धर्म एव हतो हन्ति धर्मो रक्षति रक्षितः
तस्माद्धर्मो न हन्तव्यो मा नो धर्मो हतोऽवधीत् ॥
धर्म एव हतो हन्ति धर्मो रक्षति रक्षितः
तस्माद्धर्मो न हन्तव्यो मा नो धर्मो हतोऽवधीत् ॥
This is an ongoing enterprize whose goal is to understand and encode the observed physical phenomena into a "set of fundamental principles" using the language of mathematics. Having thus established some of the elements of such a "set" using the known results of previous experiments/observations (not a prerequisite though), it then tries to predict the future outcome using those elements. This has been an astoundingly successful endeavour over the last few centuries! We have been able to understand the workings of natural laws across a wide spectrum of phenomena—from the unimaginably tiny subatomic world to the humongous and ever increasing expance of cosmos—in terms of such mathematical equations. The first revolution in, if not the beginning of, this enterprize can be attributed to Sir Isaac Newton who devised calculus to explain the everyday motion of objects including classical gravity. Since then there has been several giants like Leonhard Euler, James Clerk Maxwell, Max Planck, Albert Einstein, Erwin Schrödinger, Paul Dirac, Richard Feynman, Stephen Hawking and many others who have carried the enterprize on their shoulders. At present, we have two sets of fundamental physics theories that have been immensely successful in explaining the observations/experiments. One of these theories is the Standard Model of particle physics, which is a quantum theory meaning that it explains the physics at scales much smaller than that of an atom. The other one is the famous General Relativity theory given by Einstein that not only accurately descibes gravity as the curvature of spacetime but also explains the standard cosmology of galaxy-clusters. The hunt for a more general theory that would encompass both of these theories in appropriate limits has been the holy grail for mathematical physicists for several decades now. There have been several prominent candidates for such a unified theory like String Theory, Loop Quantum Gravity, Noncommutative Geometry, etc. but none of them have been fully successful and the hunt is still on.