Approach to Absolute

Last week the sullen heralds of total war chattered in British skies, but many a British scientist, true to a long and stanch tradition, went calmly on with his researches in "pure" or fundamental science.* One of the purest of pure sciences is the approach to absolute zero, the nadir of cold. Absolute zero is the point at which all random motions of material particles, due to heat energy, are completely stilled. It is calculated at 273.13DEG below zero on the centigrade scale, and it can be written as simply 0DEGK., meaning zero on the Kelvin or absolute scale. Scientists have never quite chilled matter to that point, and never expect to. But their approaches to it have shown them a great deal about how the laws of thermodynamics operate.

In the region of 1DEGK. (about -- 272DEGC.) certain substances lose all electrical resistance, so that an electric current flowing around a lead ring, for example, keeps going indefinitely. Liquid helium loses so much viscosity or "stickiness" that it climbs up surfaces against gravity.

By means of a magnetic-cycle cooling technique, low-temperature researchers have chilled certain salts to the astonishing temperature of .003DEGK. The method makes use of the principle that magnetization heats matter, demagnetization chills it. After preliminary cooling with liquid helium, the salt is magnetized, the heat thus generated drawn off into a jacket filled with helium vapor; then demagnetization pushes the substance down one notch further into the cold. But the limits of this method, as applied to the magnet ism of molecules, have been nearly reached.

In the issue of the British journal Na ture which reached the U. S. last week, a new approach to absolute zero, suggested by several investigators, was explained by Dr. Charles Galton Darwin. He is the calm, pipe-smoking director of the Na tional Physical Laboratory, grandson of Evolution's great Charles Darwin. In effect the method is to work down as far as possible with the magnetism of molecules, then continue with the magnetism in the nuclei (cores) of the atoms themselves. In this way, researchers can plausibly expect to get down to one hundred-thousandth, possibly to one millionth of a degree above absolute zero.

The apparatus will be intricate and the experiment laborious. Says Dr. Darwin: "Each successive stage in producing cold has called for greater efforts and has on the whole produced less results." But scientists may find that at a few millionths of a degree above absolute zero, certain sub stances become permanent magnets ; they may find nothing. They do not know for sure what they will find, and that is the lure. If England survives they will keep going.

* During World War I the late, great Lord Rutherford refused to give up his atom-splitting experiments when his help was sought on methods of submarine detection.

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