Beamed Power

>>Aerials have to conduct, you make it too thin it melts.
> This might not follow. For AC fields most of the electricity is
> carried on the skin of the conductor, so the core could be non-conductive.

Actually, skin effect makes it worse. The rest of the metal helps
conduct the heat away but that's all.

>>1 Gigawatt/km^2 = 1kw/m^2. Sounds like it my be too much for
>>aluminium foil. You'd need to do some more checking.
> That is about the same as sunlight, 1 Kw / square metre.

Sunlight reacts with metals quite differently to microwaves.

Due to the longer wavelength, microwaves set up strong currents
in the surface- that's why they reflect the microwaves in fact;
indeed all conductors reflect microwaves for that reason.

> And if the efficiency is 99%, then the waste heat to be dissipated would
> be 10 Watts / square meter.

The problem is that the hotter it gets, the higher the resistance
becomes. The higher the resistance, the less efficient it is.
The less efficient it is, the hotter it gets.

If it reaches 700C, then the aluminium melts.

>>For an example of what happens to aluminium foil when the
>>power goes too high, stick an AOL CD in a microwave for a
>>few seconds, next to a glass of water; label side up is
>>best. (It WON'T wreck the microwave, provided you include the
>>glass of water.)
> Not sure of the mechanism here or how relevant that is.
> Aluminum conducts and reflects the microwaves.
> This can be quite spectacular, I did something like that once by
> accident.

Then you know all about it.

That's past the limit of how much power aluminium can take. There
you have 600 watts going into perhaps a square foot. The question is,
what's the smallest amount of power this effect takes?

> CR.

civilization?"