This caused a storm in the auditorium. A showing of frantic hands flowered above the sea of faces and the hall broke into a growling murmur of muttering voices, discussing pro and con. The chairman came forward and spoke to Paul: "Shall I call order, or would you prefer to have a mid-lecture discussion?" Paul smiled nervously. "I was prepared for this," he said. "The rest of this will run better if we get this one point settled. It will be too long from now to the end of my lecture to make these men hold their questions." "Good!" smiled Thorndyke. He rapped for order. "Gentlemen," he said, speaking over the incomplete attention, "Mister Grayson has just made a rather shocking statement, which is cause for controversy. He has suggested himself that a mid-lecture period of questions will hasten our understanding of his theory." There was a burst of applause and the flowering of hands went up again. "Edwin Johnson," said the first man naming himself. "Granting that it takes light one hundred and forty years to cross between here and Neosol, I suggest that the entire galaxy has been coupled by electromagnetic waves for two thousand million years." "I said 'linked'," explained Paul easily. "This question is one that stumped me for a long time and was possibly the one thing that prevented the advancement of the principle long before. But the detectors we employ to detect those frequencies we term 'light' are not similar to those we use for the longer frequencies of radio, even though both are electromagnetic waves. Light will not travel along a conductor, although it is true that the longer waves will be transmitted through a waveguide made of dielectric that is transparent to them. Ergo, it is the means we use to handle these frequencies that establish the 'linkage' rather than the medium or the wave itself." "I am Fred Hughes," said the second. "Do you mean to state that the Z-wave has never been known to operate between points not previously linked by radio?" "That is right." "You've investigated everything?" "Mine is negative evidence, I admit. This is why it is hard to establish as truth. But remember, the solar system was linked by radio long before the Z-wave was discovered." "How about spacecraft?" "Once the Z-wave linkage is established by its forerunner of radio, it is complete and can not be broken." "A spacecraft employs radio until it reaches the superdrive point. Then--?" "I have had no opportunity to check this point as yet. I believe it has to do with the doppler effect. Remember that the selectivity of the radio used in space is such that a doppler shift will not detune it grossly. Obviously, superdrive will completely ruin such tuning." "But this has been tried?" "Yes. It was once hoped that we could link to Neosol that way. The connection failed as soon as the ship entered superdrive." "But interplanetary ships employ Z-wave."