# What is the effect of being sliced by an ultra-thin object? [duplicate]

Can you survive being sliced by an object if it is thin enough?

The following properties hold for this object:

• It is composed of a non-toxic, body-temperature material, equivalent in weight to carbon
• Its cross-section is as small as can possibly be, only 1x1 atom thick
• It is longer than the height of any human
• It is completely rigid
• It cannot be broken by any means

And for the circumstances to consider:

• Is it possible for this object to pass through a human without harming them?
• And if this statement holds, at what speeds does this statement hold true?
• Is there a minimum and maximum speed, which when crossed, the property no longer holds?
• Could it be a problem that the object has enough momentum to displace a human and kill it, rather than passing through it?

My thoughts are that, because human cells are much larger than an atom, and many individual cells can be damaged before a human is actually harmed, that it's possible to survive being hit by an object of this description.

• That's a lot of questions in one question. You should probably clean this up and ask as a series of questions. Also pass through in what way? All the way through a cross section or "stabbed" – bendl Apr 9 '18 at 19:34
• It will pass through the human with the longest edge first, not as a stab. – 0liveradam8 Apr 9 '18 at 19:36
• This object is a pure magic so you can have it any way you want. But is it supposed to be a wire or a sheet? – Mołot Apr 9 '18 at 19:48
• An atom of what? Helium? Or Plutonium? That's a huge size difference. – Galastel supports GoFundMonica Apr 9 '18 at 20:11
• Since you put biology and physics tags on the question, you've got to accept that something "the same weight and size of carbon" is carbon, and carbon molecules don't just pass harmlessly through the body. – RonJohn Apr 9 '18 at 21:50

It would probably kill pretty much any way you used it. To see why, you need to get down to the molecular level. A human cell is made up of a dense dispersion of proteins in water. Human bone is a composite of a mineral (apatite, basically) and collagen protein. The mineral provides most of the compressive strength; the collagen provides most of the tensile strength.

Here's a model of a fairly typical protein:

The dots are atoms and the lines connecting the dots are bonds. If a ultra-thin wire just one atom in diameter passed through it, it would break every bond creating free radical galore and push the atoms aside, basically leaving a flat plane of devastation. The free radicals produced would probably kill the cells involved. (Cells have mechanisms to scavenge free radicals, but not in this high a concentration.)

So you have a sheet of dead cells one cell thick cutting through your body. Soft tissue would probably heal if it got a chance, but I see three things which probably wouldn't heal:

• Bone -- the collagen is broken and the mineral is broken. A bone under stress would almost certainly break at that point.
• Nerves -- nerve cells would be disrupted, and there's a good chance that some of many of them would die.
• Muscles -- muscles under tension would probably rip.

If you were laying down and relaxed you might survive, but if you were standing and active (running away or in a sword fight) the consequences would likely be unfortunate.

• Will upvote when I get it back, I used all my 40 upvotes for the day :P – Ekaen Apr 9 '18 at 21:05
• It is however a good question whether this incident would lead to a quick death, or bones, nerves and muscles will have a chance to repair themselves. – Alexander Apr 9 '18 at 21:25
• Where are the free radicals coming from? I don't think cleaving proteins unbalances the charge of the remaining parts. – Samuel Apr 9 '18 at 21:41
• Ions are charged atoms or molecules. Free radicals are not ions but are atoms or molecules where some of the bonds have been broken and are thus lacking the atom which normally would be on the other end. Free radicals are extremely reactive. (The main way radiation damages cells is by breaking bonds and creating free radicals which then attack what's nearby.) H2O splitting into H+ and OH- is ionization. H2O splitting into an H and an OH (both uncharged) creates two free radicals. – Mark Olson Apr 9 '18 at 21:46
• Sure, given time. You put a broken bone in a cast so the two pieces can't move relative to each other and a few weeks later it's healed. That's why I said that the injury might be survivable if neither the bones nor the muscles were under stress. But if you're fighting and this slices through your waist, the likelihood of it healing before damage is done (3 seconds later) is pretty small. – Mark Olson Apr 9 '18 at 21:49

Single atoms don't just harmlessly pass through the body, so it's unreasonable to expect that an atom-thin wire would harmlessly pass through the body.