# How can parallax be used to measure distance?

##### 1 Answer

Jan 22, 2016

In astronomy, parallax refers to apparent displacement of a distant space object when observed from two different locations. The small angle between directions helps computing distances

#### Explanation:

The angle subtended by an arc of length (nautical) equal to radius of the the Earth subtends the angle 1 radian, nearly, at the center of Earth. If a distant space object is observed at the same time from the ends of this arc, the parallax angle can be used to compute approximately the distance of the object form Earth. The reader can now draw the so formed quadrilateral and derive the trigonometrical formula for the distance.