Constituents of Matter

Modern physics has revealed sucessively deeper layers of structure in ordinary matter. Matter is composed, on a tiny scale, of particles called atoms. Atoms are in turn made up of miniscule nuclei surrounded by a cloud of particles called electrons. Nuclei are composed of particles called protons and neutrons, which are themselves made up of even smaller particles called quarks. Quarks are believed to be fundamental, meaning that they cannot be broken up into smaller particles.

 

Family of Major Elementary Particles

Elementary particles are thought to be the smallest units of matter. They are classified by mass, spin, and electric charge.

 

Constituents of Matter

Matter is composed of tiny particles called quarks. Quarks come in six varieties: up (u), down (d), charm (c), strange (s), top (t), and bottom (b). Quarks also have antimatter counterparts called antiquarks (designated by a line over the letter symbol). Quarks combine to form larger particles called baryons, and quarks and antiquarks combine to form mesons. Protons and neutrons, particles that form the nuclei of atoms, are examples of baryons. Positive and negative kaons are examples of mesons.

 

Particle Accelerator

The big circle marks the location of the Large Hadron Collider (LHC) at the European particle physics laboratory in CERN. The tunnel where the particles are accelerated is located 100m (320 ft) underground and is 27 km (16.7 mi) in circumference. The smaller circle is the site of the smaller proton-antiproton collider. The border of France and Switzerland bisects the CERN site and the two accelerator rings.