Brent Meeker wrote: *> Neither does a cesium clock measure the change in strength of 2 large > gravitational fields. It measures the difference in gravitational > potential. *
Same thing, a gravitational field describes the gravitational potential at every point. *> **So I compared the change in gravitational potential when moving the > clock up 1cm to the change in potential when Cavendish's torsion balance > moved the sensing weights the smallest change in distance he said he could > measure 0.25mm with the weights 9" (0.23m) from the cannon balls. The ratio > of these two potentials is the product of three terms: The ratio of masses > (1.37e25 lbm/348 lbm) The ratio distances squared (0.23m/6.4e6m)^2. The > ratio of smallest measurable changes (0.01m/0.00025m). Work it out > yourself.* Brent, Cavendish's torsion balance was only sensitive enough to measure the Gravitational constant to one part in 100, and even today with the newest and best torsion balance money can buy you can only get 11.6 parts per MILLION. New Torsion Balance <https://www.nature.com/articles/s41586-018-0431-5.epdf?referrer_access_token=AvVGTXPKzx5IZ2BvbCeXZ9RgN0jAjWel9jnR3ZoTv0PGEE1clqTcXObDifjS0tqXqs3lxGXdPvbEAM8ynqscFj7fcELZiKCXKxoMnqb4-xBubiNDE73FY1mUm1mWsbpfug1i5cdw_J3iXDOJ6CG_hQg59N-6UoqggryzeBZ1jILTd2UVJhLbcIpBoaPFTFLJXW65I-Y-nAHw_1_tws_V9pImRR24QlUj8zMpiN3wmRcARzfzszmxgsUFN-4wm9nmteg2BM7LRMlz5O1FuE0_ehqjn0w0YyWray5ZATt04iM%3D&tracking_referrer=physicsworld.com> To measure the difference in Earth's gravity at 2 points one centimeter higher from the surface than the other you'd need to do better than 3 parts per BILLION. This new clock can do that, 3,900 times better than the best modern torsion balance. John K Clark -- You received this message because you are subscribed to the Google Groups "Everything List" group. To unsubscribe from this group and stop receiving emails from it, send an email to everything-list+unsubscr...@googlegroups.com. To post to this group, send email to everything-list@googlegroups.com. Visit this group at https://groups.google.com/group/everything-list. For more options, visit https://groups.google.com/d/optout.
