@futurebird there is a nuance, though, that we suspect must be part of this methodology when it's applied for-real, but don't know enough about

which is that the total isotope balance in the ecosystem is not necessarily constant over time. we have no intuition for how it would vary but suspect it's not uniform.

so if you had a time traveler who you knew just died, and they hadn't been in the present day long enough to have exchanged much mass with it, they might indeed be noticeable

@futurebird microplastics

@futurebird Individuals who lived between 1945 and about now have greater carbon-14 levels in their bodies (from the atmospheric nuclear detonations from 1945 to 1963) than anyone who lived before.

But unless more nuclear bombs get detonated, new babies born will soon have no more in them than people who died before 1945.

@davidtheeviloverlord

Well, at least one would know you'd have exciting times in your future.

60 million years ago is an interesting period in ant evolution. The ancestor of Titanomyrma was probably around and there are so many gaps in the preservation of insects you could see some really amazing things.

Before ending up like a fossil...

@futurebird though you wouldn't be able to tell when they were from specifically, and there would be plenty of "regular" explanations such as them having had unusual exposure to radiation during their life

@futurebird though you wouldn't be able to tell when they were from specifically, and there would be plenty of "regular" explanations such as them having had unusual exposure to radiation during their life

@ireneista @futurebird

At the coroner's office, after time travel has been invented:

Detective, writing into small notebook: "So, how long ago did the deceased die?"

Coroner, taking another large swig from a bottle: "Who knows? Maybe yesterday. Maybe tomorrow. Maybe right now."

@wakame @futurebird yeah lol the hidden premise of this scenario is that time travel is noteworthy in the setting, ie. not a normal part of society yet

@ireneista @futurebird

Time Traveler: "Time travel will been a rather recent invention."

Linguist: "You know what? I will simply go back in time and buy Microsoft shares instead of getting into a profession where I have to listen to eldritch abominations like 'will been'."

Time Traveler: "Microsoft? The burger chain?"

@wakame @futurebird they really should have known that that was always going to have happened

@ireneista @futurebird

Retrohistorian: "So what happened is this: A lot of time travelers, and I mean... a lot show up on April 4th, 1975, to buy a share of Microsoft.
And Billy 'Buns' Gates, always the entrepreneur, sells each of them a burger with fries, for $20, reselling food that costs $1.20 at the time.
After that, he basically bought a company named 'McDonalds' and rebranded it.
What do we learn from that? Always compare prices whenever you go."

If a person were a time traveler how might that show up in their skeleton, eg in the isotopic analysis of their teeth?

@futurebird on another note, we don't remember who wrote it but there was a short story once about time travelers who attempt to rob the library of Alexandria right before it burns down, but get caught by local law enforcement, who correctly deduce they're time travelers because......... they attempt to pass coins that are real gold, but all identical rather than showing individual variation in their manufacture

@ireneista @futurebird love that the local authorities were wise to time travel even back in the day

@futurebird though you wouldn't be able to tell when they were from specifically, and there would be plenty of "regular" explanations such as them having had unusual exposure to radiation during their life

@ireneista @futurebird
there are at least 4 different sources of natural C14 variations; high solar activity results in more cosmic rays striking the upper atmosphere, resulting in more C14, skewing dates slightly older. Low solar activity does the opposite. Similarily, up and down variations in magnetic field or ozone layer also cause C14 variations. Large scale fires of coal, oil, and gas deposits can occur naturally, and inject large amouts of old carbon that doesn't contain any C14.

@futurebird

Microplastics?

I do remember one science fiction story where a human fossil was obviously a time traveller, because:

A) a human skeleton was found in Cretaceous rock, 60 odd million years before anything human evolved

B) the scientist studying the fossil compared an x-ray of the unique pattern of bumps inside the skull, and found a modern human who matched 100%...himself.

@llewelly @futurebird oh that is fascinating. thank you for the detail!

@ireneista @futurebird
note that some trees, some corals, and some clams all make regular growth rings that are effectively "dead" after being made, and these can be counted up and used to measure year-on-year variations in carbon 14. Those resulting records of carbon 14 variations are used to interpret carbon 14 radiometric dates.

@ireneista @futurebird
there are at least 4 different sources of natural C14 variations; high solar activity results in more cosmic rays striking the upper atmosphere, resulting in more C14, skewing dates slightly older. Low solar activity does the opposite. Similarily, up and down variations in magnetic field or ozone layer also cause C14 variations. Large scale fires of coal, oil, and gas deposits can occur naturally, and inject large amouts of old carbon that doesn't contain any C14.