I'm currently working on a story and I'm having some interrogations about the plausibility of a civilization.

Quick backstory: Humans had to abandon Earth a few thousand years ago for the classic reasons. Since two hospitable planets were found, humanity was divided in two parts, based on their view of how to avoid destroying a planet again. Planet A received those who would steer technology toward sustainable development, and planet B those who would reject technology entirely. The former are the cause of my headaches. I would like them to have invented a way to create material from any substance through rearrangement, not only on the molecular level but on the atomic level too. That machine would prevent waste, by making virtually everything recyclable. Basically, you put a pound of iron inside the machine, choose to make lead out of it, wait for as long as is necessary, then walk away with a pound of lead. Would that be plausible? What would be the implications and limitations?

Some thoughts (That I might edit/add depending on answers I get):

  • I have no problem with the machine being miles and miles long/wide if necessary.

  • There could be one in every house or only one on the planet, no problem there either.

  • Ideally, focus would be one speed/capacity. Since anybody could use that, I'd like it to be as fast and efficient as possible. People could easily tone down their demands to fit the machine(s) limitations, but the faster, the better.

  • Having supraconductors and very efficient energy gathering through solar devices, energy should be available in great quantity. Would even that be enough?

  • There IS magic in the story, although only on the other planet so far. Magical implications would be acceptable, but I'd rather it stayed plausible without those.

    Anything else I should worry about? Thank you.

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    $\begingroup$ Energy costs would be prohibitive. If you do have that kind of energy to spare, why not simply build a rocket to a nearby planet and mine there instead. $\endgroup$
    – nzaman
    Mar 2, 2017 at 16:57
  • $\begingroup$ The idea would be to avoid mining a planet raw in a sustainability-first context $\endgroup$
    – Garnovski
    Mar 2, 2017 at 17:01
  • $\begingroup$ Rather than mining a planet, why not mine asteroids or dead moons? The cost to escape those gravity wells is significantly less and they already don't support life. $\endgroup$
    – Frostfyre
    Mar 2, 2017 at 17:13
  • $\begingroup$ I want this society to live in a money-less utopia, where you can get what you need by simply taking the time to make it. You want to surf? Gather 30 pounds of rock, or throw in your old bike, and build yourself a board. I want them to recycle and recycle and recycle, allowing them to live with their resources undefinately. Mining is not an option with where I want the story to go $\endgroup$
    – Garnovski
    Mar 2, 2017 at 17:19
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    $\begingroup$ Stick to molecular chemistry, then. Lead waste to lead product, iron scrap to steel, like we already do. Solar/biomass powered systems to do the separation and refabrication. What you previously described is alchemy. $\endgroup$
    – nzaman
    Mar 2, 2017 at 17:42

1 Answer 1


I'm going to keep this grounded and the only "magic" is the mechanism of splitting the atoms. I'm going to maintain the basic laws of the universe like conservation of energy and the mass-energy equivalence. Basically, "sufficiently advanced technology" magic.

There's a few basic physical laws which are important here:

  1. Energy cannot be created nor destroyed.
  2. E=mc^2: energy = mass times the square of the speed of light.
  3. The Laws of Thermodynamics.

Where Will You Get/Put All That Energy?

That is the basic, basic question of any sci-fi gadget: either getting the energy necessary or dissipating the waste energy produced.

Fission and fusion of atoms both involve a slight change of mass which in turn releases or requires a tremendous amount of energy, depends on what's being fizzed or fused. The mass is small, but the square of the speed of light is something like 9e16 m^2/s^2 which is a very big number and there are a lot of particles. 82 grams of lead contains 6e23 atoms. These numbers add up multiply up fast.

Stable Atoms Require Energy To Split Or Fuse

Fission and fusion don't always produce energy. They only do so when going from a less stable configuration to a more stable configuration. For example, helium is more stable than two hydrogen atoms, so solar fusion produces energy.

Basically, you put a pound of iron inside the machine, choose to make lead out of it, wait for as long as is necessary, then walk away with a pound of lead.

This is a particularly interesting example. You have chosen two of the most stable atoms in the universe. That means you'll have to pump in a lot of energy to change them.

Iron is the last element produced in stellar fusion just before the star goes supernova; iron is so stable even a super giant star cannot fuse iron into something else. For that you need a supernova.

