Why doesn't cutting split the atoms?
Cut something with a knife and it feels as if the atoms inside are split, but what actually parts is not the atoms themselves but the connections between atom and atom. A blade is incomparably larger than an atom and cannot cleave one; it only pries apart the weaker connections. Splitting an atom's nucleus is a wholly different realm that takes enormous energy.
I cut an apple with a knife and paper with scissors. To part something in two feels as if it means splitting something inside it. But matter, I learned, is made of atoms. So when I cut something with a knife, did I split atoms? Did the blade pass right through the middle of an atom? "Splitting an atom" sounds like a tremendous thing, yet every day I cut things without a second thought. Are cutting and splitting an atom the same act, or different ones?
Since cutting means splitting, one imagines that at the very end the knife splits atoms in half too, and that a sharp enough blade could cleave a single atom. But it is not so. Cutting cannot split an atom. What the knife parts is not the atom itself, but the space between atom and atom.
Let us return to the first question. Did cutting split atoms? No. It parted the space between atom and atom; the atoms themselves are unharmed. What shows on the cut face is the surface of atoms whose connections were just severed. Before and after the cut, the kinds and the number of atoms are the same. All that changed is how the atoms are connected. So "to cut" and "to split an atom" are wholly different phrases. One is the everyday act of changing the connections between atoms; the other is the dimensionally different act of changing an atom's nucleus. The cutting I do every day is always the former.
Top: press Lower the blade to see that the blade severs only the connections between atoms, not the atoms, and the mass parts in two. Bottom: pick weak or strong connections and apply force to see that it parts only past a threshold.
Matter is made of atoms connected to one another. It is close to each single atom joining hands to form a great mass. So to cut with a knife is to part those joined hands. It does not smash the atoms themselves but severs the connections between them and splits the whole in two. Whether you tear paper, cut an apple, or sever steel, the place that parts is always between atom and atom. In fact, the edge of a blade is enormously large and blunt compared to an atom. However sharply it is honed, a blade never becomes small enough to cleave a single atom precisely. A knife does not split atoms; it is a tool that pries into the weaker links joining atoms and pulls them apart. Even a razor's edge is an incomparably vast wedge next to an atom. That is why some things cut easily and some do not. Where the connections joining atoms are weak, they part under little force; where the connections are strong, they resist even great force. Cutting, in the end, is a contest between the strength of those connections and the force the knife presses with. A well-honed knife cuts well because it gathers force onto a narrow face and pries those connections apart more easily. Then what truly splits an atom? That is the breaking of the atom's very center, its nucleus. This is an event of a wholly different realm, taking energy beyond any comparison with cutting. The key contrast is this. Cutting changes the connections between atoms, so the atoms remain as they were. Changing an atom's nucleus, on the other hand, is a change of another dimension, in which the element itself turns into something different. It is a world entirely apart from what we do in the kitchen.
So when we cut or break or grind something, we are not smashing atoms but reweaving the connections between them. Tearing bread, snapping a pencil, cracking ice, all happen between atoms. Whether a knife cuts well in cooking is, in the end, a matter of the strength of the connections in the ingredient. A well-honed knife cuts well because it gathers force into a narrow place and pries those connections apart more easily. We spend our lives parting things, yet we have never once split a single atom. What we part is always the connections between atoms. The truly solid knots that make up the world lie far deeper than a blade's edge can reach.