Physics of Light

Dunno if this belongs in the coffee house or where, but here it goes.Disclaimer - I'm not a physicist! I'm sure that my knowledge has vast gaps.Having said that, I have a question about light - specifically about light existing as particles and as waves.Is there anyone here who knows a lot about this stuff? Or does anyone have a good forum where I could go to post a question?

Thread moved here from the Proposed New Topics forum.The topic is a slight misfit for [forum=-2], but it is a closer fit here than elsewhere.This message has been edited by AdminNWR, 02-17-2006 08:16 AM

This has been referenced on this site before. The first one discusses light, and Feynman insists that they are particles.It's probably not exactly what you want, since it doesn't discuss wave/particle duality, but it gives the intelligent layman a good starting place from whence to ask the right kind of question methinks.Its also interesting in its own right.

Possibly What do you want to know?

I wanna know:
1. Is the speed of light constant or just very very closely aproximated ?
2. What is light besides a description and manifestation of electromagnatic wave-acles thigamajiggys?
3. The light that enters a singularity, where does it go?
Sorry if these are stupid questions.

1) Constant. At least, we have never detected any variation. From the POV of relativity, it is simply a conversion factor. There is no room for it to be a dynamic quantity. It is debatable whether any change in c could be detectable as the multitude of effects would cancel out any observational effect.2) This is close to Nuggin's original question. Photons are the minimal excitations or modes of a quantum field that extends across space-time. These modes build up both the idea of "waves" upon the field, "particles", and "beams of light". All are aspects of (infinite) combinations of these modes. The bosonic photon-field cannot exist independently of the fermionic electron-field, and really they shouldn't be considered independently. Electrons are precisely the same thing, though the behaviour is qualitatively different as the electron excitations obey fermionic statistics, not bosonic statistics. This gives rise to the Pauli exclusion principle, which in turn is what gives "matter" its structure and rigidity. This is why we think of electrons as being matter, and photons being force, but this is really incorrect. Both are too inextricably linked to differentiate quite so naively.3) From the POV of GR, a singularity is an end-point (or beginning point) of space-time... an edge so to speak. It could be as simple as a dead-end, or as magical (via some deeper theory such as string theory) as a (very tight) opening to some other area of reality.Why do I get the feeling that I've just turned your three questions into thirty?

This question has also perplexed me.
A wave in water is evidence of energy passing through the medium.
Light is only a small representation of the greater electomagnetic spectrum. Electomagnetic waves are just evidence of energy passing through amedium. The nature of the medium I believe is the key.
Just a thought.

Although he doesn't directly address Nuggin's questions, if you have a few hours and a high-speed connection you can watch and hear Richard Feynman try out the lectures that eventually became "QED: The Strange Theory of Light and Matter". There's no better treatment of the properties of light for the layman.

Some kind of luminiferous aether, perhaps?

The medium/aether is the photon quantum field and its study is quantum field theory. We've been studying it for some time...Gravitation is mediated by the medium of the "metric". Its study is called General Relativity, and we've been studying that for even longer!

So then electomagnetic waves are the signature of energy passing through a particle medium of photons?

No, not really. Mechanical waves (like waves on a pond, or sound waves) can be described in terms of equations that depend on the bulk properties of a medium (like density), and a scalar field. This all works out well under classical physics.Electromagetic fields are described in terms of the Maxwell equations, and the electromagnetic field is a vector field. The Maxwell equations don't have the kind of properties under a change of coordinate system that the equations of classical mechanics do. This is a clue that there isn't a medium that they have to propagate in.The search for the "medium" of propagation for electromagnetism was refuted by the Michelson-Morley interferometer experiements in the late 1800s. This indirectly led to the development of special relativity .Cavediver is right at the deeper level of quantum field theory, electromagnetic forces involve the exchange of virtual photons between charged particles. That isn't really a medium in the sense of water or an acoustic medium, however.I get the feeling this may raise more questions than it answers as well...This message has been edited by paisano, 02-17-2006 08:44 PM

I believe the medium is there. We just do not have the tools to describe it yet.

It's not really inert. So what is it?

Yes, in a sense. Electromagnetic waves are bulk excitations (energy)of the medium of the photon field. I wouldn't describe it as a particle medium, because what we typically call a (real) particle is just one particular mode of excitation.This message has been edited by cavediver, 02-18-2006 07:26 AM