# Time for Earth to cover evidence of human presence? **URL:** \ **Category:** Factual Questions\ **Created:** [November 23, 2008, 8:23pm UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138 "2008-11-23T20:23:56Z")\ **Posts on this page:** 19\ **Page:** 3
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [November 25, 2008, 12:33am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/41 "2008-11-25T00:33:47Z")
> [@Quercus](#): > > As mentioned, the key issue is how interested and informed the observer is and what resources they have. At some point upthread I qualified it to regular Joe walking about, which you already answered. So let me change it to Indiana Jones looking for something. A critical eye, plenty of desire to look under rocks but no technology. I would have thought that sewers, subways and underground parking lots would survive for a long time, but it seems they are among the first to go, from what some have said. What would be the structure most likely to survive in recognizable and penetrable way? ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [November 25, 2008, 12:39am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/42 "2008-11-25T00:39:15Z")
> [@Alive\_At\_Both\_Ends](#): > > A previous thread on this subject: [Link](http://boards.straightdope.com/sdmb/showthread.php?t=365865) Damn, brilliant minds and all that. Thanks for the link. ---
**Author:** ![lizardling](https://avatars.discourse-cdn.com/v4/letter/l/f4b2a3/32.png) [@lizardling](https://boards.straightdope.com/u/lizardling)\ **Post date:** [November 25, 2008, 1:53am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/43 "2008-11-25T01:53:22Z")
> [@Sapo](#): > > Thanks for a great reply. The bit about the roads is particularly interesting. Yeah – here’s a blurb about archeologists using declassified sat photos to find canal systems from ancient Nineveh, on the order of three thousand years ago. [http://www.sciencedaily.com/releases/2006/04/060411224311.htm](http://www.sciencedaily.com/releases/2006/04/060411224311.htm) Same idea as with the road system – look for changes in the landscape that might not be as obvious close up. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [November 25, 2008, 3:10am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/44 "2008-11-25T03:10:03Z")
> [@](#): > > Very similar to the Face on Mars, eons after the Martians became extinct, and all traces of their cities erased. Except for being completely different. The Face on Mars is a natural formation that happens to look like a human face. Mount Rushmore in two million years would probably no longer be recognizable as a group of human faces but any goelogist could tell it was not a natural formation. ---
**Author:** ![Q.E.D](https://avatars.discourse-cdn.com/v4/letter/q/51bf81/32.png) [@Q.E.D](https://boards.straightdope.com/u/Q.E.D)\ **Post date:** [November 25, 2008, 3:14am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/45 "2008-11-25T03:14:08Z")
> [@Little\_Nemo](#): > > Except for being completely different. The Face on Mars is a natural formation that happens to look like a human face. There’s also very little air on Mars, so you can be forgiven for failing to notice that faint whooshing sound over your head. ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [November 25, 2008, 3:22am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/46 "2008-11-25T03:22:50Z")
> [@lizardling](#): > > Yeah – here’s a blurb about archeologists using declassified sat photos to find canal systems from ancient Nineveh, on the order of three thousand years ago. [http://www.sciencedaily.com/releases/2006/04/060411224311.htm](http://www.sciencedaily.com/releases/2006/04/060411224311.htm) Same idea as with the road system – look for changes in the landscape that might not be as obvious close up. Very cool. My Earth Sciences teacher had that ability to find pattern in nature. We would spend all day working a field and finding nothing, and then he would take us up a hill and show us all the “obvious” stuff we were missing. Lines of different vegetation and patterns in the creeks that drained a mountain side showing fault lines and rock layers. ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [November 25, 2008, 6:02am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/47 "2008-11-25T06:02:21Z")
By the standards of “noticeable to the average Joe without any equipment”, the answer might actually still be satellites. Geosynchronous satellites aren’t obvious to the naked eye (though they’re pretty easy to find if you’re looking for them), but LEO satellites are: If you go out and just look up, you’ll see several on a good night. The very low ones will decay quickly, of course, but higher ones can be seen in special circumstances: The Iridium satellites, for instance, are 780 km up, and can sometimes “flare” brighter than Venus, when the Sun catches them just right. Tomorrow I’ll see if I can run some numbers for how long those would last, and see if I can find some higher naked-eye birds. ---
**Author:** ![Toxylon](https://avatars.discourse-cdn.com/v4/letter/t/f05b48/32.png) [@Toxylon](https://boards.straightdope.com/u/Toxylon)\ **Post date:** [November 25, 2008, 9:02am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/48 "2008-11-25T09:02:52Z")
Millennia-old arrowheads, celts, adzes etc. are still quite commonly found by laymen just taking a walk on recently disturbed soil (like natural erosion on a slope after a heavy rainstorm). Even perishable organic rarities sometimes: the oldest bow in Britain (c. 6000 yrs.) was found by a man on his daily countryside walk, the artifact sticking upright in a bog close to the road. ---
