Russell Duncan, age 15, of Reno, Nev., for his question:
WHAT IS QUANTUM MECHANICS?
Quantum mechanics is a field of physics that describes the structure of the atom and the motion of atomic particles. It also explains how atoms absorb and give off energy as light, and it clarifies the nature of light.
Quantum mechanics goes beyond the limits of classical physics, which is based on the laws formulated by the English scientist Sir Isaac Newton. It ranks as one of the major scientific achievements of the 1900s.
Quantum mechanics has contributed greatly to the development of such important devices as lasers and transistors. It also has enabled scientists to gain a better understanding of chemical bonds and reactions.
Max K.E.L. Planck, a German physicist, introduced the idea of quanta in the 1900s to explain the spectrum of light emitted by certain heated objects. Then, about 1905, another German scientist, the famed Albert Einstein, broadened Planck's idea to explain a phenomenon called the photoelectric effect. In doing so, Einstein firmly established that light consists of energy particles that have wave properties.
In 1921, Einstein won the Nobel prize in physics for a paper on quanta. He moved to the United States in 1933 and became an American citizen in 1940.
Niels Bohr, a Danish physicist, proposed the theory of the atom's electron structure in 1913. He also showed how atoms radiate light. Scientists call Bohr's work "quantum theory" to distinguish it from the broader system of "quantum mechanics."
Louis de Broglie, a French physicist, introduced the idea of matter waves in 1924.
Then Austrian physicist Erwin Schrodinger and German physicist Werner Heisenberg independently developed forms of quantum mechanics in 1925. Since that year, these forms have been unified into a system and applied to several scientific fields including chemistry, molecular biology and solid state physics.
Quantum mechanics shows that electrons and other atomic particles of matter are associated with waves.
It isn't easy to understand quantum mechanics, but here's another look:
In an atom, tiny particles of negative electrical charge called electrons move in orbits around a nucleus of positive charge. Quantum mechanics shows that the electrons can move only in certain orbits.
Each orbit, called a quantized orbit, has a particular value of energy. When an electron is in a given orbit, it exists at a specific energy level and does not release or absorb energy.
An electron remains in this normal state as long as its atom is not distributed. But if outside forces act on the atom, the electron can change to another quantized orbit.
Another fundamental idea of quantum mechanics is the uncertainty principle. According to this principle, the position and velocity of a particle cannot simultaneously be measured with exactness.