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Ask Slashdot: After We're Gone, the Last Electrical Device Still Working?
Leomania writes: After watching a post-apocalyptic Sci-Fi short on YouTube (there are quite a few) and then having our robot vacuum take off and start working the room, I just wondered what would be the last electric/electronic device still functioning if humans were suddenly gone. I don't mean sitting there with no power but would work if the power came back on; rather, something continuously powered, doing the task it was designed for. Are we talking a few years, decades, or far longer?
Ray Bradbury asked the same question in 1950.
http://en.wikipedia.org/wiki/T...
The Cutter
The Oxford Electric Bell has been running since 1840 and will probably carry on for a long time yet
Running out of mono-propellent probably wouldn't be an issue because satellites simply don't attempt those kind of maneuvers without human input (at least I'm pretty sure), while that would definitely be a problem for LEO and Geostationary craft between those two orbits or are further out don't need regular boosts to stay going. And while reaction wheels do go bad pretty quickly (a decade or so) they aren't necessarily needed for a spacecraft to remain "operational". Sure without them they usually can't continue their primary mission but even if the craft has directional solar arrays slow rotation will give likely give them enough power for the satellite to remain in standby mode for decades, possibly a century.
The Voyager RTGs are decaying, NASA expects output power to drop below the point where it can keep a single instrument going around 2025.
The Pioneers are already long past the point where they can't send a strong enough signal to be detected.
The latest nuclear power plants for the US Navy have been designed to run without refueling for the life of the ship. That's 50 years for aircraft carriers, so the USS Gerald R Ford (CVN 78) is capable of functioning until 2065. Now I don't know how stable a nuclear power plant is when left on its own, but potentially this'll live much longer than the Voyagers.
I'm starting to regret I even said anything.
Welcome to the Internet.
Having spun a number of boards in my career, I can tell you that it is trivial to add an 0402 LED indicator, just as an indication that the 3.3 V logic rail is powered. And because it was easiest (via inertia) to keep it in than to cut it out (even as a do-not-populate instruction to the board house) that little LED stayed in the design, even though in production no one would ever see it.
Given the complexity of most satellites, I would be deeply surprised if there wasn't at least one LED on one of those boards.
The Volkswagen Beetle from the Woody Allen movie, "Sleeper"
http://www.tin.org/bin/man.cgi...
More realistically, some chemical batteries, such as good lead-acid batteries in cool, dry climates will retain a slight charge for years. But they all have a notable self-discharge rate of at least a few percent a month. The notable exception among battery technologies seems to be this:
http://en.wikipedia.org/wiki/O...
That device has been running off its battery, at an extremely low rate, since 1840. The bell is much softer now, but it shows no signs of failing.
You're wrong, but much of that progress has come from neuroscience, not computer science directly. Real progress in emulating the large scale behaviour of neural systems has been made.
AI is only a matter of time.
Either my understanding of orbital mechanics is completely wrong or that is completely incorrect. Geostationary satellites need very regular station keeping otherwise they either fall to Earth or are ejected out into solar orbit. If ejected it could remain operational for a while but if it fell back to earth the results would be obvious.
Your understanding of orbital mechanics is totally wrong. Geostationary satellites do need frequent stationkeeping maneuvers, but that is because the satellite is required to remain in a 30km box. If these maneuvers cease, as would happen with the sudden disappearance of humans, they will start to drift off their stations, eventually collecting in a couple of regions, one over the Indian ocean and the other over the Pacific. (This is due to the earth's slightly uneven gravity). Because of the vastness of space, the probability of them actually running into each other is fairly low.
A geostationary satellite would need almost the same amount of energy to come down as it takes to put it up there, and probably twice as much to escape the earth's gravity well. At the end of life of these satellites, they use the remaining fuel to boost them another 200km or so in altitude, then vent all remaining fuel (so they won't explode if there's a fuel leak), and then blow the electronics to make sure they don't interfere with anything else. They will remain in that graveyard orbit forever.
...si hoc legere nimium eruditionis habes...