how does a photon move through a space vacuum?

Question

mechanical waves cause a disturbance in their medium which results in a sort of elastic restoring force. But how can a photon travel with no medium and no displacement?

Answer 1

"The answer guy" wrote "When propagating through space, photons act like a particle. ..."

... but in any case, electromagnetic waves (which constitute light) don't need a medium to support them. (Photons are merely quanta of such electromagnetic waves.)

A changing electric field with a certain vector character induces a changing magnetic field; and that changing magnetic field in turn induces a changing electric field. Together, this means that electric and magnetic fields cooperatively induce changes in each other which lead them to effectively roll round and around each other, propagating at high speeds even through empty space, like a couple of rotating, running cats, squabbling and fighting with one another.

(This analogy is very vivid to me because I once had a pair of Siamese, brother and sister cats. Every now and then, with no apparent reason, this rotating, squabbling ball of fur made by the two cats would suddenly race from one end of the house to the other, and often be reflected back again, and maybe a third time --- it seemed to me like nothing so much as conjoined electric and magnetic fields racing through the house and being reflected off the end walls!)

If you examine carefully what happens with the electromagnetic phenomena, it involves not so much an "elastic restoring force" as "continuously reinforcing changes" taking place in the separate electric and magnetiuc fields. This makes these waves quite distinct from mechanical waves.

It was of course Maxwell who realized that such combined "electromagnetic waves" would exist. He theoretically worked out their speed (in terms of certain measured quantities which separately characterised electric and magnetic properties, quantities first measured when these phenomena were thought to be completely unconnected and disjoint). Just imagine his amazement and elation when that speed, worked out from two previously "unconnected" areas of study should turn out to be essentially the already known speed of light! That is how the identification of light with electromagnetic waves was first made, a brilliant theoretical insight.

Answer 2

Photons don't act like particles any more than waves when traveling through space. it all depends on what affect you are looking at. If you imagine a cartesian coordinate system with axes x, y and z all at right angles, the classic model of a lone photon moving in the x direction is an electric field oscillating in the z direction moving along with an magnetic field which oscillates in the y direction. The frequency of the oscillations is the frequency of the photon.

Answer 3

Because of the interaction between the electric and magnetic fields that comprise a photon. A changing electric field creates a magnetic field. Likewise, a changing magnetic field creates an electric field. These two fields are always perpendicular to each other. So, as the electric field collapses, it creates a magnetic field. Once the electric field is gone there is nothing left to create the magnetic field. So the magnetic field begins to collapse. This in turn creates an electric field. This process keeps repeating and thus a photon is born.

My physics professor explained this to me by saying 'the photon keeps pulling itself up by its bootstraps.' I like this analogy.

So I guess you could consider the 'medium' to be the fields themselves. These allow the photon to propagate with no other medium, unlike physical waves.

For more information do some research into inductors and the property of inductance.

Answer 4

what you point out was a significant question 100 years ago. Physicists generally accepted the theory that light was a wave and since they knew that light traveled through space they believed there must be a substance, which they called ether, that filled up space. They had done lots of experiments to detect ether, but could not do so.

Einstein took a bunch of different observations about properties of light and concluded that light must be made of particles, or photons, even though the movement of these photons behaved as if they were waves. He won his Nobel prize for a portion of this work - the explanation for how the photoelectric effect works, but NOT for his theory of photons because it was still controversial when he was awarded the prize 15 years later.

It is very confusing to think of particles of light that move as if they are waves. I think the best way to think about it is that light is not a type of particle that you normally can hold and it is not a wave but it's nature is something different, that we cannot fully comprehend, but the wave and particle theories are useful for explaining and predicting different properties of light.

Answer 5

First responder is on the right track. A photon does not require any sort of medium through which to propagage -- when viewed as a wave, it is simply a continuing exchange of energy between electric and magnetic fields. The failed search for a propagation medium by Michelson and Morley led Einstein to the special theory of relativity.

Answer 6

The Michelson-Morley experiment demonstrated the failure of the aether model, but astute physicists such as Poincare and even Maxwell himself could have predicted such an outcome, because it was apparent that the Maxwell Equations of Electromagnetism was not invariant with respect to Galilean transformation, but with Lorentzian. Relativity theory was a rejection of the classical aether model, but actually had little to say about the nature of the vacuum in which photons propagates. Quantum theory mathematically recognized the wave-particle duality of particles in general and photons in particular, but just as Special Relativity was incomplete and was expressed in the more general form in General Relativity with curved spacetime, so was Heisenburg-Schrodinger-Bohr quantum mechanics, incomplete, and Quantum Field Theory came into the picture, ushered in by Feynman et al. In Quantum Field Theory, the vacuum is anything but "nothing", teeming with virtual particles and their interactions, where photons are the gauge bosons for virtual electrons and positrons flitting in and out of existence in both directions in time. This quantum field is Lorentzian, which is to say is in hyperbolic spacetime, so in a sense it's a updated version of the old aether concept. Cutting edge work on QFT is incorporating it with the curved spacetime of General Relativity, and the link given cites a sample paper on this subject, and the question of the role the photon plays in it and the manner it propagates. The photon indeed plays a key role in the nature of the vacuum itself, in no small way a complex world and very far from simple "nothing".

Answer 7

When propagating through space, photons act like a particle.

Since there is nothing to impede their progress in a vacuum, they pass through it with ease.....unless they are bent or altered by strong electromagnetic or gravitational forces.

Answer 8

Photonic waves propel themselves with those two right-angle waves, electrical and magnetic. And, there IS displacement.
http://en.wikipedia.org/wiki/Electromagnetic_radiation