Longest lasting structures

[Modax]

If the human race were to be tragically wiped out by a virus, which of our famous landmarks / monuments / structures would last the longest?

-Statue of Liberty
the copper is resistant to corrosion and erosion, but liberty island will probably be under water in the long term...how will this affect the statue?

-Eiffel Tower
with no maintenance, this will rust apart in the long term, won't it?

-CN Tower
concrete structures are known to last a long time. Many concrete roman buildings are still in good condition 2000 years later.

-Golden Gate Bridge
sitting in a extremely earthquake prone area. Enough said.

-Three Gorges Dam
Largest concrete structure on Earth. But being permanently in water, will erosion get the better of it in the long term?

-Pyramid of Giza
still going strong after 5,000 years. Will it outlast the modern structures above?

[CaptainChewbacca]

History Channel did a special on this called 'after man'. Most of our cement structures use rebar, which wasn't the case with Roman construction. Rebar-reinforced concrete will start to decay after a hundred years or so.

The Statue of Liberty, Eiffel Tower, and Golden Gate will all succumb to the elements within a century or two, and I'd be very surprised if the Gate was taken out by an earthquake.

Three Gorges and Boulder Dam will last quite a while, and may actually be the largest structures that you can actually go inside to be left standing. The Pyramids will outlast the other structures, insofar as you can't really destroy a large pile of rock in an arid climate without some really nasty stuff.

I think, however, that Mount Rushmore will outlast the Pyramids, its probably got another 100,000 years as being recognizable as a sculpture.

[Count Chocula]

Add many of the monuments in Washington, DC to that list (except the Washington Monument). The Jefferson and Lincoln memorials IIRC are primarily marble and limestone, so while there will be erosion they will still be recognizable as intelligently-made structures centuries or millenia from now. My guess is that any large structure made before 1900, when steel construction really got into full swing, will last for a number of centuries.

[Solauren]

Didn't I post a timeline like 2 months ago in a 'End of the World' thread?

Why, yes, yes I did.

In summary
Within 3 years, most roads are regarded
Within 5 years, plants are growing on everything they can
Within 25 years, most windows will be gone
Within 30 years, most houses will lose roofs, concreate will begin to break down, and cars will rust apart. Paint begins to seriously peel, exposing alot to the elements.

Within 40 years, most wood structures are toast without constant upkeep
Within 60 years, Skyscrapers begin collapsing
Within 100 years, most metal bridges have collapsed
Within 150 years, most desert buildings are still more or less structurally intact (no plants or rain to trash them)
Within 200 years, most buildings will collapse, including buildings like the Empire States building and Sears tower.

Pre-metal buildings will last for centuries, but eventually, the weather will do them in.

Also, eventually, another ice age will come along and wipe the rest out, including the stone structure, excepting perhaps the Pyramids and structures in deserts near the equator. However, they will be buried by the sand, and will eventually collapse under all that weight.
Also, as the Glaciers expand and weaher patterns change, the natural forces of erosion will start to affect them more.

Ironically, our most advanced constructs will survive the longest. The we dropped on the Moon will remain intact, barring impact events, until the Sun destroys them.

[Junghalli]

I think, however, that Mount Rushmore will outlast the Pyramids, its probably got another 100,000 years as being recognizable as a sculpture.

I read in Alan Weismann's The World Without Us that it would last over 7 million years, because it's carved in a really hard rock that would only erode something like an inch every 10,000 years.

Of course the longest lasting human structures will be those on the Moon or in space. The low-orbit sattelites will burn up in the atmosphere when the stationkeeping propellant runs out, but the rest will may well last billions of years. Some of them will probably still be around when the sun dies. I mean, it'll probably take micrometeorite erosion ten million years just to erase the astronauts' footprints on the Moon.

[Starglider]

Here's a project that might interest you; a group trying to build a mechanical clock that will operate for 10,000 years. They're built a couple of interesting prototypes (based on mechanical computers) and last I heard they were trying to build the full size version at a site in Nevada. For some reason they got a lot of discussion in Singularity forums around the turn of the millenium, despite being virtually the polar opposite viewpoint.

