Word: nuclei
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Although Socialist Perrin is not suspected of being a Communist or a fellow traveler, he is certainly more acceptable to the Reds than Thibaud, who is an outspoken antiCommunist. When a learned scientific paper by Thibaud reporting a discovery concerning atomic nuclei was submitted to the Academy of Science, observers considered it more than a coincidence that two bright students of Joliot-Curie should immediately produce papers reporting similar findings. Their papers, forwarded to the academy by Joliot-Curie, switched the limelight from Thibaud, who had been getting a big play in the non-Communist press...
...cloud chamber for making atomic particles visible is a rather complicated apparatus. It contains moist air and a movable diaphragm or piston to rarefy it suddenly. This action cools the air by expansion and makes it "supersaturated" with water vapor which will condense into water droplets if given proper nuclei to condense upon. Fast-moving atomic particles provide the nuclei by ionizing (electrifying) the normally neutral atoms of the air. So particles (e.g., cosmic rays from outer space) that pass through the cloud chamber become visible as thin white trails of water droplets...
...wrong clouds, e.g., the stratiform (layerlike) clouds, which unless very thick do not contain enough moisture to matter. And they were inclined to overdo, choking the clouds with too much dry ice. A piece of dry ice falling through a supercooled cloud creates enormous numbers of ice nuclei. Too many falling pieces of dry ice create too many nuclei; they compete fiercely for the water in the cloud, but there isn't enough to go around. Result: a dense cloud of ice crystals too small to fall...
...technical problem is to start the whole process. Says Schaefer, "what we need to find out is how many artificial nuclei we need, when we should use them, and how often...
...theories of rain-formation. The old explanation, which the Weather Bureau still favors, worked in terms of complex systems of wind. Rainmakers claim that precipitation depends more on nature's providing enough particles on which, raindrops can form-or on man's providing artificial particles, like silver iodide nuclei. To explain how this "seeding" can result in a violent storm, they provide a detailed "chain-reaction" theory...