I read a book by Alan Weisman titled The World Without Us, which covers this very specific topic. According to it, among the very last man-made structures left after hundreds of thousands – if not millions – of years would be the Channel Tunnel between England and France. Another notable example would be the stone faces on Mount Rushmore, as well as some old steel bridges built in an era when engineers couldn’t yet calculate structural load precisely, so they simply overbuilt everything.
this post was submitted on 11 Jul 2025
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Showerthoughts
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A "Showerthought" is a simple term used to describe the thoughts that pop into your head while you're doing everyday things like taking a shower, driving, or just daydreaming. The most popular seem to be lighthearted clever little truths, hidden in daily life.
Here are some examples to inspire your own showerthoughts:
- Both “200” and “160” are 2 minutes in microwave math
- When you’re a kid, you don’t realize you’re also watching your mom and dad grow up.
- More dreams have been destroyed by alarm clocks than anything else
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What about plastic?
Would be there, but it would break down into micro and nano plastics it would be an invisible problem that would go unseen.
The biggest challenge for future intelligent species, and the reason why I know we're the first technological ones, is that we've mined all of the easily accessible metals and all of the easily accessible fossil fuels. Any intelligence arriving after us is going to have to make a civilization without iron, precious metals, oil, or coal. Unless you get into some sci-fi bio-engineering scenario where they're growing high tech, they're doomed to being stuck in the stone age. It's going to be hard for them to escape the planet, defend it from asteroids, deal with super-volcanoes, build advanced calculating devices... all of the stuff we would already find challenging even with all the resources we have.
Millions of years are not enough to replenish the fossil fuels, and the sun is going to start expanding before enough life lives and dies to produce any useful amount of biomass. Before then, more metals will become accessible, in places, but good luck working it at industrial levels without fossil fuels.
I'm not saying it's impossible, but we've given a severe handicap to advancing beyond a rudimentary agrarian society for any successor species; even if it's our own descendants re-arrising from a post-apocalyptic environmental catastrophe.
Lower end of Earth being in the habitatal zone being just 1 billion years left. Our consumption of the easy to reach resources before them arriving to the scene, I think you're likely right.
Upper estimates are ~3 billion for habital zone, and Red Giant phase being ~5 billion years from now for factoid funsies.
Earth would never get fossil fuels back as their formation was dependent on lacking fungi to break plants down. This is indeed our one shot.
Well, no. Arabian oil is only a few million years old and peat, a precursor to coal, is still being formed. I could imagine new oil being formed in the Gulf of Mexico and in the Indonesian archipelago
Metals are here, will recycle in the earth. Where will it go?
AFAIK metals don't really go away over time so I would think they would be easy to harvest from the metals that are here today, no?
I read a SIFI story were a future civilization was mining rebar out of collapsed cement structures and wondering how the ancients managed to get iron into rocks.
Any worked iron product rusts. If we're talking about evolutionary time scales, any exposed metal - which is most of it - is going to be unusable within thousands of years, and even rebar embedded in concrete will be gone in millions. Heck, our concrete isn't even as good as the Romans', and even that's going to break down in thousands of years.
We've stripped the raw, surface, easily accessible stuff and worked it into things that will degrade. There may be some scavenge, but nothing that can be gathered in any quantity to build an industrial society on. At best, future societies will be like medieval Japan, where iron is rare and steel precious and hoarded, only unlike Japan, there won't be a future where they can import huge quantities of the stuff from China or Australia, because getting to the deposits now requires an industry and advanced mining equipment... which is all made out of iron they won't have.
Gold will be interesting. Again, it's not just laying around everywhere just under the surface. Instead, there will be isolated pockets of huge piles of the stuff. Gold doesn't degrade, but it's all hoarded. There's a bunch in electronics, but in tiny, tiny amounts in each device; trying to salvage that is really hard, and yields trace amounts. No more nuggets the size of your thumb, or your fist. If a future civilization could build a global economy, then gold wouldn't be an issue. Uranium will be hard, as will platinum, and platinum is a useful, but consumable, catalyst, and rare even today it'll be almost unheard of in a perpetually pre-industrial post-apocalypse.
Fossil fuels are going to be the big issue, though. What's left will simply be inaccessible, and without fossil fuels you don't have plastics, industry, fertilizers at scale, global transportation, or the ability to work whatever metal you can find, at any scale.
But even rusted iron can be re-smelted, no?
Rust needs to be reduced back to ore, using a reactive, usually coke. Coke is purified coal. Coal is a fossil fuel. You can do it with charcoal, which can be made by burning wood, so it's possible without coal, just not as efficient. This assumes you can gather the rust - it tends to break down and disperse into the environment, but if you broke up concrete to get at rusted rebar and could collect the rust, you could reduce it with charcoal.
Again, it's a matter of scale. We mine iron and deposits because we can get large amounts in seams. If you're trying to harvest rust and reduced it with charcoal, you're producing iron on the scale of making knives and swords, not cars, or combine harvesters, or more rebar.
It's a chicken-egg problem. We have been able to come as far as a have because oil, coal, and iron were just laying around on the surface, in huge quantities. Those are gone, and now you need the big tools first to get at the reserves that are left.
