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Wednesday, June 08, 2011

The Impedance of Free Space



The impedance of free space is ~120π, or about 377 Ohms.

  1. What does that mean?
  2. Does nature oppose the propagation of light? 
  3. If it does, would we even see star light?
  4. Or is this a fee that, once paid, admits to a photon the right to propagate until it collides with something else?



It turns out that the "impedance" of free space is really just a ratio of strengths.


It is the ratio of the electric field strength, to the magnetic field strength.


Its numerical values are just an artifact of the definition of the ampere and the meter.

It might be interesting to work backwards and say that the impedance of free space is one and see how that could lead to a useful set of units for Maxwell's equations.




1 comment:

Anonymous said...

I have a vague idea that I want to sort out. Every conductive material has a skin depth at a specific frequency. Does free space in some way have a skin depth? Well it's a nuts idea. I'll see what happens when I try to plug in physical units into the equations.