How do we know that most of an atom is empty space? And since that is so, why can’t we just walk through solid objects?
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the electrons that orbit the nucleus repel each other, because they have a negative charge. remember, opposites attract, but if two things have the same charge they repel.
so the electron clouds of atoms tend to bounce off each other, (or bond with each other). But it’s almost impossible for the nuclei of two atoms to get close to each other.
And the nuclei of atoms repel each other VERY strongly all by themselves, because the nuclei both have positive charges.
So you can think of each atom as a teeny tiny nucleus surrouded by a large forcefield made of electrons. and there is a second, smaller forcefield that is closer to the nucleus. It’s those forcefields that prevent solid objects from passing through each other.
Not a physicist or philosopher. But was under the impression that this “atoms are mostly empty space” is a kind of conceptually wrong way of looking at things
What we know of as “non-empty space” (solid matter) is a deep-seated intuition based on the way particles interact. Which is entirely about electrical forces of particles acting on one another. There is no “solid stuff” in any other sense of the word, so the intuition essentially kind of breaks down at the microscopic scale
tl;dr: prison bars are mostly empty, but you still can’t walk through them.
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Rayleigh’s experiments involved firing alpha particles (what we now know are helium nuclei) at a thin sheet of gold. He expected the particles to bounce off in a broad spread of reflection angles, but to his surprise, almost none bounced off the gold atoms, except for a few, which reflected nearly 180° – this implies the nucleus isn’t a smooth blob (the ‘plum pudding’ module), but rather has almost all its mass concentrated into a tiny volume/dot – which we now know is a very accurate description.
So, atoms are mostly empty in the classical ‘electrons orbiting a nucleus’ sense. We can’t walk through a material because those electrons exert a strong electrostatic repulsion against the electrons in your body/clothes when you get close enough.
So _atoms_ are mostly empty_, but the force fields exerted by electrons, protons, and neutrons, fill all space per an inverse square law. Quantum mechanics adds an extra degree of blur, but isn’t necessary to explain the broad phenomenon.
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