If light explores every possible path in quantum theory, does that mean it explores paths other than straight lines? I mean is it really every possible path?

[u/ch1214ch]

[u/Muroid]

Obligatory caveat that it’s a model, the purpose of a model is to give the right end answer, and it may or may not be accurately reflective of what is “really happening” in “reality” outside the scope of its predictive power.

That all said, yes, that is correct.

[u/Dear-Donkey6628 → u/Muroid]

I feel physics should not worry about the ontology of things, it’s just the philosophers trap

[u/atomicCape]

It propagates as waves, and can go around corners and travel in non-straight lines. Very similar to sound waves; if you're around a corner, you can hear it, but maybe at resuced volume. But a non-intuitive feature of waves is that when a plane wave forms (the value of the field is the same along a plane, making a flat wavefront much wider than the wavelength) it reinforces itself to keep traveling in the same direction, if the medium doesn't change.

Since visible light has a very short wavelength (less than 1 micron) any time you're more than a few millimeters away from a source, it's effectively a plane wave and the majority of the energy tends to travel in straight lines. Diffraction fringes do form, and people can easily set up circumstances that show noticable wave effects, but for incoherent light under normal circumstances, they are not very significant.

[u/FutureMTLF]

If anyone interested I can teach you QFT for free, PM me.

[u/anoncsgoplayer]

you can study curvature by looking into Einstein and tensors. where curvature is useful however is hard to determine sometimes.

[u/FutureMTLF]

You are pronably referring to some popular physics nonsense. There are no physical paths in quantum theory.

[u/joepierson123 → u/FutureMTLF]

He's referring to the path integral formulation  https://en.m.wikipedia.org/wiki/Path_integral_formulation

[u/FutureMTLF → u/joepierson123]

Contrary to popular belief, path integrals in quantum theories like QED are "integrals" over field configurations. Statements like "light explores all possible paths" is some kind of naive interpretation of that.

[u/Category-grp → u/FutureMTLF]

anyone wanna explain why this is wrong/downvoted?

[u/siupa → u/Category-grp]

Because people don’t really understand the path integral formulation

[u/Bumst3r → u/Category-grp]

The path integral formalism works for quantum field theories and for non-relativistic quantum mechanics, in the latter of which you truly do sum over all possible paths the particle could take.

[u/FutureMTLF → u/Bumst3r]

In field theories (x,t) are just labels. You "sum" over filed configurations φ(x,t). There are no physical paths, not even particles in the classical sense. The question as possed by OP, about straight and curved paths doesn't makes sense.

[u/Familiar_Break_9658 → u/FutureMTLF]

Maybe this is an eng thing, but there is a path between you and me. Doesn't mean we will or have passed that path, but it does physically exist. And if you mess with one point of the possible pathes you will see a different result.

[u/nicuramar → u/Bumst3r]

And then you get a divergent result and have to massage it to get the physical prediction. So it’s pretty debatable if light explores all paths. 

[u/FutureMTLF → u/Category-grp]

Its fine. Most people here probably have their own theory of everything.