Earth Flag (black), Earth Day Flag, NASA photo Flag

Originally designed by Earth Day founder John McConnell, this is the official flag of Earth Day. However it is also flown by those unconnected with the movement who share a concern for the environment. 

This is a truly modern flag, based not on a symbol but an actual photograph - the only one of its kind.  The Earth flag is based on the dazzling photograph from NASA's Apollo 10 space mission in 1969 showing the full daylight side of Earth from a position over the African continent.