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The Big and the Small - Part 1The Four Forces and the Scale of the UniverseAt different scales, different forces have a predominate influence over matter.
The four fundamental forces are the electromagnetic force, the strong and weak forces, and the force of gravity. Three of these forces have been connected with a common theory: the strong, weak, and electromagnetic. Only gravity remains to be worked into the others, to create a "grand unified theory", otherwise known as the theory of everything. This effort is expected to be the driving focus of 21st century research physics. The four forces are considered fundamental because every other force we have encountered can be attributed to one of these, or a combination. The strong and weak forces are very strong, over a very limited range. The electromagnetic force is weaker than the strong and weak forces, but has a much greater range. Gravity is the weakest force by far, but has an infinite range though it does fade over distance. At the atomic scale, the strong and weak forces reign supreme. They are stronger than either gravity or the electromagnetic forces over very tiny distances. This is why a nuclear explosion is so powerful, it takes a lot of energy to break apart the bonds within the nucleus of an atom, and it turn, a lot of energy is released. On the microscopic scale, the electromagnetic force is dominant. The electromagnetic force is responsible for both electricity and magnetism, but it is also what binds atoms together to make molecules, and eventually solid matter big enough to see. The property of charge is associated with electromagnetism. Atoms can carry charge, either positive or negative. Positive atoms are attracted to negative atoms, and two atoms with the same charge repel. You can think of charged atoms behaving very much in the same way as magnets, where like poles repel, and different poles attract. Atoms don't have poles, but they have regions where one type of charge is stronger, and can have several areas that will attract or repel other atoms. Atoms that are attracted to one another will chain together to form molecules. A molecule can also carry charge, since the atoms making it up may still have unpaired regions. So, molecules can quickly clump together with other molecules to make large scale material.
The copyright of the article The Big and the Small - Part 1 in Physics is owned by Katharine M. J. Osborne. Permission to republish The Big and the Small - Part 1 in print or online must be granted by the author in writing.
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