Apparent Change In Size of Moon Is Merely an Illusion

Washington, D. C., April 23--The common observation that the full moon seems about twice as large at the horizon as it does in the sky overhead has a physiological origin in the eye-movements of human beings, Harvard psychologists told the National Academy of Sciences today.

After four years of experimental observations of the moon and sun, Edwin G. Boring, professor of Psychology, and Alfred H. Holway, a research worker in the Harvard Psychology laboratory, have disproved the theories that the observed change in size of the moon is due to head-movement, or to the fact that at horizon the moon is seen alongside familiar earth-objects.

Inexplicable Phenomenon

Although the psychologists are unable as yet to account for the physiological chain of events underlying the observed phenomenon, the experiments leave no doubt that it is the raising and lowering of the eyes which makes the moon seem to change in size.

The problem is a very ancient one, and speculation about it began with the astronomer Ptolemy in 150 A. D., they said.