More than three-quarters of all instances of human unrest—battles, upheavals, riots, revolutions, and wars—occur during the periods of the maximum number of sunspots in the Sun… So powerful is this cosmic zeitgeber that it may even influence our physical size, our longevity, our mental stability, our propensity to violence, and …

Source: How the Sun Affects Our Minds

(and not just the Sun but other celestial bodies as well)