Have you ever figured out what has caused the mass extinction that wiped out species like dinosaurs? A research suggested that cosmic impacts may be one of handful reasons.
As our galaxy passed through the galactic zone every 35 million to 40 million yeras, increasing the chances of comets showering at planets.
It's an interesting hypothesis. There is a reason for me to be skeptical. There has been no mass extinction for 65 million years and I want to see some more findings. I like some other theories.
For further reading, click on the link.
Earth Extinctions Blamed on Cosmic Speed Bump