Actually, cooled moist air has been used for many decades to make the tracks of fast charged particles visible. In one of the photographs you can see a picture of such “vapor trails.” It is a photograph through an apparatus called the Wilson Cloud Chamber. The myriads of radioactive disintegrations in the debris of a nuclear explosion can give vapor trails which coalesce into a real cloud. In this way weather might be influenced. (See pictures 11 and 12.) In spite of all this it remains highly probable that testing of nuclear explosions, as practiced at present, does not influence the weather. Radioactivity does furnish an opportunity for droplets to form. But other abundant sources are also available for droplet formation. Dust, smoke and many forms of air pollution will do the trick. Foam scattered from ocean waves evaporates and leaves a speck of salt behind. This particle of salt may be carried by the winds for many miles and may eventually become the germ around which a new drop will condense. The cosmic rays by which we are bombarded give rise to vapor trails similar to those produced by the radioactive decay products. Among the many processes of nature and the usual by-products of civilization the few atomic tests do not play an important role. This statement can stand, not as a certainty, but as a very good guess. Among the many surprises that the future holds one may be closely connected with the weather. In the age of the airplane we are getting more and more information about the air masses around us. Air travel demands this information and also furnishes it. New techniques, such as radar, can detect the formation of a cloud and can measure the size of droplets at a great distance. In fact the information received is so plentiful that one may doubt whether we can properly understand it and utilize it. Fortunately we no longer need to rely exclusively on our own brains. Human thought is a remarkable thing but it is slow. The modern computing machines, the “electronic brains,” are simpletons as compared to the apparatus which each of us wears in his skull. But the electronic computers have one advantage: they are fast. Soon they will be a million times as fast as our mental processes. The expression “fast as thought” is dated—it is a contemporary of the horse-and-buggy. The electronic machines can digest weather information as fast as it is received. Some progress has already been made. In a few years all weather predictions may be machine-made. This need not mean that weather can be predicted with certainty or for a long time ahead. The trigger processes which, starting from an insignificant and unnoticed spot of turbulence, can grow into the dimensions of a cyclone will set a limit to any art of prediction.