Pollution in several major cities, including Paris and New Delhi, is about 50 percent lower… We mark this 50th anniversary of Earth Day with Jane Goodall, one of the world’s most renowned ...

Earth Day is on Tuesday, April 22 ... They would be the inner core, the outer core, mantle and crust. What about this one: What percentage of the Earth’s surface is covered in water?

Nope, that distinction falls to Julian Koenig, an advertising writer whose first choice wasn't even "Earth Day." How about this one: Did you know that Earth Day has its own theme song? If you can ...