## The Evolution of Gravity Theories

The acceleration that objects experience as a result of the earth's mass distribution is known as gravity. All planets can be drawn toward the force's core, which is what causes them to circle around the sun. Depending on where a particular object is on Earth, the power of this typically fluctuates. The acceleration is expressed in square meters per second. It is essential for people to trace the causes that led to the discovery of gravity as a force in order to comprehend this subject fully. For this reason, the study focuses on the central evidence that motivated the invention of gravity theories, researchers behind the proofs and every scholar responsible for facilitating the existence of arguments associated with gravity.

### Evolution of Gravity Theories

Numerous theories concerning the gravity force have been invented since the early centuries. During the 4th century, Aristotle, a Greek philosopher had a perspective that any object would not be in motion without a cause. Downward movement of massive bodies is associated with nature effects that cause them to move towards the Earth’s center where they belong naturally. On the other hand, light objects often move upwards by nature. Therefore according to Aristotle, massive bodies do not move towards the earth’s center because of the external force of gravity, but rather by inner heaviness. He further argued that heavier objects tend to fall faster compared to lighter ones. He gave an example of a rolling ball across the ground that eventually comes to rest. He argues that after the ball has stopped rolling, there is no longer an external force being exerted on the ball hence its resting point is a natural place further supporting his perspective of objects often move towards their physical locations on earth.

Later on, a Roman engineer and architect named Vitruvius challenged Aristotle’s argument by presenting the idea that gravity is not dependent on an object’s weight but its nature. He gave an example of quicksilver poured into a vessel and a stone of one hundred placed upon it, the stone only swims on the surface. Though, if the stone is replaced with a scruple of gold, the latter sinks. From this experiment, Vitruvius, therefore, concluded that there is no way gravity could be dependable on a substance’s weight, but rather its nature. Additionally, another Indian scientist named Aryabhata came up with a different approach to gravity, which explained why falls are not experienced when the earth rotates. He then developed a geocentric solar system using eccentric elliptical model of the planets. All these theories were contrasting an indication that more research had to be done to establish a valid opinion on gravitational force.

A remarkable transformation began in the 17th century when Galileo Galilei, an Italian polymath realized that objective to Aristotle’s presentations, all substances experienced acceleration when falling. With this discovery and another assumption from Robert Hooke, one of the scientists in the early centuries, that affirmed that there existed a gravitational force dependent on the on verse square of the distance, Isaac Newton used them to do more research. He took an initiative of using this information in developing a standard gravity theory in the late 17th century. Resultantly, he derived the Kepler’s three kinematic laws of planetary motion mathematically, inclusive of the elliptical orbits of the then known planets and the moon. However, there needed to be a constant factor for Newton’s mathematical formula to offer reliable force of gravity results regardless of the distance or value being used in the calculations. In 1797, the gravitational constant was measured by Henry Cavendish. The final formula derived by Newton is as shown below.Force of gravity α mass of object 1 × mass of object 2

Distance from centers squaredNewton’s principle gained massive recognition from the public especially when his concept was applied in predicting the existence of other planets such as Neptune.

However, over the years, Newton’s theory showed some inconsistencies that made his approach inaccurate and unreliable. From Newton’s presentations, he had argued about the existence of Mercury’s orbit and planet Earth orbiting the Sun which had no sufficient evidence. In 1907, Albert Einstein came up with another observation, that if an observer falls from a house’s roof, no gravitational field is experienced. His central idea, therefore, was that gravitation is equivalent to acceleration. In 1915, Einstein’s developed a new theory to fill the gap created by inconsistencies in Newton’s method. He developed the theory of relativity that accounted for inaccuracies in Newton’s assumptions. The theory was based on the fact that massive objects are bound to distort in space-time which is reflected as gravity. The space-time idea was developed by Einstein focusing on the fact that all physics laws are alike for all non-accelerating observers and that if the speed of light is measured in a vacuum, it remains constant despite the rate at which the observer travels.

To deal with equations from this perspective, Einstein developed various field equations of general relativity as his theory of space-time came to be known. These equations are a set of 10 simultaneous, nonlinear and differential equations. The solutions often found from these approaches are elements of the metric tensor of space-time which are used to calculate the geodesic paths for space-time. The meaningful solutions from Einstein’s equations include the Kerr solution for rotating massive objects, the Schwarzschild solution which explains on the space-time surrounding a spherically symmetric non-rotating uncharged heavy object and also the cosmological Robertson-Walker solution which calculates the expansion of the Earth. Besides, there is the Reissner-Nordstrom solution that explains the existence of electrical charge in central objects. Evidently, Einstein’s discovery created an excellent ground for him to make more scientific innovations and mathematical inventions.

## Conclusion

Since its realization, Einstein’s theory of general relativity has seen significant acknowledgment globally because of its ability to make reliable predictions concerning various phenomena that were impossible to determine using other earlier arguments of gravitational force. For instance, the general relativity theory accounts for the expansion of the universe and gravitational lensing that were not supported by Newton’s method. It is important to note that every individual in the discussion contributed substantially in offering more information regarding gravity force. Despite the failures encountered by other methodologies, they created an excellent opportunity for more and reliable studies concerning gravity to be done. The discoveries made by Einstein are thus vital since they have made it easier for many scientific assumptions to be accounted for, further proving its reliability. Science develops continuously, and it is possible that Einstein’s theories will provide a basis for more realizations to be established in the future.

## Bibliography

Fatema, Saba, and Hassan Muhammed. “An exact family of Einstein–Maxwell Wyman–Adler solution in general relativity.” International Journal of Theoretical Physics, 2013: 2508-2529.

Fock, Vladimir. The theory of space, time and gravitation. Elsevier. Elsevier, 2015.

Sambursky, Samuel. The physical world of the Greeks. Princeton University Press, 2014.