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OK, so let's say Jim and Bob have a time machine. It's a large construct:

  • Server rooms with quite a bit of human knowledge in them
  • power generators
  • some areas to grow food
  • a voice activated terminal that reacts to literally every language.

Now, let's say that they went a little too far back than intended, and end up in North America during the last Ice Age. Jim and Bob enter a stasis chamber because the "Time Machine" function of their time machine stops working, but everything else still works. Humans find it (1780CE), accidentally activate the computer, discover Technology as we know it (except time travel), jump-start every technological revolution since then, and then accidentally let Jim and Bob out circa 2100CE.

What would be a low maintenance power source to last roughly 10k years?

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    $\begingroup$ How about a really, really big lump of coal? $\endgroup$
    – Salmoncrusher
    Oct 10, 2016 at 1:08
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    $\begingroup$ Your biggest hurdle here isn't really finding a long-term power supply, such as nuclear decay. The hard part is designing components that will survive thousands of years. The RTGs mentioned in John_H's answer are declining in power output due to problems with the thermocouples; a 20% loss after only 23 years. Even if that's exponential decay, it will be under 1% after only 475 years. Realistically, the rate of decay is probably accelerating, meaning power loss is likely much faster. $\endgroup$
    – MichaelS
    Oct 10, 2016 at 6:51
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    $\begingroup$ I believe you are looking for a zero point module or zpm. $\endgroup$
    – EveryBitHelps
    Oct 10, 2016 at 7:14
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    $\begingroup$ «What would be a low maintenance power source to last roughly 10k years?» Could the sun be considered? $\endgroup$
    – Andrea Lazzarotto
    Oct 10, 2016 at 12:00
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    $\begingroup$ Related: With current technology, what would be the best way to store energy for future generations? $\endgroup$
    – Theraot
    Oct 10, 2016 at 14:40

13 Answers 13

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A tiny piece of antimatter is all you need. (oh and a magnetic bottle to store it in and an antimatter reactor to generate the power you need but hey, you've built a time machine, so in your time you can probably buy one at hardware store)

Antimatter has an energy density of 9×10^10 MJ/kg, compared to 34 MJ/liter (around 145 MJ/gallon) for diesel fuel.

You don't say how much energy your machine needs, but let's say you need a steady 1 MW of power -- you'd need around 1700 gallons of diesel to power a 1MW generator for a day. (your antimatter reactor may be more (or less) efficient than a diesel generator, so find the specs in the owners manual and adjust numbers accordingly)

For 10,000 years, you'd need (10000 * 365 * 1700) = 6.2B gallons of diesel.

The largest supertanker in the world, the TI Class, can carry 3.16M barrels of oil, or around 132M gallons. So you'd need almost 50 of those supertankers worth of diesel -- probably more than you want to squeeze into your time travel machine.

But since antimatter is much much much more energy dense, you can get by with much less antimatter.

At 145MJ/gal of energy in diesel, 6.2B gallons is around 8.8 x 10^11 MJ

Since the energy density of antimatter is 9×10^10 MJ/kg, you'd only need (8.8E11 / 9x10^10) = 9.8 kg of antimatter (along with an equivalent amount of matter to annihilate it with, but fortunately, that's easy to find).

If you use antimatter lead (assuming the physical properties of antimatter are the same as regular matter), that's around 865 cm^3, less than a liter.

