And what were the dominant terrestrial species at said time? Would there even be any? I have zero idea of what’s the expected survival rate of an iPhone in the fossil record, but I like to imagine a giant sloth stepped on one once and we are none the wiser.
Alternative title:
“Assuming the timeline is stable and time travel is possible, but no evidence is ever found until its invention, what would be the earliest acceptable time period for time-travel tourism, and the latest cut-off point no one would be allowed to go to?”
Can’t tell precisely since there are conditions, that might conserve a piece of technology to the point that it’s still going to be recovered and recognized as OOPART.
I guess that a million years or further is relatively safe bet, but even that isn’t granted.
TIL; “Out of Place Artefact”
Do not mistake with OP ART.