A tiny cloud
Previously, the question of an inner structure of the electron was considered to be a mistake. An electron carries an elementary charge that becomes noticeable through the electromagnetic force; this is inversely proportional to the square of the distance. Now scientists at Purdue University have found different values for the charge of the electron, depending on the distance at which they make their measurements. They explain this with a new concept of the fine structure of the electron. According to David Koltick, Professor of Physics at Purdue University, one must imagine that an electron consists of a nucleus surrounded by a cloud of virtual particles. (Physical Review Letters, January 20, 1998 edition). "Virtual" means not directly measurable, but nevertheless effective. The "virtual particles" consist of pairs of electrically positively and negatively charged particles.
The negative charge of the electron core has a polarizing effect on the virtual particles, i.e. the positively charged partner in a pair tends to be oriented inward, the negative one tends to be oriented outward. From afar, the entire electron still appears negatively charged - but weaker than the bare electron core.
"The cloud of virtual particles acts like a curtain… shielding the real values of the electron nucleus," explains Koltick. The closer the measurements get to the core, the smaller the "shield effect". So the electromagnetic force cannot be considered as a constant, but it changes with the distance from the nucleus.
Another result of the investigations was the discovery that the strong force (strong nuclear force), which holds the elementary particles such as the protons together, decreases the closer they are to the nucleus. According to Koltick, there may come a point where these two forces balance each other out.
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