9 Batsh*t Crazy Theories That Might Actually Be True

2. Nemesis: The Sun's Evil Twin

In the early 80s, scientists noticed that the mass extinctions on Earth tended to come in cycles of around every 27 million years or so. This large timescale led them to think that the cause might be cosmic.

Nemesis was the not-at-all-threatening name given to a theoretical "sister star" located 1.5 light years away that may have been causing the regular extinctions. It was thought that the star was possibly a red or even brown dwarf, making it difficult to spot.

The theory is that, every 27 million years, Nemesis travels through the cloud of debris that surrounds our solar system, known as the Oort cloud. This would create a new crop of comets, booting them towards the inner solar system and increasing the likelihood that one would go careering into the Earth.

Some scientists have also suggested that the dwarf planet Sedna's distant orbit could lend credence to the theory. It could be being held in its 12,000 year orbit by this mysterious companion star way out in the outer solar system.

We have so far been unable to detect Nemesis, leading most experts to conclude that our solar system is single-starred, but it's an interesting theory nonetheless.