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?

Comments

satellites

[Anonymous Coward]

Probably satellites would last the longest, with maybe Pioneer or Voyager probes for however the RT batteries last.

Re:satellites

[AmiMoJo]

A Nokia 3310 will outlast them all.

Re:Satellites

[MarkWegman]

The orbit decays and ceases to be geosynced. But it's got a long way to go before it hits the atmosphere and burns up. Remember how much energy was needed to get it up there from low earth orbit. The satellite has to give up all of that because of the tidal effects of the moon before it's close enough to be slowed by the atmosphere. There may also be a very minor effect from the sun's radiation. I think it's safe to assume that the solar cells will deteriorate before the decay of the orbit causes a problem.

Re:satellites

[Antique Geekmeister]

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.

Re:satellites

[Strider-]

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.

Re:satellites

[dj245]

One should be very wary of the distinction between "run without refueling" and "run without regular maintenance". Even assuming that the reactor's fuel would last, the ancillary equipment associated with the reactor's operation (coolant pumps and such) and electricity generation (steam turbines) certainly wouldn't be expected to operate unattended and unmaintained for months, let alone years.

That said, the fifty-year planned lifespan of the Nimitz-class includes, if I'm not mistaken, a mid-life refuelling and complex overhaul (RCOH). To be fair, the reactor's fuel would likely last longer than the planned 20-25 years if the carrier weren't actively steaming--but I wouldn't trust the other parts to last anywhere near so long.

As a steam turbine engineer, I am fairly confident that, given a well maintained system to start with, the first failure would probably be in a stuck steam control valve. Over time, oxides build up on the valve stem, which would cause it to become stuck at some point. This would probably take 3-6 years. When that happened, the instrumentation control loop (need more steam, open valve, need less steam, close valve) would have a hiccup since it would ask for more or less demand and the valve wouldn't move. Valves stuck-open have historically caused many turbine overspeeds and resulting disasters.

Depending on exactly how the system was set up, the stuck steam valve should trigger the control system to automatically close a different valve, shutting down the plant. However, it is possible that it would result in a large kaboom as the turbine entered overspeed and the turbine blades liberated.

As for the last electrical device operating, my money would be on a solar powered yard light. The quality of those devices is generally terrible but the law of averages suggests some of them have to be on the long tail of a MTBF curve.

XKCD answered this

[slart42]

A very similar question was in an XKCD "What If?", but only in the printed book version (which has a bunch of extra chapters compared to the blog): "What would be the last artificial light source to glow when all humans were gone".

IIRC, the conclusion was that it would be status LEDs on space probes or radiation glow from buried nuclear waste.

Re:XKCD answered this

[someone1234]

Unit testing before launch?

Satellites

[Gre7g]

Solar-powered, geosynched satellites will keep going for a while.

WALL-E

[ei4anb]

you should watch WALL-E next, while pondering that question

"There will come soft rains"

[Cutterman]

Ray Bradbury asked the same question in 1950.

http://en.wikipedia.org/wiki/T...

The Cutter

Probably the Oxford Electric Bell

[Chrisq]

The Oxford Electric Bell has been running since 1840 and will probably carry on for a long time yet

a data collection device in antarctica

[lkcl]

andrew trigdell told me an amazing story back in 1999 about how he helped install Linux 0.99 on a solar-powered data collection computer in antarctica. Linux 0.99 was known to be highly stable, hence why it was chosen. it has a 56k modem which is enough to get the data back, and to check (very slowly) that it's still operational. so i think anything that's designed for long-term with those kinds of harsh remote and inaccessible conditions in mind, powered off of sustainable independent power, would be a good candidate for a device that would still be functioning even decades later.

Help Stamp Out Care Bears!

[TheRealHocusLocus]

Topic: Ask Slashdot: After We're Gone, the Last Electrical Device Still Working?
Reply Subject: Who cares?
Response: I don't care. I think that it isn't a interisting problem.

Analysis: Looks like this dim bulb has gone out.
Tally: Currently at 999 Points of Light
Who: A Child Left Behind
What: Passionate declaration of indifference.
When: 42 years after men last walked on the Moon.
Where: March For Apathy 2015 [cancelled]
Why: Dissonant aggressive demotivational pathos.
What: 's the use.
How: Did we get here?
Further Reading on this Topic: Failed Slashdot submission,

Breakthrough: Manned Space Travel Achieved Using 40-Year Old Technology

TheRealHocusLocus writes

"Paul Rosenberg has uncovered some surprising new evidence that manned space travel is not only possible, it has actually been achieved using decades-old technology. Some 40 years in the making, a tale too amazing to remain untold. With a few quaint photographs he asks, could we build this? The answer is no. Or is it? It is uplifting to read that "Productive humans have been delegated to mute observance as their hard-earned surplus is syphoned off to capital cities, where it is sanctimoniously poured down a sewer of cultured dependencies and endless wars..." for it must take something really compelling to prevent us from reaching the stars, and he has nailed it. This essay makes the case that the headliner of 2052 may well be: Breakthrough: Manned Space Travel Achieved Using 80-Year Old Technology. I can hardly wait! Down with robots."

Re:A nuclear power plant (and its control room)?

[Spazmania]

Nope. It would scram when the rest of the electric grid collapsed a few days in. The plant has to constantly output power. When the grid fails, the plant automatically goes into safe mode to avoid tearing apart the turbines. Diesel generators then start up to run the plant until grid power returns but they'd only last as long as the fuel.

Nothing associated with the public electric grid would last long without humans present.

Re:That would be useless wiring weight

[necro81]

Before launch you have connector to which you connect a computer and you can do a self diagnose on the satellite using that connection to the on board system. There is no reason to dedicate leds and leds wiring for that especially that you will need to check for many fail conditions.

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.

Re:That would be useless wiring weight

[AikonMGB]

We don't design LEDs into our own boards, and we explicitly remove them from COTS boards that we use. Generally speaking the diffusers on LEDs outgas, meaning a) they are depositing materials on your spacecraft surfaces (bad) and b) could result in a shorting risk (also bad). There may be space-grade LEDs that big-space (think Hubble, JWST, Voyagers, etc.) use but I would be surprised. There's simply no need.

"Is it plugged in? Is it turned on? Is it on frequency?" solves about 99% of basic device connection issues. An LED will make one very short portion of that slightly shorter, and then only when testing on the bench, since you can't see it as soon as you box it up. As soon as you can talk to a device, you are able to run a long form functional test on it, exercising every part of the design and ensuring everything is working correctly. If it passes, you're good. If it fails, you pull the unit.

For ground support equipment, yeah sure, throw an LED on every rail and switch output.

Re:A.I.?

[Immerman]

I don't know - a lot of current weak AI may end up being sub-systems for a strong AI - so in that sense we may well be getting closer. The problem is we have no real idea what strong AI might actually entail, implementation wise, and so have essentially no idea what if any progress we're making in that direction. At the very least we've found a great many strategies that don't work, which is in fact it's own kind of progress.

Honestly though I'm happy with the current state of affairs - weak AI may be able to get us into a lot of trouble (market crashes due to HFT algorithms anyone?) but it's nothing compared to what a strong AI would be capable of.