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:

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)