system
Given the following post, respond as if you're commenting on Reddit:
human
ELI5 how does sharpness work at an atomical level.
gpt
Have you ever pushed your finger in a piece of cardboard? It's likely you won't pierce it easily. Try again with a toothpick, and you barely meet any resistance. Assuming you used the same hand both time, the strength applied should be similar. So why the difference?

The reason is the surface where the force is applied to. The bigger the surface, the less force is applied for each mm² (or any other unit of surface). Applying a similar force to a smaller surface mean more force per unit of the surface.

Well that's the basic for sharpness too. The "sharper" it is, the smaller the surface that is directly in contact with whatever you try to cut. As such, you can more easily break the material.

Another thing to consider is that "cutting" unlike puncturing is also in part about "ripping". When you're pushing down on your blade, it's purely a matter of force over surface. But when you're sliding the blade as well, you also "Tear" the matter. Due to friction, the blade grip whatever you try to slice and pull on it. While the matter is similar, as it's also a matter of how large the surface being pulled is compared to the force applied, some material are stronger against pressure than they are against tearing and vice versa.

TL:DR: "Sharpness" mean lower surface of contact, which help in both tearing and cutting.