Earth Day began as a protest in 1970, but its meaning has evolved. Here’s how it changed - and what it represents today.

Millions of people around the world will pause, at least for a moment, to mark Earth Day. The annual event is Wednesday.

Today is Earth Day, a time to think about how to protect the planet that all of us share. Each year on April 22, Earth Day ...

Imagine Earth at a time when it was almost unrecognizable—a landscape that was barren and with barely breathable air. That is what Earth looked like about 1.75 billion years ago. But scientists now ...