On 3/14/2011 3:04 PM, Jim Lux wrote:

Not precisely true. Interplanetary space slightly dispersive. Emphasis
on *slightly*.

Kenelm Philip predicted a difference back in 1957

Modern estimates for electron density in interplanetary space of 1E6 to
1E10 per cubic meter.

dTau = e^2*Ne*L/(2*pi*m*c) * (1/f1^2 - 1/f2^2)

e= charge on an electron 1E-18 Coulomb
m = mass of an electron at rest (9.11E-31 kg)
c = velocity of light (3E8 m/s)
L = propagation distance
Ne = electron density (pick a number between 1E6 and 1E10)

f1 and f2 are the frequencies (in Hz) (assumed relatively closely spaced)

To bound the magnitudes.. for 1000 light year and 1 and 2 GHz, the
dispersion is about 1 nanosecond.


-- if you're interested in optical as opposed to RF
http://ipnpr.jpl.nasa.gov/progress_report/42-65/65I.PDF

Thanks for the link. Very nice, concise. Actually wasted some paper on it.

And I doubt sb has a hint of a clue concerning it. He'll probably think
it supports his twisted view of things.

I used to think he was a troll. I am now convinced that I was incorrect
and that the ad hominum attacks are probably deserved. Sometimes they
are the correct approach and produce results. See politics (both sides)
and national news (all) for examples.

tom
K0TAR