Re: Cerenkov light

[moroney@xxxxxxxxxxxxxxxxxxxxxxx (Michael Moroney)]

"Sorcerer" <Headmaster@xxxxxxxxxxxxxxxxxx> writes:

>"andy everett" <vze2qxq3@xxxxxxxxxxx> wrote in message 
>news:kvPlh.2312$T%3.1372@xxxxxxxxxxx

>| Nice pictures, different physics. See:
>| http://en.wikipedia.org/wiki/Aurora_%28astronomy%29

>Charged particles travelling at velocities greater than 300,000 km/sec

Impossible. Greater than c.

Charged particles travelling at greater than the speed of light _through
that medium_.  If the speed of light through a substance was 250,000 km/sec
a charged particle travelling at 270,000 km/sec would produce Cherenkov 
radiation. Analogous to the sonic boom from a jet travelling faster
than the speed of sound in air.

>in atmosphere cause Cherenkov radiation,

> and that's just what is
>happening with the aurora as these images clearly demonstrate.
> http://antwrp.gsfc.nasa.gov/apod/ap980222.html
> http://antwrp.gsfc.nasa.gov/apod/ap050219.html
> http://antwrp.gsfc.nasa.gov/apod/ap970402.html
> http://antwrp.gsfc.nasa.gov/apod/ap050222.html

The descriptions of the first three make it clear the auroras are
from the atmosphere's atoms or molecules, which is different from
Cherenkov radiation.