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How can light experience change if it is motionless in time?

Qmechanic
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Steve
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  • Light isn't motionless, it just doesn't form an inertial system in which a clock can exist... clocks require matter and matter can't move at the speed of light. No clocks... nothing to measure time with. Light does, of course, measure distance just fine. You can count its wavelengths. – CuriousOne Mar 06 '16 at 10:20

2 Answers2

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Light is composed out of zillions of photons. The ensemble does have a distribution in time dependent on how the photons combine to give the classical electromagnetic field.

A photon (in your title) is an elementary particle that moves on the geodesic with velocity c. It does not oscillate, it is the probability of finding it at (x,y,z,t) that has a sinusoidal distribution. Its only experiences are interactions with other elementary particles. It only has energy, momentum and spin, no oscilations describe it.

This is an experiment with single photons at a time,

snlphot

From left to right photons accumulate, and the last frame is the probability distribution for finding the photon at (x,y,z) which shows a wave nature. The point footprints of the photon do not oscillate.

Alternatively a photon can be described as an excitation of the photon field which excitation moves along the geodesic with creation and annihilation operators on the photon vacuum state. Motion implies time.

"motionless in time"

is a concept that comes from misunderstanding the use of limits and ignoring that the photon is massless. This almost duplicate question's answers may be useful for you.

No mass can reach the velocity of light because it will become "infinite" and infinite energy would be needed for its existence. Only zero mass particles can move with the velocity of light. Velocity means dx/dt , a space and a time coordinate, space measured by a meter and time by a clock plus a specific reference frame where the meter and clock are . A massive system with a clock on it, depending on the relative motion of the observer, will be running slower in ticking the seconds than the clock on the observer's frame. A photon from any observer reference system will be moving with velocity c with respect to that observer, and every other one, even if he/she approaches the speed of light. But the observer being massive will never hit the speed of light. That is what the special relativity equations dictate and have been found to correctly describe what nature does.

anna v
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  • Thank you.

    So photons dont oscillate. But they do experience particle interactions, presumably outside of time?

    I have made attempts to interpret conventional theories, and have achieved a level of understanding. Enough to know I'm not entirely satisfied. I say this respectfully. It seams to me conventional science has a lot of certainty on the subject of light, without actually having an answer for fundamental what it is. What is electricity? what is magnetism? they just are! I know that what you guys are telling me is based on lots of work and consideration. But it doesnt scratch my itch

     – Steve Mar 06 '16 at 11:07
  • Why are you talking of "outside tiem". Interactions happen at four dimensional points (x,y,z,t) with delta(x)delta(y) delta(z) delta(t) constrained by the uncertainty principle. – anna v Mar 06 '16 at 11:26
  • Thand you once again. I am going to take a little time to consider what you guys have said. I understand some aspects of time and motion being correlated, more of one, less of the other. Move through space at speed of light, and you cease to move through dimension of time. And I know its been tested, and gps satellites compensate for it etc. But I still have a problem with it – Steve Mar 06 '16 at 12:21
  • GPS is another story. It is a combination of specialand general relativity it is the general relativity effects that the GPS is compensating for and essentially measuring. http://www.astronomy.ohio-state.edu/~pogge/Ast162/Unit5/gps.html – anna v Mar 06 '16 at 13:56
  • Thank you Anna for the link. I havent read it yet, but the title tells me its going to be very interesting. Yes, time dilation tracks to motion, as well as gravitational potential. When they perform the calculation, do they perform them as separate calcs, then factor them together? – Steve Mar 07 '16 at 14:40
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The electric field at a point A changes based on the electric current at A and the spatial variation of the magnetic field at A.

The magnetic field at A changes based on the magnetic current at A (which is zero, since there are no magnetic charges) and the spatial variation of the electric field at A.

So that's what happens. At every point in space there is an electromagnetic field. And a current. And the two together each has a value at every point. And those values tell the field how to change.

So the field values right there change in time. The fields don't move from here to there.

Sure, for some solutions the fields here and now might look very similar to the fields that were over there a moment ago. But that's not what happened. What happened is the fields right here changed based on what was going on right here.

Now energy and momentum flows. But that's different. And momentum flows because of stress, and the stress is a real thing, as real as the electric current. And just like current flows becasue of the charge and it's velocity to give a flux of charge. There is a flux of momentum and it's called stress. The flux of energy exists too.

But if either has a velocity that's just the velocity it has. Unlike charge, it isn't a thing that flows around according to its own clock. It is completely fixed by the fields, and the fields don't move, the value at each place changes in time.

Timaeus
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  • Are you describing an EM Aether theory? (At every point in space there is an EM field) It seams like your describing EM waves passing through a medium, like waves pass through water. Water rises and falls but does not move forward?

    Do I understand you right? it seams to me that if a field changes its value in space, and it takes a particular amount of time to do so. If it can be measured changing in time, and must be considered to be influenced, and experiencing time. Are you able to make your explanation simpler and clearer please?

     – Steve Mar 06 '16 at 09:34
  • @user108448 No, I'm describing a classical field theory. In physics a field is something that has a value at every point, so a scalar field could be a temperature or pressure field (assigns a scakar at every point). A vector field could be a velocity field for a fluid, or an electric field or a magnetic field, each assigns a vector at each point. And just like a particle can change in time, a field can too. And since all it is is a value at each point then all it can do to change is change the values at each point. So it has values at each point and the values can change. No medium required. – Timaeus Mar 06 '16 at 09:38
  • @user108448 It is very similar to water rising and falling but not going forward. But instead of a third dimension of motion, it is the values that change in time. As if the prices of houses went up and down over time, the houses don't move. – Timaeus Mar 06 '16 at 09:39
  • Thank you for your answer and comments. I know your giving me good material, and its very useful. So when your calculating vector fields, do you need a time component? – Steve Mar 06 '16 at 09:44
  • @user108448 Depends on whether you are doing relativity or not. A Newtonian vector field, no. A relativistic vector field, yes. – Timaeus Mar 06 '16 at 09:47
  • My primary motivation is understanding nature, and what is actually taking place. Not just the best formula for describing a given system, a photon in time on this occasion. I am aware a Newtonian system is just a calculation tool, and a close approximation. General Relativity is a theory of gravity however, not that it really says much about whats going on. and although it basically is a field theory, its not considered to be a measure of a physical field. Is this a fair representation? – Steve Mar 06 '16 at 09:55