{"id":27593,"date":"2017-01-07T00:48:09","date_gmt":"2017-01-07T00:48:09","guid":{"rendered":"https:\/\/yaabot.com\/?p=27593"},"modified":"2024-02-14T19:03:52","modified_gmt":"2024-02-14T13:33:52","slug":"noobs-guide-theory-quantum-gravity","status":"publish","type":"post","link":"https:\/\/entropymag.co\/noobs-guide-theory-quantum-gravity\/","title":{"rendered":"A Noob’s Guide to the Theory of Quantum Gravity"},"content":{"rendered":"\n

Quantizing gravity is not as daunting as it sounds! Or is it? Over the years, several attempts have been made to successfully quantize the other fundamental forces: electromagnetic forces, strong nuclear and weak nuclear forces. To do the same to the weakest force should not be that difficult. A relatively new subject, Quantum Gravity is supposedly 21st<\/sup> century’s attempt to revolutionize modern Physics.<\/span><\/p>\n\n\n\n

Fundamentals of 20th century Physics<\/span><\/h2>\n\n\n\n
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Fundamentals of 20th century Physics<\/span>– Source<\/a><\/figcaption><\/figure>\n\n\n\n

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Max Planck’s Quantum Theory and Einstein’s Theory of General Relativity form the two fundamental theories of Physics in the 20th<\/sup> century. While Quantum theory explains the characteristics of matter and energy at the atomic and subatomic level, the Theory of General Relativity attempts explaining the gravitational force. Feynman, Bohr, Schr\u00f6dinger and Heisenberg are some of the prominent physicists who have worked in different fields of quantum physics. <\/span><\/p>\n\n\n\n

Those include subjects like behavior of electrons, photons and other subatomic particles. Einstein tweaked his theory of special relativity and published his theory of general relativity in 1915. He used it to determine that massive objects cause a distortion in space-time, which is felt as gravity. The Quantum theory explains the physical world of the ‘very small’ and the theory of General Relativity gives us a picture of the ‘very big’ of universe. Together, they claim to cover the entire universe.<\/span><\/p>\n\n\n\n

The need for a Theory of Quantum Gravity<\/span><\/h2>\n\n\n\n

However, modern physics has encountered fuzzy space-time boundaries. An example of those are the interiors of a black hole. Inside every black-hole, an in-falling object comes to an abrupt end i.e. singularity. This hints at a strong space-time curvature and shown evidence that we have reached the limits of Einstein’s Theory of General Relativity. There is a pressing need to combine the macro and micro elements of physics.<\/span><\/p>\n\n\n\n

With high density of matter compressions and energy concentrations, the laws of the micro-world become predominant. Hence, Planck’s analysis of the quantum theory comes to our rescue here. However, the length being considered in Quantum Physics needs you to zoom into a length of 1 meter in by a factor of 10 billion, and further by a factor of 1 trillion trillion. To incorporate the laws of gravity at the scale of the quantum network has been a daunting task. Attempts to do so have failed utterly so far indicating that Einstein’s Theory of Relativity does not hold answers to all our questions.<\/span><\/p>\n\n\n\n

Hence, we need a theory that amalgamates both the fundamental concepts described above and promises a better understanding of the constituents of the universe. This new theory is better known as Quantum theory and unifies several other theories.<\/span><\/p>\n\n\n\n

What is Quantum Gravity?<\/span><\/h2>\n\n\n\n
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Flow chart explaining quantum gravity – Source <\/a><\/figcaption><\/figure>\n\n\n\n

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Quantum Gravity is a physical theory that attempts to describe the gravitational force according to the principles of quantum physics, taking into account all quantum effects. The theoretical analysis of quantum gravity places emphasis on the geometrical aspects of space. <\/span>It also tries to simplify the unsolved conceptual issues of quantum gravity, including the problem of time or the interpretation of the wave function of the universe. <\/span>This division of physics unifies the 20th<\/sup> century fundamentals and provides a consistent framework to incorporate all other fundamental forces in nature. It represents various theories like supergravity, string theory and models of canonical quantization like the loop quantum gravity, in addition to discrete models of quantum gravity.<\/span><\/p>\n\n\n\n

It generally postulates the presence of a theoretical particle – the graviton<\/em>. Before we get into what a graviton is, we need to know the 4 fundamental forces of physics: Gravity, Electromagnetism, Weak Nuclear Forces and Strong Nuclear Forces<\/strong>. <\/span>Photons mediate electromagnetism, W&Z bosons mediate Weak Forces and gluons (quarks) mediate the Strong Attraction. A graviton is a virtual particle<\/em> that mediates the gravitational force. Using the concept of a graviton, the theory of Quantum Gravity aims to prove the conjuncture of all fundamental forces of the nature. To prove the theory, a number of unified theories have been predicted and studies are being conducted to check their feasibility. Some of these unified theories are:<\/span><\/p>\n\n\n\n