Coldest Cold

The "coldest cold," i.e., the nearest approach to utter lack of heat, which man has yet achieved, was attained at the University of Leyden last week. Professor W. H. Keesom, physicist chief of the cryogenic (cold-producing) laboratory there, accomplished the difficult and hazardous feat by solidifying helium gas. He reached 458.58DEG below Fahrenheit Zero, or 273.1DEG below Centigrade Zero. He was only .82DEG Centigrade above Absolute Zero, the cold end of the scale which scientists use to measure temperature independently of the properties of any substance.

Once before, in 1926, Professor Keesom produced solid helium. But the quantity was only one cubic centimeter, i. e., one-sixteenth cubic inch or one-fourth of a teaspoonful. That quantity lasted for only a moment, changing into liquid helium, a colorless, mobile liquid, which Professor Keesom's predecessor at the Leyden cryogenic laboratory, Heike Kamerlingh Onnes (1853-1926), had obtained in 1908.*

The standard method of reducing a gas first to a liquid, then to a solid, is to force it through a fine nozzle, thus causing it to expand and cool. Successive passages through the nozzle make the gas increasingly cold, requiring greater and greater pressure to force it through. Liquid hydrogen is used to absorb the heat from cooling helium. Professor Onnes found that helium would not liquefy until reduced to just below five degrees above Absolute Zero. He got the temperature down three more degrees, but could not solidify the helium fluid.

Professor Keesom last week not only solidified the gas by this method, but he produced 200 cubic centimeters of it, practically a tumblerful. With such a quantity of helium ice he can experiment.

Heat is energy which flows into matter. So far as anyone knows it is consistent with all substances. If atoms are knots of universal waves, as has been theorized, it may be at that transcendental moment when the knots get intricate enough to "materialize" as atoms that heat begins to show in them. Conversely, when all heat has been driven from a substance, as Professor Keesom almost did last week, it may be that "matter" will explode into those universal waves which man at present can call only "nothingness." What the violence of such an explosion might be, no man can guess but experimenter Keesom may yet find out.

*For liquefying helium, Professor Kamerlingh Onnes received the 1913 Nobel Prize for physics.