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.
No idea.
Hawking threw a party once to see if any time travellers would turn up.
They need to go back to when earth was very hot ball of molten metal. Anything more recent than that means there is a non zero chance that the smart phone or parts of it would remain intact. There is also a chance of turning into a fossil (the phone gets buried into some mud, the mud dries and turn into a rock, eventually the phone dissolve and disappear leaving behind its print in the rock
A phone in a region with rock or ice flow might be grinded down into fine sand within hundreds of years. A smartphone touching lava will be burned to crisp within minutes
A Nokia 3310 on the other hand would survive all of these without a scratch. 🙃
Assuming the time line is stable I would say any time in before a global catastrophic event such as the K-T dinosaur extinction event since any meddling there will be likely erased by the destruction. The latest cut-off point should be when the first true humans appeared, around 2-6 million years ago.
However, how does your novel account for not disrupting the timeline? Is the model a parallel universe, i.e. going back in time creates a new reality branch? If such is the case, then there are ethical issues for the putative time traveller.
