Although the Earth’s been decidedly blue for 600 million years, rising populations of phytoplankton caused by rising ...

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 ...

In that moment, all of humanity was captured in a ghostly fragment of a pixel swimming through an unrelenting sea of darkness — a "Pale Blue Dot" lost in a void. Carl Sagan — the astronomer ...