What is an angle?

The vectors (arrows) are at angles of 60° to each other, as the full circle measures 360° and there are six such equal angles.


When studying atmospheric optics, and astronomy in particular, it is customary to think of the surroundings (sky, soil, etc.) being a giant sphere with directions. Directions on this celestial sphere are given by angles. An angle can be thought of as a measure of rotational distance.

Example: when you turn up your stereo, you rotate the volume knob over a certain angle. You can't say that you rotate it over a certain distance, because with rotations, distance becomes a function of the distance to the point of rotation itself.

Rotations in science are measured in radians, where 6.28 radians are a full circle (2pi); more common is the degree, where 360 degrees are a full circle.

It is very important to understand the concept of angles in order to understand the science of atmospheric optics, especially halo phenomena, which are always measured in degrees.

Note: the degree measuring angular distance is unrelated to degrees of temperature, freedom, education, deterioration, etc., although the word has the same meaning: degree as in the amount of rotation. (www.weatherscapes.com)