The earth‐to‐moon distance is now known to less than 15 m as a result of combining theoretical calculations of a couple of years ago with new determinations of the moon's mass calculated from observations of Lunar Orbiters 1 and 2. The new accuracy represents about one part in two million. It is incorporated in a new 50‐year lunar ephemeris calculated by J. Derral Mulholland and William L. Sjogren of the Jet Propulsion Laboratory of California Institute of Technology. Wallace J. Eckert and H. F. Smith Jr of the IBM Watson Laboratory did the theoretical calculations on which the ephemeris is based (PHYSICS TODAY, June 1965, page 73).
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© 1967 American Institute of Physics.
1967
American Institute of Physics
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