Number of words: 531
The creation and destruction of material particles is one of the most impressive consequences of the equivalence of mass and energy. In the collision processes of high-energy physics, mass is no longer conserved. The colliding particles can be destroyed and their masses may be transformed partly into the masses, and partly into the kinetic energies of the newly created particles. Only the total energy involved in such a process, that is, the total kinetic energy plus the energy contained in all the masses, is conserved. The collisions of subatomic particles are our main tool to study their properties and the relation between mass and energy is essential for their description. It has been verified innumerable times and particle physicists are completely familiar with the equivalence of mass and energy; so familiar, in fact, that they measure the masses of particles in the corresponding energy units.
The discovery that mass is nothing but a form of energy has forced us to modify our concept of a particle in an essential way. In modern physics, mass is no longer associated with a material substance, and hence particles are not seen as consisting of any basic ‘stuff’, but as bundles of energy. Since energy, however, is associated with activity, with processes, the implication is that the nature of subatomic particles is intrinsically dynamic. To understand this better, we must remember that these particles can only be conceived in relativistic terms, that is, in terms of a framework where space and time are fused into a four-dimensional continuum. The particles must not be pictured as static three-dimensional objects, like billiard balls or grains of sand, but rather as four-dimensional entities in space-time. Their forms have to be understood dynamically, as forms in space and time. Subatomic particles are dynamic patterns which have a space aspect and a time aspect. Their space aspect makes them appear as objects with a certain mass, their time aspect as processes involving the equivalent energy.
These dynamic patterns, or ‘energy bundles’, form the stable nuclear, atomic and molecular structures which build up matter and give it its macroscopic solid aspect, thus making us believe that it is made of some material substance. At the macroscopic level, this notion of substance is a useful approximation, but at the atomic level it no longer makes sense. Atoms consist of particles and these particles are not made of any material stuff. When we observe them, we never see any substance; what we observe are dynamic patterns continually changing into one another-a continuous dance of energy.
Quantum theory has shown that particles are not isolated grains of matter, but are probability patterns, interconnections in an inseparable cosmic web. Relativity theory, so to speak, has made these patterns come alive by revealing their intrinsically dynamic character. It has shown that the activity of matter is the very essence of its being. The particles of the subatomic world are not only active in the sense of moving around very fast; they themselves are processes! The existence of matter and its activity cannot be separated. They are but different aspects of the same space-time reality.
Excerpted from Pages 202-203 of ‘The Tao of Physics’ by Fritjof Capra