**Author:** ![clayton\_e](https://avatars.discourse-cdn.com/v4/letter/c/c57346/32.png) [@clayton\_e](https://boards.straightdope.com/u/clayton_e)\ **Post date:** [November 25, 2008, 10:09am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/49 "2008-11-25T10:09:24Z")
> [@Elendil\_s\_Heir](#): > > Weisman’s book is really good. And yes, Mount Rushmore is going to be around for a looooooooooong time. Yes.. If humans disappeared in the next century or so. In the long term, however, I think that should humans still be around a few thousand years from now the uniqueness of the monument will be its downfall. Will the United States still be in existence 300 years from now? 600 years from now? One _thousand_ years from now? Considering how long empires have lasted in history the chances of this are slim. Odds are that some sort of future political movement or terrorist attack will destroy that monument. I highly doubt it would be recognizable as it is today in 500 years. The same could be said, obviously, for the Washington Monument, The Capitol Building, the White House.. etc. etc.. etc.. The mountain next to it? Yeah, that’ll probably look exactly the same, though. A nitpick, I know.. But if we’re not looking at this through the vacuum of “Humans disappear tomorrow at 3pm” the fact that humans will continue to play around with explosives and [destroy things they don’t like](http://edition.cnn.com/2001/WORLD/asiapcf/central/03/12/afghan.buddha.02/) for no particular reason… No.. That won’t be there after we’re gone. ---
**Author:** ![Little\_Nemo](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/little_nemo/32/3120_2.png) [@Little\_Nemo](https://boards.straightdope.com/u/Little_Nemo)\ **Post date:** [December 7, 2008, 5:42pm UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/50 "2008-12-07T17:42:38Z")
> [@](#): > > There’s also very little air on Mars, so you can be forgiven for failing to notice that faint whooshing sound over your head. I missed this before. I don’t know exactly how it is you think I was “whooshed”. I’m pretty sure I understood what Earl meant. He used irony to make a point. For the record, I understood the irony - I realize Earl didn’t literally believe that Martians existed. I figured that was too obvious to need mentioning. So I addressed the point I felt he was making - that the evidence of a formation that looks like a face is not proof of an intelligent species - by pointing out it’s not the resemblance to a face that’s the issue but the artificiality of the creation. ---
**Author:** ![Elendil\_s\_Heir](https://avatars.discourse-cdn.com/v4/letter/e/7cd45c/32.png) [@Elendil\_s\_Heir](https://boards.straightdope.com/u/Elendil_s_Heir)\ **Post date:** [December 7, 2008, 8:01pm UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/51 "2008-12-07T20:01:18Z")
> [@clayton\_e](#): > > …But if we’re not looking at this through the vacuum of “Humans disappear tomorrow at 3pm” the fact that humans will continue to play around with explosives and [destroy things they don’t like](http://edition.cnn.com/2001/WORLD/asiapcf/central/03/12/afghan.buddha.02/) for no particular reason… No.. That won’t be there after we’re gone. Sad but true. Too bad the Taliban weren’t toppled until nine months after the Buddhas were. ---
**Author:** ![Spoke](https://avatars.discourse-cdn.com/v4/letter/s/a88e57/32.png) [@Spoke](https://boards.straightdope.com/u/Spoke)\ **Post date:** [December 7, 2008, 9:37pm UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/52 "2008-12-07T21:37:27Z")
> [@Little\_Nemo](#): > > Another incredibly long-lasting artifact would be Mount Rushmore. It was carved out of solid granite in an area with minimal geological activity. Weisman said it will still be a recognizably artificial structure millions of years from now. Ditto the granite carvings on [Stone Mountain, Georgia](http://www.feniva.com/btwclass73/stone-mountain-picture-2.jpg). Funny to think that two of the last recognizeable images left in North America may be a giant stone carving of Abe Lincoln and a giant stone carving of Jefferson Davis. ---
**Author:** ![John\_DiFool](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/john_difool/32/19543_2.png) [@John\_DiFool](https://boards.straightdope.com/u/John_DiFool)\ **Post date:** [December 7, 2008, 11:01pm UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/53 "2008-12-07T23:01:38Z")
How much would erosion degrade these images (and the Crazy Horse monument) tho? Esp. in climes where ice forms in the winter, over a long period alternating freezing and thawing cycles can do a number on any rocky edifice, right? ---