Oh, going further offtopic I know, but they also have a Long Bets service, for people who want to put money on multi-decade or multi-century propositions. Some of the things people have bet on are quite interesting, others are amusing.

[Sky Captain]

I have question how long it will be possible to tell that technological civilization once existed on Earth after humans die out? Let`s suppose 10 million years after die off an alien expedition arrives, how hard it may be for them to find evidence of our civilization, what technological artifacts is are most likely to survive that long (ignoring items on the Moon and in orbit).

I ask this because some time ago I had a discussion with guy who argued that somewhere 10 000 to 50 000 years ago advanced civilization existed where currently India and Pakistan is located and that civilization wiped itself out in a nuclear war. As evidence he pointed out that supposedly there are descriptions of advanced technology in ancient Indian myths and archeologists have found traces of radiation and high temperature in ancient Mohenjodaro city.

It seems ridiculous to me that nearly all traces of advanced civilization can disappear in 10 000 to 50 000 year time. After all nuclear weapons are not something you can cook up in your average ancient village.

[Count Chocula]

Your friend read the Mahabharata, a source of controversy in the East and West.

As far as traces of civilization being wiped out in that time frame: erosion does a pretty good number on today's structures. Combine that with the occasional multi-million-ton ice floe as Earth goes through a cooling cycle scouring the land flat, and it's unlikely there will be any trace of our civilization in 10 million years if we went 'poof' tomorrow.

[CaptainChewbacca]

I'm pretty sure the fabled 'nuclear war' passage in the Ramayana (or whatever) was actually fabricated by our very own Duchess of Zeon.

[Molyneux]

Here's a project that might interest you; a group trying to build a mechanical clock that will operate for 10,000 years. They're built a couple of interesting prototypes (based on mechanical computers) and last I heard they were trying to build the full size version at a site in Nevada. For some reason they got a lot of discussion in Singularity forums around the turn of the millenium, despite being virtually the polar opposite viewpoint.

Oh, going further offtopic I know, but they also have a Long Bets service, for people who want to put money on multi-decade or multi-century propositions. Some of the things people have bet on are quite interesting, others are amusing.

That's...uh...a very interesting, literalist take on the Watchmaker idea.

[Sky Captain]

Your friend read the Mahabharata, a source of controversy in the East and West.

As far as traces of civilization being wiped out in that time frame: erosion does a pretty good number on today's structures. Combine that with the occasional multi-million-ton ice floe as Earth goes through a cooling cycle scouring the land flat, and it's unlikely there will be any trace of our civilization in 10 million years if we went 'poof' tomorrow.

I`m fairly sure after 10 million years it`s highly unlikely that there will be easily visible traces of our civilization, but I can imagine things made out of some strong corrosion resistant alloys or ceramics may survive if not destroyed by advancing ice sheets. I`m just wondering what is the most likely findings for visiting alien expedition to tell that technologically advanced civilization once existed on Earth. Maybe remains of nuclear waste storage facilities like Yucca mountain. Also military bunker and tunnel complexes built into hard granite rocks may survive rather long although I have no idea how common such structures are.

In case of much lesser time frames like 10 000 to 50 000 years ago it seems unlikely all visible traces of civilization can disappear. If there was technologically advanced civilization capable of manufacturing nuclear weapons in that time frame in India I`m guessing we`d find traces everywhere.

[Junghalli]

I`m just wondering what is the most likely findings for visiting alien expedition to tell that technologically advanced civilization once existed on Earth.

Probably the first thing they'll notice is the high-orbit sattelites still moving around in orbit of Earth. As long as they're above the point where they have to worry about atmospheric drag sattelites should last basically forever. Well, some of them may end up hitting each other eventually if their orbits cross.

[The Duchess of Zeon]

I'm pretty sure the fabled 'nuclear war' passage in the Ramayana (or whatever) was actually fabricated by our very own Duchess of Zeon.

