Jo-Ann Baena Cruz’ article on Halley’s Comet (VERITAS, Dec. 29) does violence to the history of science and to the scientific method. When Edmund Halley predicted that the comet observed in 1682 would reappear in 1758, he was not taking "a deep cosmic plunge"; he was only stating the necessary implications of the proposal that even comets "obeyed" Newton’s laws.

This extension of Newtonian physics to comets was the "deep cosmic plunge" Halley took, since the predictive power of Newton’s celestial mechanics (proposed only in 1687) had been tested only on the movements of the planets.

Mrs. Cruz errs when she says that Halley "determined that certain apparitions spaced 75 to 76 years apart were actually just reappearances of the same comet."

In fact, Halley took the data on the path and motion of the 1682 comet and deduced that if Newton’s laws were applied to comets: (1) the comet should travel in a large elongated ellipse; (2) it should take about 75 years to make one complete circuit; (3) any comets that appeared at roughly 75-year intervals starting backward from 1682 would have to be the 1682 comet; and (4) the 1682 comet would reappear some time in December 1758.

Mrs. Cruz’s reference to "the comet’s return-as-prophesized (sic)" presents Halley as a man with a gift of prophesy. In fact, we honor Halley more by remembering him as a hard-nosed scientist whose theory-based predictions were confirmed in the real world.

POLLY HERNANDO

Published 1/12/86