What is the area of the sun, moon, and earth with the least gravitational pull called?

The size of the Sun, the Moon, and the Earth is the largest of the Sun, the second largest of the Earth, and the smallest of the Moon.

The Sun is a star located at the center of the solar system, and it is almost an ideal sphere intertwined with hot plasma and magnetic fields. The diameter of the Sun is about 1,392,000 (kilometers, equivalent to 109 times the diameter of the Earth; It is about 1.3 million times the size of the Earth; Its mass is about 2 10 kilograms (330,000 times that of the Earth).

Earth is one of the eight planets in the solar system, with a diameter of kilometers and a volume of about 1,083.2 billion cubic kilometers. It is the third planet in order of closest to the sun, and it is also the terrestrial planet with the largest diameter, mass and density in the solar system, 100 million kilometers away from the sun.

The Moon, commonly known as the Moon, also known as Taiyin and Xuantu in ancient times, is the only natural satellite of the Earth and the fifth largest satellite in the solar system. The diameter of the Moon is kilometers, about three-elevenths of the diameter of the Earth, the volume is about 21990 cubic kilometers, and the mass is 1 81 of the Earth. It is the most massive moon relative to the planets it orbits and the second densest moon in the solar system, after Europa.

From their rotation around each other, it can be judged that the one with less mass rotates around the one with the most mass, hence the sun, the earth, and the moon.

The law of gravitation tells us that there is a force between any two objects that attract each other, and that the magnitude of this force is proportional to the product of the mass of the object and inversely proportional to the distance between them. If the Moon is a satellite of the Earth and not a satellite of the Sun, is it because the distance is so far that the gravitational pull of the Sun on the Earth is negligible compared to the gravitational pull of the Earth on the Moon

By consulting the data, we can easily know that the distance between the earth and the sun is about 100 million kilometers, the distance between the earth and the moon is 380,000 kilometers, the period of the earth's uniform circular motion around the sun is 365 days, the period of the moon's uniform circular motion around the earth is about 27 days, the mass of the sun is about 2* (10 to the 30th power) kilograms, the mass of the earth is about 6* (10 to the 24th power) kilograms, and the mass of the moon is about 7* (10 to the 22nd power) kilograms. So the distance between the Earth and the Sun is about 390 times the distance between the Earth and the Moon.

According to the law of gravitation f=gmm(the square of r), we can easily calculate that the gravitational pull of the Sun on the Moon is a little more than twice that of the Earth on the Moon. It can be seen that the gravitational pull of the sun on the moon is definitely not negligible. Then why only consider the Earth when studying the Moon?

We first need to understand two concepts, inertial frame of reference and non-inertial frame of reference. For Newton's laws of motion to be true, it must be in a coordinate system with acceleration a=0 (i.e., the reference object we regard as stationary or uniform linear motion). This coordinate system is called the inertial coordinate system, or inertial reference frame for short.

Conversely, if in a coordinate system where acceleration a is not equal to 0, Newton's laws of motion must be corrected by inertial centrifugal force in order to be true.

To get back to the point, if we take the earth as the frame of reference, assume that the mass of the sun is m, the mass of the earth is m, the mass of the moon is u, the distance between the sun and the earth is r, and the distance between the earth and the moon is r, then the gravitational force f1 of the sun on the moon is approximately equal to gmu (the square of r), because r is much greater than r, and the gravitational force of the earth on the moon f2 is equal to gmu (the square of r), taking the moon as the object of study Newton's second law f1+f2+f=ua, where f is the inertial centrifugal force of the earth, a is the acceleration of the Moon relative to the Earth. f=ma (this acceleration is the acceleration of the earth, of course, it can only be approximated by the giant of the sun), in vector operation, f1+f is only equal to zero [cover face], so f2=ua.

To sum up, the Moon is a satellite of the Earth not because the gravitational pull of the Sun on it is too small, but according to the condition that Newton's laws of motion are established, the gravitational force of the Sun on the Moon happens to be basically offset by the inertial centrifugal force of the Earth.

To be honest, these contents should not appear in the college entrance examination, the reason why I talk about these is mainly to tell you two very, very, very important facts, one is that any physical law can only be established with preconditions, and when we study, we must not hold the mentality of eating all over the world. The second is whether some of the so-called explanations that seem correct are true, and we still need to keep our eyes open.