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I read in various sources that fields in physics are some distribution of quantities at different points in space. For example, an electric field is the distribution of the value of the electric strength. But if the electric field is not a physical object (something that affects real objects and is real), but just some kind of distribution, then the property of which physical object does it reflect? In quantum field theory, everything is more complicated, where the distribution is not of values, but of entire operators. Is a quantum field a physical object? If not, what properties does it represent?

Arman Armenpress
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2 Answers2

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This is quite a philosophical question and it depends on how interpret the statement "to be a physical object". Indeed, there are very many philosophical currents in physics and they can be mostly divided into two big groups:

  • Realism: the objects described from the mathematical formulas really exist and the theories just describe what is present in nature; usually this example is made: if a tree falls in the forest and no one hears it, does it even make any sound? A realist would simply answer yes.
  • Strumentalism (antirealism): scientific theories are just tools for predicting phenomena but they need not find a counterpart in "real world". So for example the wave function of an electron does not exist in this view; it's useful for calculating the probability of finding the electron in a certain region, but it has no self existence (so, if there were other tools that could describe all phenomena without using the formalism of a wave function, then they would be equally acceptable). The strongest antirealist could also argue that the electron itself is just a mathematical object used to describe some phenomena.

So to go back to your question about fields, it's quite on you. Usually scientists tend to be realists more often than not, but this view leads to some problems in Quantum Mechanics (EPR paradox). The fact is that every measure in physics is a real number that describes the property of an object.

No one has ever measured something which is a complex number, right? And no one ever measured a field either. What you can measure is the effect of the field on a real object. After a lot of thinking about QM and reading lots of papers about paradoxes I quite let go the realistic view because it looks like it leads to too many problems and everything seems to have more sense when you accept that some theories are just that: theories. So my answer is no, fields are not "real objects" the way you're intending them in my opinion. Someone else will tell you yes, they are and (for the moment) we don't know who's right. Anyway, it doesn't have a lot of physical importance, it's a merely philosophical difference.

Emanuele Giordano
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But if the electric field is not a physical object (something that affects real objects and is real)

According to this definition, the electric field is a physical object. The electric field affects real objects and is itself real.

Dale
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