Although the Earth’s been decidedly blue for 600 million years, rising populations of phytoplankton caused by rising temperatures are once again causing the world’s oceans to turn green.

St. Patrick’s Day usually conjures images of partying, Catholicism, Irish nationalism and, perhaps most famously, the color ...

For a long stretch of Earth’s history, our planet might have looked green from a distance, instead of the pale blue dot we know today. Earth’s green period, which lasted from around 3 billion ...