If a human being was shrunken to 1/2744th of his original size (his atoms being shrunken as well), what would be the immediate and long-term biological effects on the body, given that the natural world around him remained the same size? Would it immediately be more difficult to breathe? Would the air molecules affect him differently? Would regular-sized bacteria around him effect him more harshly? Would everyday sounds become painful to his inner-ear?

I know there are a million other technical considerations, but this question is only about the biological concerns.

sidenote: I saw the movie Downsizing yesterday, which was really a kick-in-the-balls for worldbuilding as it doesn't really appear like they thought about the world that was being created at all, aside from a few things for comedic effect. (It was also just an awful movie)

  • $\begingroup$ Are you assuming that the shrunken human has shrunken atoms or just fewer atoms? This is a key consideration. $\endgroup$ – Slarty Dec 24 '17 at 0:18
  • $\begingroup$ Shrunken atoms, will update post also. $\endgroup$ – aks. Dec 24 '17 at 0:35
  • $\begingroup$ Read *Life at low Reynolds number" by Edward Purcell. You can find it online in a second. In short, the viscosity of water and air is just too high. $\endgroup$ – Karl Dec 24 '17 at 11:02
  • $\begingroup$ In a world whith shrunken atoms, your scalebar is 1/2744th too. How would you know the difference? And he can't be the only thing that's shrunk, because how would his shrunk molecules metabolise normal sized food, water or air molecules? $\endgroup$ – Karl Dec 24 '17 at 11:06
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    $\begingroup$ "Shrunken atoms" + tag : science-based. I'm sorry, what? $\endgroup$ – imallett Dec 24 '17 at 11:21

Would it immediately be more difficult to breathe? Would the air molecules affect him differently? Would regular-sized bacteria around him effect him more harshly? Would everyday sounds become painful to his inner-ear?

Immediately: he would not be able to breathe (normal size oxygen is not good). By the same token, air pressure is now a billion times smaller - he's in high vacuum, and dies of decompression (with miniaturized oxygen and nitrogen boiling out of the blood and causing embolisms) within a few seconds. If he instinctively tries to hold his breath, he'll die much faster of a pulmonar rupture.

Immediately: he can no longer see. His retina is now sensitive to a real-world wavelength 2744 times shorter, at the border with X rays. Without an X-ray source to illuminate his surroundings, he's in the dark. Conversely, the infrared radiation he emits is now 2744 times more energetic and becomes hard ultraviolet; he becomes a millimeter-sized sterilizing lamp.

Almost immediately: his surroundings should feel "sticky", with Van der Waals forces anywhere from 2744 to 7.5 million times stronger depending on atomic interactions.

In a few moments: his body would continue generating the same heat as before, about 100-200W. But now he has to shed it from a surface which is thousands of times smaller. If his height is reduced by a factor of 143, his surface is now almost eight million times smaller, and its equilibrium temperature must increase by the fourth root of 7.5M, from around 300K to 15600K - which is around 15330 °C. Or more, since that formula accounts for radiative cooling while a human body is mainly cooled by atmospheric conduction and evaporation. According to an alternate interpretation of the theory, heat is now unable to escape from his body towards the environment, either from skin or airway water evaporation, which means that he'll quickly cook alive. His body temperature will exceed 43 °C within twenty-thirty minutes, at which point death by hyperpyrexia occurs; decomposition will raise it further somewhat, not that he'll care anymore. The increase in temperature may bring his body radiation into X-rays or even soft gamma range, and instead of a small sunburn his micro-corpse can now bequeath bone cancers.

Possibly: his body surface has a greater atom per square real millimeter ratio of anything nearby, and any electrostatic surface charge now exerts an invincible attraction on matter. He'll quickly be swamped in dust, grit and dirt from the ground unless he uses some kind of antistatic metal jumpsuit with internal capacitors.

Possibly: the electrons emitted by the body have the same charge as a normal electron but have a Coulomb repulsion radius which is now negligible (charge/volume ratio has increased enormously). Most positive ions happening to float nearby therefore undergo catalysed nuclear fusion, adding macroscopic havoc of unknown proportions (possibly insignificant, but I wouldn't bet on it) to the already considerable microscopic mess.

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    $\begingroup$ Is "dies of explosive decompression" actually a thing, I thought that was an invention of films; geoffreylandis.com/vacuum.html. I believe the main problem is suffocating, and if you can avoid that; blood pooling and other circulatory effects. What i've seen is: conscious for up to 15 seconds and survivable for up to 90 seconds $\endgroup$ – Richard Tingle Dec 24 '17 at 18:29
  • $\begingroup$ Well, he'll not actually explode (unless he tries to hold his breath), but nitrogen and other gases will quickly bubble out of blood and cause embolisms. Good point, though. $\endgroup$ – LSerni Dec 24 '17 at 19:09

He would suffocate, because there is no oxygen with properly sized atoms. Neurons start to die after 4 minutes.

Also, pressure wouldn't work as we know it and brownian motion would beat him pretty bad, and possibly give him effects of being in vacuum.

Other than that - hard to tell, depends on how exactly shrinking works.


Molecules have a very fragile balance of forces. By shrinking the atoms and the space between them (you have to shrink the space, else you'd have a human sized nothingness with mini atoms) you are moving them closer together.

The effect would be way stronger electrical field forces between atoms (force increases with smaller radius).

Basically, every molecule would break into it's mini atoms, leaving only a cloud of fastly dispersing mini atoms. (Probably even electrons, protons and neutrons, not even atoms).


Well let's say that we shrank you down to that size based on ratios so the ratio of atoms that made you up then is the same to you shrunken self. Everything would be dark because your eye design isn't good at that size. You couldn't breathe because your hemoglobin would be so small.

As for if you just shrunk the empty space between your atoms to get that small, you would break a lot of stuff you stand in because you would be exerting the weight of a full grown man the surface area of a dime. Also to survive like that you need air, food, and water with the same amount of empty space as you to survive. So honestly downsizing is either deadly or more expensive depending on which method you take.

I'm not sure about the biological side effects of the empty space one but and I can't think of any others for the ratio decrease option. And I hope the movie isn't that bad I wanted to see it.


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