**Author:** ![Steve\_MB](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/steve_mb/32/5339_2.png) [@Steve\_MB](https://boards.straightdope.com/u/Steve_MB)\ **Post date:** [December 7, 2008, 11:23pm UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/54 "2008-12-07T23:23:02Z")
> [@Little\_Nemo](#): > > So I addressed the point I felt he was making - that the evidence of a formation that looks like a face is not proof of an intelligent species - by pointing out it’s not the resemblance to a face that’s the issue but the artificiality of the creation. The [Face on Mars](http://en.wikipedia.org/wiki/Face_on_mars#The_Face_on_Mars) doesn’t really look all that much like a face when you get a good look at it – the original Viking picture just happened to catch the right arrangement of shadows. It would take a few million years of erosion for the features of Mount Rushmore to become blurred enough to make it possible to reasonably doubt that it’s an artificial structure, and a few million more to really erase the evidence. That said, another bit of evidence (upon excavation, not casual observation) might be the sudden appearances of a wide range of plant and animal species all over the planet, far from their earlier habitats – potatoes in Europe, rabbits in Australia, etc. (Horses in America might not help make the case, though; after a few million years it might be impossible to notice that they’d ever been absent.) ---
**Author:** ![Sapo](https://avatars.discourse-cdn.com/v4/letter/s/ec9cab/32.png) [@Sapo](https://boards.straightdope.com/u/Sapo)\ **Post date:** [December 8, 2008, 7:37am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/55 "2008-12-08T07:37:50Z")
I got to see the “Life after Humans” show in the History Channel. It was actually pretty good. It could have been edited down to 30 minutes (from its 2 hours) and some of the CGI were kinda lame, but it was entertaining and educative. Try to catch it if you haven’t and this topic is of interest to you. ---
**Author:** ![Gymnopithys](https://avatars.discourse-cdn.com/v4/letter/g/fbc32d/32.png) [@Gymnopithys](https://boards.straightdope.com/u/Gymnopithys)\ **Post date:** [December 8, 2008, 11:46am UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/56 "2008-12-08T11:46:13Z")
What about the negative evidence: the untold number of living organisms that have been wiped out. They will never recover. ---
**Author:** ![Quartz](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/quartz/32/267_2.png) [@Quartz](https://boards.straightdope.com/u/Quartz)\ **Post date:** [December 8, 2008, 5:53pm UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/57 "2008-12-08T17:53:34Z")
> [@Gymnopithys](#): > > What about the negative evidence: the untold number of living organisms that have been wiped out. They will never recover. Compared with major events like the asteroid that killed the dinosaurs or other mass-extinction events, humanity has had very little impact. ---
**Author:** ![tzimmerman](https://avatars.discourse-cdn.com/v4/letter/t/278dde/32.png) [@tzimmerman](https://boards.straightdope.com/u/tzimmerman)\ **Post date:** [December 9, 2008, 2:45pm UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/58 "2008-12-09T14:45:18Z")
> [@Chronos](#): > > Strictly speaking, all orbits decay, but geosynchronous satellites are up high enough that it would take a fantastically long time, longer than the lifetime of the Sun. > > Come to think of it, the Voyagers, Pioneers 10 and 11, and a few other outer-system probes will outlast the Sun, even. Lots of luck finding them, though. I would think that constant pummeling by micro-meteors and trace gasses would eventually erode the orbit, or at least pulverize it. Eventually being a few million years at most.. I really have trouble believing it’s going to be there two billion years from now when the sun envelopes it. ---
**Author:** ![clayton\_e](https://avatars.discourse-cdn.com/v4/letter/c/c57346/32.png) [@clayton\_e](https://boards.straightdope.com/u/clayton_e)\ **Post date:** [December 9, 2008, 11:11pm UTC](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138/59 "2008-12-09T23:11:28Z")
I’m wondering how long nasty chemicals would stick around and what their long term impact would be. All the chemicals in those giant storage containers won’t be in them forever… and there wouldn’t be anyone to clean it up. So here and there we’ve got a bunch of ecological bombs waiting years… or even decades, to spurt out. The area around these containers would be nasty for a while… or rather, downstream would be pretty nasty. What’s the worst nastiest chemical we’ve got just sitting in huge storage containers, has a very very very long lifespan before being broken down, and is effective even if it’s watered down to parts per billion? Also, If you’d happen to survive to the end of the world… In that book by Weisman, I believe it was in (not 100% sure, though, I’ve read a few books on the subject and that one I read just after its release which was a little while ago), It is mentioned that the nuclear plants would have coolent automatically pumped in to stop a chain reaction and the rods would be dropped into a reaction retardant sleeve (graphite?). All of this works great… Until eventually the system breaks down when the diesel powered pumps run out of fuel. Even if there is some contingency plan for this I doubt every plant is built the same. At least one of the 500ish plants (after the next 40 or so are built) will do something nasty. Find a good Geiger counter and use it. Or better yet just get a map of nuclear plants and make sure you don’t settle downwind or downstream. Still use the Geiger counter daily. [Previous page](https://boards.straightdope.com/t/time-for-earth-to-cover-evidence-of-human-presence/474138.md?page=2)