Theory of Everything: Unification Of Physics!
A Theory of Everything or Physics Unification is a set of theories explaining the basic laws of the universe.
Based on the curvature of space-time discovered by Einstein in the 1910s, the Space-time Model extends General Relativity to all components of the universe. It solves up to 50 enigmas of Modern Physics. Therefore, we may call the Space-time Model “Theory of Everything”. Moreover, this Physics Unification Theory is fully compatible with the most recent experimentations.
A theory of everything (ToE) is an unsolved problem. And if discovered, it would present a hypothetical single, all-encompassing, coherent theory of physics that explains and links all theories in the universe. It is the final, ultimate, or master theory.
Many long decades have passed since physicists realized that the theories of quantum mechanics and gravity don’t fit together. Therefore the combination of both the two remains unsolved. In the last few decades, researchers have pursued the problem in string theory and loop quantum gravity. However, their practitioners consider them incompatible.
In 1915, Einstein discovered General Theory of Relativity. According to Einstein, space and time are not separate and independent entities. Instead, they were only different directions in a single object called space-time. Moreover, this space-time was warped and curved by the matter and energy in it. To understand this, consider a sheet of rubber, with a weight placed on it, to represent a star. The weight will form a depression in the rubber and will cause the layer near the star to bend, rather than staying flat. If one now rolls marbles on the rubber sheet, their paths will bend, instead of being straight lines.
In 1919, a British expedition to West Africa observed light from distant stars. This light passed near the Sun during an eclipse. Thus, they found that the images of the stars were shifted slightly from their regular positions. This indicated that the paths of the light from the stars had been bent by the curved space-time near the Sun. General Relativity was confirmed.
Why Do We Need Theory Of Everything?
Currently, the two great pillars of physics are General Relativity and Quantum Mechanics. General Relativity describes the behavior of objects of cosmological proportion, while Quantum Mechanics describes objects on the atomic scale. These two theories work wonderfully in their respective domains and have not contradicted any experiment conducted to date.
However, there are phenomena in the universe which require the attention of both of these theories. For example, the singularity of a black hole needs both General Relativity for the black hole’s massive gravitational field and Quantum Mechanics for the tiny space in which it occupies. When these two theories come together, for physics unification, they go haywire and yield non-sense answers such as infinity. The assumptions break down, as you correctly pointed out.
It is somewhat curious that two theories, which describe events in the same universe, should be incompatible with each other. After all, the universe works. The universe does not break down. Our theories should at least meet the same standards. The fact that they do not mean we have yet to understand what’s going on. We have to look deeper.
So to answer this question, we look for unified theories (unification of Physics) partially because we are unsatisfied with our current ones. And partially because we want to make things simpler. The history of scientific discovery has shown again and again that the laws of nature are quite simple at its core. Things often appear complex because we do not have the full story yet. Once we collected all the puzzle pieces, we will begin to piece them together. There could be a theory that unites everything we know, and it would be simple and elegant. And hence, we get Physics Unification Theory.
The Possibility Of Physics Unification
Finding a theory of everything would be a staggering achievement, finally making sense of all the weird and beautiful things in our universe. Many physicists agree that one is just around the corner. Hawking has been one of many physicists trying to come up with a “theory of everything” to explain everything about our universe. He was following in the footsteps of Albert Einstein, who tried and failed to devise such an approach.
Stephen Hawking famously declared that a “theory of everything” (or physics unification) was on the horizon, with a 50 percent chance of its completion by 2000. Now it is 2010, and still no such theory. But according to him, there may not be a final theory to discover after all. No matter; he can explain the riddles of existence without it.
Purpose of String Theory is to reconcile general relativity (gravity) with quantum physics. A new connection (supersymmetry) exists between two fundamentally different types of particles, bosons, and fermions. Not to forget the existence of other extra unobservable dimensions to the universe.
In the early 1990s, string theory was struggling with a multiplicity of distinct theories and approaches. Instead of one theory of everything, there was five. Beginning in 1994, though, physicists noticed that, at low energies, some of these theories were “dual” to others. This means a mathematical transformation makes one theory look like another, suggesting that they may just be two descriptions of the same thing. Later, scientists showed one string theory as dual to 11-dimensional supergravity. Thus, a theory describing not only strings but membranes, too. Many scientists believe that this supergravity theory is a part of an ultimate one. This theory is “M-theory”, of which all the different string theories offer us mere glimpses.
String theory is a cold theory of everything. This means it describes everything in a cold universe, like an AdS space of flat space. Our universe is not cold, it’s thermal, and it will stay thermal because we have a cosmological constant. Thermal string theory is not yet formulated. So we can’t describe our universe just yet, but we can explain cold universes well.
The consistency conditions on string theory make it pretty clear that there is probably no other theory consistent with quantum mechanics, General Relativity, and the holographic principle. This means we already know a lot about what the theory of everything looks like.
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