From childhood if there’s one thing we have seen it is if we drop any object from a height, it always comes down to the ground. Have you ever wondered what such force drives this? What makes that object fall to the ground? What makes a Planet revolve around the sun? Hundreds of years ago, same question was asked by Isacc Newton, one of the greatest scientists to have lived till now. He asked a simple question, what makes an apple fall down to the ground?
The answer was gravitation. Gravitation of a body is defined as its ability to attract other objects having a mass with a force that is directly proportional to the product of their masses and inversely proportional to the square of distance between them.
It is defined as
F= G Mm/R^2
Where m= mass of the first body
M= mass of the second body
R =distance between both the bodies
G= universal gravitational constant (6.023 / 10 ^-23)
In other words, gravitation of a body is defined as the ability to attract other masses.
In year 1905, a patent clerk physicist known by the name of Albert Einstein published a theory known as the Special Theory of Relativity (STR) which described the motion of particles in moving from one coordinate system to another with the help of Lorrentz Transformation, how the speed of time and length of an object behave when going from one coordinate system to another(Time Dilation and Length Contraction). STR helped in the confirmation of Maxwell’s Equations (Equation which stated how electricity and magnetism are related to each other and how light is an Electromagnetic Radiation).
But this theory could not define motion of particles in the areas where gravitational forces were considered. Therefore, A New theory known by the name of General Theory of Relativity (GTR) was put forth by Albert Einstein which also included gravitation. The STR was a special case of GTR where gravitational forces were very low and STR reduces to Newtonian Mechanics where velocity of particles were very slow as compared to the speed of light.
The GTR defined gravitation as a curvature of Space and Time where mass bends the space time. In the famous words of John Wheeler, a renowned physicist,” Mass tells Space where to bend and Space tells Mass where to go.”. This statement holds a very powerful conjecture in Physics and has laid the foundation of Modern Physics.
This definition of gravity gave rise to a new field in Physics named as “Relativistic Physics” and it has given rise to a lot of mysteries in the field of physics like “The Unified Theory which sought to unify The General Theory of Relativity and Quantum Mechanics” , ”Black Holes”, “Hawking Radiation’” etc. These problems remain a mystery till now.