Earth is the only known habitable planet. A gassy envelope mostly of oxygen and nitrogen extends 300 miles above our surface.

By Swati Hegde, Ph.D. The Water Center, University of Pennsylvania A clean and safe water supply along with effectively managed...

By Samira Mehta Long, slimy, black bugs,—dozens—swam across the water’s surface in a white, plastic bucket. A woman bent over it and...

What I am about to share could save the earth from pollution. People should stop driving cars and ride bikes. Every day a lot of people...