How to put 170 atoms in an atom

You might already know that atoms are mostly empty space. Physical size behaves a bit weirdly at the atomic scale, but essentially the radius of an atom’s nucleus is tens of thousands of times smaller than the radius of an electron’s orbital. That’s the same ratio as a single grain of sand1 to a football field.2 So what can we fit in all that space? Well, if you build it just right, you can fit a bunch more atoms of the same element – theoretically over a hundred. Yes, scientists actually did this, and no, it doesn’t violate the laws of physics. You just need one really big atom, and a bunch of really cold normal ones.3 Let’s start with the big atom. An atom consists of a nucleus and the electrons that surround it. So if you want to make an atom bigger, you can move the outermost electron farther out from the nucleus. This is called “electron excitation”, and it happens when an electron absorbs extra energy and temporarily jumps to a farther out, more loosely bound orbital. This…