For example if the Betelgeuze system had a planet, with a theoretical large telescope on that planet and looked back at earth. It would see life and civilizations from the 15th century a.d. (~500 light years distance)
For example if the Betelgeuze system had a planet, with a theoretical large telescope on that planet and looked back at earth. It would see life and civilizations from the 15th century a.d. (~500 light years distance)
OP’s criteria is for an equal (equivalent) alien civilization.
If they were to have what we have, they would be able to detect (infer) atmospheric composition filled with the byproducts of industrialization. It’s not ideal, but IMO we’re halfway there. I can’t recall the system’s designation, but there was some hubbub about one where the Sun’s light was interrupted by some huge mass which seemed to not follow an irregular (hypothetically artificial and intelligently controlled) orbit. I can’t wait for the tech to improve, this is exciting stuff.