Quantum gravity can be described in one word as a missing puzzle piece in the understanding of the known universe. In order to find this piece one needs to combine quantum theory and general relativity. There is no doubt about these theories that they have revolutionized the world of physics. Quantum theory describes the behavior of matter at the smallest scale. Quantum theory describes the behavior of matter at very small distances for instance the attraction of elementary parnge as it sounds, it has accurate answers for predicting the outcomes of experiments. That’s the reason physicists have learned to live with it.
Gravity is the force that makes apples fall off the trees. At the start there were problems with the newton’s view of gravity, in the start of the 20th century, it was the major conflict and this conflict was solved by Einstein’s theory of General Relativity (Learn more about this conflict here). The gravitational attraction between bodies is just a consequence of the way in which space, time and matter interact with each other. According to the Theory of General Relativity, the geometry of space and time becomes distorted by large masses and other bodies move around this large mass on a distorted fabric of space time, this appears to be that they are influenced by their gravitational attraction. The discordance of geometry means that in the vicinity of extremely heavy objects, the sum of the three angles in a triangle can be different from 180 degrees. There can be regions in space which are bigger on the inside but can’t be seen from the outside. General relativity explains that why the time in the clock of GPS satellite orbiting the earth, runs a little bit faster than the clock on the surface of the earth which is quite important for the accuracy of the GPS.
Now both the Quantum theory and The General Relativity have advanced our understanding of the physics of objects at different scales, but there are some situation where both theories point at totally opposite directions. Classical physics is sufficient in explaining our daily life problems. General Relativity beautifully describes the gravitational force between the massive objects like galaxies and stars. Quantum theory on the other hand accurately describes what happens at the smallest length scales but only when the gravitational effect is negligible. So what about the situation in which involves the objects which are very heavy and very small at the same time. To describe such a situation we need a Theory of Quantum Gravity, which combines both quantum theory and general relativity. To understand most of the physical phenomenon, quantum theory and general relativity are sufficient, but there still is a gap which needs to be filled and quantum gravity can fill this gap and can bring us one step closer to a complete understanding of the known universe. We understand very little about the big bang and the center of black holes. Big Bang started with small particles so in order to understand this we need quantum theory and same goes for the center of the black hole. Physicists are very interested in quantum gravity because right now it’s one of the last puzzles to understand the known universe completely. Quantum gravity can answer, what precisely happens at the center of a black hole? What is dark matter? Why the cosmic microwave backgrounds are uniformly distributed? And finally, what was there before the Big Bang?
(If you find any error or miscalculation in this article then please feel free to share in comment and if you want to expand this article then comment below)