Applied and Pure Science: Physics

views updated

Applied and Pure Science: Physics

Electricity. The investigation of electricity was popular in the mid eighteenth century. In 1753 British colonist Benjamin Franklin (1706-1790) developed the lightning rod in Philadelphia to prevent damage from lightning strikes. In 1780 Italian scientist Luigi Galvani (1737-1798), a professor of anatomy in Bologna, noticed that frogs’ legs contracted if an electrical spark was applied, a phenomenon he called “animal electricity.” His interest was shared by Alessandro Volta (1745-1827), a physics professor at Pavia, who around 1795 proved that it was possible to generate electricity by connecting two different types of metal, later producing the first electrical-current battery in 1800. In England, electrical currents were run through substances such as alkalis or salts to examine their chemical composition. In 1800 engineer William Nicholson (1753-1815) was the first person to use electricity to break water into its constituent elements, oxygen and hydrogen. In 1807, using the same methods, English scientist Humphry Davy (1778-1829) announced his discovery of two new heretofore unknown elements, potassium and sodium, which he had isolated from compounds, thus showing how other elements could be identified. These developments linked electricity with chemistry, providing evidence that the various branches of science were fundamentally linked, an idea that proved extremely important in the twentieth century.

Electromagnetism. During the nineteenth century, scientists gradually uncovered linkages between electricity and magnetism. In 1821 Englishman Michael Faraday (1791-1867) conducted a series of deliberately planned investigations, discovering that a magnet needed

to be moved near an electric conductor to attract current. The results of Faraday’s experiments were the basis for the new science of electromagnetism, as well as the foundation for the new electrical industry that emerged rapidly toward the end of the nineteenth century. In 1837 English scientists Charles Wheatstone and William F. Cooke patented a practical application of current electricity, an electric telegraph. In the same year American inventor Samuel F. B. Morse (1791-1872) patented a similar device. Morse also contributed to telegraphy by formulating an alphabetic code of dots and dashes. It was first tested in a long-distance transmission in 1844, when the first U.S. telegraph line was completed between Baltimore and Washington, D.C. The telegraph industry developed rapidly. London and Paris were linked in 1854, and the transatlantic telegraph cable was laid in 1858. Such rapid communication tied the world together as never before. The telegraph showed the potential of electricity, but most other practical applications of Faraday’s findings in electromagnetism took more than fifty years to implement because of difficulties involved in working out effective systems to generate electrical current through mechanical action and questions of how to operate machinery using electricity.

Radio. Faraday’s findings were rendered into convincing mathematical equations in 1865 by Cambridge University professor James Clerk Maxwell (1831-1879), who showed that light was an electromagnetic phenomenon. Electromagnetic oscillations give off potentially audible waves similar to light waves, which vibrate at much lower frequencies. Demonstrated conclusively in 1888 by two physicists working independently, German Heinrich Rudolph Hertz (1857-1894) and Englishman Oliver Joseph Lodge (1851-1940), this finding was the basis for radio communications. A practical wireless telegraphy emerged in the following decade, after discoveries by Lodge and Italian Guglielmo Marconi (1874-1937).

Electric Lighting. Maxwell’s wave theory was put into practice by an international group of scientists, who made the use of electrical power a part of everyday life. In 1867 William Siemens (1823-1883) found that electrical current from one machine could stimulate an electromagnet in another. This dynamic principle of electricity was the foundation of the dynamo, which made possible the widespread production of relatively inexpensive electricity. This discovery stimulated a rush to find practical uses for it. In 1879 American inventor Thomas Alva Edison (1847-1931) and English chemist Joseph Wilson Swan (1828-1914) independently developed the incandescent light bulb. Two years later, Edison discovered how to transmit electrical energy over long distances without significant loss of current. It took decades to put this technology into practice, however, because networks of generators had to be built and linked together. Once the generators were constructed and the wires were strung, however, electricity gradually became available to almost everyone, regardless of where they lived. Not at the forefront of the scientific advances underlying the electrical industry, German industrial leaders were among the first to capitalize on

“This text has been suppressed due to author restrictions”

the practical potential of electricity. They quickly became the world leader in the manufacture of motors, equipment for the generation and transmission of electricity, and appliances such as lightbulbs and lamps. Although the United States was a much greater producer of electricity, German exports of electrical equipment were almost 300 percent more than those of the United States, as well as 250 percent greater than those of Great Britain.

Telephones. The development of the telephone is a good example of a process of technological invention that emerged in the mid nineteenth century. That is, scientific understanding of the theory preceded the emergence of demand. Inspired by the experiments of German physicist Hermann von Helmholz (1821-1894) with reproducing sound, Scotsman Alexander Graham Bell (1847-1922), residing in the United States, developed the telephone in 1875-1876, while exploring the nature of sound and speech. Bell filed the patent application for his invention first, but another American, Elisha Gray (1835-1901), invented his own version of the telephone at nearly the same time. In fact, the telephone used concepts and machinery available since the development of the telegraph, and Italian Innocenzo Manzetti (1826-1877) had demonstrated an earlier prototype in 1865. None of these inventions was of widespread practical use, however, until the invention of the switchboard, which was installed in 1878 in New Haven, Connecticut, to operate the world’s first telephone exchange. Telephones were adopted more gradually in Europe and did not become widespread until after World War II.