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    $\begingroup$ I applaud you sir! This is the most plausible explanation yet! $\endgroup$
    – CaptClockobob
    Oct 12, 2016 at 16:58
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    $\begingroup$ @CaptClockobob Except, keeping antimatter as a fuel source in a ship would be highly dangerous. What would prevent it from exploding rapidly due to the ship crashing? I'd think a time machine would want a fuel source that can be easily managed and is somewhat safer. After all, planes run on gas, ships run on gas, cars run on gas, etc. The only exception is nuclear submarines but they don't have to worry about that as much. There's a reason we don't put WMD level fuel sources in everyday vehicles. It is just not safe at all, even in the future. What if a terrorist used a TM to blow up a city? $\endgroup$
    – user64742
    Oct 28, 2016 at 23:14
  • $\begingroup$ @CaptClockobob - So put it in a safer container. Federation starships have been using Antimatter fuel sources for a long time with few accidents. Sure it's a risk, but so is timetravel, one slight miscalculation or inaccuracy in positioning and you may materialize inside solid earth, so carrying a bit of antimatter is not much risk in comparison. $\endgroup$
    – Johnny
    Oct 28, 2016 at 23:28
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    $\begingroup$ I'm sure in 2055 antimatter is available in every corner drugstore, but in 2018 it's a little hard to come by! (aw The Great Duck beat me to it) $\endgroup$
    – intrepidhero
    Aug 27, 2018 at 17:20
  • $\begingroup$ Antimatter may be too energy dense, what's the minimum, one atom:one antiatom reaction output? $\endgroup$
    – Ash
    Aug 27, 2018 at 17:39
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It is possible to have a radioisotope thermoelectric generator and have it last for a long time; though the power produced would decay over time according to the half-life of the radioactive element used. The plausible explanation for such a situation would be that the time travel portion of the machine requires many orders of magnitude the amount of power than the stasis pods and computer need to continue operating.

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    $\begingroup$ As I shill in this post, a Thorium-230 radioisotope generator could produce low power (0.5W per kg) with a 75000 year half-life. $\endgroup$
    – kingledion
    Oct 10, 2016 at 2:46
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Geothermal connection. Give the room some sort of connection to an underground heat source.

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    $\begingroup$ Geothermal power is a good choice, but your answer can be improved with more details about what is involved supplying geothermal power. $\endgroup$
    – a4android
    Oct 10, 2016 at 6:26
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    $\begingroup$ Why would one build geothermal capability in a time machine? $\endgroup$
    – beppe9000
    Oct 10, 2016 at 12:21
  • $\begingroup$ Why wouldn't they? assuming that it ends up in a sensible place eg stays in the same place in relation to the earth surface $\endgroup$
    – Topher Brink
    Oct 10, 2016 at 17:27
  • $\begingroup$ 10k years is a long time for old faithful to stay faithful rather than, say, blow up. $\endgroup$
    – candied_orange
    Oct 11, 2016 at 2:32
  • $\begingroup$ Geothermal energy depletes over time. After 5 years, a station will usually see a substantial drop in thermal energy available. Geothermal is explicitly NOT a good source for sustainable long term energy production. Here is a paper discussing geothermal regeneration (page 5) $\endgroup$
    – kingledion
    Oct 11, 2016 at 14:03
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How about this:

The time machine is powered through a wormhole. Those that build the device figured that just such a situation could arise and before they constructed the time machine they spent a lot of time to build a generator powering it where- and whenever it will be. The energy is just time-travelled to the machine. In fact this generator was placed in the far future when the sun swallows the earth. The device, now within the sun, drains energy directly from the dying star. The absorbed energy at the same time keeps the generator from being molten by exposure to the sun.

If time-travel works, why should this technology not work, too?

Edit: I meant the generator to have its own time travel option that is just there to send the energy to when it is needed.

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    $\begingroup$ From the question "the 'Time Machine' function of their time machine stops working" $\endgroup$
    – Ben Voigt
    Oct 10, 2016 at 16:43
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    $\begingroup$ @BenVoigt Shame, though. This is a cool idea. $\endgroup$
    – Devsman
    Oct 10, 2016 at 17:55
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    $\begingroup$ @BenVoigt Maybe that just means the ability for people to travel using it is broken. Time traveling power could use a separate mechanism. $\endgroup$
    – mbomb007
    Oct 10, 2016 at 18:58
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    $\begingroup$ @wizzwizz4: I was just giving "just send replacement parts" as an example of what kind of answers you get if you start arguing that the restrictions in the question really don't mean what they say (exactly what mbomb007 is arguing). $\endgroup$
    – Ben Voigt
    Oct 10, 2016 at 19:54
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    $\begingroup$ What if the generator had its own time travel mechanism that it used to send the power? The other end wouldn't need time travel to receive it. $\endgroup$
    – Darcinon
    Oct 10, 2016 at 20:19
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Coming up with a self-contained power supply that will last for such a long time will be tricky. But what about...

Piggy-backing on existing power sources that are maintained by someone else?

