In July of 1899, while tracking lightning storms alone with his magnifying transmitter in his Colorado Springs laboratory, Tesla observed a series of unusual rhythmic signals which he described as "counting codes." Having just detected cosmic radio signals for the first time and after ruling out solar and terrestrial causes, Tesla concluded that the signals must be from another planet and he suggested that it could be some attempt of communications from an intelligent life-form on either Venus or Mars.
Scientists published a study in 1996 replicating Tesla’s experiment and showing that the signal was in fact caused by the moon Io passing through Jupiter’s magnetic field. An alternative explanation is that Tesla may have heard Marconi's wireless telegraphy demonstrations in Europe.
Letter to George Scherff by Nikola Tesla - July 4, 1899:
"We are getting messages from the clouds one hundred miles away, possibly many times that distance. Do not leak it to the reporters."
Nikola Tesla - Christmas 1900:
To the American Red Cross, New York City.
The retrospect is glorious, the prospect is inspiring: Much might be said of both. But one idea dominates my mind. This — my best, my dearest — is for your noble cause.
I have observed electrical actions, which have appeared inexplicable. Faint and uncertain though they were, they have given me a deep conviction and foreknowledge, that ere long all human
beings on this globe, as one, will turn their eyes to the firmament above, with feelings of love and reverence, thrilled by the glad news: "Brethren! We have a message from another world, unknown
and remote. It reads: one… two… three…"
The problem of increasing human energy - The Century Illustrated Magazine - Nikola Tesla, June 1900 - Pp 175 - 211 (see P. 209):
"My measurements and calculations have shown that it is perfectly practicable to produce on our globe, by the use of these principles, an electrical movement of such magnitude that, without the slightest doubt, its effect will be perceptible on so me of our nearer planets, as Venus and Mars. Thus, from mere possibility, interplanetary communication has entered the stage of probability"
"I recognized that an efficient apparatus for, the production of powerful electrical oscillations, as was needed for that specific purpose, was the key to the solution of other most important electrical and, in fact, human problems. Not only was communication, to any distance, without wires possible by its means, but, likewise, the transmission of energy in great amounts, the burning of the atmospheric nitrogen, the production of an efficient illuminant, and many other results of inestimable scientific and industrial value. Finally, however, I had the satisfaction of accomplishing the task undertaken by the use of a new principle, the virtue of which is based on the marvelous properties of the electrical condenser. One of these is that it can discharge or explode its stored energy in an inconceivably short time. Owing to this it is unequaled in explosive violence. The explosion of dynamite is only the breath of a consumptive compared with its discharge. It is the means of producing the strongest current, the highest electrical pressure, the greatest commotion in the medium. Another of its properties, equally valuable, is that its discharge may vibrate at any rate desired up to many millions per second".
Some planet affected his machine - New York Sun - January 3, 1901:
"Movements on instrument repeated many times. Concludes it to be a message from another planet."
Letter to the editor of the New York Sun - January 9, 1901:
"I did not state that I had obtained a message from Mars, I only expressed my conviction that the disturbances that I obtained were of planetary origin"
Talking with planets - Collier's weekly - February 9, 1901 - Pp. 4-5 (reprinted as Chapter XVI - Electrical comunications with planets - Polyphase Electric Currents and Alternate-Current Motors - by Silvanus P.Thompson - Volume 4 of The Library of Electrical Science, Collier and Son, NewYork - 1902 - pp. 225-235):
"As I was improving my machines for the production of intense electrical actions, I was also perfecting the means for observing feeble efforts. One of the most interesting results, and also one of great practical importance, was the development of certain contrivances for indicating at a distance of many hundred miles an approaching storm, its direction, speed and distance traveled.
It was in carrying on this work that for the first time I discovered those mysterious effects which have elicited such unusual interest. I had perfected the apparatus referred to so far that from my laboratory in the Colorado mountains I could feel the pulse of the globe, as it were, noting every electrical change that occurred within a radius of eleven hundred miles.
I can never forget the first sensations I experienced when it dawned upon me that I had observed something possibly of incalculable consequences to mankind.
Ifelt as though I were present at the birth of a new knowledge or the revelation of a great truth. My first observations positively terrified me, as there was present in them something mysterious, not to say supernatural, and I was alone in my laboratory at night; but at that time the idea of these disturbances being intelligently controlled signals did not yet present itself to me.
The changes I noted were taking place periodically nd with such a clear suggestion of number and order that they were not traceable to any cause known to me. I was familiar, of course, with such electrical disturbances as are produced by the sun, Aurora Borealis, and earth currents, and I was as sure as I could be of any fact that these variations were due to none of these causes.
The nature of my experiments precluded the possibility of the changes being produced by atmospheric disturbances, as has been rashly asserted by some. It was some time afterward when the thought flashed upon my mind that the disturbances I had observed might be due to an intelligent control.
Although I could not decipher their meaning, it was impossible for me to think of them as having been entirely accidental.
The feeling is constantly growing on me that I had been the first to hear the greeting of one planet to another. A purpose was behind these electrical signals.”
Nikola Tesla, 1907:
"I refer to the strange electrical disturbances, the discovery which I announced six year ago. At that time I was only certain that they were of planetary origin. Now, after mature thought and study, I have come to the positive conclusion that they must emanate from Mars"
Nikola Tesla, 1909:
"To besure, we have no absolute proof that Marsisinhabited... Personally, I base my faith on the feeble planetary electrical disturbances which I discovered in the summer of 1899, and which, according to my investigations, could not have originated from the sun, the moon, or Venus. Further studysince has satisfied me they must have emanated from Mars."
Nikola Tesla, 1919:
"During my experiments there [Colorado Springs, 1899], Mars was at a relatively small distance fromus and, in that dry and rare fied air, Venus appeared so large and bright that it might have been mistaken for one of those military signaling lights... I came to the conclusion that [Mars] was sufficient to exert a noticeable influence on a delicate receiver of the kind I was perfecting... my ear barely caught signals coming in regular succession which could not have been produced on earth, caused by any solar or lunar action or by the influence of Venus, and the possibility that they might have come from Mars flashed upon my mind."
Nikola Tesla, 1921:
"The arrangement of my receiving apparatus and the character of the disturbances recorded precluded the possibility of their being of terrestrial origin, and I also eliminated the influence of the sun, moon and Venus. As I announced, the signals consisted in a regular repetition of numbers, and subsequent study convinced me that they must have emanated from Mars, this planet having been just then close to the earth."