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I see no epistemic problem with a singularity existing. After all electron are singularities in the EM field, of a sort. Why shouldn't a lot of electrons togeth

by ajkjk 2y ago

I see no epistemic problem with a singularity existing. After all electron are singularities in the EM field, of a sort. Why shouldn't a lot of electrons together form a giant singularity?

Analemma_ 2y ago
I'm not at all an expert in this, but my limited understanding is that electrons are only "singularities" in classical EM; in quantum field theory they're just solitons of the underlying quantum field and can be analyzed with no infinities present. We haven't found a QFT equivalent for gravity yet, but I think the broad consensus is that the gravitational singularities will disappear once we do.
- ajkjk 2y ago
  Afaik even in qft they are effectively singularities, but I'm not an expert in that yet. It's not that they are infinities, it's that they're point discontinuities in the A field.
  - Jensson 2y ago
    In qft there are no singularities, everything are fields. Particles are just such fields, a singularity in qft would mean you have a Dirac delta shaped field, I don't think such a field exists in reality and I don't think many working physicists would believe in them either. The big reason they can't even come up with math for the black hole singularities is just because the theory doesn't support working with such Dirac shaped fields. Edit: When they say electrons doesn't have a size, what they mean is that there is no limit to how small you can make an electron, not that it is always compressed into a point.
antognini 2y ago
Truth be told, we don't really know that electrons are singularities in the EM field. Classically that's the case, of course. But in QFT, as you start to probe to shorter distances (and higher energies), our theories eventually break down because gravitational effects cannot be ignored. (For instance, how do you describe the EM field at distances shorter than a Planck length? The energies needed to probe to that limit would collapse the system into a black hole.)
- Jensson 2y ago
  > Truth be told, we don't really know that electrons are singularities in the EM field We do know they aren't such singularities. QFT says they aren't, the electron is a quantum field spread out over an area it isn't a point particle. QFT is the most well tested theory in existence, so if we can't call that "know" then we don't know anything at all in physics. What we don't know if whether there is limit to how small that quantum field can get, but we do know it can't become a point, due to the Heisenberg uncertainty principle that states that for a particle to be a point it would have to have infinite momentum. Note: Heisenberg uncertainty principle was named at the time when people still believed quantum fields were probability distributions, but since then we have established that the quantum field is the particle and not just a probability of where the particle is. That means the Heisenberg uncertainty principle establishes a relationship between momentum and size instead of just knowledge.
contravariant 2y ago
Yeah about that. Turns out position and momentum are a bit more complicated than we thought when electromagnetism was first described. Suffice it to say an electron that has a singular position is about as realistic as one that has a single momentum but exists everywhere in space.

by ajkjk 2y ago

I see no epistemic problem with a singularity existing. After all electron are singularities in the EM field, of a sort. Why shouldn't a lot of electrons together form a giant singularity?

Analemma_ 2y ago

I'm not at all an expert in this, but my limited understanding is that electrons are only "singularities" in classical EM; in quantum field theory they're just solitons of the underlying quantum field and can be analyzed with no infinities present. We haven't found a QFT equivalent for gravity yet, but I think the broad consensus is that the gravitational singularities will disappear once we do.

ajkjk 2y ago
Afaik even in qft they are effectively singularities, but I'm not an expert in that yet. It's not that they are infinities, it's that they're point discontinuities in the A field.
- Jensson 2y ago
  In qft there are no singularities, everything are fields. Particles are just such fields, a singularity in qft would mean you have a Dirac delta shaped field, I don't think such a field exists in reality and I don't think many working physicists would believe in them either. The big reason they can't even come up with math for the black hole singularities is just because the theory doesn't support working with such Dirac shaped fields. Edit: When they say electrons doesn't have a size, what they mean is that there is no limit to how small you can make an electron, not that it is always compressed into a point.

antognini 2y ago

Truth be told, we don't really know that electrons are singularities in the EM field. Classically that's the case, of course. But in QFT, as you start to probe to shorter distances (and higher energies), our theories eventually break down because gravitational effects cannot be ignored. (For instance, how do you describe the EM field at distances shorter than a Planck length? The energies needed to probe to that limit would collapse the system into a black hole.)

Jensson 2y ago
> Truth be told, we don't really know that electrons are singularities in the EM field We do know they aren't such singularities. QFT says they aren't, the electron is a quantum field spread out over an area it isn't a point particle. QFT is the most well tested theory in existence, so if we can't call that "know" then we don't know anything at all in physics. What we don't know if whether there is limit to how small that quantum field can get, but we do know it can't become a point, due to the Heisenberg uncertainty principle that states that for a particle to be a point it would have to have infinite momentum. Note: Heisenberg uncertainty principle was named at the time when people still believed quantum fields were probability distributions, but since then we have established that the quantum field is the particle and not just a probability of where the particle is. That means the Heisenberg uncertainty principle establishes a relationship between momentum and size instead of just knowledge.

contravariant 2y ago

Yeah about that. Turns out position and momentum are a bit more complicated than we thought when electromagnetism was first described. Suffice it to say an electron that has a singular position is about as realistic as one that has a single momentum but exists everywhere in space.