Since the time travelers are from the future (as of when the new time travelers discover it), sufficient research could give them insight as to what kinds of power sources will be available. And since it's a time machine, it's a good idea to include alternate methods of powering the thing for exactly this reason. In 1985, for example, plutonium is available at every corner drug store, but in 1955, it's a little hard to come by.

How effective these solutions will be depends on the power requirements for your machine, but here are at least some ideas:

Beginning in 1900 or so, the machine could run on induction from radio waves, especially when some towers are powerful enough to broadcast anywhere on earth, including the depths of the ocean. A little later into the century, the machine could simply plug into a wall outlet.

Beginning in the late 18th century with the industrial revolution, mechanical transmission came to be, and while this involves moving parts, sufficient handwavium or sufficient determination on the part of the people who discovered the time machine could allow the necessary gear and shaft to still rotate and power the machine.

Speaking of handwavium, you're gonna have to build the whole machine of it in order for it to still function at all after ten thousand years.

Before the industrial revolution, it will be difficult to communicate to anyone who would discover it that this is a machine that does something, and that it needs user-provided power. But supposing that you somehow could, coal has been a known power source for a very long time. Perhaps leaving a little coal in the machine could help the users to understand.

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    $\begingroup$ "In 1985, for example, plutonium is available at every corner drug store, but in 1955, it's a little hard to come by." And that 1985 drug store is also known as... terrorists. +1 for the movie reference. $\endgroup$
    – user64742
    Oct 10, 2016 at 22:20
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Peter F Hamilton has a neat idea for such a power source. It's called the Niling d-sink.

It's described here: http://peterfhamilton.wikia.com/wiki/Niling_d-sink

as a "hole in space-time that can be filled with energy". Although I imagined it as a battery that is bigger on the inside than the outside.

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    $\begingroup$ That is just one step away from the Tardis, make the Pocket Dimension/space Habitable. Could be interesting story wise, but also needs some explaining regarding how it is maintained and accessed. $\endgroup$
    – Ryan
    Oct 10, 2016 at 18:48
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Ten thousand years rules out anything with moving parts - which is almost all power sources known to modern man.

Anything that runs on fuel is likewise out.

There are only four things that will generate any power of note for that long.

One - geothermal power. However, this would require moving parts, and would wear away well before you get to 10K years.

Two - radioactive elements. This would generate a very small amount of power for a very long time, but that power would diminish exponentially with the half-life of its fuel.

Three - the sun. Solar panels have no moving parts and require essentially no maintenance if they get rained on every so often. Though, location and local weather conditions could make this infeasible as well.

Four - make one up :) Even if the time machine is broken, sending a single photon back in time every so often would allow the machinery to pull energy straight from vacuum.

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There is a device called a "thermoacoustic heat engine" (more details at Wikipedia). It has only a single moving part, a piston (which could be maglev for zero wear and tear - i.e. a really long life). This device converts heat into electricity by creating a standing wave resonance in a gas (almost invariably helium) filled tube, this can drive a magnet back and forth through a coil to generate electricity.

Unlike with Radioisotope Thermoelectric Generators, the active parts can be far far away from your nuclear fuel, so the radiation is of little concern. The hot end it just a specially designed gas filled pipe while all the important stuff can be placed far away. If you want a really long lasting generator (and/or a hard science solution), I think you'd be hard pressed to beat a Radioisotope Thermoacoustic Generator.

They work just as well as fridges too (and musical instruments - see Rijke tube) and at least one person has made liquid nitrogen with one (maybe you could use them in your long life stasis pod?)

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Siphon power from the future

I admit that this is a pretty unusual idea, but it simply put goes like this:

You need energy to power the stasis pods and things, therefore you pull a bootstrap paradox. Just make more power when you have time available and send it to the past so that they survive and you learn that you need to send power back so they don't die so that you know you need to send power back.....

You get the point.

Alternatively, (and this could explain near infinite amounts of power in time machines) one could transport power to the time machine using time travel and then just put that power back where it was when you are no longer damaged/have large power sources available. A time machine only needs a large enough battery to be able to cannibalize power at profit. It's not perpetual motion. It's just borrowing power from throughout history to recharge the batteries. Of course, there is a downside to this. One could easily wreck a computer by accident, start electrical fires, or worse kill a person because you siphoned electricity from their body and didn't put it back quite right.

You know... everyday things we see in the world... right?

