The World Is Made of Subatomic Particles

According to contemporary physicists, the world is made of several types of objects, collectively referred to as subatomic particles. These particles can be also thought of as manifestation of something yet more fundamental, known as quantum fields. There may be as many as 10⁸⁹ identical copies of some of these particles in the present universe. The forms of matter are all composed of various combinations of only three types of subatomic particles – protons, neutrons, and electrons. Dozens of other type of particles can be produced momentarily in the laboratory, however, and are thought of having existed in large numbers in the early universe.

All subatomic particles are defined by possessing a few qualities, such as mass, spin, and electric charge. Two particles are of the same type, if all of these qualities agree. Otherwise, they are considered to be different particles. Particles of the same type are, as far as we know, truly identical in these properties of mass, spin, and charge rather than just very similar. If all photons, the particles that make up light, were not identical, lasers would not operate.

The subatomic particles readily convert into one another on colliding. The kinetic energy of motion of light particles can be converted into the energy associated with mass (rest energy) of heavy particles. In many cases, even isolated particles can convert spontaneously into others, the latter being lass massive. In all such transformations, only a few properties, such as the total electric charge, remain unchanged. The subatomic particles do not act like the changeless building blocks imagined by some Greek philosophers. In the last few years, physicists have realized that even those subatomic particles which exist have changed radically over the lifetime of the universe. It appears that evolution takes place on all levels of matter, not just on the more complex levels of living things. The driving force behind this evolution is the expansion of the universe, which by changing the environment in which particles are found, changes the particles themselves.

Under the conditions in which physicists usually observe subatomic particles, their defining properties are not perceived to vary, giving these properties an illusion of stability. However, at immense temperatures and densities that prevailed in the early stages of the universe, the properties, such as mass, of some particles would have been very different from what they are now. This situation is related by nature to the variability of a liquid such as water. Under a fairly wide range of temperatures water remains liquid and its properties do not change very much whatever the temperature within this range. Subjecting water to much lower temperatures or heating it to above 100º Celsius changes its properties abruptly. This type of change, in which the properties of a substance change drastically as a result of a small variation in its environmental conditions, is called a “phase change” by physicists.

The presumed change in the properties of subatomic particles at very high temperatures is also considered to be a phase change, one that involves the properties of space, as well as of the particles in it. In other words, the particles do not react directly to a temperature change but to some alterations in space, the medium, in which they find themselves.

It is easy to boil or freeze water, but very difficult to duplicate in the lab the extreme conditions present at the birth of the universe. Yet physicists have become convinced of the theory that atomic particles, and space itself, went through momentous phase changes during and after the Big Bang. The rapid cooling following primordial explosion is thought of having generated several phase changes. After an incredibly short time (perhaps a microsecond), the subatomic stuff of the young universe became stabilized, combining into the particles that make up matter today.