[tatjam]

It's absolutely insane how, if humanity disappeared today, we would become really hard to detect in pretty short time scales.

[tsol]

I imagine the enormous metal structures we put up are the longest standing evidence, simply because metal is normally found unrefined in earth's crust

[haltist]

Metal corrodes. Ever seen an old car sitting in the sun and rain for a long time? It turns to rust and then disappears.