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Comment by divbzero

9 hours ago

> Primary sources:

> Maskelyne’s notes: https://doi.org/10.1098/rstl.1775.0050

> Hutton’s notes: https://doi.org/10.1098/rstl.1778.0034

> Cavendish’s notes on his own experiment: https://doi.org/10.1098/rstl.1798.0022

I got to reproduce Cavendish’s experiment when I was a student. Love that we can easily read the primary source today, archived and indexed by DOI.

5 comments

divbzero

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CobrastanJorji  4 hours ago

I'd love to know what a sufficiently high precision plumb bob is like. Is it very tall? How on Earth does one calibrate it?

neitsa  8 hours ago

> Using the stars as a reference, Maskelyne’s team found that the plumb lines on either side of the mountain pointed just 0.0152 degrees apart.

I'm really interested in knowing how they could get such a precise measurement (even accounting for errors), especially in the field (outdoor). There's no figure depicting the apparatus they used, I wonder how it looked like.

Sometimes, I just ponder at how ignorant I am. If I was tasked with the same assignment, I'd definitely fail and this was performed 250 ago!

  • throwway120385  8 hours ago

    Maybe something similar to a vernier caliper.

    From Wikipedia:

    > The first caliper with a secondary scale, which contributed extra precision, was invented in 1631 by the French mathematician Pierre Vernier (1580–1637).[1] Its use was described in detail in English in Navigatio Britannica (1750) by mathematician and historian John Barrow.[2] While calipers are the most typical use of vernier scales today, they were originally developed for angle-measuring instruments such as astronomical quadrants.

    https://en.wikipedia.org/wiki/Vernier_scale

    So it would have been a contemporaneous technique with that initial angle measurement, and the use of a Vernier scale for angular measurements would have itself been common.