Now I know what you are going to say.

But the time travel systems broke down

No, their ability to travel through time was destroyed. However, energy movement is probably quite easy. After all, energy = mc^2 which means tremendous amounts of energy are very small in mass once they have been fully processed and so transporting them into the ship could be accomplished via a simple computer component/circuit that the protagonists might not even be aware of. Heck, the additional upside is that since the energy is brought into the ship directly without processing, there is no need for any large-scale power generators. If anything, I would imagine the ship to have massive batteries in the case of system failure, in which case the batteries would serve as a several year backup to prevent complete stranding.

So why doesn't the ship just bootstrap its own power?

Well, that's the thing about a bootstrap paradox. A bootstrap paradox cannot truly create a physical entity. After all, everything ages and decays aside from the very fabric of space-time (which even then is debatable I imagine). So anything in a bootstrap paradox would instantly decay into oblivion. A bootstrap paradox is meant for bringing knowledge in a cycle, or an abstract concept (I believe one story I read once literally involved someone bootstrapping a soul into existence, or maybe bootstrapping it to prevent its nonexistance). Bringing matter in a cycle like that is... impossible.

Why not continually borrow from the future ship and have a generator on board?

That is a perfectly valid option! In fact, this is nothing more than my design, which is intended to be as efficient and small as possible. I'm imagining what I believe would work as a ship that has minimal "extra parts". In essence, the ship merely needs a time travel component and it has power. And the time travel component need not be the same time travel component as the one providing power.

In fact, just to throw one extra thing out there, the computer system on this ship are going to no matter what by far be extremely efficient and fast at processing. The reason for this is that every single thing that does not require interaction by a user can just be bootstrapped to the beginning of the calculation and so... those values were never calculated, just read from memory. Want the first 10 billion prime numbers to be placed in these memory slots in the computer? Fine, it will be sent there instantly.

The only downside that could potentially hurt such a computer is memory management. I'm not saying that the memory would be inefficient, rather what I mean to say is that the computer will have to no matter what spend time sending data to the past and depending on the time travel system, this might take a lot of time. Because of such a fact, a computer system on one of these ships will want to use as little memory as possible and probably doesn't do bootstrapping by default. It is probably a command used in writing the program. Most likely it is something like an if, while, or for statement that says something along the lines of: "bootstrap { code }".

However, I might be quite wrong, actually. Since memory and throughput (the time it takes to process something) generally live in an inverse relationship, the sudden lack of any need to make things efficient for time could lead to data in programs being dramatically reduced at the assembly code and binary levels in a large scale attempt to optimize programming in general in preparation for the new "Temporal Hardware".

And how was this relevant?

Well, I just demonstrated the fact that there is a very obvious use for the time travel technology that is not used for transportation and as a result I have shown that while the characters are truly stranded, they might still have time travel tech on the ship. They just cannot use it to go anywhere due to its size.

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From Dr. Who the tardis has a blackhole inside of it for power. Even a blackhole a few feet (10-20) across would probably be enough, but you could make it any size you wanted.

Clearly, a sun,blackhole,supernova are your only good options. If you have time travel you either have the tech or you traveled to the future or to planet another race and got the technology.

Even better yet, as long as the core maintains it gravity, throw any random bits of garbage into, and it gets ripped apart for fuel. Probably maintain the whole ship at full power, if you want it to for a billion years.

Clearly, you will need a strong force field to contain it, and it will have to have at least 3 layers of redundancy and automated processes to self repair. The repair circuits would also need at least 3 layers of redundancy.

However, If you developed time travel none of these problems should be an issue. The tech to solve these problems should already exist. Otherwise, travel a million years into the future 1st trip, and retro-fit your ship.

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    $\begingroup$ Actually, the Doctor is never real consistent on energy sources. Sometimes it is a large sun, sometimes it is a black hole, sometimes it is the energy of time itself, and sometimes it is something as simple as "the Tardis uses reality to recharge itself". See the episode in season 2 when they go to the parallel Earth. They get stranded cause the Tardis isn't compatible with that reality. $\endgroup$
    – user64742
    Oct 11, 2016 at 2:26
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    $\begingroup$ Yes, I remember that. Journey into the center of the tardis episode it was the "eye of harmony". 33:02 An exploding star in the process of becoming a blackhole. The funny part is there is a rift in cardif that they use to "top it off". $\endgroup$
    – cybernard
    Oct 11, 2016 at 2:36
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    $\begingroup$ Sometimes I wonder if the tardis just grabs whatever energy it can find without damaging things, lol. $\endgroup$
    – user64742
    Oct 11, 2016 at 3:47
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A Dyson Sphere around a red dwarf is basically unlimited power, although I'm not sure that's what you're asking for.

