All this had become clear gradually and I might tell you one of the important considerations; yes, we can construct weapons, explosions of sizes as big as you ever please, but if they are to be delivered, if they are to be used in a conflict, what is the useful size? I would like to tell you something that is exaggerated and unrealistic and too big but illustrates the point I want to make. - Make something hundred thousand times bigger than what happened at Hiroshima. Can be done, we know how to do it, it will be very expensive, hard to deliver, not hard to make, and will really destroy, really everything in a radius of about ten miles. It also will take a chunk of air, ten miles across, and throw it out into interplanetary space. - Not satisfied, make it a thousand times bigger still, what will be the effect? It turns out that the destruction on the surface of the earth will have hardly increased. Why? Because the pressure is propagated by the presence of the atmosphere. If you make something a thousand times bigger, the main effect will be that the same amount of air, very little more, will be thrown out into interplanetary space but with thirty times the velocity. When it came down in the course of time to the actual construction of these objects, the important advantage in the hydrogen bomb was not its size, it was its adaptability to a variety of purposes. For military purposes there is a limit what is useful, and actually the smaller and the more deliverable something is the more effective it can be.