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very-based-redditor t1_j9ob5vz wrote

Reply to comment by gsohyeah in What does it mean for light to be an excitation in the electromagnetic field? by Ethan-Wakefield

I have a very basic question. What is a field? I mean I know what the definition is, but what is it really? What makes a field, a field? Do they even exist? How does light, which is an excitation in a field, interact with physical things?

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Not_Pictured t1_j9oktkf wrote

All of our understanding of physics comes from making up models of reality and seeing how close to reality they match. The model of reality that treats all particles as excitation in fields is part of the single most accurate model humanity has ever come up with.

Is this model a true analogy of reality? Yes? Maybe?. At some level our 'real' understanding of realty turns into a version of "shut up and calculate" or "we don't know". It 'seems' reality is a bunch of rubber sheets stacked on top of each-other. Waves and ripples move through them and the energy from one sheet can transfer into other sheets like as if they touched eachother. Waves in one can 'bump' and create waves in other fields. "Physical things" are again just excitations in one or more of these rubber sheets.

The best answer to "what is a field?" is the definition of a field because that's what the model of reality assumes it is. True or not.

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Implausibilibuddy t1_j9ou88q wrote

> The model of reality that treats all particles as excitation in fields is part of the single most accurate model humanity has ever come up with.

Isn't that just "ether theory" with extra steps?

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agate_ t1_j9pgp8i wrote

It’s “ether theory” that works. We adopt or discard models of the universe based on whether they make accurate predictions, and the ether theory of light didn’t.

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sticklebat t1_j9y2cji wrote

Superficially, kind of? There are many differences though. One is that the ether was proposed in order to provide a rest frame for light, whereas the fields upon which modern physics is based are fully relativistic. Another is that the ether was thought of as a physical thing thing with density, velocity, etc., and whereas fields can’t really be described in those terms, at least not as directly. It’s more that fields can give rise to them.

TL;DR an ether theory is similar to fields in that they permeate all of space, but they’re fundamentally different from each other in properties and mechanics.

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Skarr87 t1_j9p6zqh wrote

A field in quantum field theory (QFT), which is what this is about, is something that has a value at each point at space time. This value can be 0 but not null. More specifically every point in space is a quantum object that is a harmonic oscillator and according to QFT this is actually what everything is. Everything is emergent from these values, for example a particular wavelength of light is a particular value of these oscillators in the electromagnetic field of oscillators and its movement through space is just this value propagating through these oscillators like a wave. Objects can have values from multiple fields. For example a neutrino interacts with the Higgs field and the weak field but not the electromagnetic field so it is famously hard to detect. It also means that light literally does not exist to it.

In my head they are kind of loosely analogous to splines where one dimensional values can control the motion or path of an object through space.

What are these oscillators and do they actually exist? We don’t know. Maybe? Probably? I believe the current consensus is they may be fundamental as in they aren’t made of anything and are irreducible but in physics every time we have thought this we were shown to be wrong. The thing is it seems to be correct, very correct. This model has made predictions that turned out to be experimental verified later.

The problem is it’s essentially a purely mathematical construct and we’re getting into the realm of philosophy asking if it’s real or not. It depends on what math actually is/describes. It might be that at the very basic level of everything all there really is is math. All we can say for sure is QFT works very well.

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TinyTarget t1_j9ohdyh wrote

Phisical things consist of atoms, which consist of subatomic particles, which are disturbances in their coresponding fields, so fields interact with other fields.

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