Computing Earth's Mass Before G ```Name: Aaron Status: student Age: N/A Location: N/A Country: N/A Date: N/A ``` Question: What were the ways of computing the mass of the earth in the 17th and 18th century? Replies: This link may help: http://curious.astro.cornell.edu/question.php?number=207 Burr Zimmerman Aaron, The first recorded methods I know of were done in the middle of the 18th century. One involved measuring the period of a pendulum on solid ground at sea level and on a plain very far above sea level. This can provide a ratio of the Earth's average density and the density of the ground that is above sea level. A second involved deflection of a pendulum near a mountain. Using a star as a reference, deflection of a pendulum on top of a mountain and near the same mountain could provide a ratio of Earth mass to mountain mass. Both are recorded in an 1893 essay by J. H. Poynting: The Mean Density of the Earth. A digitized copy of the text can be accessed currently through Google at http://books.google.com/books?id=dg0RAAAAIAAJ&printsec=titlepage &source=gbs_v2_summary_r&cad=0#v=onepage&q=&f=false Dr. Ken Mellendorf Physics Instructor Illinois Central College Click here to return to the Physics Archives

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