William Herschel (1738 to 1822) had shown in 1800 that optical radiation extends beyond the visible red rays, but his thermometers were too insensitive to detect energy beyond that quite close to the visible spectrum. Another quarter of a century elapsed before technology advanced sufficiently for such measurements to be made. The measurements that were then made were beset with obstacles arising from political upheavals and cholera epidemics as well as scientific uncertainties. These probably would have deterred most of us, but one man of sterner stuff undertook pioneering research that opened a new vista in optical phenomenology.
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