"Well"--Kendall grinned--"it amounts to the same thing. The point is, light doesn't. Let's run over that theory again. Light is not only magnetic; but electric. Somehow it transforms electric fields cyclically into magnetic fields and back again. Now what we want to do is to transform an electric into a magnetic field and have it stay there. That's the first step. The second thing, is to have the lines of magnetic force you develop, lie down like a sheath around the ship, instead of standing out like the hairs on an angry cat, the way they want to. That means turning them ninety degrees, and turning an electric into a magnetic field means turning the space-strain ninety degrees. Light evidently forms a magnetic field whose lines of force reach along its direction of motion, so that's your starting point." "Yes, and _that_," growled Devin, "seems to be the finishing point. Quite definitely and clearly, the graph looped down to zero. In other words, the field closed in on itself, and destroyed itself." "Light doesn't vanish." "I'll make you all the lights you want." "I simply mean there must be something that will stop it." "Certainly. Transform it back to electric field before it gets a chance to close in, then repeat the process--the way light does." "That wouldn't make such a good magnetic shield. Every time that field started pulsing out through the walls of the ship it would generate heat. We want a permanent field that will stay on the job out there. I wonder if you couldn't make a conductor device that would open that field out--some special type of oscillating field that would keep it open." "H-m-m-m--that's an angle I might try. Any suggestions?" Kendall had suggestions, and rapidly he outlined a development that appeared from some of the earlier mathematics on light, and might be what they wanted. * * * * * Kendall, however, had problems of his own to work on. The question of atomic energy he was leaving alone, till the present experiment either succeeded, or, as he rather suspected, failed as had its predecessors. His present problem was to develop more fully some interesting lines of research he had run across in investigating mathematically the trick of turning electric to magnetic fields and then turning them back again. It might be that along this line he would find the answer to the speed greater than that of light. At any rate, he was interested. He worked the rest of that day, and most of the next on that line--till he ran it into the ground with a pair of equations that ended with the expression: dx.dv=h/(4[pi]m). Then Kendall looked at them for a long moment, then he sighed gently and threw them into a file cabinet. Heisenberg's Uncertainty. He'd reduced the thing to a form that simply told him it was beyond the limits of certainty and he ran it into the normal, natural uncertainty inevitable in Nature.