"I have had no opportunity to check this on an interstellar scale. I shall at the earliest opportunity. It is my belief that the radio beacons between earth and Venus, for instance, are maintained at both ends by receiver and transmitter, the receiver being used to control the transmitter and keep the beam properly centered and to check its presence. This contact made in both directions along the spacelanes, maintains the operation of the Z-wave on the ship, running at higher than the speed of light. The radio is, of course, useless. But the Z-wave, propagating at some figure we cannot measure yet, suffers no doppler effect." "I am Grant Lewdan," said the third. "Has the Z-wave ever been tried in the depths of interstellar space?" "Yes." "Did it work?" "Up to a certain point." "Then why didn't they pursue it?" "This answer demands that we all understand the psychology of the human being and the mechanics of the scientific method. I will answer this first by analog: "Presume for the moment that radio cannot propagate across a space that communication has not crossed previously. Then consider Marconi on his first attempt to send radio waves across a hundred feet of vacant lot. What is the method used in testing an unknown method of communication? The transmitter is started, and the operator either calls or signals by waving his hands, that the transmitter is now working. As soon as the hand signal is seen the receiver is checked, found to be working. Remember, this radio works because of the previous linkage by communication in accordance with our hypothesis. Success is noted. "Then the distance is increased by many miles from mountain top to mountain top and a blinker system is employed to carry the experimental information back and forth. Again the transmitter is started and the blinker used to inform the other party that he is to watch for the radio's response. Again, it works, since communications have been established. For the third time, the radio equipment is separated by the antipodes of the earth and a telephone or telegraph connection is established. Again the transmitter is started and the signal is sent; again there is success. Now, gentlemen, the inference is that radio will work to a distance encompassing the entire earth. "Now postulate a spacecraft taking this same equipment to the Moon. Lacking radio, no means of communication are practical. Let us say Venus instead, gentlemen, since a magnesium flare might be used from Luna. So, on Venus, there is no means of communication other than radio, which depends first upon the establishment of other means of communication ere it will work. "A failure is noted. "Now," smiled Paul, "this is what happened in deep space. I would like to read an excerpt from the Communications Expedition Number Three: