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How long after man is gone...

F

farmkid

Commodore
Commodore
Here's a question I've pondered about: If humans were to disappear today (make up whatever scenario you want to explain that, it doesn't matter), how long would it take for all, and I mean ALL, traces of man to disappear from the planet? By that, I mean if another intelligent species were to evolve, or aliens landed and explored the planet, that they would never find evidence that a previous intelligent species had lived here. As a related question, what would be the most durable evidence, or what would be the last thing to disappear?

Here are my thoughts of what the last evidence would be, but I have no idea how long they would take to be gone: cities and/or landfills as an artifact-rich layer in the rock strata, oil and exploratory wells as deep holes (sometimes filled with cement or other material) in the crust, open pit mines, massive species die-off in the fossil record without a concomitant asteroid strike or other natural disaster, the vehicles and other artifacts left on the moon, or maybe even graveyards with lots of bones found in boxes. Do you think any of those things would ever completely disappear, or will evidence of our existence remain until the Earth is engulfed by the sun? Do you think any of these things will outlast the Voyager and Pioneer space probes?
 
I think you're going to have to wait for the end of the Earth itself. While we make a lot of stuff that breaks and crumbles in only a few years -- skyscrapers might last a few centuries -- a lot of the little things we make might last forever. Consider a tungsten carbide drill bit. It won't corrode. The workbench on which it sits might rot and the drill in which it's mounted might fall apart, but the drill bit itself and many of the components won't be appreciably affected by time.

I imagine a lot of jewelry will withstand eons, too. Buried in the ground by the passage of time, these things would have to be subducted under a continental plate before they'd be destroyed, but there are places on this planet that are billions of years old.

We'll leave, at the very least, a nice thick layer of abandoned technology strata behind for future archaeologists to find.
 
farmkid said:
how long would it take for all, and I mean ALL, traces of man to disappear from the planet?
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We've found fossils well over 600 million years old, so I suspect signs of mankind will last considerably longer than that, maybe billions of years.

Here are my thoughts of what the last evidence would be...
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I suspect the artifacts left on the moon will outlast most everything we leave behind on the Earth. I think the Voyager and Pioneer probes will still exist billions of years after the sun becomes a white dwarf star.

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The carbide tungsten drill bit is a really creative example, that's awesome! :lol:

Yeah, makes you wonder about our industrial facilities. Surely, all of the manmade radioactive material would stick around so if some alien species came knocking, even if our infrastructure crumbled and collapsed - even if physical geological processes completely hid all traces of industrialized society - sophisticated enough means of remote sensing would detect much-higher-than-naturally-occurring concentrations of radioactive isotopes in the planet's crust from all the stuff we've created... not to mention all the artificial alloys. (assuming the radioactive half lives were not exceeded).

Were an alien civilization to come setting up archeological digs, I would say that one of the most probable first detectable signs of a former civilization here would be traces of steel.
 
John O. said:
Were an alien civilization to come setting up archeological digs, I would say that one of the most probable first detectable signs of a former civilization here would be traces of steel.
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And a human doll — that talks!
 
You might want to watch Life After People, it's a nice watch and gives you an idea about how fast the obvious traces of humanity would disappear. The more subtle traces would probably remain a very very long time, longer than the planet would be in any good shape.
 
some satellites that are high enough to stay up without falling back to earth might stil be there
 
YellowSubmarine said:
You might want to watch Life After People, it's a nice watch and gives you an idea about how fast the obvious traces of humanity would disappear. The more subtle traces would probably remain a very very long time, longer than the planet would be in any good shape.
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I haven't seen it, but I am aware of that series. As I understand, it focuses on more obvious traces. I'm more interested in the more durable traces that will last much longer. What got me thinking about it in the first place was something (I don't remember what; perhaps it was a discussion on the probability of intelligent life on other planets) that made me ponder the possibility that perhaps we aren't the first intelligent species on the earth. I wondered whether it's even possible that another species with the same intelligence and technology as mankind existed at any point in Earth's history and has disappeared and left no trace that we could find. I don't believe that to be the case, but I just wondered whether it's even possible.
 
farmkid said:
I wondered whether it's even possible that another species with the same intelligence and technology as mankind existed at any point in Earth's history and has disappeared and left no trace that we could find. I don't believe that to be the case, but I just wondered whether it's even possible.
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With the same technology as us today possibly not - the traces left behind would be too difficult to miss. Even less advanced ones would leave some obvious traces behind - even the most primitive stone tools are way too obvious to any archaeologist, and we've found such from 2.6 million years ago. But since no humans existed back then, it's obvious that another intelligent species were using them, does that satisfy you? :P

It's also expected that complexity and intelligence increases over time, and this makes it less likely for such past developments, but I claim that all these developments are not linear and since we share the planet with other pretty intelligent creatures right now, such possibly existed in the past (it's obvious for primates, but possibly also non-primates).

