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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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    What do you mean by "physical object"? You use the word a lot in this question, but you should define it or describe in the question what it means for something to be a "physical object" – Dale Jan 27 '21 at 20:50
  • @Dale For example, energy is a property of some physical system or physical entity. And the field is a property of what? After all, a field is a distribution of properties, a distribution of values. – Arman Armenpress Jan 27 '21 at 20:57
  • A distribution of physical values or physical operators in spacettime is a physical object, indeed. What is the question? – Cosmas Zachos Jan 27 '21 at 21:05
  • If an electric field is not physical then how can it affect the motion of charged particles such as electrons ? – gandalf61 Jan 27 '21 at 21:14
  • For example, there is a temperature field. It determines the temperature in different parts of space. And the temperature itself is the value of the particle velocity. The electric field determines the tension in different parts of space. The tension itself is the value of what? – Arman Armenpress Jan 27 '21 at 21:33
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    @Arman Armenpress that did not clarify your question. Please clarify your question by editing the question itself (not a comment) by including an explicit definition of what you mean by the term “physical object”. A statement that “energy is a property” does not in any way help explain what you mean by “physical object”. Please be direct in explaining the term “physical object” and please do so in the question itself. – Dale Jan 27 '21 at 23:07
  • Related. – rob Jan 27 '21 at 23:33
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    So, I know asking you to define what you mean by "physical object" may seem strange, but, it's actually crucial to your question. E.g. do you mean "something of substance" that you can maybe touch? Or do you include something that's spread out through space that you can't necessarily touch, but is real and it's affecting things. E.g., would you consider light a physical object? How about radio waves? Those are fields. How about the gravitational field, that holds the Earth in orbit, even though we're so far away from the Sun? How about the distribution of temperature in a room? – Filip Milovanović Jan 28 '21 at 02:25
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    Can someone explain the possible causes of downvotes here? It's for my understanding, because even if the question is not completely clear and well posed I wouldn't downvote it. At a certain level a confused question can be a huge chance for the OP to clarify many things to themselves – RenatoRenatoRenato Jan 28 '21 at 07:08
  • @Filip Milovanović I mean something, is real and it's affecting things – Arman Armenpress Jan 28 '21 at 07:10
  • @Dale I mean what affects real objects, for example, a device, what is real. – Arman Armenpress Jan 28 '21 at 07:32
  • @Arman Armenpress so your definition of “physical object” is anything “what affects real objects”. Then please put that definition IN THE QUESTION ITSELF!!!!!! – Dale Jan 28 '21 at 12:35
  • @Dale Added. And what will that change? All have already put downsides. – Arman Armenpress Jan 28 '21 at 13:26
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    @RenatoRenatoRenato I rarely downvote questions but I downvoted this one because of the questioner’s fixed insistence that an electric field is not physical, but must be something else. Their question is like asking “if red is not a colour then what is it ?”. – gandalf61 Jan 28 '21 at 13:51
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    @ArmanArmenpress perhaps you would not have had so many downvotes if you had listened to my advice the first time. – Dale Jan 28 '21 at 13:53
  • @Dale Yes, it is a pity. But I need an answer. Do you know the answer? – Arman Armenpress Jan 28 '21 at 13:55

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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  • If the field is not a real object, then what affects the real device? Nothing? Or does something affect and we interpret it as a field? – Arman Armenpress Jan 28 '21 at 07:08
  • Think about the gravitational field. Nowadays we've quite understood that i'ts caused by deformation of spacetime. But gravitational field existed as a theory much before we knew that. Newton invented this gravitation force (and later it was included in the field theory) for explaining the attraction between corpses, without actually knowing WHAT causes it. So I'd say that curvature causes gravitational interaction and we interpret it as a field. Same goes for other fields, but more often that not we don't have a clear explanation of what underlies the field. – Emanuele Giordano Jan 28 '21 at 23:19
  • Curvature of what? Space-time? Then you endow space-time itself with physical properties in order to deprive the field of these properties. It seems to me, based on your considerations, it is better to say this: we interpret some physical phenomena as a field, but it is not known what they really are. And this is not a matter of physics. – Arman Armenpress Jan 29 '21 at 13:02
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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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