The invisible mortar holding the building blocks of our universe together

Space · Published 31 October 2026 Swipe more like this →

In short: Quarks are the fundamental ingredients of matter, but they cannot exist in isolation. They require a specific type of subatomic "mortar" to bind into the protons and neutrons that form atoms. This interaction is so powerful it defines the very structure of our physical reality.

At the most basic level, matter is composed of quarks—fundamental particles found at the center of atoms. While we are familiar with protons and neutrons, these are actually composite structures made of three quarks each. To understand how they stay together, physicists look to the strong nuclear force. This is one of the four fundamental interactions of the universe, acting primarily on subatomic scales to bind quarks into hadrons. This force is distinct from gravity and electromagnetism because it operates exclusively on subnuclear scales. It also differs from the weak force, which affects both quarks and leptons.

The history of understanding these particles began in earnest during the 1950s with high-energy collision experiments that revealed a vast "particle zoo" of hadrons. To categorise such configurations, a framework involving quarks was presented by scientists during 1964, first naming three varieties: strange, down, and up. The discovery of the heavier charm quark in 1974 was a pivotal moment, helping build the Standard Model—the overarching theory describing elementary particles and their forces. Early research identified mesons as short-lived particles made of a quark paired with an antiquark. The initial model only included the three lightest types of these fundamental building blocks.

Modern research continues to push into the unknown. While quarks are well-mapped, scientists are still discovering exotic structures like XYZ states that do not fit neatly into conventional models. Recent work at the Thomas Jefferson National Accelerator Facility involved using high-energy photon beams to interact with proton targets. These experiments aim to uncover new ways that quarks and gluons combine, providing deeper insight into how nature's fundamental forces actually construct matter. The Gluonic Excitations (GlueX) Collaboration produced these signals in Experimental Hall D. Scientists were originally searching for a confirmed XYZ candidate but found two different structures instead.

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