So, let's see:
Other intelligent primates: Most certainly did exist
Other intelligent non-primate species: Probably
Tool-using non-human primates: Most certainly did exist
Other species using tools: I'd say yes, but nothing that we would recognize as such. Many animals today use tools that we would never recognize unless we saw them using them.
Primates having an advanced spoken language: Possible, even probable (but less advanced than what you call a language)
Other species having an advanced spoken language: Possible (but less likely)
Written language in non-human species: Probably not (no evidence of any such), but not impossible

And I believe that's as far as you can go. It's possible that some much more advanced species did exist and we missed them, but it's not very likely. Spoken language leaves no traces, they could have been doing fine without advanced technology and advanced tools, and a written language could have existed with all evidence of it erased somehow (unlikely). Nothing as fun as species of dinosaurs flying rockets to the moon, unfortunately. Though there's always a chance you know, even if it is almost zero. ;)

-------

Here's one possible (but very unlikely) story: Millions of years ago an advanced civilization began to develop (possibly dinosaurs or some other species unrelated to us). The centre of this civilization was on a lost continent that's now submerged in the ocean (such as Zealandia), which is why we never explored it. They had no use of houses as shelter, no use of clothes and no use of things like knives, so one of the most obvious traces would never be found. They developed sea-faring vessels, but they all ended up submerged, and they never liked the other continents that much, so the settlements were rare, they loved to stay on their home continent. They were already using paper for writing by the time they moved to other continents, so it was easy for the writings to get lost. They did develop advanced technology, they did send unmanned space probes through the solar system, but they did everything on their main continent, so all of it is lost and buried under the sea, which is why we have never seen any of it. Not the most plausible account, but it could have happened.

It's also possible that some aliens got lost in space, found our solar system, settled on Earth at some place that we haven't studied yet, and then went extinct because they had no means to recreate their own technology. Or they could still be among us, though biological studies and especially DNA testing would have found them by now. Anyway, that's far far more likely than the previous one, even with the unlikelihood of species doing interstellar travel.xx
 
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A few years ago there was a book about this subject "The World Without Us" that was a pretty big hit.

Then there was some Nat'l Geo show about it.
Then some other program on Discovery or The History Channel.

Then a series of programs, "Life After People" as mentioned and then I think a series of some kind.

The whole idea spawned some kind of cottage industry about Earth sans Man.

Have you checked any of this stuff out already?
There's a lot of it out there.
 
YellowSubmarine said:
With the same technology as us today possibly not - the traces left behind would be too difficult to miss. Even less advanced ones would leave some obvious traces behind - even the most primitive stone tools are way too obvious to any archaeologist, and we've found such from 2.6 million years ago. But since no humans existed back then, it's obvious that another intelligent species were using them, does that satisfy you? :P
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The stone tools you mention are only 2.6 million years old. What I'm wondering is if all traces of our civilization could ever be gone. Would it take a billion years? 5 billion? 10 billion? ever? As someone mentioned above, I kind of figured it might take subduction of all the current crust to absolutely destroy it all, but maybe not. Will that ever happen? Will the sun swell to a red giant and engulf the earth first?
 
farmkid said:
The stone tools you mention are only 2.6 million years old. What I'm wondering is if all traces of our civilization could ever be gone. Would it take a billion years? 5 billion? 10 billion? ever? As someone mentioned above, I kind of figured it might take subduction of all the current crust to absolutely destroy it all, but maybe not. Will that ever happen? Will the sun swell to a red giant and engulf the earth first?
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Even though the film and series I suggest look at the obvious traces which would disappear really quick, they do mention things that would remain for a longer period of time and give suggestions and information that you could use to infer more.

A few examples:
1. The monument on Mount Rushmore is carved in solid granite. It's one of the things that will survive really really long time. But how long is that? The granite erodes at 2.5 cm per 10000 years, or 2.5 meters of it will be gone in 1 Ma. That means that in a few hundred million years its artificial origin will be unrecognisable.
2. The Great Pyramid and other similar monuments. It's very robust but it will be gone faster. However, while nature has great forces of destruction, it also has great forces of preservation. Long before the pyramids are gone they will be consumed by the sand where they can survive in a recognizable shape for a long time (I'm not sure how long, but I assume for a near eternity).

Look at the history of fossils and how long some of them have been preserved. It's true that bones are much more robust than things that make up buildings or tools, but it's not their robustness that saved them for us, it's the preservation forces, the fossilization processes, etc. It's completely possible that in a 4 billion years someone discovers a present-day mobile phone. All of its components would be gone, and it could be only a footprint left in a rock, but its shape would be undeniably of artificial origin. Some presumed fossils of micro-organisms are dated as 2 Ga old, etc.

The main problem is that they are far too many man-made objects. Any one of them could disappear completely, in fact you can name any random man-made object, say that it will be completely gone in 100 Ma, and you will be correct with almost certainty. But some of them will make it, one way or another, and it will remain for billions of years, or possibly even much longer than that, and wherever you dig on Earth, you'd discover something that suggests that humans were here. It's inevitable. Of course, the discovered human fossils would be few enough that the pseudo-science folk could claim that they don't prove an advanced, let alone space-faring civilization, or something like that.

Of course, it will all disappear one day. Whatever preservation forces act on it (it could get preserved on a stone that gets ejected into space), it will one day suffer from proton decay (lower limits on the proton half-life are 6.6×10^33 years), or by quantum tunnelling much much slower if proton decay doesn't happen.
 
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Psion said:
Consider a tungsten carbide drill bit. It won't corrode.
Click to expand...

Future archaeologists will probably think they served ritual purposes. Past civilizations made them of tungsten carbide, because they knew they wouldn't corrode, which symbolized a long fertility.

They'll also find random bits of stone with holes in them, that exactly match the diameter of these metal penises, and those stones were no doubt where the sticks were placed during sun worship, where they would harness the sun's rays during the solstice and be invigorated.
 
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