The Mysterious Parallax

Parallax is an apparent difference or displacement in the apparent position of an object viewed along two different lines of sight. The word was first used in the 16th century, around 1570. A parallax is measured by the angle of inclination between two lines. The term is derived from the Greek word parallaxis, which means alteration. Nearby objects have a larger parallax than more distant objects when observed from different positions. It can be used to determine distances.