Seeing with Heat

Infra-red rays are hard to observe; their waves are too long to be seen as light and too short to be heard in radio receivers. But they can be measured as heat on a bolometer--a machine with metal strips whose electrical conductivity is altered by heat rays falling on them.

Last fortnight Dr. Donald H. Andrews of Johns Hopkins University described a bolometer to top them all. Its sensitive surface is columbium nitride cooled by liquid hydrogen to minus 432DEG F. At this temperature--close to absolute zero--columbium nitride becomes "superconductive"; its electrical resistance almost vanishes. When a heat ray hits it and warms it only one millionth of a degree, it gives a clear electrical signal.

This "superconductive bolometer" can register heat from a man's body 500 yards away in total darkness. If hitched to a proper scanning device, it makes a rough picture of any warm object. Dr. Andrews, who had himself "photographed" by the bolometer (see cut), thinks it will be useful in searching for heat leaks from buildings, is sure it has a future in medicine and astronomy. It might also have war possibilities, such as guiding an atom-armed rocket toward the warmth of a blacked-out city.

This file is automatically generated by a robot program, so reader's discretion is required.