If atoms are mostly empty space, why do things look and feel solid?

Published: October 20, 2021

Many things we've been taught at school are simplified to make them easier to understand. In reality, electrons don't orbit the nucleus like planets orbit the sun:

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It's better to think of electrons as a flock of insects where you can't distinguish a single insect but you can see the entire flock.

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The paths of different electrons vary. Some move faster and some slower. The path of each electron remains mostly the same but can sometimes change as long as no electron moves on the same path as an another one. According to Pauli exclusion principle, two or more identical fermions cannot occupy the same quantum state within a quantum system simultaneously or, simplified in layman's terms, electrons can't "move on the same path".

Even though electrons move indefinitely, they need energy to move to a higher energy path. Respectively, an electron releases energy when it moves to a lower energy path. For example, when an electron is hit with light, it might move to a higher energy path.

Now, if we shine light on a table, the light won't reach very far because the electrons "like" to take their part of the light's energy. This energy is almost instantly released and we see this as light reflecting from the table. This is why things look solid.

If you decide to touch the table with your hand, the electrons on your hand move very close to the electrons of the table. When the electrons of an atom move close to an another atom, the electrons' paths change. This is because the electrons can't move on the same path next to each other. Thus, the electrons of the atoms must move to a higher energy path. This requires energy which doesn't come from light but the force used to move the atoms closer.

Moving two atoms close to each other requires energy since the electrons need to "make space" by moving to higher energy paths. In the case of a hand and a table, there is a massive amount of atoms and pushing them close to each other requires enough energy to stop our hand. This is why things feel solid.

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