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 ...

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 ...

With 3D printed arms of fixed measurements, the depth reading from a set of digital calipers can be used to calculate the radius of a curve. Specialized tools that focus on one particular job tend to ...