[AlexAndScripts]

https://en.m.wikipedia.org/wiki/Silurian_hypothesis

Would we know if they went to space? How long would a geostationary satellite remain?

It's both haunting and brilliant to think about the idea of entire other intelligent species and civilisations having lived on this planet without us ever knowing. Fire and iron and cities and empires and "great people", cultures and religions and stories and families... Civilisations and species rising and falling throughout the eons. It feels a little reminiscent of Sagan's "Pale Blue Dot", but on the scale of time, not space. I wonder if they might have considered this too.

[Aerroon]

From what I understand an industrial civilization would've left evidence that would've been found by now. Building ruins, mines, unnatural concentrations of certain elements that let us determine atmospheric composition etc.