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The Servant of Science
| Article
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19580 |
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Section : |
NATURAL SCIENCE
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| Issue
Date : |
11 / 1991 |
2,404 Words |
| Author
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Kurt Stehling
Kurt Stehling is chief scientist emeritus for the National
Oceanic and Atmospheric Administration (NOAA). |
Much of our understanding of the nature of the atom, the composition of chemical compounds, identification of elements, minerals, the sun, stars, and other stellar objects, biological specimens, and the like derives from the interpretation of the spectra (a series of line, or band, images) they produce either naturally or artificially. The cornerstone of twentieth-century physics, quantum mechanics, partly resulted from correctly interpreting the complexities inherent in the sun's spectrum. That spectrum, by the way, revealed helium, otherwise undetectable, as an element in the solar spectrum in the late nineteenth century.
While Isaac Newton first detected the colored bands (spectrum) produced by a prism's dispersion or breakup of white light, it remained for nineteenth century experimenters to detect, analyze, and interpret the many dark lines scattered among Newton's colored continuum. He failed to notice these with his simple experiment. Early nineteenth-century investigators, such as Joseph von Fraunhofer, devised the first simple spectroscope with a prism, an entrance, or aperture slit, plus focusing optics. [The combination was necessary to bring out the many lines.] It was another German, Gustav Kirchoff, who in 1859 discovered that the dark lines in the sun's spectrum were actually the signatures of the many elements in its glowing mass. He also noted, as did his colleagues and successor, that the location or position, or wavelengths, of the lines within any spectrum (solar or otherwise) is always the same.
By the end of the nineteenth century, physical scientists, astronomers, and chemists had fairly well unraveled the many subtleties of spectra with improved spectroscopes, and sensitive photography and measuring machines that could very accurately measure the positions and spacing between spectral lines. Eventually, the even greater dispersing power made available by more advanced supersensitive spectrographs showed that most "solid" lines were actually composed of a hyperfine structure of many lines.
With the discovery of the electron in 1897, it was suspected by around 1900 that the oscillations of an atom's electron were responsible for the line signature of an atom. It was further discovered that several other processes were at work in and around the atom. From detailed studies of the hyperfine structures, theorists were able to confirm, indeed, that the spinning of the electron(s) and the nucleus itself were largely responsible. It was further discovered, by around 1910, that not only thermal and electric forces, but also magnetic forces could influence the electron's oscillations to produce broadening
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