Bobbing for extinctions

The ways the Universe can deal out death are as numerous as they are terrifying. Asteroid impacts, nearby stars exploding, wandering black holes... I spent a year or so thinking of nearly every method of cosmic catastrophe I could while writing Death from the Skies!^*. I wrote a whole chapter on what dangers lurk in our own Milky Way galaxy, and I was surprised to find out the Sun's orbit around the center of the galaxy is a potential problem. The galaxy is flat, like a CD (in fact, the proportion is right if you stack about 4 CDs together). The Sun does not orbit the center of the galaxy in a nice, flat plane, like planets do around the Sun. Instead, it bobs up and down like a cork in water, making about four cycles for every one time it orbits the galaxy (which takes about 200 or so ...