The universe's strongest force actually gets weaker as particles get closer

Science · Published 25 October 2026 Swipe more like this →

In short: Why don't protons fly apart despite their intense electrical repulsion? The answer lies in Quantum Chromodynamics (QCD). This theory reveals a force so powerful it acts like a cosmic glue, binding the very building blocks of matter together through a bizarre property called color charge.

Hideki Yukawa, a physicist from Japan, introduced a major theory regarding the strong nuclear force during 1934. To explain why protons and neutrons stay together in the nucleus, he suggested a massive mediator particle. Using Einstein’s E=mc² and Heisenberg’s uncertainty principle, he estimated this particle's mass at 100 MeV, which was remarkably close to the actual 138 MeV value of the meson.

By 1964, the focus shifted to quarks—fundamental particles that combine to form baryons like protons and neutrons. However, a crisis emerged: certain particles, like the delta particle, appeared to contain three identical quarks. This seemed to violate the Pauli exclusion principle, which forbids fermions with the same properties from occupying the same space. To solve this, physicist Wally Greenberg proposed 'color charge.' Quarks aren't identical; they possess three types of color (red, green, and blue) that must combine to form a neutral 'white' state.

The mechanics of QCD are unique because of the gluon, the particle that transmits the strong force. Unlike photons in electromagnetism, which are neutral, gluons carry color charge themselves. This means gluons interact with one another, creating a phenomenon called quark confinement: quarks are never found alone because the force between them grows stronger as they are pulled apart. On the other hand, these particles display 'asymptotic freedom,' which D.J. Gross, H.D. Politzer, and F. Wilczek identified as a state where interactions diminish significantly as quarks approach one another.

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