>>13049707It's clearly not obviously detectable.
There is also the big issue that we're looking at the past.
300 million light years away means we're only able to look at things that happened there 300 million years ago.
That's about 1000 times the entirety of human history from the earliest fossil of homo sapiens.
A lot can happen during that time. There could be a new galactic empire a million years old building dyson spheres in its own galaxy, and we'd be oblivious of its existence.