No, I modified to incorporate into fiction a version which was fabricated by UFOlogists in the 1960s from a version fabricated in the 1930s by Theosophists from the original.

An Indian government cultural website then found my quote and put it up as though it was actually real and actually in the Mahabharata.

[Sky Captain]

I`m just wondering what is the most likely findings for visiting alien expedition to tell that technologically advanced civilization once existed on Earth.

Probably the first thing they'll notice is the high-orbit sattelites still moving around in orbit of Earth. As long as they're above the point where they have to worry about atmospheric drag sattelites should last basically forever. Well, some of them may end up hitting each other eventually if their orbits cross.

Wouldn`t the pressure from solar wind change orbits of satellites till they crash or leave earth permanently. Most satellites are rather lightweight and with large solar panels which may work as solar sails. I think in a time span of hundreds of thousands to millions of years satellites may get significant delta v from solar wind.

[Sky Captain]

I'm pretty sure the fabled 'nuclear war' passage in the Ramayana (or whatever) was actually fabricated by our very own Duchess of Zeon.

No, I modified to incorporate into fiction a version which was fabricated by UFOlogists in the 1960s from a version fabricated in the 1930s by Theosophists from the original.

An Indian government cultural website then found my quote and put it up as though it was actually real and actually in the Mahabharata.

I did a little googling on this subject and apparently there are countless of websites promoting anything from long lost advanced civilizations to visiting aliens who built ancient monuments and engaged in nuclear wars. However there are practically no hard evidence suggesting anything of this was true. Only thing I find curious is vitrified stone walls and sand found in some ancient sites indicating exposure to high temperature.

[Junghalli]

Wouldn`t the pressure from solar wind change orbits of satellites till they crash or leave earth permanently. Most satellites are rather lightweight and with large solar panels which may work as solar sails. I think in a time span of hundreds of thousands to millions of years satellites may get significant delta v from solar wind.

That's a good point, I hadn't thought of that. I guess the exact effects of solar wind and light pressure would depend on things like the configuration and orientation of the sattelite, but over millions of years I could see it destabilizing the orbit and either sending it crashing into or escaping from Earth. There's also gravitational interactions with the sun and moon to consider.

If that happens then my guess is the first thing that the aliens will notice is human structures on the moon, like the stuff left by the Appollo expeditions. The moon isn't going anywhere (not for many billions of years anyway), and it's expected to probably take up to 10 million years for natural erosion there just to cover up the astronauts' footprints. So the stuff sitting over there will stay recognizably artificial and obvious for a long time. I wouldn't be surprised if some of them lasted until the sun burned out.

[Sky Captain]

Wouldn`t the pressure from solar wind change orbits of satellites till they crash or leave earth permanently. Most satellites are rather lightweight and with large solar panels which may work as solar sails. I think in a time span of hundreds of thousands to millions of years satellites may get significant delta v from solar wind.

That's a good point, I hadn't thought of that. I guess the exact effects of solar wind and light pressure would depend on things like the configuration and orientation of the sattelite, but over millions of years I could see it destabilizing the orbit and either sending it crashing into or escaping from Earth. There's also gravitational interactions with the sun and moon to consider.

If that happens then my guess is the first thing that the aliens will notice is human structures on the moon, like the stuff left by the Appollo expeditions. The moon isn't going anywhere (not for many billions of years anyway), and it's expected to probably take up to 10 million years for natural erosion there just to cover up the astronauts' footprints. So the stuff sitting over there will stay recognizably artificial and obvious for a long time. I wouldn't be surprised if some of them lasted until the sun burned out.

Yeah things left on the moon will last very long that`s nearly certain, but I`m not sure what is most likely technological artifacts still remaining on Earth after 10 million years for aliens to find. My guess is structures built into hard granite may survive since there are natural caves that have lasted millions of years. Nuclear waste storage places may also show up. In case of waste leakage there may appear unnatural isotope ratios in nearby area, but I`m not sure how easily detectable that would be.

