easy peasy

The only way we can measure a planet's mass is through its gravity as per your link - This needs a gravity model free of mathematical errors.

There are no known mathematical errors, apart from using

*Newtonian Gravitation* in lieu of

*General Relativity*. Apart from a minute discrepancy in the

*precession of the perihelion* of the planet

*Mercury* GR is not necessary.

There are some "errors" from other planets, but they are very small and depend on the

*inverse cube* of the distance to the other object not the

*inverse square*.

In any case, they can be corrected for when doing a detailed numerical simulation - a closed solution with three or more bodies is as yet not possible.

Since Fsm > Fem after calculation therefore shouldn’t moon revolve the sun in its separate orbit?

This was my answer to that question from the previous post:

**This bit is a very good question and is more than enough for one answer. **

Part of the answer is that, as you say, the sun's gravitational field (gravity) near earth is greater than the gravitation field of the earth at the moon.

The sun's gravitational field (gravity) near the earth, however, *changes only slightly over the radius of the moon's orbit around the earth.*

In other words, the whole earth-moon system is attracted by the sun by almost the same amount, so the moon orbits the earth.

But, the earth-moon system travels around the sun at a much higher tangential velocity than the moon's velocity around the earth.

So the motion is an orbit around the sun at the same radius as the earth with just *a little wriggle, with a period on one month, to make it orbit the earth*.

This diagram, to scale, shows just half a month. This just shows half a month. If I wanted to show a longer time period, the motion of the Earth and moon around the Sun would make it super-difficult to see the motion of the moon relative to the Earth. |

*Read in detail in: *WIRED, Does the Moon Orbit the Sun or the Earth?

There are many more references on this, as at first it seems a little puzzling.

**Physics Stack Exchange, Why does the moon not revolve around the sun directly?**

Then one that brings in *Gravity Wells*, **EXPLAIN xkcd, Gravity Wells**.

And there are plenty more. Just search for "Why does moon orbit the earth and not the sun?".[/b]

There are 4 possibilities in the current model - impov

1- When the earth is in between the sun and moon: Shouldn't the combined effect of earth and sun alter the orbit of the moon and its speed as well

2- when the moon is in between earth and sun: Either Moon should fall to the sun instead of earth or at least there should be a reduction in its speed and the change in its orbit around the earth

There will be some effect, but what matters is not the

*absolute value* os the sun's gravitational field near the earth, but on how

*much it changes* during the moon's orbit.

The sun's "gravity" at the

*barycentre of the earth/moon system* is what keeps the

*earth/moon system* in orbit around the sun.

3- Moon should revolve the sun in its separate orbit instead of orbiting the earth

No it shouldn't! That has been shown in all the above references.

It is not as though the moon is sitting stationary 384,400 km from the earth between the earth and the sun, it is orbiting the earth.

So half a lunar orbit later it will be on the far side of the earth, so being pulled closer to the earth.

In one orbit, the effects of the

*sun's gravitation* cancel out.

Don't forget that

Out here, at the distance we orbit the sun, the gravitational pull of the sun is only *0.0006 of the strength of the earth's gravity* on the surface of the earth.

or about 0.006 m/s

^{2}.

4- The current orbit of the earth around the sun doesn't fit for both earth and moon if there is a combined effect of binary plates (earth and moon) on sun

It does fit perfectly well, though I can't follow your "combined effect of

*binary plates* (earth and moon) on sun" is meant to mean.