why does light propagate? Why is it not stationary?

Answer 1

Light is an electromagnetic wave (made up of two orthogonally positioned fields, an electric field and a magnetic field).
We know that a changing ("fluxing") electric field will generate a magnetic field. We also know that a fluxing magnetic field creates an electric field.
Light is a self propagating wave....it does not require a medium in which to travel. This is because the electric field in light generates a magnetic field which in turn generates an electric field, ....., and so on.

Light always travels at the speed of light, in ANY frame of reference. No matter how fast you are traveling, you will ALWAYS measure the speed of light to be the same in a given medium.

The speed of light, by definition, is exactly 299,792,458 m/s.

EDIT:
"jimdempster", you seem to be a little mixed up.
First off, light emitted from the surface of the sun takes about 8 minutes (not seconds) to arrive on Earth.
Secondly, the time dilation you describe is incorrect from the point of view of the photon. In the photon's own reference frame (traveling at the speed of light), time is behaving "as normal" for itself, but as it looks onto the rest of the universe, everything is going by in a flash so to speed. From someone else (not traveling at the speed of light) watching the photon, the photon appears to be frozen; time seems to have stopped for it. At the speed of light (as seen from some outside, "resting" observer), time becomes infinitely dilated, but to the object itself in its own reference frame, it senses nothing wrong.
However, in the object's reference frame which is traveling at the speed of light, lengths/distances become contracted [shortened]. At the speed of light, lengths become infinitely contracted (shortened to nothing), which is a weird thing to think of indeed.

Answer 2

Light is a moving particle flux that follows the formula of a wave.
Since light are moving micro masses and come from a source as a flux it can map out the shape of an object and get reflected back to your eyes which acts as a lens to contain the information in terms of a picture and gets put together by the brain who interprets the image.
If light was a disturbance of a medium just like sound is a molecular disturbance of a material than it would be a wave.
It could then be a standing wave and go no where.
However motion of particle masses or large masses as well all move in an oscilliatory manner ;this is what Louis De Broglie called matter waves.Therefore all oscilliatory motion follow the same rules. This explains why the confusion about the nature of light = it is not Both a particle and wave,this is really a misnomer.. It a micromass which follows the same rules and reason for moving as any structured masses.This explains what happens when objects move.Or any other type of masses structurred or unstructured.
Therefore light cannot be a stationary , but is a continual moving flux of particles masses which are very directional and do not bend but can bedeflected., other wise it could not do the job its doing;that is it enables us to see and observe the Universe.

Colors of light is really the radiation of micromasses at different spacing moving at the same velocity relative to the receiver of the light.
From the spacing we can calculate the frequency that the particle collide with a surface just as if it was a wave.
Does this make sense to you?
This is the reality of light propagation so often misinterpreted.

Answer 3

How Does Light Propagate

Answer 4

Stationary in reference to what? Motion and stillness require a reference point. Light is in motion at the same speed for all observers, so it cannot be stationary for any specific reference point. Some matierials, such as metal at the proper thickness, are opaque to visible light so it does not "propagate" or travel through those materials.

Answer 5

Maxwell proved that light has to propogate, and calculated the required speed:
Light waves are the result of interaction of electric and magnetic fields as described by Maxwell's equations. These equations show that a time-varying magnetic field creates an electric field, and conversely, a time-varying electric field creates a magnetic field. The equations can be solved to derive the case in which the electric fields and magnetic fields vary in such a way that each creates the other in a self-sustaining interaction. When this is done, the result is an equation of a travelling wave that moves at the speed of 1/sqrt(e0*m0) in free space. e0 and m0 are electrical properties of space called permitivity and permeability. It turns out that the speed of light in a vacuum is exactly that value. In order for the waves to exist, they have to propogate at speed c=1/sqrt(e0m0). The fact that this speed is independent of the speed of the observer or the source led directly to the special theory of relativity.

Answer 6

what a great question! i love this question. i feel like a fool for answering before reading all the other replies but i can't wait.

of course light does not 'move' in time. being timeless it does not propagate at all in that sense or dimension. in the same sense if i am sitting totally still i do not move in space yet i continue to 'propagate' in time.

my best guess is that the timed rate of change of its magnetic field component causes the timed rate of change of its electric component (blah blah blah) and is selfsustaining (naturally occurring) and is a process that requires space to occur in but not time.

the light you see from the sun or moon or mars hasn't aged a single fraction of a second. it is never not its birthday moment and it will live its entire life (every aspect of its travels through space and prisms here on earth) in the same single moment, whether it lasts 8ish minutes coming from our sun or a million light years. light of course doesn't experience (the travel time of)space no matter how far it has travelled to get here.

it must be like living your entire life in a single moment and then suddenly ending up in the dog star system.

all i'm saying is that we humans propogate in our own 'space'. light's 'space' requires a little imagination to get an effective feeling for.

Answer 7

All light is created by the process of electrons settling down to a lower 'orbit' around an atom. In order to do this, a packet of energy must be ejected (a 'photon', or single packet of energy).

When the photon was created, it left the atom at the speed of light (the speed of light in whatever medium the photon was created in), so they travel at that speed until they strike something else. Propagation is inherent in their creation (or you'd never see them).

There have been recent developments in physics in getting photons to slow down (in certain mediums), but is it because they are in a certain medium, not a property of the photon.

Interesting thought experiment: how long does it take light to travel from the sun? 8 seconds (at the speed of light in a vacuum). But from the perspective of a photon, traveling at the speed of light, its 'clock' has stopped, so no time has transpired on the photon. So then, how long does it take a photon to travel to the Andromeda galaxy? From the photon's perspective, its clock has stopped, so no time at all! Strange universe!

Answer 8

Actually, it can be stationary.

http://news.bbc.co.uk/1/hi/sci/tech/1124540.stm

That point aside, light is energy from a radiating source, and it moves away from that source at the speed of light until the energy is absorbed by something. Light is energy that has been set in motion. In it's broadest sense, energy is motion. So your question can be reworded as, "Why is light, light?"

(I'm not very satisfied with this answer and, unless someone puts up a good answer, I may do an edit after I think of a better way to say this.)

Answer 9

Because it is a wave. That's what waves do, they propagate.

Think of a wave in the ocean or a piece of string. These are examples of what is called a transverse wave, that is the "stuff" that is doing the waving is moving at a 90deg. angle to the motion of the wave. So a little bit of the stuff or "medium" moves out of its previous location, and when it does this it exerts a pull on the stuff immediately adjacent to it. This happens because the medium is continuous, it is all touching. The newly moved bit of medium gets to moving, and so on and so forth, you now have a wave. The displacement of the medium is proof that a wave carries energy.

With light the medium is the electromagnetic field. And the characteristic speed at which waves in this particular medium travel is light.

Answer 10

It doesn't. Propagation refers to sexual reproduction. It does, however, move. It is not "stationary" because it it not matter. It is a manifestation of energy. Energy moves. Matter remains at rest unless acted upon by force. (Inertia; Newton's Laws of Motion.) You might as well ask why electricity doesn't stay in one spot. But if it did, you would be asking in the dark.