The universal gravitational pull acting between objects is called gravitational force. Sir Isaac Newton introduced the universal law of gravity in 1687 and used it to explain the observed motions of planets and moons. In this article, we familiarize ourselves with Newton`s law of universal gravity. The force acting between the Sun and the Earth is an example of a gravitational force. Gravitational fields are also conservative; That is, the work of gravity from one position to another is independent of the orbit. As a result, there is a gravitational potential field V(r), so Newton`s law of universal gravity can be written as a vector equation to account for the direction of the gravitational force as well as its magnitude. In this formula, the amounts in bold represent vectors. The first two conflicts with the above observations were explained by Einstein`s theory of general relativity, in which gravity is a manifestation of curved space-time and is not due to a force propagating between bodies. In Einstein`s theory, energy and momentum distort space-time near them, and other particles move in orbits determined by the geometry of space-time. This allowed for a description of the motions of light and mass that was consistent with all available observations. In general relativity, the gravitational force is a fictitious force resulting from the curvature of space-time, since the gravitational acceleration of a body in free fall is due to the fact that its world line is a geodesic of space-time.
In Newton`s law of gravity, we found that mass is a decisive quantity. We consider that mass and weight are identical, but in reality they are different. Weight is the gravitational force exerted on an object of a certain mass. The weight of the object can be obtained by multiplying the mass of the object m by the acceleration due to gravity g on the surface of the Earth. The measured acceleration due to gravity at the Earth`s surface is about 980 cm/second/second. He never, in his own words, « assigned the cause of this power. » In all other cases, he used the phenomenon of motion to explain the origin of various forces acting on bodies, but in the case of gravity, he was unable to experimentally identify the motion that generates gravity (although he invented two mechanical hypotheses in 1675 and 1717). Moreover, he refused to propose even a hypothesis about the cause of this force, arguing that it was contrary to solid science. He lamented that « philosophers have hitherto tried in vain to seek in nature the source of gravitational force, » because he was convinced « for many reasons » that there were « hitherto unknown causes » that were fundamental to all « phenomena of nature. » These basic phenomena are still being studied, and although there are many hypotheses, the final answer has not yet been found. And in Newton`s General Scholium of 1713 in the second edition of the Principia: « I have not yet been able to discover the cause of these properties of gravity from phenomena, and I do not feign hypotheses. It is enough that gravity really exists and acts according to the laws I have explained, and that it serves abundantly to explain all the movements of the celestial bodies. [34] As shown in the figure, the masses m and me are attached to both ends of the beam. The beam is attached to a solid support with a string.
The cord is attached to the center of the beam so that it can achieve balance. Now two large masses M`et M are lowered next to them. The gravitational force between the two pairs of masses causes the string to twist in such a way that the amount of torsion is compensated by the gravitational force. The gravitational force can be measured by appropriate calibration. Since we know the value of the masses and the distances between them, the only unknown quantity is G in the universal law of gravity. Thus, the value of G is calculated from the measured quantities. The universal law of gravity can explain almost everything from how an apple falls from a tree to why the moon revolves around the earth. Watch the video and understand the beauty of the law of universal gravity. In situations where one of the dimensionless parameters is large, general relativity should be used to describe the system. General relativity is reduced to Newtonian gravity within the limit of small potentials and low velocities, so Newton`s law of gravity is often called the low gravity limit of general relativity. Assuming SI units, F is measured in newtons (N), m1 and m2 in kilograms (kg), r in meters (m), and the constant G is 6.67430(15)×10−11 m3⋅kg−1⋅s−2.
[35] The value of the constant G was first accurately determined from the results of the Cavendish experiment by British scientist Henry Cavendish in 1798, although Cavendish himself did not calculate a numerical value for G. [6] This experiment was also the first laboratory test of Newton`s theory of gravity between masses. It took place 111 years after the publication of Newton`s Principia and 71 years after Newton`s death, so none of Newton`s calculations could use the value of G; Instead, he could only calculate one force in relation to another force. This is a generalization of the vector form, which is especially useful when more than two objects are involved (for example, a rocket between the Earth and the Moon). For two objects (e.g. Object 2 is a rocket, object 1 is the Earth), we simply write r instead of r12 and m instead of m2 and define the gravitational field g(r) as: Newton`s law of universal gravity is generally stated as being that each particle attracts all the other particles of the universe with a force directly proportional to the product of its masses and inversely proportional to the square of the distance between its Centres. [Note 1] The publication of the theory became known as the « first great union » because it marked the union of the gravity phenomena previously described on Earth with known astronomical behaviors. [1] [2] [3] The first laboratory test of the theory of gravity between Newton`s masses was the Cavendish experiment, conducted in 1798 by British scientist Henry Cavendish. [6] It took place 111 years after the publication of Newton`s Principia and about 71 years after his death.
