Template:Are You Sure/April 9

• ... that physicist and academic Thomas Johann Seebeck (9 April 1770 – 10 December 1831) discovered the thermoelectric effect?

• ... that Édouard-Léon Scott de Martinville (25 April 1817 – 26 April 1879) made the oldest known recording of an audible human voice, a visual recording of audio data; and that it was first be played back in 2008?

• ... that mathematician and electrical engineer Charles Proteus Steinmetz promoted the development of alternating current, formulating mathematical theories which will advanced the expansion of the electric power industry in the United States?