FIGURE: The diameter of the Sun and its distance away from us are related by the apparent angular size of the Sun. The ratio of the diameter to the distance is equal to the size of the angle in radians.
The angle subtended by an object on the sky. The angle may be measured in units of radians, or in units of degrees, arc minutes (1 degree = 60 arcminutes), and arc seconds (one arc minute = 60 arc seconds). For example, the angular size of the moon in the sky is 30 arc minutes. The human eye cannot resolve details smaller than a few arc minutes. The best telescopes in space (e.g. Hubble Space Telescope) can resolve details as small as a hundreth of an arcsecond.
FIGURE: The diameter of the Sun and its distance away from us
are related by the apparent angular size of the Sun. The ratio of the
diameter to the distance is equal to the size of the angle in
radians.