An alien spacecraft flies past Earth on a tour of the universe. They spot some apparently intelligent creatures and decide to leave them a present. The artefact is effectively a perpetual motion machine. It is a closed, indestructible metallic box with an axle projecting from one side - the axle has a rough surface. In theory it could have a wheel attached to it. It rotates at a constant rate of about one revolution per second and is pretty much unstoppable.

Unfortunately humans have not yet invented the wheel. A band of hunters find the cube shaped device which weighs the same as two men.

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In this society - reliant on wood, hide, bone and stone tools - is there any use that they can find for the artefact or have the aliens wasted their time and a perfectly good artefact?


closed as off-topic by Samuel, Frostfyre, Thucydides, Aify, JDługosz Aug 2 '15 at 17:28

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  • $\begingroup$ Well, perpetual motion by itself, with no way of reproducing it, is not actually useful, as long as there are other ways of getting energy more quickly. I think the fact that it's "indestructible" and "pretty much unstoppable" would be more useful, but I'm still not sure what practical applications that feature would have. The axle is circular, I assume? (Relevant answer about perpetual motion: worldbuilding.stackexchange.com/questions/1086/… $\endgroup$ – sumelic Aug 1 '15 at 21:37
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    $\begingroup$ Only a few hundred years! Seems like sort of a lame present then. What sort of answers do you want; just brainstorming about possible ways to use this thing? $\endgroup$ – sumelic Aug 1 '15 at 21:50
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    $\begingroup$ If that machine isn't quite heavy the homo-what-have-you-s can point the end of the spindle at a dry wood and generate heat front the 60rpm let there be light!😇 or use it to sharpen tools or create cave drawings or steer a log floating on water hint: magus effect😎 too many to list due to words limit😓 $\endgroup$ – user6760 Aug 2 '15 at 0:25
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    $\begingroup$ @user6760 - well you could make it an answer ;-) (but the artefact is quite big as you can see) $\endgroup$ – chasly from UK Aug 2 '15 at 0:45
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    $\begingroup$ Erm... since when a perpetual machine will run out of juice? I think this one isn't just big it must have been unique(do not work as intended = spoiled) no worry didn't you said indestructible and unstoppable, lasso vines to adult mammoth and attach other end to spindle ta da you got yourself a mammoth trap lol😋 I'm thinking of automatic catapult... $\endgroup$ – user6760 Aug 2 '15 at 11:15

Short term lose

The cavemen/plains dwellers aren't going to get it. They have no concept of a rotary tool. The equivalent to what they've done is take a PC and gas generator back to ancient Greece and said "Here, play with this." It's too far out of their realm of experience for them to even start.

Long term gain

The battery in the cube has died and been dead for millennia. An explorer in Africa finds the cube and takes it back to the British Museum where it sits as an odd curiosity till modern technology learns how to crack the case and start to reverse engineer the mechanism and battery. Then it turns into something amazing! If a device like that were discovered now, it would catapult our understanding of long running power sources and exceptionally low wear mechanisms.

  • $\begingroup$ I think the "perpetual" part of perpetual motion machine means it doesn't have a battery that will run out. I think you have the right idea though. It would probably be hidden or buried because it's dark magic and will be found by a more capable civilization. $\endgroup$ – Samuel Aug 2 '15 at 2:49
  • $\begingroup$ @Samuel: charley from the UK said that it had a battery that would run out, but this information is only in the comment chain below the original post and not actually in the question for some reason. $\endgroup$ – sumelic Aug 2 '15 at 5:18
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    $\begingroup$ @sumelic Oh. So it's not a perpetual motion machine at all. It's a motor with a battery... Alright then. $\endgroup$ – Samuel Aug 2 '15 at 5:40


Just wait until you see the sparks that fly when the primitive wheel-less inhabitants get frustrated with it and petulantly throw it in a river.

Given the aliens offloaded the thing in the first place, I'm assuming its the cheap model. You know, the one which doesn't have nice water-tight seals. Phryxian power cells prefer environments where the humidity stays below 100%, thank you very much.

It may not have been as profound of a gift as the monolith Clarke's "Firstborn" dumped there a few hundred thousand years earlier, but wow were those fireworks something to behold!



Do those people know fire, and how do they start it? If they use a hand or bow drill, the opportunities should be obvious.

Grinding Grain

Are they using agriculture? Homo sapiens in the late stone age certainly did. Press a flat stone against the axis and pour in grain.

  • $\begingroup$ Yes they do have fire - that would definitely be worth them trying. Also they could sharpen tools with it I reckon. I don't know if they have agriculture though - I don't think so. $\endgroup$ – chasly from UK Aug 2 '15 at 23:22
  • $\begingroup$ I have added fire back into the illustration. I removed it at first for no particular good reason. $\endgroup$ – chasly from UK Aug 3 '15 at 10:19

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