How long would it take for infastructure to fail if humans disapeared?

Question

This question is similar to this one, which wanted to know what the world would be like 10,000 years after humans disappeared. Almost all traces of human activity would be gone from the earth - only the most corrosion resistant objects would be left.

However, I was thinking, with all the automated systems around now, how important are humans? Obviously things like bearings in wind farms and hydroelectric dams would fail, and there are parts in nuclear reactors that also need maintenance to stay running, but just how long would infrastructure like the power grid and the internet stay up and running if all humans suddenly vanished? Obviously, after the main power grid shut down, most of the internet would follow shortly after, but I'm guessing some places have pretty good backup systems in place, which would hold out for a while. I'm thinking that with all the automated systems in factories and other industrial facilities, there may be specialized machinery that could perform repairs, but may not necessarily be programed to do so.

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Then I got another crazy idea. What if, after the humans disappeared, a powerful AI took over, while the internet was still running, and was able to control robotic systems like the ones in factories, and was able to produce reliable repair bots, that could perform the maintenance that humans do? Could an AI stay operating for the foreseeable future if humans were not around to constantly repair things?

Just how important are humans to the continuation of the infrastructure and systems we have built?

Answer 1

Not long at all. After the first major storm in a given area, electrical service would be down, and that could be tomorrow. The power plants producing the electricity have to be monitored and their output varied to balance grid power and demand; left at a constant power output, the grid would alternate between blackouts and overpower trips like the type that caused the New York blackout in the 70s. Water infrastructure would collapse within a year or so as the pipes corroded because nobody was monitoring the anti-corrosion chemicals at the treatment plants (and what was already in the lines got used up). Most media outlets are only programmed a day or so in advance and still require human decision-making in real-time regarding things like local vs national ad time. Liquid fuels have very short shelf lives; gasoline fresh out of the pump today would be unusable in a year, so in that same time the tanks at the service stations would be fouled. Fuel gases will last longer, but when a line goes it would be bad for everything in the area.

Roads and bridges might last 3-5 years before they became impassable by the average car. They'd fare worse in northern climates where colder winters cause shrinking and cracking coupled with frost heaves that tear the asphalt apart. In southern climates the roads would last longer without any road traffic to wear them down, at least in the places that don't have to deal with erosion (or that were engineered to resist erosion from the ground up).

Large buildings would resist weather until their exterior structure was compromised, and since many high-rises are mostly glass, a good hailstorm would do it. Then wind and water get in, rot starts taking hold, ice heaves in the smallest cracks it can find and within a couple decades the building's done for.

So, inside about 5 years, much of the basic utilities would have to be torn out and replaced, and after about 20 years of Earth's fury there'd be nothing manmade still in usable shape.

Answer 2

Humans are still pretty integral to the infrastructure. Even "automated" systems usually just make it possible for humans to coordinate efforts (in large-scale distributed systems like the power grid). Humans are also required for their ability to adapt to sudden environmental changes (think power lines going down in a storm). If your AI was in charge of an automated factory that was largely solar- or geothermal-powered it might have a chance, but to somehow take over a remote factory and have it start turning out repair bots and keep a distributed system like the power grid or network backbone working would be a bit of a stretch.

OTOH, if an AI were built to survive (reliable power and built-in self-repair capabilities), I could see it possibly sending out repair bots to maintain or repair selected bits of infrastructure it required (e.g., water and sewer probably wouldn't be high on the list, but power and comms would be).