Lyman, Theodore (1874–1954)

US physicist whose work was confined to the spectroscopy of the extreme ultraviolet region.

Lyman was born in Boston and studied at Harvard, and briefly in Europe at Cambridge and Göttingen. His working life was spent at Harvard, where he became professor in 1921.

When Lyman began his research, the ultraviolet end of the spectrum had been observed by enclosing the spectroscope in a vacuum with fluorite windows. Using a concave ruled grating instead of a fluorite prism, Lyman discovered false lines in the ultraviolet due to light in the visible region, and these came to be called Lyman ghosts. He established the limit of transparency of fluorite to be 1,260 Å (1 Å = 10−10m) and looked at the absorbency of other suitable solids but found none better. He also examined the absorption of various gases. By 1917 Lyman had extended the spectrum to 500 Å.

A series of lines in the hydrogen spectrum discovered by Lyman 1914 was named the Lyman series. He correctly predicted that the first line would be present in the Sun's spectrum.

In the 1920s Lyman began to examine spectra in the ultraviolet region of helium, aluminium, magnesium, and neon. His last paper was published in 1935 on the transparency of air between 1,100 and 1,300 Å.

Lyman was also a traveller and naturalist. From the Altai mountains of China and Mongolia, he brought back the first specimen of a gazelle Procapra altaica and 13 previously unknown smaller mammalian species. A stoat became known as Lyman's stoat, Mustela lymani.

Lyman, Theodore (1833–1897)

US zoologist and soldier. He was one of the first trustees of the Museum of Comparative Zoology and he pursued his studies both at home and abroad. He volunteered during the Civil War and was present at several important occasions; his letters to his wife, published as Meade's Headquarters, 1863–65, Letters of Col Theodore Lyman from the Wilderness to Appomattox (1922) are a valuable source for students of the Civil War. He was a member of the House of Representatives (1883–85). Lyman was born in Waltham, Massachusetts. He graduated from Harvard University in 1855 and worked under Louis Agassiz.