The MYSTERY of HOTTER and COLDER (May, 1936)
The MYSTERY of HOTTER and COLDER
THE STRANGE effects of extreme heat and cold on common substances is arousing interest in what may become a field of sensational discovery.
For years man has sought to extend his command of temperature and pressure, but until quite recently he was restricted to the ordinary temperatures found in nature. Today there are about ten special low-temperature laboratories scattered about the world. After twenty years, the low-temperature laboratory at Leyden, Holland, has succeeded in coming within five-thousandths of a degree of absolute zero, which is —273 degrees Centigrade. This establishes a record for cold that is likely to stand for some time.
On the other extreme, astronomers have made measurements of star temperatures that go beyond 40,000,000 degrees Centigrade. In still another related field, high pressure, Prof. P. W. Bridgman, of Harvard, has succeeded in changing the structure of many common substances by subjecting them to pressures equal to those several hundred miles below the surface of the earth.
At present man is far from equaling the internal temperatures of the stars. For a brief instant it has been possible to reach 20,000 and 30,000 degrees Centigrade in the laboratory. This was accomplished by exploding wires with tremendous electrical discharges. For a longer period of time it is possible to reach 5,500 degrees Centigrade by focusing the rays of nineteen high-power lenses in a solar furnace. The atomic hydrogen torch has made it possible to develop as high as 3,800 degrees Centigrade on a small spot. Beside the internal temperatures of the stars, however, these artificial temperatures are comparatively feeble.
For general purposes, it may be said the difference between the greatest heat and the greatest cold thus far produced by man is 5,773 degrees Centigrade, although he has, for a fraction of a second, gone as high as 30,000 degrees Centigrade and extended the temperature range up to 30,273 degrees Centigrade.
It is likely that men will be able to go beyond that figure, but it is extremely unlikely they will be able to exceed the cold of absolute zero. Greater cold is not known anywhere, not even in the upper reaches of space.
Why search for very high temperatures? We have reason to believe that if we could generate and control temperatures of 100,000 degrees or more, it would be possible to create new substances and find new properties for old substances. In the realm of extreme cold, the present interest centers around some recent experiments tending to show it is possible to freeze animals into a state of inactivity, as if they were dead. After remaining inactive for some indefinite period, the animal is revived by slow thawing and the application of stimulants.
Although there is reason to doubt that men can remain in a state of “suspended animation” by being frozen into a state of inactivity, there is no doubt that microbes can do so. Immersed in liquid helium at a temperature of —450 degrees Fahrenheit and kept there for weeks at a time, germs have come out alive and kicking, none the worse for their experience. This shatters many of our illusions about the frailty of microbes. There is much to say for their stamina. Prof. Bridgman’s work with high pressures has brought him into the realm of “hot – and cold ice.” Examining many solid substances, he discovered they pass through significant crystalline changes when subjected to high pressure. So far, he has distinguished some queer varieties of ice. “Hot ice Number one” may be heated to a temperature too hot to bear with the hand if enough pressure is applied to prevent it from melting.
To produce “hot ice Number one,” Prof. Bridgman applies a pressure of 90,000 pounds. To convert this product into “hot ice Number two,” he applies a pressure of 375,000 pounds. “Hot ice Number two” is hotter than boiling water when it melts, and it can be made to melt at a much higher temperature merely by raising the pressure. Besides the hot ices, Prof. Bridgman has produced a new form of cold ice.
High pressure on other substances effects profound changes. Rubber loses its elasticity and becomes a translucent horny material; paper is similarly affected. Having achieved this much in the application of high pressures, man’s present efforts are directed toward raising the temperature limits.
For the present, the method of raising a temperature of 5,500 degrees Centigrade in a hotspot sun furnace might bear improvement by some more efficient method of focusing the sun’s rays. However, the general belief is that if we are really to pass into the realm of high temperatures, we must first learn how to handle the slippery and mysterious atom.
It may be that the intense sustained heat and light of the stars is due only to high temperatures and pressures. The youngest stars radiate the most energy. One youngster, called Plaskett’s star, is held to have a central temperature of 500,000,000 degrees Centigrade. According to Sir James Jeans, “all processes which are affected by temperatures of less than 7,500,000,000,000 degrees leave the total number of electrons and protons in a star unimpaired.” This is a little more heat than we are prepared to handle on our planet, and indeed, it is more than is ordinarily discussed by astronomers.
The thermocouple device on the Mount Wilson telescope has already measured the surface temperatures of many heavenly bodies. Star surface temperatures range from 6,000 degrees Centigrade to 23,000 degrees but the interior temperatures are much higher. That of our sun, for instance, is estimated at 40,000,000 degrees Centigrade.
The absolute zero of temperature is —273.15 degrees Centigrade. Beyond this no one has ever gone. The boiling point of helium lies about four degrees above this. By reducing pressure on the liquid, it has been possible to reach within one degree of absolute zero. In the low-temperature laboratory at Leyden, Prof. W. J. DeHaas has reached the all-time low of only five-thousandths of one degree above absolute zero. Thus man has achieved a temperature which has not, so far as is known, been reached by nature herself. Interstellar space is held to be three degrees above absolute zero.
On the earth’s surface, the highest recorded difference between the hottest spot and the coldest spot is only 124 degrees Centigrade or 223 degrees Fahrenheit. The coldest spots where readings have been made are Alaska, —82 degrees Fahrenheit, and Siberia, —87 degrees Fahrenheit. The hottest spots are Death Valley, Calif., 134.1 degrees Fahrenheit, and Azizia, Tripoli, 136.4 degrees Fahrenheit.
Tungsten and graphite are among the substances with the highest known melting points. The highest temperature recorded with burning fuel is 2,000 degrees Centigrade, while an oxyacetylene torch flame may reach a temperature of 3,500 degrees Centigrade. The atomic hydrogen flame, 3,800 degrees Centigrade, is sufficient to melt or vaporize every known substance with the possible exception of carbon and the grinding material, tantalum carbide.
For the extremes of temperature, the ordinary mercury thermometer will not work. To measure the cold around absolute zero, it is necessary to employ a magnetic thermometer. This method increases in sensitivity as the temperature is lowered. Above 500 degrees Centigrade, the mercury thermometer must be discarded. It is necessary to use gas thermometers up to the melting point of platinum, 1,755 degrees Centigrade. For reading above the melting point of platinum, a form of optical thermometer is used. This works on the assumption that flame colors vary according to the temperature. But near the maximum temperatures obtainable by man, it is quite difficult to get accurate readings.