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Question: If atoms are mostly nothing, why are things solid?

Asked by willemh to Sara, Kimberley, Julia, Drew, Amy on 15 Jun 2011.

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  • Photo: Drew RaeDrew Rae answered on 14 Jun 2011:

    Hey, cool question. What you feel when you touch something are the forces between the atoms in your hand and the atoms in the thing you touch. Instead of “bumping atoms” you are “bumping energy fields”. If you try to touch a +ve end of a magnet with another +ve end of a magnet, they move away from each other. It’s a bit like that (except we aren’t magnetic).

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  • Photo: Amy MacQueenAmy MacQueen answered on 15 Jun 2011:

    Hey! I think its pretty much because of the way they are held together – the forces between them as Drew said! Depending on how the same atoms are held together makes a different to their properties – like graphite in a pencil vs diamond – they’re both carbon atoms in different arrangements! :)

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  • Photo: Sara Imari WalkerSara Imari Walker answered on 15 Jun 2011:

    Hello willemh. I like all these physic-sy kinds of questions! Drew is right! Things are solid because of electrostatic repulsion between atoms. Atoms don’t like to be in the same spot because they have these massive electron energy clouds surrounding them that don’t like to stack on top of each other. For gases and liquids this isn’t a problem – the atoms are energetic and moving around a lot so they aren’t near each other so much. However for a solid – the atoms are tightly packed so the electrostatic repulsion keeps them lined up in nice orderly patterns like what Amy has described with graphite and diamonds. We feel these as solid because all those tightly packed atoms are waaay tinier than we are.

    Want to hear something really wild? Under cases of extreme gravity – like the explosion of massive stars – atoms can become so tightly packed that the electrostatic repulsion is no longer enough to keep the atoms apart and they condense in on themselves forming what we call “electron-degenerate” matter. Such tightly packed atoms make up what we call white dwarf stars. White dwarfs are soooo dense that a teaspoon literally weighs a tonne! Sirius is a the brightest star in our night sky, it is actually a binary star (two orbiting each other) where the fainter companion is a white dwarf. So you’ve probably seen the light from one of these crazy objects and not even known it!!

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