The degree of biodiversity on Earth goes through cyclic decreases about every 62 million years; this has been going on for at least 542 million years. Recent research links this periodic decrease in species with the movement of the solar system through the galaxy. As the solar system orbits the center of the galaxy, it also moves up and down through the plane of the galaxy. More species die off when the Earth is most exposed to cosmic rays from outside the galaxy, at the high point of the solar system’s upward movement, which takes it above the galactic plane. Life is a chancy thing.
Cosmic rays and life on Earth
