In what orbit does the moon rotate around the sun?

Question

We all know from physics that the planets rotate around the sun on an elliptical orbit.But since the moon orbits the earth,which in turn orbits the sun,would its orbit look like a helical spring while observing from the sun?

Answer 1

The orbit of the moon is distorted by the earth and vice versa. The orbits are also distorted slightly by the other planets. However, the distance between the earth and the moon is about 1/400 of the distance from the earth to the sun. Because of that, the moons orbit is always curved towards the sun even though it isn't a perfect ellipse.

Answer 2

A helical spring is a three-dimension structure. If you slid down a pole in a firestation, spinning around it as you slid, your head would trace the shape of a helical spring. That's not what the Moon does, its motion always keeps it near the plane of the ecliptic.

The Moon's speed around the Earth is lower than the Earth's speed around the Sun. That means that even on the Moon's "backswing", it's moving forward as seen from the Sun.

An observer on the Sun, carefully measuring the Moon, would see that it is always moving counter-clockwise as seen from solar North. It moves toward and away from the Sun, completing a cycle every month. It's also sometimes North of the plane of Earth's orbit, and sometimes South, and whether that happens when the Moon is closest to the Sun or furthest from the Sun changes over a cycle of one year.

Answer 3

The moon moves round the earth in an elliptical once in a lunation and the earth moves round the sun in an elliptic orbit once in a year. Therefore the path described by the moon in the course of a year is a wavy curve around the sun.

The moon goes round the earth about 12.5 times in one year. Therefore its path crosses the earth’s orbit about 25 times, if the planes of the orbits of the moon and earth are assumed to be coplanar.

But a hasty conclusion will be that the path is alternatively convex and concave to the sun. Actually the path is always concave to the sun.

If A, B, C, are three consecutive points where the orbit of the moon cuts the earth’s orbit (ecliptic), between A and B both the moon’s path and earth’s path are concave to the sun. Similarly between B and C also the paths are concave to the sun. But if the earth’s path was inside, the consecutive path of it will be outside.

Answer 4

In the representations of the Solar system, it is common to draw the trajectory of the Earth from the point of view of the Sun, and the trajectory of the Moon from the point of view of the Earth, in a way that seems to suggest that the trajectory of the Moon circles around the Earth in such a way that sometimes it goes backwards. In fact, this never occurs. Unlike most other moons in the Solar System, the annual trajectory of the Moon is very similar to the one of the Earth and is always curved in the same way, concave towards the Sun, and nowhere convex or even looped towards the Sun.[3][4]

A corollary of this observation is that the Moon always falls towards the Sun and not towards the Earth, said otherwise: as the Sun exercises more (about twice as much) gravitational force on the Moon than the Earth, the combined Sun-Earth "pull" that determines the path of the Moon is always directed inwards, towards the Sun.

Answer 5

The moon's motion relative to the sun is like a helical spring - you are quite right about that.

If you looked at it from one spot on the sun, though, you wouldn't see it like that - it would look as though it was zig-zagging up and down the sky, and occasionally it would disappear when it was hidden by the earth.