system
Given the following post, respond as if you're commenting on Reddit:
human
If atoms are 99.99999...% empty space, how do we see anything?
gpt
Atoms are *not* 99.99999...% empty space. This is a misconception propagated by elementary education and is based on a model of the atom (the Rutherford model) that was shown 100 years ago to be false. Electrons in an atom are not solid little balls that orbit the nucleus like planets orbit the sun, with a vast chasm of empty space between the electron and the nucleus. Rather, electrons in an atom are smeared out into wavefunction clouds *that fill the entire atom*. These clouds (often called "orbitals") are not formed simply because a solid little electron is traveling too fast for us to pinpoint it, nor is it formed because we simply don't know where to look to find the solid little election. The cloud *is* the electron. Electrons are quantum particles, and as such, they are complex beasts that act somewhat like waves (clouds) and somewhat like particles. In a stable atom left to itself, the electrons act mostly like waves. Therefore, the electrons in an atom literally spread out in the wave state to fill the atom, and there is no empty space. But this concept has little to do with why we can see objects made out of atoms.

Humans see objects by detecting the visible light that comes from the object. Visible light (red to violet) has a wavelength that is a thousand times larger than an atom. Therefore, when visible light hits an object made of many atoms (e.g. a metal spoon), it is not really interacting with one isolated atom at a time. Light is interacting with many atoms at once. Furthermore, when atoms bond into a solid structure, they don't act like independent atoms anymore. The atoms bond into an integrated structure, and the outer electrons smear out into waves that stretch over many atoms. So when you have sunlight reflect off of your metal spoon and into your eye, allowing you to see the spoon, there is not really a stream of photon particles, each individually interacting with different, separate atoms. Rather, you have photons spread out over the size of many atoms, interacting with electrons spread out over many atoms. You aren't really seeing atoms when you look at an object. You are looking at the bonding lattice of the atoms. That is why carbon can be black when arranged into a graphite lattice and clear when arranged in a diamond lattice.

What is this interaction? It is the electromagnetic interaction. Light is a fluctuation in the electromagnetic field, and electrons carry electric charge. Because of their electric charge, electrons can destroy, create, and redirect photons. As far as visible light and everyday objects are concerned, its the outer electrons that are each spread out over many atoms that mostly allow us to see objects.