• Quick note - the problem with Youtube videos not embedding on the forum appears to have been fixed, thanks to ZiprHead. If you do still see problems let me know.

Dumb idea no.3

DrMatt

Graduate Poster
DrMatt
Joined
May 10, 2002
Messages
1,414
Here's another silly idea of mine that I figure I had better pass on to my betters for evaluation and eventual discarding.

What's the current best physical model of refraction in stuff like glass and crystals?

If it's something done with quantum mechanics.... See if there isn't a way to derive the same or a darned similar bending of light from the gravity of the nuclei of the materials, i.e. from general relativity.

If that alternate explanation can be made to work, see if the two explanations can be fused into a GUT.

...Or vice versa.

That's it, I have no idea, I just woke up in the middle of the night saying to myself "light... bends... huh?" and figured the chances are that somebody with the ability to pursue it has already had this idea, but if not, it'd be a shame if I kept it to myself and it turned out to be useful.

Okay, I've done that. Now I can :slp:
 
Well, the basic theory which determines how light bends in a medium is called Snells' Law:

n1 * sin(theta1) = n2 * sin(theta2)

where n1 is the index of refraction of the first medium (i.e., vacuum = 1) and n2 is the index of refraction of the second medium (i.e., water, glass, ect > 1). Theta1 is the angle at which the light strikes the boundary between the media, and theta2 is the angle of refraction.

I think the index of refraction has mainly to do with the density of the material the light is travelling through. No QM here; this is a basic law of optics.
 
Yes, GR predicts light bends. No, that can't explain refraction.

There is probably a QM explanation of refraction, but I'm more familiar with the classical calculation. You calculate the electromagnetic interaction of the wave with the particles of the material, and can derive the index of refraction and how it depends on wavelength very accurately.

Gravity is very much weaker than electromagnetism. We do not see gravitational effects at the particle level unless we have extraordinarily sensitive equipment and can mask out the EM effects (there is an ongoing experiment, at Brookhaven I believe where they are constructing a blob of anti-hydrogen one anti-particle at a time, in order to measure the behavior of antimatter in gravity).

GR is a tiny correction to gravity, seen only when gravitational forces are extremely large (or again, when the apparatus is extremely sensitive). We see measurable relativistic light bending near suns, but not near ordinary bits of matter on earth. And when we see it, the effect is not predicted or measured to be dependent on wavelength, unlike refraction.
 
rppa said:
There is probably a QM explanation of refraction, but I'm more familiar with the classical calculation. You calculate the electromagnetic interaction of the wave with the particles of the material, and can derive the index of refraction and how it depends on wavelength very accurately.
Click to expand...

You can calculate the index of refraction "classically" if you're given the susceptibility and permeability of the material. But you need quantum mechanics if you want to calculate those quantities from scratch (rather than just measure them), so in a sense it still rests on quantum mechanics.
 
Gravity is very much weaker than electromagnetism.
Click to expand...
Example my dad told me he saw on TV:

"Let's say I jump off the Empire State Building. I accelerate at the leisurely pace of 32 feet per second per second. But when I hit the ground, the electromagnetic repulsion between my valence electrons and those of the sidewalk stop me like *snaps fingers* that!"
 
BronzeDog said:
Example my dad told me he saw on TV:

"Let's say I jump off the Empire State Building. I accelerate at the leisurely pace of 32 feet per second per second. But when I hit the ground, the electromagnetic repulsion between my valence electrons and those of the sidewalk stop me like *snaps fingers* that!"
Click to expand...

...or when you lift a bottle of beer to your mouth you're defying the mutual gravitational attraction between the bottle and the entire planet.
 
Get the book QED The Strange Theory of Light and Matter by Richard Feynman for a good (or at least understandable by nonphysicists like me) quantum explanation of all sorts of optical phenomena, including refraction (page 50 in my copy). Typical of Feynman, it's great!
 
Refraction doesn't bend all light waves to the same degree (that's why a prism can split sun light into a spectrum). Gravity bends light to the same degree regardless of wave length.

I think that difference pretty much makes the idea a non-starter.
 
LucyR said:
...or when you lift a bottle of beer to your mouth you're defying the mutual gravitational attraction between the bottle and the entire planet.
Click to expand...
True, but it's not quite as vivid an image. :)
 
LucyR said:
...or when you lift a bottle of beer to your mouth you're defying the mutual gravitational attraction between the bottle and the entire planet.
Click to expand...

Lies. That's a damned dirty lie.

When you lift a bottle of beer towards your mouth, it's the attraction between the Tasticles in your mouth and the up-Hops in the beer that overcomes gravity.

For the love of the Flying Spaghetti Monster's Meat Sauce!

:D
 
You must log in or register to reply here.

Back
Top Bottom