JF Ptak Science Books Quick Post
[New York Times, September 18, 1921, here]
And so there came a time in 1923 and 1924 when it was determined that when the Earth next came into closest proximity with Mars (closest in opposition for a century) that efforts would be made to determine whether or not there was anyone around on that planet. The idea of the radio being a powerful-enough instrument to be used in such a way was initiated in 1896 by Tesla, and soon followed at the turn of the century with support for the idea by Marconi and Kelvin. (This interest was perhaps ignited after both Tesla and Marconi detected unexpected and steady signals that they thought were extraterrestrial but which were in fact ionospheric radiation--and of course there was Percival Lowell and his self-derived belief in Martian intelligence as described by the thought that there were canals on the surface of Mars.
This was a massive-idea effort: a U.S. government initiative demanded five minutes of radio silence per hour over a 36-hour period in the vast hope that transmitters closed down that if there were any radio signals being directed towards the Earth from Mars that they could be more easily detectable.
This was the magnificent "National Radio Silence Day". And it was extraordinary that i twas supposed to affect every radio in the country.