The clearest Earth Day in 50 years: how far can you see?

Today is the 50h anniversary of Earth Day. Conceived by Wisconsin U.S. Senator Gaylord Nelson and brought to life by a 25 years old Denis Hayes, Earth Day burst forth on April 22, 1970, during the then never-ending Vietnam War and two weeks before students were shot dead at Jackson State and Kent State universities as campuses erupted over the U.S. invasion of Cambodia.

Our country and our planet has known massive strife. In 1970 it was also a very dirty, polluted, world.

But Earth Day and follow up actions by millions of Americans of all ages had an immediate impact. By the end of 1970, the N...