Microcosmology: Atom In Jain Philosophy & Modern Science: [1.3.6] Atom in Modern Science - New Physics - Forces Known in Nature

The universe, according to physicists, is held together by four fundamental types of glue (force). In other words, all known forces in nature can be grouped into four categories according to their strength. This division is empirical (i.e., man made) for the convenience of explaining partial theories. It is quite possible that all the four types of forces are but different aspects of a single force.

In order of the decreasing strength, they are:

1. Strong nuclear force
2. Electromagnetic force
3. Weak nuclear force
4. Gravity (gravitational force)

1. [1] Quarks are dealt with in a later part of this chapter.

   The strongest force is the 'strong nuclear force' that is the binding force of the nuclei. It not only binds the nucleons, protons and neutrons together in the nucleus of an atom, but binds the constituents (quarks) of these nucleons together. [1] The strong force deserves its name, because it is 100 times stronger than the familiar electromagnetic force. In fact, it is the strongest force known in nature. It has to be strong because it has to keep mutually repulsive protons; not only in close proximity, but also keep them bound together very tightly. It has the shortest range of all the forces known in nature. For example, only if a free proton comes within about one ten-trillionth 10-13 of a centimetre of the nucleus, it is suddenly sucked into the nucleus with a force one hundred times more powerful than the repulsive electromagnetic force. One ten-trillionth of a centimetre is about the diameter of the proton itself. At a distance, only slightly greater than its magnitude, the proton is relatively unaffected. Strong force interactions are very very fast i.e., they take about 10-22 seconds. (Weak force reactions take about 10-10 seconds). Because of the short range, it can never appear as a force at macroscopic level and cannot be experienced in the everyday world.

2. Electromagnetic force is encountered in everyday world and holds together the atoms and molecules. Every subatomic particle has a positive or a negative charge or it is neutral. Positively and negatively charged particles are attracted to particles with opposite charge and repelled by those with the same charge. It varies inversely as the square of the distance separating the particles. It enables atoms to join together to form molecules and it keeps electrons in orbit around nuclei. At this level, it is the fundamental glue of the universe. It is much stronger than the gravitational force. For instance, the force between two electrons is 10-40 times bigger than the gravitational force.

3. Weak (nuclear) force is the least known of the four forces. Its existence was inferred from the time required by certain subatomic interactions. Whereas strong force interactions happen in about 10-23 seconds, weak interactions take a much longer time i.e. about 10-10 seconds. In all probabilities, this force and the electromagnetic force are different manifestations of the same force operating at distances between particles.

4. Gravitational force: The weakest of the four is the gravitational force which is universal, i.e., every particle exerts/feels it. It is essentially a long-range force, i.e., it acts over large distances, whereas the other three forces are sometimes attractive and sometimes repulsive, this one is always attractive. It holds together the solar systems, galaxies, etc. On the subatomic level, its effect is so negligible that it is ignored altogether.