Can we build a telescope that can see the lights of an Extraterrestrial City on another planet?

It’s not impossible, but the secret to resolving smaller details at greater distances is to increase aperture size. It’s easy to do this with radio astronomy as you don’t need a single gimungous antenna; a series of smaller antennas spread out will work just as well (VLA). But to apply the same principle to the visible light spectrum is a challenge.

@RealEyesRealizeRealLies I saw that article, too. They claim that today’s technology could barely detect Tokyo from Pluto. So technology will have to make huge advances.

One can imagine a very large array of very small telescopes that self-maintain precise positions relative to one another & beam powerful signals back to Earth. It’s theoretically plausible.

Carl Sagan in Contact imagined an alien-built, world-size object covered with antennae of various sorts that picked up Earth’s first analog TV transmission in the 1940s and echoed it back to Earth digitally—decades later!

With the technology now available, it’s not even possible to literally “see” planets. All we can see are shadows and orbital “wobbles” when they pass in front of their associated stars. That is, we can “infer” that planets exist, but we can’t even see them for certainty. So that hope will have to wait for awhile, I’m afraid.

A sufficiently advanced society will be efficient with their use of energy and will keep the light on the ground when and where they need it, not shining it up and out into space.

@RealEyesRealizeRealLies
I read the research you speak of. It maybe possible. Often new methods are discovered this way.

Well any SETI research is a long shot. But we have already imaged individual planets (on iPhone in an airport so can’t link to it right now) but the images havent been the quality of seeing lights. But we can detect atmosphere composition and with new telescopes and interferometers it is technically possible.

Yes. We need to find the most powerful gravitational lens (a huge galactic supercluster) with the planet hidden behind it. The lights of the City would be greatly amplified.