A Theory on Light

[Star Cannon]

I've been thinking (lo and behold!) about the light and sound waves. Sound has to go through something to get to point A to point B.
If light is just another wave, was does it have to go through to get from the sun to planet Earth? What is there in space that allows the planets and stars to just not crush into one mass and for light to travel at all? There are so few up there molecules that I'm thinking something in space is literally keeping everything 'spaced'. Like an ocean of some sort of matter that we have no real way to measure.

Star Cannon

[Hypnos]

Electromagnetic waves do not require a medium to propagate (easily shown with some vector calculus from Maxwell's equations).

Sound is a pressure disturbance that propagates in a material.

[Star Cannon]

Oh. Okay. I didn't know that. Thanks!

[Hypnos]

That being said, there is plenty of mystery in light. For example, why do all massless particles have the same finite speed limit?

[jimkopelli]

Because I said so.

[Hypnos]

Because I said so.
Great, now I can submit my thesis :D

[cloakable]

Because I said so.
Great, now I can submit my thesis :D

No, he's wrong, I'm the Deity here. :D :ph34r: .

[Melody]

cuz like the velocity prolly related to the mass and stuff

so if the mass is all massless

then

the speed is all same

[int]

That being said, there is plenty of mystery in light. For example, why do all massless particles have the same finite speed limit?

Are there such things as massless prticles? I mean, if E=mc^2 and c is a constant, and E cannot equal 0 (assuming, according to my understanding, energy is always present in particles) then m has to be > 0, no?

[Hypnos]

That being said, there is plenty of mystery in light. For example, why do all massless particles have the same finite speed limit?

Are there such things as massless prticles? I mean, if E=mc^2 and c is a constant, and E cannot equal 0 (assuming, according to my understanding, energy is always present in particles) then m has to be > 0, no?
The mass in E=mc^2 only applies to massive particles, where m = (rest mass) x (relativistic factor).

For massless particles, E = pc in all frames since massless particles travel at speed c.

The _real_ critical equation in relativistic kinematics is mc^2 = sqrt(E^2 - (pc)^2) (here m is the rest mass).

[int]

The mass in E=mc^2 only applies to massive particles, where m = (rest mass) x (relativistic factor).


OK.



For massless particles, E = pc in all frames since massless particles travel at speed c.


What's p defined as?



The _real_ critical equation in relativistic kinematics is mc^2 = sqrt(E^2 - (pc)^2) (here m is the rest mass).

OK. I'll get there eventually. I'm just starting to get back into all this stuff again. :)

[Hypnos]

For massless particles, E = pc in all frames since massless particles travel at speed c.


What's p defined as?

Particle momentum. In the case of light, seen from quantizing the classical electromagnetic field.

[Melody]

particle momentum...

what is particle momentum's units?

like regular momentum has m v.

although i know relativistic units are nifty and units in general are based on standards and not meaningful by themselves

[Hypnos]

particle momentum...

what is particle momentum's units?

like regular momentum has m v.

although i know relativistic units are nifty and units in general are based on standards and not meaningful by themselves
Quantum massless particles have energy (planck's constant) * (frequency), and momentum is that divided by the speed of light.

In relativity, E together with vector momentum form a "covector", a 4-component entity that transforms properly from one frame of referenence to another.

[Laeskis]

Light is funny in a lot of ways. It really does have momentum but no mass.
I'm glad somebody proved it to me...I was thinking of looking it up sometime. A 10 year old kid could figure out the relationship...I figured it out with a little qualitative style analysis a while back; but math is quite beyond me. (actually, I hate it with passion....it is booooring.)
Hypnos is right, ya folks should listen.
That's my...1 cent worth. yawn

[Melody]

In relativity, E together with vector momentum form a "covector", a 4-component entity that transforms properly from one frame of referenence to another.

*nods*

speaking of transformations, there is an exercise problem in one relativity book that I have been stuck on. I looked for this energy-momentum 4-vector in Gravitation and saw Lorentz transformation relations that will probably help me solve said exercise problem. After I have some breakfast. Eggs and hash browns with tabasco sauce mmmm

maybe i make new topic aboot the problem

it is a mathematical problem that should be simple but i prolly havent looked at it appropriately

[KentOhio]

Can someone tell me how the massless particles are formed? Or are they always there, and when they become luminent are ''set free?''

[Hypnos]

Can someone tell me how the massless particles are formed? Or are they always there, and when they become luminent are ''set free?''
Why can't massless particles be created/annihilated just like massive particles?

The _field_ that does this stuff in interaction with other fields is always present, due to a symmetry in space itself. At least that's the thinking in sort of the "traditional" quantum field theory point of view.