What is the true shape of light/soundwaves

[vger]

This might be one of those no-brainers that is actually REALLY easy to make sense of but hey, it's late at night, and this is a conundrum I never really thought about before, and the more I tried to wrap my brain around it, the more I felt like the most accurate analogy was similar to trying to draw a picture of a black hole... but since we can't perceive curved space, all we can do is draw something similar, that of a 3D object influencing 2D space (classic funnel diagram). So I was thinking specifically about radio waves, but a wave at any part of the light spectrum will do. I presume the best evidence we have for its behavior is the double-slit experiment. But the drawings of how a wave works still describe, essentially, particles moving in one direction, and then the other, rhythmically. Now, I can stretch my mind to conceive this, but then I start trying to imagine it as something moving in 3 dimensions; a signal being fired in 360 degrees*3 simultaneously...

 

How does one even try to visualize something this in the form of waves? Is is all a SINGLE wave? Is it millions of tiny ones, all going in slightly different directions? What the heck would this look like in 3 dimensions? Or even two for that matter, if you could see every nuance of the light being sent? Can this even be conceived without "ascending" to the 4th dimension? I never had much of a struggle with this when thinking of it as a laser beam or a flashlight (which was what science books always used for this), but then trying to think of more complex examples, the idea of a light wave suddenly feels much more theoretical. A single "noise" expands outward from the source as a rapidly expanding sphere. Even if looking at it from 4D, how can that possibly look like a wave?

Edited July 3, 2018 by vger

[p1t1o]

@vger

When we describe EM radiation as a wave or a particle, we are just painting those concepts over our observations. Sometimes it appears to behave like a wave.

What its "true physical nature" is is anyones guess at this point. If sometimes it does not appear to match your idea of what "waves" are well then you wont be the first to notice that, the term "wave-particle duality" exists for a reason. Physicists can often talk about light as both photons and electromagnetic waves even within the same sentence!

My gut feeling is that "fields" are artefacts of underlying spacetime, like a crease in paper, and not objects stuck on top of it.

 

Sound though, is well characterised and is merely propagating changes in pressure. When you do a thing with a slinky and watch waves move up and down it, you are quite literally seeing sound.

 

Outwardly expanding spherical waves are very possible, Im not sure how to explain it better!

Edited July 3, 2018 by p1t1o

[SchweinAero]

One part of your question is indeed easy to visualise. Here, I animate how sound would look if you could 1) see air pressure as darkness, and 2) see in super-slow motion. Bear in mind that the wavefronts are spherical, so this is how it would look from any direction. The usual mental image of expanding concentric circles is really pretty accurate.

[cubinator]

I think light has more than three dimensions at a small scale, so it makes sense for it to be difficult to visualize.

[Wjolcz]

I've been wondering this myself recently, but then:

1 hour ago, cubinator said:

I think light has more than three dimensions at a small scale, so it makes sense for it to be difficult to visualize.

So, I don't think it's even possible to imagine what it would look like.

[cubinator]

9 minutes ago, Wjolcz said:

 

So, I don't think it's even possible to imagine what it would look like.

I believe it is possible for a human brain to visualize four-dimensional space, with at least simple objects like a hypercube or perhaps a Penrose triangle. If you had a very, very good idea of the theory of how light behaves, and also managed to get your brain to see in 4D, you might be able to "see" what a light beam really does as it travels through space. But it would be really hard to pull off.

[HebaruSan]

A single photon is like this (in classical mechanics, at least):

A magnetic field oscillating in one plane, with an electric field oscillating perpendicular to it.