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Thanks to Ian, for telling us about his new blog. Many of the things he is finding and posting are similar to my own interests (but I usually avoid what I call “horrible depressing misfortune” and “man’s inhumanity to man” stories unless they are really big or really strange. )
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Ian Chapeski said
Hey I am a huge Xeno fan just started blogging yesterday so here it is http://thevitreousphantasm.blogspot.com !!!
Fritz said
Regarding this on your site:
“In 1960, before the Apollo missions, Encyclopedia Britannica reported the neutral point to be 20,520 miles from the Moon. A Moon with 1/6 Earth’s gravity should have a Neutral Point between 22,078 – 25,193 miles from the Moons surface. Yet after the Apollo missions, Time magazine July 25, 1969 said “At a point of 43,495 miles from the moon, lunar gravity exerted a force equal to the gravity of the Earth, then some 200,000 miles distant” In 1973 Encyclopedia Britannica, gave a new neutral point distance of 39,000 miles. The problem with all of this is, a neutral point of 43,495 miles would make the moon with not 1/6th (16%) the Earth’s gravity, but 64%. A moon with 64% of Earth’s gravity would require way more fuel and power than was supposedly available in the Apollo missions.”
All the distances quoted are incorrect. The figures “22,078 – 25,193 miles from the Moons surface” are probably correct if this is taking the elliptical orbit into account.
The way to find the average distance is to use the average distance from earth to the moon and plug it into Newton’s formula (Universal Law)
g = G x M1 x M2/d2
As the forces at the neutral point are zero you just equate two formulas.
G x Me x Mn/de2 = G x Mm x Mn/dm2
Where
Me = earth mass
Mn = mass at neutral point
Mm = moon mass
de = distance from earth to Mn
dm = distance from moon to Mn
Therefore:
G x Me x Mn/de2 = G x Mm x Mn/dm2 divide both sides by G and Mn
becomes:
Me/de2 = Mm/dm2 take square root of both sides
Me^0.5/de = Mm^0.5/dm cross multiply
81^0.5 = de/dm substitute masses of earth and moon (earth = 81 times moon)
9 = ratio of de to dm. Average distance to moon is 239,000 miles, therefore distance to neutral point is 23,900 miles
Fritz