Earth Science: Elementary Particles – Fundamental Forces
In the 19th century, James C. Maxwell unified the theories of electromagnetism and optics. Today quantum field theory brings together three of the four fundamental forces of nature, excluding only gravitation.
In principle, gravitation and the electro- magnetic force operate over any distance, but their influence decreases in proportion to the square of the distance of separation. That is all the two forces have in common, however.
Currently gravitation can only be described using the general theory of relativity (Albert Einstein, 1915), but this theory breaks down at the level of elementary particles. On the other hand, quantum electrodynamics (QED), a description of electromagnetism using quantum field theory, explains all of the interactions within atomic electron shells as well as among atoms and molecules, with great precision.
The strong and weak interactions.
The discovery of radioactivity by Antoine Henri Becquerel with husband and wife team Pierre and Marie Curie brought two additional natural forces to the attention of physicists. One is even more powerful than electromagnetic interactions and is thus called the strong interaction. Its force particles are called gluons.
Only quarks are affected by this force, since they are the only particles (besides gluons themselves) to possess a so-called color charge. In analogy to visual color, there are three kinds of color charge, and three quarks of different colors produce a color-neutral proton. The strong interaction is so well shielded that it only affects particles at distances smaller than 33 to 50 feet (10 to15 m).
The weak interaction or weak nuclear force (100 billion times weaker than electromagnetism, but still 1,025 times stronger than gravitation) is involved in processes such as radioactive beta decay. All known particles are affected by this interaction. Its basic effect is the transformation of quarks into electrons or neutrinos, and vice versa. Here, too, the distance over which the force operates is extremely small.
The weak and strong interactions are the causes of radioactivity-that is, the transformation of atomic nuclei accompanied by the emission of various kinds of radiation. Radioactive alpha decay is a special kind of nuclear fission, with two protons and two neutrons (an alpha particle) splitting off from the nucleus together.
In beta decay, electrons are emitted as beta radiation, while the emissions of gamma decay are extremely high-energy protons (gamma rays). Other decay processes within large nuclei, such as their fission into two fragments, produce energy, as does the fusion of two lighter, weakly bound nuclei.
THE “NOBEL FAMILY” CURIE
Marie Curie received two Nobel Prizes. The first, shared with Antoine Henri Becquerel and her husband Pierre Curie, was in the field of physics for the study of radioctivity, in which she played a key role in the discovery of forces within the nucleus.
The second was awarded to her for her work in chemistry. Her daughter Irene Joliot and son-in-law Frederic also received Nobel Awards, making them a true “Nobel Family”