I am looking for small(ish) human made things that could be findable in 5 Million Years and clearly show to the finder an artificial origin. I am not thinking of big things like ports, dams, Mount Rushmore, ABC-bunkers or ICBM silos but something a person could carry for some distance. Would (some) rubber tires survive that long when a lot of them are dumped together and buried anaerobically? Would gold/silver/alluminum coins last that long? Gold ingots? Coca Cola bottles? Titanium screws, carbide drills? Glass panes, photoelectric panels, roof tiles? And if so, under which conditions?
I assume the finders to be intelligent but technically not sophisticated: no knowledge of Chemistry, Physics, Plate Tectonics comparable to our current level. Something like the Egyptians when they built the pyramids, the Chinese 1,000 yrs. ago, the Mayas or the Incas.
Any ideas?
I once read that stainless steel tools last pretty much indefinitely. The author said that if humans disappeared, chimpanzees could evolve into an intelligent tool-using species in a few million years. And if they did, they would be able to dig up our stainless steel knives and forks and spoons and use them. Which I thought would probably have a strange impact on chimpanzee religion.
Cut diamonds?
Glass. In fact the people concerned about nuclear waste dumps proposed seeding the area around them with glass disks with a “stay away” symbol. But then they had to figure out what symbol would still mean “stay away” - for tens of thousands of years.
Baked clay (pots, bricks, cuneiform accounting tablets) hold up pretty well.
Twinkies.
In land fills some glass bottles should last 1,000,000 years or more. Though glaciation will probably crush most. The surface of the earth is less than 2 million years old. A lot happens in a million years. Many ice ages.
The stainless steel tools are unlikely to survive that long. 316 Stainless should last only about 1200 years.
We will probably leave a chemical signature but even nuclear waste won’t be radioactive in 1,000,000 years.
Diamonds are interesting, they tend to be small and signs of their being worked might be able to hold up that long. Though crushing will affect them.
While the Earth will reliably crush, erode and churn many robust materials over a million years, look up to the sky and there are satellites that will remain intact. Some will fall to Earth from time to time.
On the Moon those lunar landers and various bits of junk will last as long as they are not hit directly by a meteorite. The Mars rovers will be subject to erosion, but a far slower rate than on Earth. Such things may last for millions of years.
Who knows? There may already be artifacts from lost civilisations up there waiting to be found. I think someone made a movie about that.
Any jewelery made from diamond and pure gold should survive indefinitely as long as it isn’t ground up somehow.
Stone tools? The oldest ever found are 3.3 million years old already, give or take.
Voyagers 1 & 2, Pioneers 10 & 11 possibly in some alien museum. Other space debris not to close to a gravity well. Not sure what solar and interstellar dust, radiation, and debris will do.
Those specific spacecraft, along with New Horizon, are very, very unlikely to be found by any alien civilization. They’re more likely to recovered by humans than anyone else. After all, we know where they are. But I doubt they’ll be recovered by humans. Most likely, they’ll gradually become more and more fragile due to cosmic rays. Eventually, they’ll hit some bit of space dust and shatter.
As far as diamonds, contrary to a certain marketing slogan, they don’t last forever. I’m not sure what time frame, but eventually they’ll convert to graphite.
Since glass might last that long, microprocessors and photovoltaic cells should be identifiable in five million years. Although not as such by the civilization described in the OP. Need microscopes to see the circuits.
That’s what I get for passing along something I read without verifying it first.
I did some checking after your post and you’re right. Stainless steel does not last indefinitely. It starts corroding in just a few decades underground and would not last more than a few centuries.
Really? I believe that anything on Mars will be sandblasted into dust long before a million years. Maybe a couple of thousand years tops.
Needs to be in the right spot of course; in millions of years, some chunks of crust will be pushed back down into the mantle, melting away, and glaciers, erosion, etc. will scour or pulverize a lot of what’s left. Not to mention if humans are still around and busy for the next hundred thousand years, there may be drastic changes to the Earth’s crust.
But, assuming no major changes to the Earth different from the last five million years, there will be plenty of artifacts findable in five million years.
Gold items, ceramic jewelry or other objects, glass (if nothing crushes it, a cell phone screen should last indefinitely, even while the metal case rusts to nothing).
And even something relatively short-lived, like a key or baseball or bottle cap, could end up in just the right kind of mud and make an impression that hardens to rock and is observable in five million years.
So this is an interesting question. If humanity died out, how would things play out and over what timeframe with all the artificial satellites?
Well, many diamonds were formed in the Precambrian, so I’d say they would last for at least half a gigayear.
Mars sand storms aren’t quite how it’s depicted on The Martian. Mostly the very fine dust gets picked up by an atmosphere that’s a hundred times thinner than Earth’s, wafts about a bit, and falls on things like exposed solar panels. The rovers are more likely to get buried than blasted.
Probably be a couple of 1990 Hondas still driving around.
And that sediment layer from 1999 made entirely of AOL CDs.
Well we know of at least one car up there in orbit around the Sun. The Tesla Roadster.
Says here there is good chance it won’t bump into anything for at least 15 Million years.
Though, of course, your mileage may vary!