Yeah, I thought about adding the caveat “unless they evolve to live on land”, but I was lazy.
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Also space dust and lunar quakes.
https://science.nasa.gov/science-news/science-at-nasa/2006/15mar_moonquakes
The Apollo 12, 14, 15, and 16 instruments faithfully radioed data back to Earth until they were switched off in 1977.
Damnit!
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It’s been a staple of science fiction for at least 80 years starting with Lovecraft and continuing right up to Tim Powers.
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Lovecraft was writing this sort of thing before the 1920s. His whole ouevre was based on the idea that there had been other civilizations on Earth before ours, some native, some extraterrestrial colonists.
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Also, it can be really hard to know for sure whether something is a stone tool (or a byproduct of tool production) or not. You see controversies all the time over whether lithics at a particular site might have been trampled by animals or banged in a stream instead of worked by humans. I worked with a guy who had never seen tools made out of crappy rhyolite before, and he nearly discarded a great deal of debitage without recognizing it. It was only as archaeologists began looking at how modern people make stone tools and experimenting with making stone tools that we got a better idea of what wasn’t natural. If an earlier civilization made things a lot differently than humans do, it would be hard to recognize.
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I read somewhere that the total amount of earth excavated in human history is enough to cover the Earth’s surface ankle deep.
Edit:
Humans as major geological and geomorphological agents in the Anthropocene: the significance of artificial ground in Great Britain
http://rsta.royalsocietypublishing.org/content/roypta/369/1938/1056.full.pdf?maxtoshow=&hits=80&RESULTFORMAT=1&andorexacttitle=and&andorexacttitleabs=and&andorexactfulltext=and&searchid=1&FIRSTINDEX=0&resourcetype=HWCIT
(Okay, granted, the ancient astronaut on the cover of this book wasn’t from Earth, but it’s still extremely evocative. I loved this series growing up.)
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I bet Ubisoft is furious they went with the Doctor Who reference instead of the Assassin’s Creed one.
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You can read it here…
The Green Maurder begins on page 34:
Wikipedia has the astronaut’s footprints left on the Moon eroding away after 1 million years due to space weathering.
What a great series!
We can find fossils of something as fragile as dinosaur eggs from up to 190 million years ago, but we somehow missed an industrialized society?
How many dozen eggs have been found… from 100s of millions of years of dinosaurs?
Somewhere between 50 and 200 billion T-Rex’s probably walked the earth in the 40 million years they existed. and we have fossils of some part of 47 of them. Roughly one in every billion animals are fossilized. it will happen to less than 10 people living today. In industrial civilization could have millions of beings, none of whom are ever fossilized.
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Maybe they made it to the asteroids, before they sent the K-T one against their enemies. At least they left their marks on Ceres.
They had to act before their enemy’s battle-station around Saturn became fully armed and operational.
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There has been a lot written about the the emotional effect of finding out that there is other intelligent life “out there”, even if it’s only an incidental radio signal.
Would the effect of discovering other intelligent life “back then” be different?
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According to the Paleontology types I used to work with at the Academy of Natural Sciences, there were bipedal dinosaurs with brains as large as a man’s, mostly therapods. And it’s already demonstrably true that the human brain is not spectacularly space efficient - mynah birds have near-human intelligence in a brain the size of a walnut. AFAIK there’s no way to truly know (yet) but perhaps T. Rex was smarter than Einstein.
The problem is determining what parts of our civilization are not necessary - would a non-human race have anything we’d recognize as material culture, that would withstand the processes of time?
At one point I said to some folks at the Academy, “OK, then, the first great civilization was in the carboniferous era. It was entirely based on plant-derived plastics, as there was not any oil yet, and our existing petrochemical deposits are the remains of their vast cities and industrial complexes, rendered into coal and petrochemicals by the passage of time. Prove or disprove!” For every objection one of the scientists came up with, there was another who could refute it, and it went on for a long time before we all realized we weren’t being paid to have fun.
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Absolutely - but my point was that of the stone tools that don’t get worn down and are complex enough to be clearly identified as such, those that do manage to get preserved (i.e. ended up in a sedimentary layer that turned into rock) may not be particularly identifiable as tools when they’re discovered, given that it’s a rock in rock (whereas fossilized bones and shells end up looking different from surrounding stone). And it’s stone tools that are most likely to be preserved, due to the sheer number of stone tools that would exist before any other types of preservable tools were invented. Sure, delicate things can be preserved, but mostly they’re not. Given the time window where these tools and the species that made them might exist in the fossil record, it could be pretty easy to overlook them, even if they did get preserved - there are species that were extremely widespread for very long lengths of time, yet we don’t even have full fossil remains, if any. To make matters worse, intelligent species are likely, like humans, to have originated in one location, but whose intelligence would then allow them to spread out (assuming they even did so) quite rapidly, potentially leaving only the thinnest, tiniest of traces in the geological record, potentially disappearing in a fraction of a million years. We don’t have a whole lot of insect fossils, despite the fact that they’ve completely covered this planet for almost half-a-billion years. Microchips that existed for a century at best? Not likely.
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Somehow I think finding proof of “back then” intelligent life would be more disruptive than finding aliens. ET can at least be obliquely excused for existing because they’re not from here, and thus not necessarily subject to the unwritten contract we have with Beardy Sky Man for total dominion of Earth. But older intelligent life on this planet that was, ostensibly, created specifically for us to rule over? That’s gonna leave a mark…
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A piece of obsidian or flint embedded in sediment is going to stick out like a sore thumb. In aggregate, sure, noticing that you have a stone tool embedded in the rock would take a miracle. But in sandstone or in shale, it’s going to stick out and be noticed just like a fossil.
As others have noted upthread, a metal using civilization 60 or 100 million years ago would have left a ton of evidence of its existence behind, because we’d see a very sudden change in the elemental composition of the rocks. I’m arguing that even if we only hypothesize stone tools, the sheer number of stone tools (and scrap from making them) that we have left behind in the places where we have lived for even a few tens of thousands of years suggests that the Saurians would have left behind enough tools to show up in the record.
