Monday, August 18, 2014

Can't Touch This

A surprisingly common notion that comes up in science popularization is that nothing ever touches. This comes up things from youtube videos to the remake of Cosmos. As far as the scientific facts go, they're right. When you touch something, say when you pick up a ball, the electrons in the atoms of your fingers repel the electrons in the atoms of the ball, so the atoms in your fingers never come near the atoms in the ball. Near, that is, relative to the size of an atom.

But I wouldn't say that means nothing ever touches. Rather, it's a microscopic description of the macroscopic phenomenon of touch.

As an analogy, consider temperature. You can feel temperature as things feel hot or cold. You can measure temperature with thermometers. You can come up with laws that describe how heat flows from hot things to cold things. But on a microscopic scale, temperature is just speed. When atoms and molecules vibrate faster, they're hot. When they vibrate slower, they're cold.

But that doesn't mean that temperature doesn't exist. Rather, that's what temperature is. Thermometers still work, and the laws of thermodynamics are still accurate. They just refer to an emergent property of a complex system, rather than fundamental property.

I would argue the same applies to touch. Electrons repelling each other is what touching is.

Admittedly, this is entirely an argument over semantics. It's just about the definition of the word "touch", rather than any actual facts. But I think this definition is better and more useful. Because if nothing ever touches (except maybe where fusion occurs, like in the heart of a star), then the word "touch" never makes any useful distinctions, which is the purpose of a word.

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