In a world of superheroes the job of blacksmith is given to the very strongest of them.


Is splitting an atom in a human-scale piece of work by using a human-scale tool even theoretically possible?

If so and a superhero blacksmith struck his work with such superhuman strength that he randomly split one atom, how hard would he have to strike? What would he notice?


The action of this question takes place on our Earth.

The superheroes are from another dimension, so effectively they are magical beings when they visit our world.

The superheroes look like us but have as much strength as needed.

The tools look like ordinary Earth blacksmith's tools and are the same sort of size. They are made of ordinary elements and compounds found in our natural universe of Earth and the Milky Way but these can be any elements in any combination.

The work can be of any shape and size from that of a horseshoe upwards. It also is made of ordinary elements and compounds found in our natural universe of Earth and the Milky Way. Again any elements and compounds are allowable.


The blacksmith is not trying to split atoms. He just does it accidentally by being too strong.

The superhero is human-sized and shaped, and holding a human-scale hammer. If the blow accelerates from zero to 'the necessary velocity' in a distance of about 2ft (0.6m) - will the hammer survive the journey? In other words is there some kind of speed/acceleration limit before destruction of the tool occurs, simply by being swung.

  • 1
    $\begingroup$ Just the one atom? $\endgroup$
    – Spencer
    Feb 21, 2019 at 23:08
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    $\begingroup$ OK. So does the atom have to be split by (macroscopic) mechanical force, or can the hammer have a built-in neutron emitter? $\endgroup$
    – Spencer
    Feb 21, 2019 at 23:24
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    $\begingroup$ "splitting an atom" meaning splitting the nucleus, or just knocking away an electron? $\endgroup$
    – Alexander
    Feb 21, 2019 at 23:37
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    $\begingroup$ @JustinThyme: He doesn't even have to hit his finger. The human body is naturally radioactive; about 10,000 atoms decay in the human body per second -- including 3 to 5 uranium atoms... $\endgroup$
    – AlexP
    Feb 22, 2019 at 0:24
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    $\begingroup$ not directly, he can however create fission as a byproduct of fusion if he swings it hard enough, an object a relativistic speeds will create a fusion corona in the air as molecules are unable to get out of the way fast enough. $\endgroup$
    – John
    Feb 22, 2019 at 0:35

1 Answer 1


Yes, you need to bring down the hammer with sufficient speed. But if there is no limit, not a problem.

I will explain this in terms of using a fusion initiated fission reaction (the reverse of the normal situation in H-bombs).

Step 1. cause a Deuterium, Tritium fusion reaction. The necessary step is to bring the atoms together with sufficient energy to overcome the Coulomb Barrier. Due to quantum tunneling effects, this is considerable easier to achieve that would otherwise. However, this still results in fusion temperatures on the order of 15 million degrees C in the sun's core.

But the energy required to overcome the barrier, is considerably higher than a mere 15 million degrees in the core. This works because gas particles follow a distribution of high and low speed particles, so the few particles that are 100 million degrees are fast enough to sustain the fusion reaction.

What you really want to know though is velocity, not temperature. Someone has already done the calculation and 3.15 x 106 m/s is enough for Protium/Protium fusion, which is about 0.01c, Deuterium/Tritium fusion is easier, requiring only about 70% as much velocity.

When Dueterium/Tritium fuse, the result of the reaction is in several forms, this includes a neutron at 14.1 MeV.

When this neutron strikes a U-235 atom, it will split (only about 7-8 MeV needed by the neutron to cause this fission). Mission accomplished.

What does our brawny hero notice? Nothing at all. The resulting 200 MeV output is about 3.2 x 10-11 Joules. i.e., energy equal to 3.2 microwatts for a span of 10 microseconds. The energy from a grain of sand falling 1 micrometer is larger.

The tremendous thunderclap from moving the hammer at relativistic velocities will be far more significant. Not to mention the newly generated mushroom cloud from all of the other fusion reactions that occur at the same time.

Note that the fusion reactions will be occurring in the air as the hammer approaches the target. Fine tuning the hammers speed so that only a single fission occurs at the target is unrealistic in the extreme, you are moving billions of billions of atoms around at relativistic speeds. The chance of only a single fission event is essentially zero.

Compare with the classic treatise, relativistic baseball.

[Added] This answer simply assumed the hammer though made of natural materials was magically accelerated (mixing fantasy and science is based on messy assumptions)

No hammer can survive the necessary acceleration. Assuming a generous 1 meter path for the accelerating hammer, it will require 45 trillion gravities of acceleration. For 0.6 meters, 75 trillion gravities.

Well, a quick calc, as a limiting case assume the hammer is simply a 10 cm cube of perfect carbon nanotubes. Mass = 1.6 kg, tensile load is about 1.2x1015 pascals (1.6 kg * 7.5x1014 m/s2 / 0.01 m2). Theoretical tensile limit of carbon nanotubes is about 300 GigaPascals. I.e, the tensile strength required is at least 4000 times the theoretical tensile strength. And this is based on extremely optimistic hammer design, i.e., the bending strength of a normal hammer is much less than tensile strength of the material.

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    $\begingroup$ In reading this, I just realized exactly how dangerous it is to be around Flash. He is just a bundle of nuclear fusion AND fission, at the speeds he is purportedly moving at. Perhaps the basis of a new question - how radioactive IS Flash? $\endgroup$ Feb 22, 2019 at 1:25
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    $\begingroup$ I think your analysis disagrees with the conclusion. You show that a hammer at 3150km/s is fast enough to cause fusion. No tool is going to withstand that, nor transmit enough force to cause an acceleration up to those speeds. The fastest man made object ever, a Helios satellite, topped out at 70km/s. The superhero may have hands capable of such acceleration, but the tool is going to give out during the swing! $\endgroup$
    – Cort Ammon
    Feb 22, 2019 at 2:24
  • $\begingroup$ @Cort Ammon but superheroes don't use ordinary hammers, they have custom tools $\endgroup$
    – Alexander
    Feb 22, 2019 at 5:03
  • $\begingroup$ @JustinThyme I think the answer is "none". Remember that he uses the Speed Force. In other words, it's the writers' handwave to remove any problems Flash has with physics. For example, that's why he can grab somebody and run without the person being rended into shreds. $\endgroup$
    – VLAZ
    Feb 22, 2019 at 5:58
  • $\begingroup$ @Gary Walker - Thanks for your answer. I think Cort Ammon has made the point that was worrying me. The superhero is human-sized and shaped and holding a human-scale hammer. If the blow accelerates from zero to 'relativistic velocities' in a distance of about 2ft (0.6m) - will the hammer survive the journey? In other words there is some kind of speed/acceleration limit before destruction of the tool occurs. I should have mentioned explicitly that I wanted that factored in. $\endgroup$ Feb 22, 2019 at 9:09

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