Space/Science — HabitableZone

Space/Science » in reply to Re: You guys are both wrong:)

Newton's law...
Nick Hoffman — (archived)

F=GMm/(R^2)
A=GM/(R^2)
Where M is the big Mass
G is "big G"
R is distance

Acceleration on a test particle in LEO due to the Earth = g times [6371 km/(LEO+6371 km)]^2

For LEO=400 km, A=0.885g

Acceleration on the same particle due to the Moon = g times (Mass Moon/Mass Earth) times (R Earth/R Moon)^2

For MM/ME = 1/81, and R Moon = 400,000 km,
A= 1/81 * (6371/400,000)^2
= 1/81 * 0.000254
= 3.13 *10^-6 g

Acceleration on the same particle due to the Sun = g times (Mass Sun/Mass Earth) times (R Earth/R Sun)

For MS/ME = 3.33*10^5, and R Sun = 139,600,000 km,
A= 6.03 *10^-4 g

Of course, the "test particle" can be an entire spacecraft.

This tells us that the Sun's gravity is ~200 times more important than the Moon's in determining the Earth's orbit.

Also, out of interest, the force of gravity on the "surface" of the Sun is ~ 7g

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