Why do Atoms Look Like the Solar System?

If you compare pictures of an atom and our solar system, it seems that they are both assembled the same way with the sun and nucleus being the same and the electrons and planets orbiting the same. Is this coincidence or is our solar system one big atom? Also, why does the suns gravitational pull keep us orbiting around it instead of pulling us into it?
- Luke (age 36)
Ohio

Hi Luke,

I don't think it's a coincidence that many atomic pictures look like solar systems. However, there is no deep connection between the two either. Rather, I think humans tend to look for patterns, and one of the first ideas physicists had when constructing a model of the atom was to base it on our solar system.

We now know, however, that this beautiful idea is wrong. In reality, an atom doesn't look anything at all like the solar system. In the solar system, planets are constantly falling towards the sun, but also traveling so quickly in a sideways direction that they never actually fall into the sun. The planets are quite localized, and follow precise orbits governed by the laws of gravity.

In contrast, we now know that electrons, unlike planets, are governed by quantum mechanics. They don't have exact locations or trajectories, but rather exist around the atomic nucleus in a sort of probability "cloud." If you see a drawing of an atom in which electrons are dots which orbit the nucleus, remember that this model isn't correct. It isn't a terrible model, and it's easy to understand, but it misses some hugely important physics.

For example, if atoms were solar systems held together by electromagnetism instead of gravity, then radiation would rapidly cause the atoms to collapse, and the universe we know would never have formed. 

Hope that makes sense. You can find a lot more information about the quantum mechanical structure of the atom on this website and on the web in general.

David Schmid

(published on 08/15/2013)