w = G . (4/3)[pi]R^3[Delta]m/R^2 = G . (4/3)[pi]R[Delta]m, (1)
and
p = GMm/d^2 (2)
Encyclopaedia Britannica, 11th Edition, "Grasshopper" to "Greek Language" Volume 12, Slice 4 · 第 8 / 63 题