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    $\begingroup$ I'm looking for something a LOT smaller. $\endgroup$
    – CaptClockobob
    Oct 10, 2016 at 1:19
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    $\begingroup$ This does not provide an answer to the question. Once you have sufficient reputation you will be able to comment on any post; instead, provide answers that don't require clarification from the asker. - From Review $\endgroup$
    – Magic-Mouse
    Oct 10, 2016 at 10:17
  • $\begingroup$ @CaptClockobob If you have power over spacetime, as in a time machine, you will be able to fit a red dwarf in a hazelnut. $\endgroup$
    – user8976
    Oct 10, 2016 at 13:01
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    $\begingroup$ @what I don't know about shrinking a red dwarf, but if your time machine works through spacetime wormholes, it's an "easy" dodge to say that the power source exists in the future somewhere off in space, and then you have a constantly open wormhole to transmit any power that's needed locally. $\endgroup$
    – R.M.
    Oct 10, 2016 at 14:18
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    $\begingroup$ @R.M. If I remember correctly, the TARDIS is powered by a miniaturized supernova, so why not the same here? Or, if we can't shrink the star... What's stopping us from creating a reactor room large enough to contain the star that is slightly out of phase with the current plane of existence so it's accessible from within a portion of the ship that only exists inside, and doesn't exist outside of the physical ship... $\endgroup$
    – Taegost
    Oct 10, 2016 at 20:19
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I'm suggesting the Kugelblitz. What fancier way to power your craft than a black hole made out of light?

Using high-power lasers you could create a black hole, and use the hawking radiation as a source of power. Basically a battery.

For ideal output its life should be made to be about 8 years.(For space exploration at least) But it could be tuned to anything you like, even 10 000 years. Perhaps create multiple ones to get long-term power.

Another alternative is to just feed the black hole with arbitrary matter. It works on sand, water, air or whatever you happen to have. So after its created its basically a matter - energy converter.

The output of a 4.5 year lasting, 600 000 tonne black hole would be 160 Petawatts. I think you could get by with much less, though that would increase the mass significantly.

The problem is the immense amount of energy needed. The common options include using nano robots to convert mercury(the planet) into a dyson sphere of small solar panels.

Creating the 8year blackhole would take about a week(If I remember correctly) of the suns output. But the evaporation time(thus the output power) reduces exponentially with weight/energy input. So it might be possible.

Good video about Kugelblitz(Also includes other stuff)

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  • $\begingroup$ How do you prevent matter from entering the microscopic black hole, thus increasing its mass and potentially swallow a large amount of Earth? $\endgroup$
    – M.Herzkamp
    Oct 11, 2016 at 12:39
  • $\begingroup$ @M.Herzkamp The black holes mass isn't significant enough to have a strong gravitational pull. Also the energy leaving through hawking radiation stops matter from falling in. Though I would imagine this being in a vacuum chamber and used similarly to an RTG. $\endgroup$
    – akaltar
    Oct 11, 2016 at 13:41
  • $\begingroup$ I was talking about the one you want to feed "sand, water, air or whatever you happen to have". Any black hole that is feedable sounds very dangerous and maybe not stable enough for 10k years without maintenance ;-) $\endgroup$
    – M.Herzkamp
    Oct 11, 2016 at 15:11
  • $\begingroup$ @M.Herzkamp I think that by definition its the most stable and reliable thing possible. Though it was designed to work in zero-G, I think you could suspend it using magnets. Or simply use a future anti-gravity kit..... $\endgroup$
    – akaltar
    Oct 11, 2016 at 15:56
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Human beings would be a good power source they keep multiplying so you have an inexhaustible supply someone with technological knowledge that is advanced enough to build a time machine must be able to come up with a way to process lifeforms into usable sources of energy.

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