National Geographic : 1974 May
Elusive prey, ingenious traps: Does the nucleus of the Milky Way emit faint gravitational waves, in dicating a possible black hole? Professor Joseph Weber (left) of the University of Maryland may have detected them with an alumi num-cylinder antenna, foreground. Crystal sensors on the surface translate minute gravitational vi brations into electrical impulses for recording. Unlikeliest of telescopes is that developed by Dr. Raymond Davis, Jr., (below) to measure the sun's output of tiny massless neutrinos. Hoping to "catch" the particles, which can easily pass through the entire earth unaffected, Dr. Davis submerges a 100,000-gallon tank of cleaning fluid in water nearly a mile down in a South Dakota gold mine, where it is safe from bombardment by other radiation. A few of the neutrinos presumably collide with chlorine atoms in the fluid, changing them into atoms of radioactive argon 37 that can be separated and counted.