> 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

> 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 https://en.wikipedia.org/wiki/Synthetic_radioisotope [1] https://en.wikipedia.org/wiki/List_of_radioactive_nuclides_by_half-life#1030_seconds https://en.wikipedia.org/wiki/List_of_radioactive_nuclides_b...