Ball, R[obert] S[tawell], Sir, 1840- [from old catalog] · New York, H. Holt and company · leaf 100
a point F p move so that thedistance p s is con-stantly equal to thelength of the per-pendicular p q letfall from p upon thestraight line a b, thenthe point p traces outthe curve which iscalled a parabola. Itcan be shown that ifwe imagine one focusof an ellipse to re-main fixed while theother focus… … 82 Astronomy. in the focus at s may often be moving in an ellipsewhich is so extremely long that the part of the orbitwhich we see near the sun is indistinguishable byour observations from an exact parabola. CHAPTER XII. PARALLAX. § 66. Distance of the Moon from the Earth.— To obtain precise…
Astronomy
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