Image of MIT Spectroscopy Laboratory MIT Spectroscopy Laboratory
MIT Spectroscopy Laboratory and the MIT Wavelength Tables, George Harrison, 1930s

When you look out at the neon lights of a city, or at the colors of the plasma globes in this exhibit, you’re seeing the characteristic colors emitted by an element or a mixture of elements when energy is pumped into them. Professor George Harrison’s 1939 collection of wavelength tables was a landmark accurate listing of more than 100,000 different wavelengths generated by different elements. The first publication of the MIT Wavelength Tables astonished most people because the process of measuring wavelengths was known to be very time-consuming. Harrison made use of Vannevar Bush’s pioneering differential analyzer technology and the efforts of dozens of women workers funded by the Works Progress Administration to speed up radically the effort. After World War II, Harrison’s focus shifted to producing more advanced spectroscopic instruments, particularly by making diffraction gratings larger and more optically precise. In 1955, he developed the “MIT B” ruling engine. The echelle grating on display—and those still being made at Richardson Grating Laboratory in Rochester, NY—are considered to be nearly perfect.

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