Published on *Zwillingssterns Weltenwald* (https://www.draketo.de)

*- a Filk on "X as in Fox [1]" by Cecilia Eng -*

Once we believed in the speed of the light,

and experiments show that what we thought is right,

But we search our math for another sight,

*'Cause we hope that the truth is in there.*

When we measure the speed of something somehow,

we can only check against the distance, but now

we'll show that we get it from Maxwell', and wow!

*We will know that the truth is in there!*

First we take a sheet of charge at hand,

then we move it by an unseen command,

and nabla rot B shows the field where we stand,

*And we know that the truth is in there.*

Now that formula says, our field's everywhere,

when about the electrics we never care,

but that can't be true, for our world's still there,

*And we know that the truth is in there.*

Since nabla rot E is -dB/dt,

a field can never change at once all that we see,

It takes some time, which gives us the v,

*And we guess that the truth is in there.*

So now we take a small square far from the sheet,

when we check the change in B, it then shows quite neat,

It is width times the speed times B, which we need,

*To see that the truth is in there.*

For we also know that an electric field,

round a loop is (as Stokes will quickly yield),

Just the length of the loop times the strength of the field,

*That's a clue that the truth is in there.*

For now we take both and make the loop small,

so the length in a field is its width, and we call,

"E is v times B", which gives us all

*To believe that the truth is in there.*

We then do the same for nabla rot B,

But there's a c squared so we easily see,

E is also c squared times (B divided by v),

*And we see that the truth is in there.*

For with these we can easily tell,

that v must be c which we like so damn well,

For now we are sure we're right when we yell,

*We know that the truth is in there!*

So what do we know from this funny tale?

The strength of the fields leads us through the veil,

and gives us the speed of light without fail,

*So we see that the truth is in there!*

Now we only need to measure the attraction of charge,

and then the attraction of flowing charge,

and the root of their quotient might be quite large,

*But it gives us the truth that's in there.
The invariant truth that's in there.*

*Jepp, that's a way to get the speed of light from the Maxwell equations [2] and the knowledge that our world still exists :)*

*I hope you enjoyed reading the song as much as I enjoyed writing it!*

**Links:**

[1] http://www.filkshop.de/item/59//Cecilia%20Eng%20-%20Harmony%20in%20Practice

[2] http://en.wikipedia.org/wiki/Maxwell's_equations#General_formulation