Why can't you pull apart a magnet?
Quantum chromodynamics
Why can't you pull apart a magnet?
Imagine trying to pull apart a magnet in your pocket. No matter how hard you try, it won't split into two separate pieces.
In QCD, quarks are like the parts of a magnet. They can't be separated because the force between them doesn't weaken as you try to pull them apart. This idea is called quark confinement.
Example
If you have a magnet with 2 north and 2 south poles, you can't split it into individual north or south poles.
Remember this
Quark confinement explains why quarks are always found together in particles called hadrons.
Text adapted from Wikipedia, licensed under CC BY-SA 4.0.
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