Jul 13, 2020 05:31 PM
https://backreaction.blogspot.com/2020/0...thing.html
EXCERPTS (Sabine Hossenfelder): . . . Before we start, let me remind you what physicists mean by a “Theory of Everything”. For all we currently know, the universe and everything in it is held together by four fundamental interactions. That’s the electromagnetic force, the strong and the weak nuclear force, and gravity. All other forces that you are familiar with, say, the van der Waals force, or muscle force, or the force that’s pulling you down an infinite sequence of links on Wikipedia, these are all non-fundamental forces that derive from the four fundamental interactions. At least in principle.
Now, three of the fundamental interactions, the electromagnetic and the strong and weak nuclear force, are of the same type. They are collected in what is known as the standard model of particle physics. The three forces in the standard model are described by quantum field theories which means, in a nutshell, that all particles obey the principles of quantum mechanics, like the uncertainty principle, and they can be entangled and so on. Gravity, however, is described by Einstein’s theory of General Relativity and does not know anything about quantum mechanics, so it stands apart from the other three forces. That’s a problem because we know that all the quantum particles in the standard model have a gravitational pull. But we do not know how this works. We just do not have a theory to describe how elementary particles gravitate. For this, we would need a theory for the quantum behavior of gravity, a theory of “quantum gravity,” as it’s called.
We need a theory of quantum gravity because general relativity and the standard model are mathematically incompatible. [...] What physicists mean by a theory of everything is then a theory from which all the four fundamental interactions derive. This means it is both a grand unified theory and a theory of quantum gravity.
This sounds like a nice idea, yes. But. There is no reason that nature should actually be described by a theory of everything. While we *do need a theory of quantum gravity to avoid logical inconsistency in the laws of nature, the forces in the standard model do not have to be unified, and they do not have to be unified with gravity. It would be pretty, yes, but it’s unnecessary. The standard model works just fine without unification.
So this whole idea of a theory of everything is based on an unscientific premise. Some people would like the laws of nature to be pretty in a very specific way... (MORE - details)
https://www.youtube-nocookie.com/embed/mdu9KvLxHFg
EXCERPTS (Sabine Hossenfelder): . . . Before we start, let me remind you what physicists mean by a “Theory of Everything”. For all we currently know, the universe and everything in it is held together by four fundamental interactions. That’s the electromagnetic force, the strong and the weak nuclear force, and gravity. All other forces that you are familiar with, say, the van der Waals force, or muscle force, or the force that’s pulling you down an infinite sequence of links on Wikipedia, these are all non-fundamental forces that derive from the four fundamental interactions. At least in principle.
Now, three of the fundamental interactions, the electromagnetic and the strong and weak nuclear force, are of the same type. They are collected in what is known as the standard model of particle physics. The three forces in the standard model are described by quantum field theories which means, in a nutshell, that all particles obey the principles of quantum mechanics, like the uncertainty principle, and they can be entangled and so on. Gravity, however, is described by Einstein’s theory of General Relativity and does not know anything about quantum mechanics, so it stands apart from the other three forces. That’s a problem because we know that all the quantum particles in the standard model have a gravitational pull. But we do not know how this works. We just do not have a theory to describe how elementary particles gravitate. For this, we would need a theory for the quantum behavior of gravity, a theory of “quantum gravity,” as it’s called.
We need a theory of quantum gravity because general relativity and the standard model are mathematically incompatible. [...] What physicists mean by a theory of everything is then a theory from which all the four fundamental interactions derive. This means it is both a grand unified theory and a theory of quantum gravity.
This sounds like a nice idea, yes. But. There is no reason that nature should actually be described by a theory of everything. While we *do need a theory of quantum gravity to avoid logical inconsistency in the laws of nature, the forces in the standard model do not have to be unified, and they do not have to be unified with gravity. It would be pretty, yes, but it’s unnecessary. The standard model works just fine without unification.
So this whole idea of a theory of everything is based on an unscientific premise. Some people would like the laws of nature to be pretty in a very specific way... (MORE - details)