Venus and earth: engaged or divorced?
Proponents of astronomical catastrophism have made much of the supposed resonance between the earth and Venus, in which Venus rotates exactly four times between the times of its closest approach to earth (inferior conjunction). Astronomers have maintained that the gravitational forces are too slight to force a resonance lock. This has led to speculation that the two planets were once much closer. The most recent measurements of the rotational period of Venus show it to be 243.01 days rather than the 243.16 days for exact resonance. I.I. Shapiro (of MIT) and his colleagues, who made the measurements, wonder whether Venus may be just approaching or just escaping a resonance lock. Whichever the case, the near-resonance is not likely to be a coincidence.
(Anonymous; "Venus and Earth: Engaged or Divorced?" Astronomy, 7:58, October 1979.)
Comment. If Venus is just escaping resonance lock, how long ago was the lock exact? A few thousand years? And how close were the two planets?
Reference. The solar system is full of curious resonances. See ABB4 in our Catalog: The Sun and Solar System Debris. This book is described here.