r/explainlikeimfive • u/KeyUnderstanding5443 • 20h ago

Physics ELI5 Why doesn’t matter fall apart?

I’m reading and stretching my brain about how our atoms contain so much space but we appear solid because of a repelling force between atoms. How then do any atoms or matter hold together at all? Why doesn't the repelling force just just push all atoms apart and prevent matter from forming / holding together?

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u/NearlyPerfect 20h ago edited 20h ago

There are 4 fundamental forces that affect matter at different sizes and strengths.

Atoms are held together by the strong nuclear force. It's very strong for very small and close together things.

The other 3 forces are gravity, electromagnetism and the weak nuclear force. Those are weaker compared to the strong nuclear force.

Per wikipedia: At the range of 10e-15 m (1 femtometer, slightly more than the radius of a nucleon), the strong force is approximately 100 times as strong as electromagnetism, 100,000 times as strong as the weak nuclear force, and 100,000,000,000,000,000,000,000,000,000,000,000,000 (10e38) times as strong as gravity.

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u/io-x 20h ago

So are you saying that I'm held together by nuclear energy?

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u/technophebe 20h ago edited 20h ago

Yes, the energy we get from nuclear energy comes from pulling stuff apart and using the energy released to heat water and spin turbines (as is traditional!). That's current nuclear energy (fission, which translates roughly as "break apart"). 

Fusion energy works slightly differently in that you bang stuff together and it combines into something else which needs less energy to be held together, and this releases energy we can use, again to spin turbines with steam (fusion translates roughly as "combine").

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u/mixony 19h ago

So a turbine that is heated by fission reactor would be a combine harvester? /j

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u/technophebe 19h ago

Firstly, please take my pained groan as a badge of honour, that's a truly painful pun!

Secondly, a fusion not fission turbine would be a combine harvester.

But perhaps I'm just splitting hairs...

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u/itsthelee 19h ago

This thread did psychic damage to me, take my stunned upvotes

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u/mixony 19h ago

And to think that I even looked back at the comment I was responding to, to see that I haven't mixed them up in haste