I was thinking about the concept of Utility Fog, programmable matter that can replicate a physical structure. They can be made to form air, furniture, and even entire buildings, with sufficient programming.

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Given the case that they are mass produced to be able to create relatively anything, like the stuff I mentioned above, the next issue would be about how they can be controlled. Looking at the description from the site above, it seems that people have a direct interface with the Utility Fog, as if the Utility Fog was mind controlled, probably with a brain cap that allows for such an interface. So, when people think they want to have a couch rather than just a chair, the Utility Fog will respond to their thoughts and make just that.

However, I have realised a problem, that does not seem to be addressed. If people no longer actively think about what they want the Utility Fog to be, or turn off the brain cap, won't the stuff just collapse back into a bunch of nanomachines in the air? So, I wonder, what sort of mechanism or programming might help to solve this issue, keeping the furniture in place even when the person does not actively think about them.

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    $\begingroup$ why wouldn’t the fog have a stay in place routine? $\endgroup$ Jan 31, 2021 at 9:08
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    $\begingroup$ what kind of hard-science are you looking for here, considering that you are also asking for a reality check? $\endgroup$
    – L.Dutch
    Jan 31, 2021 at 9:46
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    $\begingroup$ This question reminds me of the classic film Forbidden Planet, where an entire race was wiped out because their mind-controlled machines started obeying their subconscious wishes - all that violence beneath a civilized veneer was their undoing. $\endgroup$ Jan 31, 2021 at 9:56

5 Answers 5


boolean permanent = true

It seems a rather trivial question. You've made something that can shape, colour and add properties (flex, conductivity, etc.) to itself to your desire. How difficult would the next step be that you consider an object finished or permanent and the fog to obey? Probably you barely need to spare the thought. Only if you would actively think of changing the object, the fog would change shape again.

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    $\begingroup$ Yep, it acts like an obedient dog, stays sat where it's told until given the "kill" or lie-down and roll over command. $\endgroup$ Jan 31, 2021 at 9:20
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    $\begingroup$ And probably you want it to be a ritual of some kind to restart it, so you don't accidentally think that something is in the way and have it vanish. $\endgroup$
    – Mary
    Jan 31, 2021 at 21:00


Given that the fog is remotely controlled, it will be very susceptible to hacking. You might wake up one morning to find that a prankster has turned your bed into a skip, complete with garbage. Or your house might now be in the middle of the street and look like a Swiss chalet complete with snow but no bathroom.


As in virtual worlds, some people would specialise in creating objects and the rest of us would pay good money for the designs. As for the materials; we would order fog online. It would arrive in the shape of a human that would deliver itself to your door and then dissolve into a shapeless mass on command - or into whatever you wanted to purchase.

It would be the ultimate Lego for kids.

Keeping shape

With regard to staying in the required shape, this stuff would stay where you put it until ordered to change. The connectors would be spring loaded to stick together and would require power to disassemble.

  • $\begingroup$ Like the keeping shape just like the lift brake mechanism ;D $\endgroup$
    – user6760
    Jan 31, 2021 at 11:30
  • $\begingroup$ Grey Goo World ending anybody $\endgroup$
    – Anderas
    Jan 31, 2021 at 12:44
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    $\begingroup$ @Anderas That only applies if utility fog can turn mundane objects into utility fog. Which, I suppose, it probably can; it just needs to form itself into a utility fog factory… $\endgroup$
    – wizzwizz4
    Feb 1, 2021 at 12:55
  • $\begingroup$ I think if enough of that stuff is there, a hacker could program it to block arteries or windpipes. That's not exactly the Grey Goo apocalypse but if no-one survives, no-one will discuss that detail. $\endgroup$
    – Anderas
    Feb 2, 2021 at 7:03

We have tons of machinery which has the very same "issue" when they are not used: printers, computers, cars, ships, rockets. Basically everything!

In your case the utility fog will still need to have a power supply to stay idle. If that power supply happens to be a RF source, the emitter of the can be configured in such a way that the power supply only extend to a certain volume. Anything that goes out of that volume will be powered off, and the buffer energy it has will be used to try to return back.


Fog does not stay together.

Like a robot servant who turns off the light when you leave the room, the utility fog would slump into inert particles when not needed. Everything in the room made of fog would dissipate into drifts on the floor. What would be left would be a non-fog AI - some Alexa like Argus entity which watches everything and knows where its masters are. When one of them approaches, Argus prompts the fog to reassemble the foosball tables, pinball machines and bar stools.

If you are not one of its masters, you would find yourself in the empty space. When you enter, Argus might ask who you are. Or it might already know. The fog is ready, and there are options for the fog in this space that are not as hospitable as the game room.

  • $\begingroup$ This would be particularly useful when keeping the shape costs more than reforming the shape over and over again. $\endgroup$
    – GOATNine
    Feb 1, 2021 at 19:33

I would say the fog stays together using magnetic flux pinning.

This link explains the phenomenon: https://en.m.wikipedia.org/wiki/Flux_pinning

Now I don't know all the equations and stuff, because I'm but a layman but in principle it's when a superconductor gets enveloped in a magnetic field it shields it from all other magnetic fields and causes a repulsive force that pins it in place.

And since electromagnetism is stronger than the other fundamental forces, you could postulate that you could provided you had enough power use this phenomenon to create connections stronger than any normal matter. However I'm not sure as I don't know the math.

Now to make this possible you would make your little nano fog particles little spheres with connection points, half of them made of room temp superconducting material and the rest are miniature electromagnets.

Basically when power is applied they stick together like a magnetic Velcro and you can vary the strength of the field to vary the strength of the attraction.

  • $\begingroup$ Yes to flux pinning, no to the rest. Electromagnetism isn't more powerful than the intramolecular force or - except in extreme cases - the intermolecular force. A magnetic field strong enough to overcome either of these force categories would be damaging to humans. Not to mention requiring a physically huge power source for each one of your 'dust' particles. Better to use small amounts of broadcast power to create physical linkages - literal molecular-scale velcro. $\endgroup$
    – Corey
    Jan 31, 2021 at 23:26
  • $\begingroup$ @Corey thanks for enlightening my ignorance I'll change it up when I can. $\endgroup$
    – Efialtes
    Feb 1, 2021 at 0:40

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