Szczepan Bialek wrote:
"Jim Lux" napisal w wiadomosci
...
Brian Howie wrote:

" It was known that different frequencies travel with different speeds
on a
long cable".

Is the same in air and space?
Yes in air , and no in space.

B
Depends what you mean by "space".. perfect vacuum, sure..

But what's between the planets in the Solar System isn't a perfect vacuum,
and so, it shows dispersion due to the presence of small amounts of
ionization.

Granted, it's generally a better vacuum than you are likely to achieve on
Earth by mechanical means.

Speed of waves in a dispersive medium is temperature dependent.

Maybe.. depends on the medium, I should think, and the mechanism of the
dispersion. Some dispersion might be due to ionization (which may or
may not be temperature dependent).

In the Solar System the temperatures are decreasing with the distance from
the Sun.


Temperature in a vacuum and with ionized particles is tricky to define.
It has to do with mean free path and the velocity of the particles.
When the number density gets down in the "few atoms per cubic meter" and
the mean free path gets to be meters or km, I think you need to start
thinking in different ways.

One common confusion is an assumption of a particular velocity
distribution in charged particles and then using the 11000K = 1 eV relation.