Lead is also extremely stable. Unlike iron, it's the final decay product for many radioactive isotopes. For example, if you start with a hunk of Uranium 238 that will decay (naturally in about 4 billion years) to Thorium 234. After about a month that decays to Protactinium 234 for about a minute then you get Uranium 235 for another 200,000 years or so. It spends about 70,000 years bumming around as Thorium, fools around as Radium for 1000 years, spends a quick 4 day holiday as Radon 222, and finally bounces around between various isotopes of Polonium, Bismuth and Lead before finally landing on Lead 206 forever.

enter image description here

Those atoms are all unstable, except the last one Lead 206. Each step of that reaction, each time the atom spontaneously fizzes or fuses, that releases energy.

Because lead and iron are so stable, transforming them into anything else will soak up a tremendous amount of energy. Fusing iron or larger is a net loss of energy.

Fission and Fusion Need To Overcome Very Strong Forces

You can't just go in with a pair of very tiny magical tweezers and pull atoms apart. Atoms are extremely tightly bound together.

Fission is knocking a particle away from the nucleus. The nucleus is held together by the strong force which is, you guessed it, very, very strong, but only at very short ranges. It's strong enough to keep all those positively charged protons, which want to fly apart because of the electromagnetic force, tightly packed together.

Fission must overcome the strong force with a lot of energy, like a whizzing neutron smacking into the nucleus, plus some luck with quantum tunneling to jump that last gap. This can jostle the nucleus enough such that a particle gets far enough away for electromagnetism to overcome the strong force and it goes whizzing off.

Fission Does What It Wants

You can't just pull a bunch of protons and neutrons off lead until you get iron. Fission decay chains are pretty well defined and will do what they want. You'll need to find a chain that results in iron, or introduce more magic.

Fusion is a bit better behaved. You can smack helium into various particles to pile on the weight. Stars create iron this way through the silicon-burning process, once they're done fusing oxygen and happens at 3 billion Kelvin. And then the blast wave from the collapsing core of the star smacks into it. So we're talking a lot of energy and pressure.

In Summary: Not Without A Lot Of Handwavium

What you're asking for is the Star Trek replicator.

enter image description here

And yes, it is possible that you'd use nuclear fission and fusion to get your captain a cup of tea it represents such a staggering abuse of energy and technology that even the writers of Star Trek couldn't handle it and started introducing galleys into their ships.

This is the same reason we don't turn lead into gold, even though we can. While it's technically sustainable in that we're not mining the remnants of supernova, it's staggeringly inefficient unless you have a tremendous source of energy... like an anti-matter warp drive engine. But even that anti-matter has to be produced with energy from somewhere, it's like the high capacity batteries of Star Trek that sometimes blow up. Better to mine the remnants of supernova, carefully recycle the elements, and use plain old chemical reactions.

Then again, we're all using mobile supercomputers, a global spanning fiber optic network, and an orbiting satellite positioning system to look at cat videos, play games, and order pizza. All for $20/month.

enter image description here

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    $\begingroup$ Slow clap Wow, thanks for the answer. It was way more complete than I would have anticipated. Since you've been really helpful, I'd like to ask another question. Let's say they have acces to a magical whatever that creates or soaks up energy without limitation. What would be the dimensions of such a machine, in your estimation? Thanks a lot, by the way. That was a great answer. $\endgroup$
    – Garnovski
    Mar 2, 2017 at 18:07
  • $\begingroup$ @Garnovski Thanks! As for your other question, we try to discourage too much discussion in comments. If you want to ask another question, do it as another question. When you do, link to it here and I'll have a look. $\endgroup$
    – Schwern
    Mar 2, 2017 at 18:10
  • $\begingroup$ $20/month for mobile contracts? I wish. $\endgroup$ Mar 2, 2017 at 18:33
  • $\begingroup$ @Garnovski - Oh, please, you're asking who would win a fight, a dragon or a unicorn? If you have a "magical whatever" there is simply no way to tell how big it is, or how much it weighs, or what color it is. It's MAGIC. It doesn't follow rules. it's wish-fulfillment. So just wave your hands (or your wand) and do whatever is convenient. Just don't call it science, and don't try to engineer it. $\endgroup$ Mar 2, 2017 at 18:55
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    $\begingroup$ @WhatRoughBeast Whoa there! That's not how WorldBuilding works. Let them ask their question and we'll see what answers turn up. $\endgroup$
    – Schwern
    Mar 2, 2017 at 19:01

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