Speculation about the possible existence of intelligent life on the Moon and nearby planets (see life on Mars and life on Venus) led to numerous proposals for ways of communicating with any inhabitants there might be on these worlds. Various methods of visual signaling were suggested in the 19th century, including those of Gauss (1822), von Littrow (1842), and Cros (1869).

 

In the 1890s, at the height of the canal controversy (see Mars, canals), interest was focused on communicating with advanced Martians (see Galton, Francis and Pickering, William Henry). This interest was intensified by the announcement of the Guzman Prize and by reports of lights on the surface of Mars, which were taken by some to be efforts by the inhabitants to send signals to Earth (although in War of the Worlds, H. G. Wells offered a more disturbing alternative).

 

The dawn of the 20th century saw the first attempts and conjectures concerning radio communication with the planets, by Tesla (1901), Todd (1909), and Marconi (1919).¹ These were to pave the way for efforts to detect and transmit interstellar radio signals several decades later (see SETI).

 

Reference

1. Jackson, C., and Hohmann, R. "An Historic Report on Life in Space: Tesla, Marconi, Todd," paper presented at 17th Annual Meeting of the American Rocket Society, Los Angeles, November 13-18, 1962.