Portal:Physics/2006 Selected articles

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This is an archive of entries that appeared on Portal:Physics's Selected Article section in 2006.

January 1, 2006 - Soap bubble


A soap bubble is a very thin film of soap water that forms a hollow shape with an iridescent surface. Soap bubbles usually last for only a few moments and burst either on their own or on contact with another object. Due to their fragile nature they have also become a metaphor for something that is attractive, yet insubstantial. They are often used as a children's plaything, but their usage in artistic performances shows that they can be fascinating for adults too. Soap bubbles can help to solve complex mathematical problems of space, as they will always find the smallest surface area between points or edges.

Soap bubbles can exist because the surface layer of a liquid (usually water) has a certain surface tension, which causes the layer to behave as an elastic sheet. A common misconception is that soap increases the water's surface tension. Actually soap does the exact opposite, decreasing it to approximately one third the surface tension of pure water. Soap does not strengthen bubbles, it stabilizes them, via an action known as the Marangoni effect. As the soap film stretches, the concentration of soap decreases, which causes the surface tension to increase. Thus, soap selectively strengthens the weakest parts of the bubble and tends to prevent them from stretching further. In addition, the soap reduces evaporation so the bubbles last longer.

January 17, 2006 - Superconductivity
Superconductivity is a phenomenon occurring in certain materials at low temperatures, characterized by the complete absence of electrical resistance and the exclusion of the interior magnetic field (the Meissner effect). Superconductivity is a popular device in science fiction due to the simplicity of the underlying concept - zero electrical resistance - and the rich technological possibilities. For example, superconducting magnets could be used to generate the magnetic fields used by Bussard ramjets, a type of spacecraft commonly encountered in science fiction. The most troublesome property of real superconductors is the need for extremely low temperatures. Superconductivity is an essentially quantum mechanical phenomenon, and cannot be understood simply as the idealization of "perfect conductivity" in classical physics. (read more...)

June 6, 2006 - Edward Teller
Edward Teller was a Hungarian-born American nuclear physicist of Jewish descent. He was known colloquially as "the father of the hydrogen bomb". Teller was an immigrant to the United States during the 1930s, and was an early member of the Manhattan Project to develop the first atomic bombs. During this time he made a serious push for the first time to develop fusion-based weapons as well, but they were deferred until after the war. After his controversial testimony in the security clearance hearing of his former Los Alamos colleague J. Robert Oppenheimer, Teller became ostracized by much of the scientific community. He continued to find support from the U.S. government and military research establishment. He was a co-founder of Lawrence Livermore National Laboratory, and was both director and associate director for many years. In his later years he became especially known for his advocacy of controversial technological solutions to both military and civilian problems, including a plan to excavate an artificial harbor in Alaska using thermonuclear explosives. Over the course of his long life, Teller was known both for his scientific ability and his difficult interpersonal relations, and is considered one of the key influences of the character Dr. Strangelove in the 1964 movie of the same name. (more...)

September 2, 2006 - H II region
An H II region is a cloud of glowing gas and plasma, sometimes several hundred light years across, in which star formation is taking place. Young, hot, blue stars which have formed from the gas emit copious amounts of ultraviolet light, ionising the nebula surrounding them.

H II regions may give birth to thousands of stars over a period of several million years. In the end, supernova explosions and strong stellar winds from the most massive stars in the resulting star cluster will disperse the gases of the H II region, leaving behind a cluster such as the Pleiades.

H II regions are named for the large amount of ionised atomic hydrogen they contain, referred to as H II (pronounced 'aitch two') by astronomers (H I ('aitch one') being neutral atomic hydrogen, and H2 (also 'aitch two') being molecular hydrogen). H II regions can be seen out to considerable distances in the universe, and the study of extragalactic H II regions is important in determining the distance and chemical composition of other galaxies. (more...)

Image: NGC 604, a giant H II region in the Triangulum Galaxy.