No. 31: Jan-Feb 1984
Even since the sunspot cycle was discovered, a few people have been trying to prove that it is caused by the influence of the planets, particularly Jupiter with its 11.86-year period. A century of various correlations has convinced almost no one. John P. Bagby has now introduced a new piece to the puzzle of solar-system cyclic behavior. While searching for possible perturbations of the planets due to a tenth major planet or a dark massive solar companion (MSC), he discovered that the perihelia of the outer planets (orbital points closest to the sun) were being disturbed with an average period of 11.2 years. This is almost exactly the sunspot period.
This serendipitous finding caused Bagby to wonder whether some common influence was causing not only the sunspot cycle and those perturbations in outer-planet perihelia but also cyclic volcanic and seismic activity on earth. Some correlations indeed do indicate a sun-earth link of some sort. Bagby suggests two possibilities:
(1) Mutual resonance effects between the planets, (2) The effects of a massive solar companion.
(Bagby, John P.; "New Support for the Planetary Theory of Sunspots," privately circulated paper, 1983.)
Comment. Even "farther out" is the thought that gravitational waves or some unrecognized influence from the galaxy or beyond causes the whole solar system to "ring." In this context, see again the above item on solar vibrations.