Quantum Physics Does Something Weird When Atoms Touch

When you press your finger on a phone screen, your finger stops moving at some point.

The phone screen pushes back.

and you feel a force.

That's a perfectly valid definition of what touch is in everyday life.

But what does this mean at the atomic level? Does it mean that the atoms of the glass never actually touch the atoms on your skin? Perhaps because their respective electrons repel each other? Well, that's true, but that's not the entire reason your finger does not go straight through the glass.

Let's zoom in to these atoms and see what happens.

First, you should visualize what an atom looks like, at least approximately.

An atom is made up of a tiny, positively charged nucleus surrounded by a cloud of negatively charged electrons.

To give you a dramatic visual of scale, if the atom were the size of the largest football stadium in America, the nucleus would be the size of a pea.

at the 50 yard line.

And the electron cloud would be like a cloud of tiny nets that buzz and spread throughout the entire stadium.

The cloud represents the wave function of the electron.

Even a single electron's wave function would be represented throughout every part of the stadium.

We cannot know exactly where a NAT is, only the probability of finding it at certain locations in the stadium.

So, you know, this is the reason that it's not quite correct to say that the atom is mostly empty space because the cloud of NATs representing the wave function of the electron is spread everywhere in the stadium.

So it's more accurate to say that atoms are mostly empty in terms of mass concentration because almost all the mass is at the nucleus, the P at the center of the stadium.

but electron wave functions extend throughout the atom.

Anyway, when two objects come close, it's not like solid marbles hitting.

It's more like two fuzzy clouds trying to occupy the same space.

Now we hit the real crux of the feeling of touch.

Electric charge.

What do I mean? Electrons have negative charge.

So when the atoms of your finger approach the atoms of the glass screen, what meets first? The electron clouds meet electron clouds.

And what do like charges do? They repel.

That's Coulomb's law.