algebra, and people utilizednhis work in theories on electromagnetism and quantum physics.

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nApparentlynhe showed his talent early. Astronomer Bishop Dr. John Brinkley saidnof 18-year-old Hamilton, “This young man, I do not say will be, but is, the first mathematician of his age.”