Re: What If ET Does Not Use Radio Waves

Wasn't it Matt Giwer who wrote:
In order to be able to see artificial lights on a planet at a distance of 10 light years, we'd need to build a telescope with a (synthetic) aperture of something like 100 kilometres. Projects currently being considered for launch in the next 20 years have synthetic apertures no greater than 100 metres.

You say the next 20 years. I was thinking about 50 years where the design concepts are being developed today. So make it an entire century from now. What's the rush?

I was thinking of putting telescopes in earth or solar orbit and using their separation as the baseline.

I don't think that there are any serious designs being worked on for such large separations yet. You can't just take designs that work for 100 metres separation and expand them to work for thousands of kilometres. One significant problem is that you have to fly the mirrors in a formation that's accurate to the precision of less than a wavelength of the light that you're trying to capture, but the measurement and adjustment signals are subject to light speed delays.

As well as the problem of raw resolution, there's also the problem that the planet is rather close to a sun that's billions of times brighter.

I guess those problems may be resolvable, but I don't see it happening until an awful long time we've already determined whether there's a technological civilization on the target planet by observing the spectrum of the pollution in their atmosphere.

--
Mike Williams
Gentleman of Leisure
.

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