This is material for No Stupid Questions or Ask Lemmy communities, not a Showerthought
Showerquestions
Showerexistentialdreads
I question my showers.
Sorry, you're right, will do for next time:) I guess I wrote my inner questions while showering than crafting this as terminal thoughts.
A totally not serious answer. Today, I was sitting across from a Starbucks and staring at the logo. It is really weird. I started thinking that if something were to happen to civilization, all these cups, sleeves, merchandise and plastic stir sticks emblazoned with the Starbucks logo may cause future archaeologists to think that we worshipped some half fish woman thing (or whatever the logo is supposed to be).
Alternatively, this xkcd could be fun to do.
You should check out the "documentary" (for lack of a better word) called ~~"After Us"~~ "Life After People." It is specifically about what Earth might look like if humans just suddenly vanished from the face of the Earth.
Seems interesting and tried looking it up without success. Could it be "Life After People" or "Aftermath: Population Zero"?
Life After People is what I was thinking of.
Came here to suggest this.
Cats basically just move along without a blip.
According to What If, a layer of processed hydrocarbons in the geological record.
See the Silurian hypothesis:
The Silurian hypothesis is a thought experiment, which assesses modern science's ability to detect evidence of a prior advanced civilization, perhaps several million years ago.
which assesses modern science’s ability to detect evidence of a prior advanced civilization,
We can't, we know we can't.
It doesn't even take lizard people millions of years ago.
Past 50k years is a blank spot. Anatomically modern humans have been around for at least 300k years.
They say it took the ice age ending so we could have agriculture, but that ignores we had 3-4 ice age cycles before the last one where humans were running around. Plenty of time for agriculture each cycle.
Even then, during the last ice age the Sarah desert was a lush rain forest the entire time.
The modern timeline is very Euro-centric, which is an incredibly naive view considering the glaceriers from an ice age are basically a giant bulldozer that erases everything. It plows down mountains. Obviously we won't find any evidence there, it keeps getting erased every ice age.
And the places around the equater that would have fostered large settlements, are under the ocean due to those glaciers melting.
Just like with everything else, it's incredibly ignorant to think we know everything and there's no missing pieces of the puzzle
As a violent psychopath once said:
The absence of evidence is not the evidence of absence.
At least for our civiliſation, there would always be the echoes of ſignals like the Aracebo Meſſage that would be around for future civiliſations to catch regardleſs of what happened here on Earth.
It's still a matter of timescale, as in "how far future are we talking?". On a stellar scale, they'd need to get here in the next billion years or so before the expansion of the sun boils off everything above the lithosphere. On a geological scale, it's only a couple hundred million years 'til everything that isn't already buried or washed into the sea is getting squashed into a new pangea. On a climatological scale, corrosion and decay/overgrowth will render almost all artifacts unrecognizable within a couple of thousand years, though it'd be a few tens of thousands before our impact on the atmosphere is nulled. On a human timescale, the inverse-square law means that our radio signals are only detectable without astronomically-sized antennas within a shell of a few dozen light years or so.
I've thought about the idea of some future civilization thinking they're the first and then finding subway tunnels and the flags planted on the moon
I fucking hate Graham Hancock
would remain in five or six million years if we all just vanish?
Literally nothing...
10-20k years left and the only thing left would be like Mount Rushmore and other giant stone monuments.
At 5-6 million years it would only be the layer of plastic in landfills from before bacteria evolved to break it down and nuclear test sites if the future society does isotope testing there. Both things that have much more logical explanations than an ancient civilization with no other evidence.
In theory eventually any earth we lived on would be lost to tectonic plate movements and it would be like we were never here. And then the sun explodes so...
Depends on the time period honestly. Biggest signs are gonna be massive buildings or infrastructure projects. I wonder how long voyager will last just drifting?
We got rocks over 4 billion years old. But you're right, very little would survive after 100-200 million years.
I vaguely remember there being a doco on what would happen to the earth if people disappeared. I remember it showed the cities getting all grown over, but it stopped and talked about each stage and what would happen.
More than they're going to get otherwise. Also this is a series of questions, not a shower thought.
It is pure conjecture to say any other "intelligent" and industrious species would arise, but many modern constructions would have little to no sign of existence. Any metal, even most stainless steels, would be rusted away or buried many feet deep after millions of years. Even plastics and cement would be deteriorated enough that there would mostly just be the greatly disturbed strata that would give big clues that something either catastrophic or massively industrious happened. Only very rare areas that are geologically stable and have low corrosion would have much of a chance to retain anything recognizable, like how only some cave paintings are still around today.
So, maybe a couple military bases might retain enough structure to piece some things together, but it'll still be a mess by the time another equivalently ~~self-centered~~ intelligent species comes about.
Very little, if anything, would remain of our civilization in five or six million years. At least I wouldn't think so, aside from what we have floating in outer space. Six million years is an awfully long time, and it's not like our consumer-based society builds things to last...
The Earth would finally be safe.
Earth the planet is totally alright with everything we do. It's been through much tougher times.
We only endanger ourselves and other living creatures.
They would thrive