An independent French researcher

Jean-Pierre Desmoulins was an independent French researcher working, like many in this tradition, entirely outside institutional astronomy — pursuing the old and persistently controversial idea that the gravitational alignments of the planets play a role in triggering solar activity. His most notable contribution, developed in 1989, was a piece of original software analysis that put this idea to a direct, visual test against real sunspot data — and produced a genuinely striking result that independent researchers, including Ray Tomes, have continued to build on since.

The J-E-V alignment index

Desmoulins wrote a simple program, in Turbo Pascal, to calculate the "most aligned days" for Jupiter, Earth, and Venus — the three bodies long suspected, on tidal grounds, of exerting the strongest gravitational influence on the Sun among the planets. His method tracked how closely these three bodies lined up with the Sun over time, producing a continuous "planetary alignment index."

He then plotted this index directly against the observed sunspot number series — and the two curves tracked each other closely. Crucially, the match wasn't limited to the ordinary 11-year rhythm: the timing of historical anomalies in the sunspot record also showed up as anomalies in his purely gravitational index. The extended quiet period known as the Dalton Minimum (roughly 1790–1830) and the onset of a modern quiet period sometimes associated with the work of solar researcher Theodor Landscheidt both appear as periods where Desmoulins' alignment index falls out of its normal phase relationship with the solar cycle — exactly where the real sunspot record shows unusually weak or irregular activity.

As later researchers have noted, Desmoulins' planetary index has proven good at predicting when a solar minimum will occur, cycle after cycle, but not at predicting how deep or strong that minimum — or the following maximum — will actually be. That's an important, honest limitation, and one shared by essentially every planetary theory of sunspots proposed over the roughly 160 years since the idea was first raised.

The bimodal distribution

The finding that has drawn the most lasting attention, though, is Desmoulins' discovery that the sunspot cycle length is not simply "eleven years" — it clusters into two distinct groups. Rather than sunspot maxima recurring at one typical interval with random scatter around it, his analysis of Jupiter-Venus-Earth alignments showed the real, physically preferred intervals were 10.4 years and 12.0 years — two separate peaks, with comparatively few cycles falling in between. He produced a histogram of the actual historical sunspot cycle lengths that visibly showed this same two-humped, bimodal shape, rather than a single smooth peak centered on 11 years.

Ray Tomes, who worked with Desmoulins' ideas directly, has offered a specific mechanical explanation for where the two preferred periods come from. Starting from an assumed perfect Jupiter-Venus-Earth alignment, the second subsequent Jupiter-Venus conjunction period gives only a moderate re-alignment, but the fifth gives a genuinely good one — after an interval of 3.244 years. Good realignments then keep recurring at every fifth Jupiter-Venus period after that, gradually drifting worse, until an extra two periods have to be inserted to reset the pattern. Run this logic forward and it generates exactly the two clustered intervals Desmoulins found empirically: 10.38 and 12.00 years for the underlying gravitational maxima, with the best full three-body realignments taking roughly twice that long (20.76 and 24.00 years).

This isn't an isolated, fringe observation either. NASA solar physicist Robert M. Wilson independently identified a comparable bimodal pattern in sunspot cycle lengths directly from the observational record — finding the data best fit by two groups, a shorter cluster around 122 months and a longer cluster around 140 months, separated by a gap straddling the overall mean of 132.7 months (very close to 11 years). That a mainstream solar physicist, working from the raw cycle-length data alone with no reference to planetary alignments, found the same two-humped structure is a notable point of independent corroboration for the phenomenon Desmoulins had already identified through his gravitational index.

An uncertain legacy

Desmoulins' original website, where his software and full results were once available, no longer exists, and — as Ray Tomes has noted — the pages have not been properly preserved on the Internet Archive's Wayback Machine either. What survives is mostly secondhand: discussion and reproduced graphics on other researchers' sites (notably Tallbloke's Talkshop, which has hosted detailed commentary on his J-E-V alignment graphic), and the accounts of researchers like Ray Tomes who corresponded with him and built on his findings directly. This makes Desmoulins a strong candidate for the kind of preservation effort aimed at independent researchers whose original work risks being lost even though its influence persists in the literature that cites it.

Why it matters

The planetary theory of sunspots remains genuinely contested territory in solar physics — taken seriously by a persistent minority of researchers and treated skeptically by much of the mainstream, in large part because a clear physical mechanism strong enough to explain the effect has been hard to establish. But Desmoulins' specific contribution — the bimodal 10.38/12.00-year structure — sits on a slightly different footing than the broader debate: it's a testable, quantitative claim about the shape of the sunspot cycle-length distribution, independently echoed in Wilson's purely observational NASA study. Whatever the eventual verdict on planetary forcing as a mechanism, the underlying empirical pattern Desmoulins first drew attention to appears to be real.