http://news.yahoo.com/s/space/20061127/sc_space/galacticbabyboominfluencedlifeonearthGalactic Baby Boom Influenced Life on Earth
By Sara Goudarzi
The stellar baby boom period of the Milky Way sparked a flowering and crashing of life here on Earth, a new study suggests.
Some 2.4 billion years ago when the Milky Way started upping its star production, cosmic rays--high-speed atomic particles--started pouring onto our planet, causing instability within the living. Populations of bacteria and algae repeatedly soared and crashed in the oceans.
The researchers counted the amount of carbon-13 within sedimentary rocks, the most common rocks exposed on the Earth's surface. When algae and bacteria were growing in the oceans, they took in carbon-12, so the ocean had an abundance of carbon-13.
Many sea creatures use carbon-13 to make their shells. If there is a lot of carbon-13 stored in rocks, it means life, the origin of which is still unknown, was booming. Therefore, variations in carbon-13 are a good indicator of the productivity of life on Earth.