Breakthrough in our understanding
of the inner structure of matter

J.I. Friedman, H.W. Kendall and R.E. Taylor were key persons in the research team which discovered an inner structure in the protons and neutrons of the atomic nucleus. Their series of investigation constituted the now so well-known SLAC-MIT experiment.
     Knowledge of the inner structure of the atom has increased successively. Between 1910 and 1940, the nucleus of the atom and its nucleons (protons and neutrons) were discovered. During the 1950s, a large number of particles, termed hadrons, were discovered, whose properties resembled those of the nucleons. They behaved like members of different families. To be able to describe these families theoretically, three building blocks, quarks, were introduced. Now all hadrons then known could be built up of these quarks and their antiparticles. This allowed great conceptual simplification, and the quark concept was immediately taken seriously. Quarks were sought both in nature, e.g. in sea water, meteorites and cosmic radiation, and in experiments using high-energy accelerators. No quarks were found. After a time, the most popular explanation of the absence of the quarks was that they were only "mathematical quantities" in the equations of physics. Not until the SLAC-MIT experiment of 1968 were the first traces of quarks seen.
     The discovery was made when protons and neutrons were illuminated by beams from a giant "electron microscope" – the two-mile-long SLAC accelerator. An inner structure was then seen and interpreted to mean that quarks represent the fundamental building blocks of protons and neutrons. Signs were also seen of the electrically neutral "glue", gluons, that binds the quarks together. All the earth's matter, including our human bodies, consists to more than 99% of quarks and their associated gluons. The little that remains, is electrons.