Caesium was discovered in 1860 by Robert Bunsen and Gustav Kirchhoff at Heidelberg, and it was the first element found with the aid of the spectroscope, an instrument they had just developed. Examining the mineral water from Durkheim in Germany, they saw two bright blue lines in its spectrum that did not belong to any known element. The name comes from the Latin caesius, meaning sky-blue. Bunsen had to evaporate tonnes of mineral water to isolate enough of the new alkali metal. Caesium is the most reactive of the stable metals, and it melts just above room temperature. Its atomic transitions are so regular that since 1967 the international definition of the second has been based on caesium, and caesium clocks are the foundation of precise timekeeping worldwide.
Before and after
- 20 October 1859Birth of John Dewey
- from 25 October 1859 to 1 January 1862Prussian expedition to East Asia (1859-1862)
- 24 November 1859On the Origin of Species
- 15 December 1859Birth of L. L. Zamenhof
- 1860Discovery of caesium
- 1860Introduction of Finnish markka
- from c. 1860s to 1890sSecond Industrial Revolution
- c. 1860sRise of modern art
- c. 1860sImpressionism
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The era
This moment belongs to the Industrial era (1760 CE to 1914 CE), steam, factories and revolutions. You can also browse everything in the 19th century.