NASA Earth Science Communications announced closure of The Earth Observer in December 2025. It preserves archives that document nearly 37 years of EOS missions and satellite data.

Learn how we know the Earth is round, and the science behind the shape of our gravitational field.

The center of Earth lies around 4,000 miles under our feet — but what lies beneath the outer crust and the inner core? When you purchase through links on our site, we may earn an affiliate commission.

CU Boulder professors explain Earth Day’s history, impact, what it’s become and if it’s still relevant If you were at the University of Colorado Boulder in April 1970, you were likely aware―very aware ...