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> Are quantum fields actual elements of reality Yes. Just as Schroedinger/Heisenberg quantum theory describes the behavior ("reality") for particles on a smal

> Are quantum fields actual elements of reality Yes. Just as Schroedinger/Heisenberg quantum theory describes the behavior ("reality") for particles on a small scale, quantum-field theory describes the behavior of fields on a small scale.

danbruc 11y ago
In the meantime I looked for a lecture I watched some time ago and where I remembered that it suggested that fields are not real. This lecture leaves no doubt that fields are not real but just a mathematical tool. The relevant part are the first 30 minutes. I am still not absolutely confident about that but just because it is so often suggested, including the people in this thread, that fields are real. But I am now at least almost convinced that particles are real and fields are not. Really worth watching. https://m.youtube.com/watch?v=tnA7bh7dTqY https://m.youtube.com/watch?v=tnA7bh7dTqY
- Rusky 11y ago
  What exactly makes something "not real" and only a tool? Is relativity "just a mathematical tool" because planets don't have differential equation solvers in them?
  - danbruc 11y ago
    Real is probably a bad word and I can't really give a sharp definition but I can provide an analogy. Take a soccer field with two teams and a ball on it. I would prefer to describe that as 23 particles of a few different kinds (ball, field player, goal keeper) and different properties (team membership, mass, fitness, whatever). You could certainly invent a ball field and a field for both teams that are zero everywhere except where the ball or a player is located but you certainly wouldn't suggest that there are ball and soccer player fields in the universe even if they perfectly describe what happens on the playing field. On the other hand we could certainly agree that there are really players and a ball located somewhere on the field with specific masses, velocities and so on. Maybe you can look at it from a point of redundancy. If you describe ball and players as particles with locations and momenta you get a description that naturally matches what is going on. If you use a field description you have to place a lot of constraints on what is allowed and what not, players disappearing, a second ball appearing and so on. The field description has just a lot more degrees of freedom than the particle description and you have to impose a lot of constraints to suppress field configuration that are not physically possible. So it also a kind of Occam's razor argument to pick a simple and minimal description.
    - Rusky 11y ago
      Quantum physics is not about a game of soccer. It's about phenomena that do things that actually do look strange when just looking at particles. I don't see how a "natural" description is any different from the word "real" here- fields describe things particles can't, especially when trying to use your "natural" intuition.
      - danbruc 11y ago
        If you haven't yet watch the first half hour of the lecture I linked to - this makes the point way more clear than I ever could in a few comments. And it essentially settles the question. Besides the fact that there are so many people claiming that fields are real but at least for the moment I will assume that they are just wrong or until I hear a convincing argument that this point of view is wrong. There are some hints in some of the comments here that fields are really necessary in some circumstances but they are not specific and I am not knowledgeable enough to judge them. Will have to do some research on that. And by the way I am in no way suggesting any classical particle model, even without fields you still have the entire quantum mechanical machinery and there are certainly non-classical things going on. The question is whether you really need fields to describe some aspects of nature or if good old quantum mechanics is good enough and quantum field theory just makes things mathematical more accessible.
        Rusky 11y ago
        "Good old quantum mechanics" is quantum field theory.

danbruc 11y ago

In the meantime I looked for a lecture I watched some time ago and where I remembered that it suggested that fields are not real. This lecture leaves no doubt that fields are not real but just a mathematical tool. The relevant part are the first 30 minutes. I am still not absolutely confident about that but just because it is so often suggested, including the people in this thread, that fields are real. But I am now at least almost convinced that particles are real and fields are not. Really worth watching. https://m.youtube.com/watch?v=tnA7bh7dTqY https://m.youtube.com/watch?v=tnA7bh7dTqY

Rusky 11y ago
What exactly makes something "not real" and only a tool? Is relativity "just a mathematical tool" because planets don't have differential equation solvers in them?
- danbruc 11y ago
  Real is probably a bad word and I can't really give a sharp definition but I can provide an analogy. Take a soccer field with two teams and a ball on it. I would prefer to describe that as 23 particles of a few different kinds (ball, field player, goal keeper) and different properties (team membership, mass, fitness, whatever). You could certainly invent a ball field and a field for both teams that are zero everywhere except where the ball or a player is located but you certainly wouldn't suggest that there are ball and soccer player fields in the universe even if they perfectly describe what happens on the playing field. On the other hand we could certainly agree that there are really players and a ball located somewhere on the field with specific masses, velocities and so on. Maybe you can look at it from a point of redundancy. If you describe ball and players as particles with locations and momenta you get a description that naturally matches what is going on. If you use a field description you have to place a lot of constraints on what is allowed and what not, players disappearing, a second ball appearing and so on. The field description has just a lot more degrees of freedom than the particle description and you have to impose a lot of constraints to suppress field configuration that are not physically possible. So it also a kind of Occam's razor argument to pick a simple and minimal description.
  - Rusky 11y ago
    Quantum physics is not about a game of soccer. It's about phenomena that do things that actually do look strange when just looking at particles. I don't see how a "natural" description is any different from the word "real" here- fields describe things particles can't, especially when trying to use your "natural" intuition.
    - danbruc 11y ago
      If you haven't yet watch the first half hour of the lecture I linked to - this makes the point way more clear than I ever could in a few comments. And it essentially settles the question. Besides the fact that there are so many people claiming that fields are real but at least for the moment I will assume that they are just wrong or until I hear a convincing argument that this point of view is wrong. There are some hints in some of the comments here that fields are really necessary in some circumstances but they are not specific and I am not knowledgeable enough to judge them. Will have to do some research on that. And by the way I am in no way suggesting any classical particle model, even without fields you still have the entire quantum mechanical machinery and there are certainly non-classical things going on. The question is whether you really need fields to describe some aspects of nature or if good old quantum mechanics is good enough and quantum field theory just makes things mathematical more accessible.
      - Rusky 11y ago
        "Good old quantum mechanics" is quantum field theory.