# Original problem with maxwell's that led to special relativity

1. Feb 19, 2012

### idea2000

I've been searching through google and through various sources trying to find more details
about the original problem with maxwell's that eventually led to relativity. I'm not sure I understand the problem fully as most sources seem to only talk about it casually before moving on. Is it possible that someone could direct me to some other sources, or even better yet, provide a more detailed picture of what was going on? Thanks

2. Feb 19, 2012

### idea2000

The specific question that I have is why does maxwell's predict a constant speed of light regardless of reference frame?

3. Feb 19, 2012

### Last_Exile

Hi,

Maxwell's equations showed that (1) a changing magnetic field produces an electric field and (2) a changing electric field produces a magnetic field.

Combining these suggested the possibility that perhaps they could be combined in such a way as to co-operate with one another. That is, each could create and sustain the other. In effect, radiate away from a source.

Maxwell was convinced this could happen but the self-sustaining pattern would have to obey certain constraints. One of these was that the pattern of fields would have to travel through space at a speed precisely determined by the Maxwell equations.

When Maxwell was able to determine the value for c given by the constants used in his equations he found that it matched almost exactly to the (then) determined value for the speed of light.

The question then became "speed relative to what?"

4. Feb 19, 2012

### harrylin

You could first read the bottom of:

http://www.gap-system.org/~history/HistTopics/Light_1.html [Broken]

In summary, Maxwell proposed a wave theory of light that models light as a transverse electromagnetic wave, or, as he put it: "light consists in the traverse undulations of the same medium which is the cause of electric and magnetic phenomena". The propagation speed was assumed to be a medium constant c, which is contained in the Maxwell equations*.

Maxwell and others thought that it should be possible to detect our speed relative to that medium, just as one should be able to detect for example the speed relative to air by experiments with sound. However, such experiments did not work. Instead it appeared that the same laws of optics are valid in every inertial reference system, and that was very puzzling. How can Maxwell's theory be valid relative to any inertial reference system?

Next you could read Einstein's summary of the problem here:

http://www.bartleby.com/173/5.html
http://www.bartleby.com/173/7.html

Harald

*Due to a change of unit system that is less obvious today; see for details the bottom of:
http://en.wikipedia.org/wiki/Magnetic_constant

Last edited by a moderator: May 5, 2017