The 2023/24 History of Astronomy lectures kicked off with a stunning two-for-one combination of lectures by Dr Jane Clark. Dr Clark started with a comprehensive run down of the history of astronomy covering Aristotle (great communicator but lousy physicist!), Apollonius of Perga, Alexander the Great, Ptolemy and Copernicus. This led us inevitably to Tycho Brahe.
Tycho was a cultured aristocrat of private means who was skilled in both Latin and Greek. Indeed, Dr Clark described how she had needed to understand both to transcribe some of his works that are only available in older Latin – two years of modern (if there is such a thing) school Latin ill-prepared her for this task and Google translate proved inadequate.
Tycho Brahe setup two observatories in Hveen, an island between Denmark and what is now Sweden, but was Danish land at the time. His first was Uraniborg which was also his residence. As his instrumentation gained ever more accuracy it became susceptible to wind, so he built a second, Stejerneborg. This was largely underground to avoid wind-induced movement.
One of the aspects that Brahe was good at was maths. This was not only well before calculators, it was before log tables, meaning that multiplication and division were time consuming and laborious tasks. Everything at this time was expressed as angles. Planet and comet positions were recorded as angles to stars. Tycho Brahe claimed to have invented the process known as Prosthaphaeresis, which converted an equation with a number of multiplications:
which, although it has more terms, is simpler to compute by hand.
Tycho’s large instruments were all designed to measure these angles. He managed to do this to previously unprecedented accuracy. The recording of his Mars position information was the basis for his assistant, Johnannes Kepler to derive his three laws of planetary motion, and in doing so positioned the Sun at the centre of the solar system. This in turn led to Newton deriving his now famous universal law of Gravitation Attraction.
There was a short discussion on how Brahe recorded time. Dr Clark asserted that he only had access to water clocks, with Mike Dryland explaining that Brahe had access to time pieces from Bürgi.
After questions, with us having some time left in the room, Dr Clark gave a short talk on Christopher Wren and his contributions to astronomy.
Overall, this was an excellent start to our season which bodes well for the rest of the year.
