Meaning of Gravitational Field
To analyze the concept of the gravitational field, we must first understand what gravitation or gravity is: it is the attraction of bodies according to their mass (the physical magnitude that is responsible for reflecting the amount of matter in the body).
This gravitation is produced by the action of the force of gravity, a force that planet Earth exerts on bodies towards its center. The sector of space at whose points the intensity level of the force of gravity is defined is known as the gravitational field.
This is a field of forces that has the ability to represent gravitation. Suppose that, in a space X, a mass R is located. This mass, by the law of gravity, will generate a certain physical situation: the gravitational field. As for the intensity of the gravitational field, it can be measured according to the gravitational acceleration that the body acquires in this field.
It is important to note that the space around the aforementioned mass R has different characteristics depending on whether the mass is present or not: in this context, we say that its presence generates a gravitational field. In the same way, if we brought another mass closer to the first one, we could appreciate a certain interaction between the two.
Of course, the existence of this field around the first mass cannot be assured beyond the scope of speculation, because we can only appreciate the gravitational field once we approach the second mass, which is called a test or witness.
A body, located at any point in space, produces a gravitational field that is identical to the quotient between the force of gravitational attraction that the element in question exerts on a witness mass that is in the place and the value of the same mass witness.
The way of understanding the gravitational field varies according to scientific theory. For relativistic physics, it is a second-order tensor field. In contrast, Newtonian physics considers the gravitational field as a vector field. According to one position or another, the field will be useful to solve different problems.
Precisely, the needs of each problem directly affect the way in which we treat the gravitational field. As indicated in the previous paragraph, according to Newtonian physics, it must be represented by a vector field, that is, an expression that associates a vector to each point (a physical quantity that is made up of a length and a direction).
One of the concepts necessary to understand the vector field is that of field lines, which serve to improve the visualization of a static vector field, either magnetic or electrostatic, among other options. In short, the use of these lines helps to generate a map of the gravitational field and its appearance we can say that they are open.
For Newtonian physics, the definition of gravitational field is the force experienced by a given particle if it is faced with a mass distribution, taking into account the unit of mass as a reference for the calculation. This leads us to conclude that it has the dimensions of an acceleration; however, scientists normally express its intensity in newtons per kilogram.
We understand by tensor field, the way in which relativistic physics represents the gravitational field, to one in which a tensor is associated to each point in space (an algebraic entity that has more than one component, used for the generalization of the matrix, the vector and the scalar in such a way that they do not depend on a coordinate system).