LETTERS.

Gravity Waves Explained

I have been a NASA Goddard Space Flight Center astrophysicist for over 35 years, and I retired not long ago. I have been working in relativistic astrophysics since the early 60s and have published numerous articles in scientific journals on the application of general relativity to astrophysics. In 1963, I co-edited with William F. Hoffman (now professor of astronomy in the University of Arizona) a book Gravitation and Relativity, in which the theory and experimental detection of gravitational waves were among subjects discussed. Since then, of course, there have been many new developments in this subject.

The article, "Measuring Gravity Waves" by Skip Campisi (Electronics Now, October 1999) contained a number of critical mistakes that I feel obliged to point out. First of all, the name "gravity waves" is erroneously used. "Gravity waves" is a term used by geologists to describe the wave generated in either the atmosphere, oceans, and the land through the variation of gravity caused by a number of quite earthly reasons. For example, the tidal effect of the moon raises and lowers the height of the land with respect to the earths center by approximately 1 cm and generates a kind of gravity wave, which is monitored closely by geologists using a sensitive gravity meter. This kind of wave is associated with Newtonian mechanics and has nothing to do with Einstein s theory of relativity. The proper term used to describe the kind of waves associated with Einstein's theory of gravity and mentioned in this article is "gravitational waves." Second, the arguments used in conjunction with Figure 1 to show that light travels at 2c or 1/2c speed is wacky at best; and had one of the most prominent founders of quantum mechanics, Wolfgang Pauli, been alive, he would have called it "not even wrong."

The kind of devices described in this article will certainly detect ...