On 08/20/2017 10:15 AM, Sjouke Burry wrote:

But these very clever aliens have worked out how to use galactic scale
gravitational lensing to survey the comms of lesser inteligencies.

********.
Lensing more noise/weak signal does not change the ratio,
and does not make for better reception.
And your lensing works only over millions of light years.
Which leaves you micro-micro-micro watts of received power.

If you're going to start using gravitational lensing for your telescope
it's probably "easiest" to just directly image planetary surfaces in the
area of the visible spectrum. i.e. just literally spy on them visually.

And you definitely don't need millions of light years of distance to
leverage lensing, you just need to get your telescope up an out of the
Sun's gravity well and out to a focal point of the gravity lens of the
Sun itself to get enormous amplification; in the visible spectrum we're
talking amplification factors on the order of 10^10.

About a third of a light-year away is where you'd need to be; to get
there in a reasonable time (less than a human lifetime) you'd need an
engine that could push the carrier vessel up to an average of around 1
million mph.