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Gluons are hard to study because although they exist in nature all the time, they are so small and require so much energy to break them away from quarks (about 2 trillion degrees) that scientists have only been able to find more about them from particle colliders such as the Large Hadron Collider at CERN.
- Cox, Brian; Cohen, Andrew (2011). Wonders of the Universe. HarperCollins. p. 109. . https://archive.org/details/wondersuniverse00coxb_864.