Talk:Jean Richer

> This number gives a time difference of 8.1 minutes

Actually 2.8 mm gives 2 minutes: ½*0.0028*1440, as per the pendulum equation

$t=2\pi {\sqrt {\frac {\ell }{g}}}\Rightarrow {\frac {dt}{t}}={\frac {1}{2}}{\frac {d\ell }{\ell }}\Rightarrow dt={\frac {1}{2}}{\frac {d\ell }{\ell }}t.$

130.233.138.45 (talk) 10:26, 10 February 2015 (UTC)

Actually Richer's report is here: [1]

http://i59.tinypic.com/34fgsjk.png

http://i59.tinypic.com/iomcdx.png

On the length of a pendulum of seconds of time

"One of the most considerable observations which I made was that of the length of a seconds pendulum ... compared with the one in Paris, their difference has been found to be a line and a quarter, the one in Cayenne being less than the one in Paris, which is 3 feet 8 lines and 3/5. ..."

-> Relative shortening: .002837 [a foot is 144 lines]

130.233.138.45 (talk) 11:27, 10 February 2015 (UTC)