# IFRs and EM waves

1. Sep 14, 2007

### alvaros

Inertial frames of reference ( IFRs ) and Electromagnetic ( EM ) waves.

What would happen if you move at c velocity ? ( at the same velocity of a EM wave )
Maxwell equations are valid ?
No relativity, please.

2. Sep 15, 2007

### alvaros

What do x, y and z mean in Maxwell equations ?
They must be measured respect to an IFR ?
I have no idea.
What was the approach before 1905 ?
Any comment would be appreciated.

3. Sep 15, 2007

### Astronuc

Staff Emeritus
The models we have wouldn't make sense for a reference frame traveling at the speed of light, certainly not for matter.

Here is Maxwell's approach in 1861 - http://vacuum-physics.com/Maxwell/maxwell_oplf.pdf

x,y,z are Cartesian spatial dimensions (coordinate system), because EM fields exist in space and their magnitude (intensity) varies with distance.

J. C. Maxwell, A Dynamical Theory of the Electromagnetic Field -
http://www.journals.royalsoc.ac.uk/content/yw7lx230g0h64637/fulltext.pdf [Broken] (probably best to use 'save target as'.)

Last edited by a moderator: May 3, 2017
4. Sep 15, 2007

### alvaros

To Astronuc: Thank you for your answer and the links.

But I wanted somebody guide me on the path EM waves -> Relativity , not just showing the theory. I want to view the need of relativity.
Thats the reason I said "no relativity, please"
What happen if we just consider classical IFRs and EM theory ?
Some books I read state that relativity is implicit in Maxwell equations. ( ?? )

5. Sep 15, 2007

### cesiumfrog

Yes, that is exactly why this thread is nonsensical.

For example, Maxwell's equations say EM waves move "at speed c". Not just "at speed c relative to the source", but always at c. At first this was interpreted to mean that Maxwell's equations are only valid in some special reference frame (the ether frame), which matches nicely with other classical waves (the speed is always constant relative to the medium) but has since contradicted experiment and inspired Einstein to propose the theory that Maxwell's equations are valid in all inertial reference frames. We can't ignore relativity in classical electromagnetism.

Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook