Re: What If ET Does Not Use Radio Waves

On Nov 2, 7:58 pm, Matt Giwer <jul...@xxxxxxxxxxxxxxxxxxxxxxx> wrote:
Mike Williams wrote:
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.

I did not invent this idea. I have about them in the conceptual design phase.

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 you know what you has to be corrected it is all in the engineering.
Nothing is going to move them even a fraction of a wavelength once in orbit.
There is some experiment in earth orbit now in what is described as a
"formation" where knowing the precise separation distances are important.
Probably looking for gravity waves. I forget just what they are doing.

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.

For us it is 92,000,000 miles away from a star with a 400,000 mile radius.
Physically blocking the star's light appears doable. We do it right now on
that satellite observing the solar wind.

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.

Thus spake Al Gore. We are at most a century away from being all electric
powered by fission or fusion. There goes the quantity of pollution would could
be considered a unique sign of an industrial society.

Good point, because there's essentially zero artificial pollution to
behold on Venus, whereas all of their energy is locally renewable, and
in terrific surplus at that.

Oops! forgot that you still don’t believe in the regular laws of
physics, especially if ever required to function off-world.

~ Brad Guth Brad_Guth Brad.Guth BradGuth BG / “Guth Usenet”


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