Physics: 1904

Rayleigh, Lord pronounced RAY lee, (1842-1919), an English physicist, made many important discoveries in a wide variety of fields. He received the Nobel Prize for physics in 1904 for studying the density of gases and for discovering and isolating the element argon.

Rayleigh worked in many fields, initially concentrating on mathematics and later looking at almost the whole range of physics. His research included studies of sound, wave theory, color vision, electrodynamics (the study of electric currents), electromagnetism, light scattering, and the density of gases. He also studied viscosity (the resistance of a liquid to changing its shape), capillarity (the movement of the surface of a liquid, caused by surface tension), elasticity, and photography. His work led to the setting up of standards for the measurement of current, electromotive force, and resistance.

John William Strutt was born in Essex, England, and graduated in mathematics from Cambridge University in 1865. He became Baron Rayleigh when he inheirited the title in 1873. In 1873, Rayleigh became a fellow of the Royal Society, one of the world's leading scientific organizations. He served as its president from 1905 to 1908.

About Argon

Argon, pronounced AHR gon, is a chemical element that forms 0.94 percent of Earth's atmosphere. Most ordinary light bulbs are filled with argon and a little nitrogen. Argon is also used as a shielding gas in arc welding to protect the metal from oxygen in the air. Lord Rayleigh and Sir William Ramsay discovered it in 1894.

Argon is a colorless, odorless, tasteless gas. It does not react readily with other chemicals. This chemical element is classed as a noble gas. Its symbol is Ar. Its atomic number (number of protons in its nucleus) is 18. It has a relative atomic mass of 39.948. An element's relative atomic mass equals its mass (amount of matter) divided by 1/12 of the mass of carbon 12, the most abundant form of carbon. The freezing point of argon is -189.2 °C, and its boiling point is -185.7 °C. Its density is 0.00166 gram per cubic centimeter at 20 °C at sea level.

Argon is continuously released into the atmosphere through the decay (breaking down) of radioactive potassium in Earth's crust. When the potassium decays, it changes into argon. Commercially, it is obtained as a by-product in the manufacture of liquid air.