Today in History – December 20, 1899 – Carbon Arc Lamps generate light by way of a spark between two carbon nodes. However, they also produce a constant humming noise while running. Since they were widely used in Europe (installed before the invention of the electric light bulb in the United States), a British physicist and electrical engineer, William Duddell was appointed to solve the noise problem in 1899. During his experiments, Duddell found that he could control the audible frequencies by varying the voltage supplied to the lamps. It’s possible that Duddell was aware of similar findings by a Dr. Simon of Frankfurt, Germany a year earlier (who showed that the modulated arc produced modulated light as well as sound, allowing the German Navy to make telephone calls between ships with an arc searchlight and a photosensitive selenium cell). However, it was Duddell that attached a keyboard to the arc lamps, creating one of the first electronic instruments, The Singing Arc, that was audible without the use of an amplifying system (which had yet to be invented). Other pre-20th-century electronic instruments include the Clavecinlectrique, the Musical Telegraph, and the Telharmonium.

Also on this date in 1951, the first electricity generated by nuclear power powers four lightbulbs. And in 1977, the first space walk was made by Cosmonaut Grechko of the Salyut.

For more information, see the Engineering Pathway‘s resources on electronic music; breeder reactors and nuclear power; and the Salyut, space exloration and aerospace engineering. For related educational resources, visit the Electrical Engineering Education, Aerospace Engineering Education,or Nuclear Engineering Education disciplinary communities.