More than 2,000 years ago, pretty much every educated human knew the Earth was round. There are some pretty obvious clues, after all. If you travel south, you see stars and constellations you’ve never ...

The radius of a circle or a sphere is the distance between the center and the edge. The radius can be used to calculate a circle's diameter, area and circumference. Likewise, a sphere's volume is ...

Researchers have made a precise measurement of the size of the proton -- a crucial step towards solving a mystery that has preoccupied scientists around the world for the past decade. The world's ...