I read this somewhere…years ago.
In the early days of wireless telegraphy, radio operators would often broadcast signals to see if anyone who might be picking them up would respond.
Several operators reported their code groups would be picked up again tens of minutes later. These incidents were apparently quite common, and some were reported in reputable journals.
Key operators have a distinctive “fist” or rhythm to their Morse code transmissions, they can identify the hand that is keying, so they knew it wasn’t someone waiting a few minutes and then repeating their message. This was their fist. They concluded it had to be an echo.
No one thought much of it at the time, it was felt that the transmissions had been reflected back to earth by chance alignments of plasma clouds floating around in the solar system. There was no way that signal could be bouncing around the ionosphere that long without being totally attenuated, so an astronomical phenomenon was postulated as an explanation for the echoes.
It wasn’t until years later that someone actually took the time to do the math, and calculated that any radio signal transmitted with the equipment of those days would have had to travel distances on the order of several AU, and that inverse square law would have weakened the signal to the point of undetectability.
THe same could be said for the return pulse after the reflection. It was simply out of the question for the non-directional antennas of those days to either transmit a pulse that strong, or their primitive receivers pick up the echo. It wasn’t until the 40s that someone managed to bounce a pulse off the moon, and that was with a powerful parabolic radio telescope. The moon is only light-seconds away.
As far as I know, no one has ever come up with an explanation for this phenomenon. The article where I read this (sorry, I can’t remember where) suggested there may have beeen an alien interstellar probe orbiting around the sun, programmed to return any transmissions it picked up verbatim, to alert the originator of its presence.
Supposedly, this hasn’t happened since the early decades of the 20th century. Whether it is a real phenomenon, or its cause, reamins a mystery.
Has anyone heard about this?