** Gravity on Earth vs Moon **

Gravity is a concept associated with matter. A gravitational field is defined for masses, there is a gravitation field around every mass that is proportional to the mass, and inversely proportional to the distance from the mass squared. Gravity on the earth, and the moon are extremely important when it comes to scientific experiments such as satellite launches, calculating satellite orbits, manned space missions, calculating paths of asteroids, and many more. There are several methods for mapping gravitational field of the earth and moon. Some are very precise methods and some methods have a considerable margin of error. In this article, we are going to discuss the methods of measuring gravitational fields of the earth and moon, the anomalies of gravitational fields of these two objects, importance of precise mapping of gravity of the earth and moon, the magnitudes of these two fields and their differences.

**Gravitational field of earth**

The gravitational field of the earth is easily calculable, if we assume the earth as a perfect sphere. If that is the case, by simply substituting the mass of the earth and the radius of the earth to the equation g = GM/R^{2} we can get a value for ‘g’ on the surface of the earth. But, the gravitational field of the earth is not uniform. Therefore, more advanced and precise techniques such as satellite mapping are required to measure the correct gravitational field of the earth. The mean or normal gravitational field strength on the surface of the earth is 9.8066 meters per seconds squared. This varies with the altitude and latitude of the place.

**Gravitational field of moon**

The gravitational field of the moon cannot be measured directly using scientific experiments performed on moon. It is necessary to use remote techniques such as satellite mapping. The only problem of using satellite mapping to map gravitational field of the moon is the synchronous rotation and revolution of the moon. Because of this reason, only the near side of the moon is precisely mapped. The far side of the moon is not mapped correctly. The moon also has gravitational anomalies. Since the mass of the moon is approximately 1/80 of the earth, and the radius is approximately 1/3.7 of the earth, a simple calculation shows that the gravitational field on the surface of the earth is equal to 1.63 meters per seconds squared. This is 16.7% percent of the gravitational field intensity of the earth. That means a mass of 100 kilograms that would give a weight of 980 N would give a weight of only 163 n on earth. This is approximately 1/6th of the weight on earth.

• Gravity or gravitational field intensity on the surface of the earth is equal to 9.8 m/s • The earth’s gravitational field is very precisely mapped, while gravitational field of the moon is poorly mapped. • The gravity of the earth is strong enough to keep an atmosphere, while the gravity of the moon is not strong enough. |