What Is Theory of General Relativity?
The theory of general relativity is a concept by The Great Albert Einstein from a paper he published in 1915. Physics at a simple level is divided into classical physics and modern physics. The general theory of relativity plays a very major role in modern physics.
Sir Isaac Newton during his times, conceptualized gravity and the laws of motion. Although Sir Isaac Newton described and conceptualized gravity, he was not sure how it occurred.
Newtonian mechanics started breaking in the quantum world and ceases to work out of its closed system.
When the great Albert Einstein came up with general theory of relativity, it became a base for modern physics, overcoming the boundaries of Newtonian physics. Einstein’s general theory of relativity explained how gravity occurs.
Space-Time
Space-time is a concept from the general theory of relativity. It is a model that incorporated ‘Time’ as the 4th dimension into the 3 dimensional universe that we observe. Space-time is a like a rubber fabric upon which the everything exist.
Space-time bends with respect to the mass upon it. The bend creates a well, where nearby celestial objects fall into it, which we describe as gravity. This explained how gravity occurred.
According to the general theory of relativity, the bend in space-time created by objects with mass upon it, created gravity. Even the objects falling into the well has its own gravity, but not powerful enough to overcome their pulling counterparts. It is like a tug of war. The object with the higher mass wins.
Although general theory of relativity overcame Newton’s concepts of gravity, it is not yet incorporated into the quantum world. Quantum mechanics has its own functions and rules.
Light
Einstein said that nothing can be faster than the speed of light in vacuum. Light needs no medium to propagate and Einstein said that the speed of light in vacuum is constant irrespective of the speed of the observer. He postulated the same through equations.
According to his famous mass-energy equivalence
E = mc²
mass can be interpreted in the form of energy. When objects with mass accelerates, its kinetic energy increases along with its mass.
When the speed of the object reaches the speed of light in vacuum, the mass becomes infinite and the energy needed to move it should be infinite which is not possible as it is against the law of conservation of energy and hence any object with mass cannot go faster than the speed of light in vacuum.
Light always takes shortest path to travel. When the space-time is curved due to presence of some immense mass upon it, light also bends along with it, that doesn’t mean gravity bends light, but indirectly it is.
That is the reason light bends near heavy celestial objects like black holes as explained in our post earlier.
Gravity
Getting deep into the theory, Einstein believed that gravity is a wave that travels at speed of light in vacuum. A recent study by Laser Interferometer Gravitational Wave Observatory (LIGO) proved that gravity as meant by Einstein is actually a wave and it travels at the speed of light in vacuum.
Incorporating gravity into quantum mechanics is a long time wish for theoretical physicists and we hope that science achieves it soon.
The String Theory is there for a long time, which is told to be the “Theory of Everything” has some potential to incorporate gravity into quantum physics but it has its own challenges. That is for another post in Thinkestry
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