[madd0ct0r]

The stuff on the moon may last, but how obvious is it to find? Surely most of it is covered in dust from when the lander took off?


British modern structures have a design life of 120 years normally. Most can exceed that - masonary arch bridges for example.

As for spotting radiation sites - there is a spot in africa that exibihits unusal isotopes indicating it may have been a natural reactor in the past.
Very little humans do will leave a permenant mark on the landscape.

[Junghalli]

The stuff on the moon may last, but how obvious is it to find? Surely most of it is covered in dust from when the lander took off?

The stuff Appollo left behind aren't the only human artifacts on the moon. There were unmanned probes that landed there as well. And I believe among the artifacts left on the moon was a reflective plaque designed to be used in experiments with bouncing light off it, so at least some of the stuff wasn't covered up.

[cosmicalstorm]

Considering that humans have died virtually everywhere on this planet I'd say there is going to be a fair amount of fossilized human skeletons even dozens of millions of years in the future.

[CaptainChewbacca]

I'm pretty sure the fabled 'nuclear war' passage in the Ramayana (or whatever) was actually fabricated by our very own Duchess of Zeon.

No, I modified to incorporate into fiction a version which was fabricated by UFOlogists in the 1960s from a version fabricated in the 1930s by Theosophists from the original.

An Indian government cultural website then found my quote and put it up as though it was actually real and actually in the Mahabharata.

I thought I remembered something like that. You'd think the Indian Government would be more spot-on with regards to their own culture. I remember I once wrote a cryptic prophecy for one of my scifi universes, and showed it to my friend, who promptly paled and asked me 'is this real?!'.

[FSTargetDrone]

The stuff on the moon may last, but how obvious is it to find? Surely most of it is covered in dust from when the lander took off?

Not only are the reflectors left behind by the Apollo astronauts not covered in Lunar dust, they are still used to this day to measure the distance between the Earth and the Moon:

July 20, 2004: The most famous thing Neil Armstrong left on the moon 35 years ago is a footprint, a boot-shaped depression in the gray moondust. Millions of people have seen pictures of it, and one day, years from now, lunar tourists will flock to the Sea of Tranquility to see it in person. Peering over the rails … "hey, mom, is that the first one?"

Will anyone notice, 100 feet away, something else Armstrong left behind?

Ringed by footprints, sitting in the moondust, lies a 2-foot wide panel studded with 100 mirrors pointing at Earth: the "lunar laser ranging retroreflector array." Apollo 11 astronauts Buzz Aldrin and Neil Armstrong put it there on July 21, 1969, about an hour before the end of their final moonwalk. Thirty-five years later, it's the only Apollo science experiment still running.

University of Maryland physics professor Carroll Alley was the project's principal investigator during the Apollo years, and he follows its progress today. "Using these mirrors," explains Alley, "we can 'ping' the moon with laser pulses and measure the Earth-moon distance very precisely. This is a wonderful way to learn about the moon's orbit and to test theories of gravity."

Here's how it works: A laser pulse shoots out of a telescope on Earth, crosses the Earth-moon divide, and hits the array. Because the mirrors are "corner-cube reflectors," they send the pulse straight back where it came from. "It's like hitting a ball into the corner of a squash court," explains Alley. Back on Earth, telescopes intercept the returning pulse--"usually just a single photon," he marvels.

The round-trip travel time pinpoints the moon's distance with staggering precision: better than a few centimeters out of 385,000 km, typically.

Targeting the mirrors and catching their faint reflections is a challenge, but astronomers have been doing it for 35 years. A key observing site is the McDonald Observatory in Texas where a 0.7 meter telescope regularly pings reflectors in the Sea of Tranquility (Apollo 11), at Fra Mauro (Apollo 14) and Hadley Rille (Apollo 15), and, sometimes, in the Sea of Serenity. There's a set of mirrors there onboard the parked Soviet Lunokhud 2 moon rover--maybe the coolest-looking robot ever built.

