KentuckyFC writes: The origin of the solar cycle is one of the biggest mysteries in science. Astronomers have watched the ebb and flow of sunspots over an 11-year cycle for centuries. More recently they've discovered that the Sun's visible and x-rays luminosities also change over the same period. Nobody knows what causes this cycle but various astronomers have noted the extraordinary correlation between this period and the orbit of Jupiter (11.8 years) as well as various tidals resonances associated with Saturn, Earth, Venus and Mercury. These tidal forces are too small to influence the Sun so astronomers have discounted this idea. Now a group of physicists say an even more exotic process may be at work. Their idea is that the Sun is bathed in a constant stream of dark matter particles and that the gravitational fields of the planets focus this stream on the Sun as they pass through it during each orbit. It is this pulsing flow of dark matter that causes the 11-year solar cycle. This kind of gravitational lensing is well known for light so why not also for the slower moving, heavier particles that physicists believe make up dark matter, they ask.