Bit by bit, the physicists have filled the gaps in the electromagnetic spectrum, which runs from X rays at the short end, through light and heat, to miles-long radio waves at the other. One big gap remained between the infra-red (heat) waves and the shortest radio waves (about .8 mm.) that man's apparatus could generate. Last week Dr. Hans Motz of Stanford University told how the gap has been filled.
Dr. Motz's "millimeter-wave generator" is made up, first, of a linear accelerator that produces a pulsed beam of electrons about £ inch in diameter. The electrons, whose energy is 2,000,000 electron volts,...