Relativity: Einstein's Theory Of Gravity

The general theory of relativity is nothing but it is the Einstein's theory of gravity. It is based on two fundamental principles:

The principle of relativity which states that all the systems of reference are equivalent with respect to the formulation of the fundamental laws of physics.

The principles of equivalence, these principles of equivalence are divided into two categories the weak one which states that the local effects of motion in a curved space (gravity provides a curved space according to the general theory of relativity) are not different from those of an accelerated observer in at space. And the strong one states that the consequence of any local experiment (whether it is a gravitational or not) in a freely falling laboratory

g_μυis defined as the space-time metric. The space-time metric expresses all the geometric and causal structure of space-time.

General relativity is the discovery that space time and gravitational field are the same entity. So what we assume in general relativity is that Space-time is itself a physical object similar to that of the electromagnetic field. General relativity is the discovery that there is no space-time at all.

Although there are number of experimental confirmations of general relativity that have been found but there still a possibility that it does not hold exactly on very large scales, or in very strong gravitational forces. But the theory breaks down at the Big Bang where quantum gravity effects became very strong. The initial state of the universe is, at the beginning of the Big Bang, was a singularity.

Quantum mechanics

Quantum Theory was come across with the Planck's theory of quanta in the spectrum of black body radiation which cannot be explained with the help of classical

For the time independent case, the Schrodinger equation takes the form ((-ħ^2)/2m ∇^2+V(r))ψ(r ⃗ )=Eψ(r ⃗ ) (1.7)

Where E are the energy eigenvalues.

Many applications of quantum theory have led to successful models of nuclear physics and as a consequence, many physical phenomena can now be described using quantum interactions. The electromagnetic and weak nuclear interactions are unified into one force while the strong nuclear interaction is a force of a similar nature known as a gauge theory. Together these forces and all observed particles are combined into one self consistent theory known as the Standard Model of particle physics.

There exists, however, a distinguished scale where one would expect that typical quantum-gravity effects can never be neglected. This scale is found if one combines the gravitational constant (G), the speed of light (c), and the quantum of action (ħ) into units of length, time, mass (and energy).These are called the Plank unit.