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Why can’t gravity take into account the electron wavefunction? Electromagnetism and other forces work well with electrons in a superposition

eigenket 3y ago
Gravity can and must "take this into account" somehow. The problem is we don't really have a working theory of gravity which does this. There are a bunch of proposals, including this one but none of them are really complete or fully satisfying right now.
DiogenesKynikos 3y ago
The theory of electromagnetism had to be completely reworked in order to take quantum mechanics into account. The modern theory, developed from the 1920s-40s, is called "Quantum Electrodynamics." The older theory of electromagnetism (Maxwell's Equations) is the classical limit of the modern quantum theory. General Relativity is in the same situation now as Maxwell's Equations were before Quantum Electrodynamics was developed. Everyone knows that a quantum version of the theory is necessary, and that that theory will have a classical limit that is equivalent to the old theory. It's just that finding a quantum version of General Relativity is way more difficult than finding a quantum version of Maxwell's Equations. The tricks that worked for electromagnetism don't work for gravity.
- kolinko 3y ago
  Thanks for the reply!
- AnimalMuppet 3y ago
  > Everyone knows that a quantum version of the theory is necessary "Everyone knows" is not any kind of evidence. It's not even really an argument. It's, essentially, a statement that an assumption is widely shared. And, if I understand the article correctly, it may not in fact be necessary.
  - DiogenesKynikos 3y ago
    It's not a question of evidence. General Relativity does not explain how gravity interacts with quantum matter, so it must be updated. There is a whole set of no-go theorems that constrain how gravity can interface with quantum mechanics. The theory presented in this paper does modify GR to interface with quantum mechanics, albeit in a very strange way.

eigenket 3y ago

Gravity can and must "take this into account" somehow. The problem is we don't really have a working theory of gravity which does this. There are a bunch of proposals, including this one but none of them are really complete or fully satisfying right now.

DiogenesKynikos 3y ago

The theory of electromagnetism had to be completely reworked in order to take quantum mechanics into account. The modern theory, developed from the 1920s-40s, is called "Quantum Electrodynamics." The older theory of electromagnetism (Maxwell's Equations) is the classical limit of the modern quantum theory. General Relativity is in the same situation now as Maxwell's Equations were before Quantum Electrodynamics was developed. Everyone knows that a quantum version of the theory is necessary, and that that theory will have a classical limit that is equivalent to the old theory. It's just that finding a quantum version of General Relativity is way more difficult than finding a quantum version of Maxwell's Equations. The tricks that worked for electromagnetism don't work for gravity.

kolinko 3y ago
Thanks for the reply!
AnimalMuppet 3y ago
> Everyone knows that a quantum version of the theory is necessary "Everyone knows" is not any kind of evidence. It's not even really an argument. It's, essentially, a statement that an assumption is widely shared. And, if I understand the article correctly, it may not in fact be necessary.
- DiogenesKynikos 3y ago
  It's not a question of evidence. General Relativity does not explain how gravity interacts with quantum matter, so it must be updated. There is a whole set of no-go theorems that constrain how gravity can interface with quantum mechanics. The theory presented in this paper does modify GR to interface with quantum mechanics, albeit in a very strange way.