The moon appeared about 4.51 billion years ago, a little later than Earth. The most popular hypothesis is that the Moon was formed from fragments left after the" Giant Collision " of the Earth and Theia-a planet similar in size to Mars.
The moon is the only extraterrestrial astronomical object visited by humans. Orbit Since ancient times, people have tried to describe and explain the movement of the moon. Over time, more and more accurate theories emerged.

The basis of modern calculations is the Brown theory. Created at the turn of the XIX-XX centuries, it described the movement of the Moon with the accuracy of measuring instruments of that time. At the same time, more than 1,400 terms (coefficients and arguments for trigonometric functions) were used in the calculation.

Modern science can calculate the motion of the moon and verify these calculations with even greater accuracy. Laser location methods measure the distance to the Moon with an error of several centimeters. Not only do measurements have this accuracy, but also theoretical predictions of the Moon's position; expressions with tens of thousands of terms are used for such calculations, and there is no limit to their number if even higher accuracy is required.

In the first approximation we can assume that the Moon moves in an elliptical orbit with eccentricity 0,0549 and the semimajor axis of the orbit geocentric 384 399 km (while the semimajor axis in the system relative to the center of mass of the system "Earth — Moon" is 379 730 km away due to the effect of the moon's center of mass is not in the center of the Earth, and in the distance 4670 km not specified 434 days. The actual motion of the Moon is quite complex, and many factors must be taken into account when calculating it, for example, the flatness of the Earth and the strong influence of the Sun, which attracts the Moon 2.2 times more strongly than the Earth.