Why is it so difficult to show the Sun, Earth and Moon on a diagram?

This means that if we know the distance of the Earth from the Sun, we can calculate the speed of the Earth that will give it a circular orbit. (Granted, Earth’s orbit isn’t a perfect circle, but it’s close enough for our purposes here.)

But what about the Moon? There is a gravitational interaction between the Moon and the Earthbut also between the Moon and the Sun. Which is stronger?

Let’s calculate the acceleration the Moon would have if it only interacted with the Sun. For distance, we can use the distance between the Earth and the Sun, which is essentially the same. (Haven’t you been paying attention?) Using the known values, I get an acceleration due to the sun with a value of 5.9 millimeters per second squared.

Now let’s imagine that the Moon only interacts with the Earth. Recalculating, I obtain an acceleration of the moon of 2.7 millimeters per second squared. So when the moon interacts so much With the Earth as with the sun, the solar interaction is stronger. Of course, the movement of the Moon depends on the sum of these forces. Look at this diagram the Moon on opposite sides of the Earth:

On the far side of the Earth, the gravitational force of both the Earth and the Sun are in the same direction. This net force will cause the Moon to move in a circular path around the Sun. On the sunny side of the Earth, the forces are in opposite directions. However, the solar force is greater, so the net force is still towards the sun. So the Moon moves in a circular path whose center is the Sun.

We have the first proof that the Earth could have been a big “snowball”

Some strange rocks from Colorado, in the United States, support the idea that about 700 million years ago our planet was covered from the poles to the equator by thick layers of ice.

Well, let’s go back to that erroneous (but common) diagram showing the path of the Moon as it orbits the Sun. Notice that at some points the Moon curves toward the Sun and at others it curves away. Well, to bend moving away from the Sun, the net force would also have to move away from the Sun. Guess what? I just demonstrated that never happens. Since the gravitational interaction between the Sun and the Moon is greater than that between the Moon and the Earth, the net force always points toward the Sun. That means the Moon is always moving in some kind of path that always curves toward the Sun.

Is that true? Yes. Look, I can try it. Here is a graph of the trajectories of the Earth and Moon as they orbit the Sun over the course of half a month. The blue curve is the trajectory of the Earth going from left to right, and the red one represents the Moon.