In this way, for decades, researchers have carefully traced the moon's orbit, and they've learned some remarkable things, among them:

(1) The moon is spiraling away from Earth at a rate of 3.8 cm per year. Why? Earth's ocean tides are responsible.

(2) The moon probably has a liquid core.

(3) The universal force of gravity is very stable. Newton's gravitational constant G has changed less than 1 part in 100-billion since the laser experiments began.

Physicists have also used the laser results to check Einstein's theory of gravity, the general theory of relativity. So far, so good: Einstein's equations predict the shape of the moon's orbit as well as laser ranging can measure it. But Einstein, constantly tested, isn't out of the woods yet. Some physicists (Alley is one of them) believe his general theory of relativity is flawed. If there is a flaw, lunar laser ranging might yet find it.

NASA and the National Science Foundation are funding a new facility in New Mexico, the Apache Point Observatory Lunar Laser-ranging Operation or, appropriately, "APOLLO" for short. Using a 3.5-meter telescope with good atmospheric "seeing," researchers there will examine the moon's orbit with millimeter precision, 10 times better than before.

"Who knows what they'll discover?" wonders Alley.

More and better data could reveal strange fluctuations in gravity, amendments to Einstein, the "sloshing" of the moon's core. Time will tell ... and there's plenty of time. Lunar mirrors require no power source. They haven't been covered with moondust or pelted by meteoroids, as early Apollo planners feared. Lunar ranging should continue for decades, perhaps for centuries.

There are 4 NASA reflectors and one on each of the two (formerly Soviet) Lunokhod Rovers, but only one of those is still used (the position of one rover is not known with enough precision to use the reflector--more about that here).

Note that the reflectors left behind by the Apollo crews were placed within walking distance from where the landers came down, at least in the case of Apollo 11:



That's the reflector in the foreground and the lander in the background. The reflector is still used, despite the upper stage of the lander lifting off relatively close by. Any dust that may have been stirred up apparently hasn't been a problem.

[Patrick Degan]

The stuff on the moon may last, but how obvious is it to find? Surely most of it is covered in dust from when the lander took off?

Only the upper ascent stage of the LEM ever launched off the Moon. The lower descent stage was it's launchpad, therefore the upper stage engine never fired into the dust on the surface. No air means no displacement when the engine fired, so again no dust got kicked up. You can see it in videos of Apollo 15, 16, and 17 when they set up cameras to televise the astronauts returning to orbit.

[Bedlam]

Considering that humans have died virtually everywhere on this planet I'd say there is going to be a fair amount of fossilized human skeletons even dozens of millions of years in the future.

I'm not sure how many Fosillised Humans their would be, although their are a fair number of us, we havn't been around for very long and only a very tiny proportion of all deaths would form fossils under special conditions. Also fossils would be hard for a alien to find, they would have to actually look and often dig for them rather than just have they lying around.

Anyway could you tell how inteligent humans were from a fossil?

[hongi]

Considering that humans have died virtually everywhere on this planet I'd say there is going to be a fair amount of fossilized human skeletons even dozens of millions of years in the future.

I'm not sure how many Fosillised Humans their would be, although their are a fair number of us, we havn't been around for very long and only a very tiny proportion of all deaths would form fossils under special conditions. Also fossils would be hard for a alien to find, they would have to actually look and often dig for them rather than just have they lying around.

Anyway could you tell how inteligent humans were from a fossil?

Fully agree. And we've only reached such great numbers within the last couple of thousand years. That's like a blink of an eye in geologic time. If everyone on Earth just dropped dead now, the vast majority of people in urban centres would not be fossilised (concrete floors not being very conducive to fossilisation), the vast majority of rural living people would die in their homes or die in the open field to be scavenged etc. The lucky few skeletons in our graveyards, or those of us who died under silt, that are fossilised are going to be scattered and distorted by the landscape changing for millions of years. And if aliens did land on Earth, it's just as likely those few fossils will be underneath oceans or mountains or a mile underneath rock.

IOW, I really doubt aliens would be able to construct even one full human skeleton from our left over pieces.