Determining the position of a star or other object in three-dimensional space is an important concept in astronomy. Finding stellar longitude (called right ascension) and latitude (declination) is easy enough, but it is much harder to find the radial distance to those objects. This lesson teaches how the distances to nearby stars are measured using the parallax effect: as the Earth orbits our sun, the positions of the nearest stars seem to wiggle back and forth compared to more distant stars. [26:03]