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snowcelt
2003-Sep-26, 04:41 AM
How come we do not put a radio telescope here? I understand that there is a high % of free electrons in this zone (150km to 1000km). If this zone can handle long range radio frequencies could it not detect long distance radio frequencies?

Pinemarten
2003-Sep-27, 09:23 AM
"Free electrons" ?
Wherewhere?
I want some!
It may lower my power bill.... :wink:

Eroica
2003-Sep-27, 04:52 PM
Unless I've completely misunderstood things, I don't think the Appleton Layer would be an appropriate location at all for a radio telescope. When Marconi, on 12 December 1901, tried to send radio signals from Cornwall, England, to Newfoundland, Canada, other physicists said he was wasting his time. Radio waves, like light waves, travel in straight lines. They can't bend around the Earth's curvature. But amazingly, Marconi's signals were detected in Newfoundland. The signals, it turned out, had been reflected back to Earth by a layer of charged particles (like your "free electrons") in the atmosphere. The Appleton Layer is one such layer. It is particularly good at reflecting high-frequency radio waves back to Earth.

Radio astronomy, however, is about receiving radio signals from outer space. Layers of charged particles in the atmosphere are more likely to reflect such waves back into outer space. I have always assumed that the best place for a radio telescope would be out in space, far away from the ionosphere and the Van Allen Radiation Belts.

Hopefully someone who actually knows about these matters will post here soon.

Pinemarten
2003-Sep-28, 04:04 AM
I tend to agree with Eroica.
An exo-atmospheric receiver would work quite well, but I think funding to 'look for little green men' is lacking at this point in our history.

tracer
2003-Oct-01, 12:01 AM
Tut tut, Pinemarten -- SETI ain't the only thing a radio telescope's good for!