So, we’re all made out of cells, right? And these cells are really super tiny, so why is it when we accidently cut ourselves, like a papercut or from glass, the sharp edge just doesn’t push the cells to the side?
Further, do those edges push aside out individual atoms too, or somehow have we just been avoiding death via splitting atoms?
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> DISCLAIMER: this is not the “right” answer, but i think it is clear enough without being utterly wrong.
Why do sharp things cut *at all* ?
Whenever something is bound to something else, this binding has a strength.
It works for people holding hands, cells sticking together in a tissue, molecules with other molecules, atoms to atoms and even sub-atomical particles with other particles.
The nature of this bounding varies from case to case (muscular – electro magnetic – strong nuclear force) but the final result is that the two “particles” resist being separated.
An external or internal “agent” can sever this binding by opposing and overcoming the strength that defines it.
In our most basic description of these bindings, the strength that defines them is the **energy density** -> it means how much **energy** is contained in a specific **volume** of the material.
This means that if the binding has a strength of 1 energy density, if you apply more than 1 energy density, you will break that bond.
**Energy density** is (by definition) equal to **pressure** (how much **force** is applied to a specific **surface**).
Sharp blades offer a very small surface, allowing for high pressure even with small forces. This means that the **pressure** of a blade is enough to overcome the **energy density** of some of the bindings that define your body.
A blade, for example, can break the binding between two tissue molecules, but can’t break the binding between atoms inside a molecule, and even more so can’t break the binding between sub atomic particles.
It can all be described as matter of how energy dense is a binding, and how energy dense is your cutting agent.
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