MAA Glossary


An astronomical measure of distance. It names the distance that light travelling at its speed of 186000 miles per second (300000 km/s) traverses in the course of a year - almost 6000000000000 miles.

Extreme edge of visible disk of the sun, moon or planet.

Longitude difference:
Difference between the longitude of a certain location and a standard longitude (such as the meridian of Greenwich or the longitude employed for the Standard Time belt).