A new calculation of the moon's orbit, completed during the past year by W. J. Eckert, director of the IBM Watson Laboratory and professor of celestial mechanics at Columbia University, and H. F. Smith, Jr., a research associate at Watson Laboratory and a graduate student at Columbia, has predicted lunar positions with such precision that it has corrected a fluctuating error of 3/10 second per eighteen months in the astronomical time standard. The extreme accuracy of the calculation has also yielded a suggestion that the moon may be denser near the surface than it is in the center. The prediction rests on angular‐momentum considerations necessary to explain a discrepancy of ten parts in seven million in the motion of the nodes of the lunar orbit.

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