On: Would it be possible to detect an industrial civil...

[nobody9999]

> Wouldn't metal dissolve over thousands of years? I'd be on the lookout for plastics.

That's not a bad idea, but finding synthetic isotopes[0] with extremely long half-lifes[1] (e.g., Tellurium-128) would clinch the deal.

[0] https://en.wikipedia.org/wiki/Synthetic_radioisotope

[1] https://en.wikipedia.org/wiki/List_of_radioactive_nuclides_b...