The combined times and distances of events are measured in linear distances, frequency of occurrence, and degrees of angulation.

By international agreement, linear distances are measured in units derived from wavelengths corresponding to the oscillations of the krypton 86 atom.

The length and duration of an event traveling in a linear path is the product of the linear distance and velocity, and is measured in units of meters and seconds, and their multiples or submultiples.

The distance light travels in 1 second is 3 times 10 to-the 8th meters. The time it takes for light to travel 1 meter is 3.3 billionths of a second.

The length and duration of an event traveling in a cyclical path is the product of the angular distance and velocity, and is measured in degrees of arc of a plane angle.

The frequency of occurrence of an event is the angular velocity at a distance of one complete cycle, or conversely the number of cycles traveled per unit of time.

One complete orbit of the Moon about the Earth equals 360 degrees. The diameter of the orbit measures a linear distance of about 1023 meters, and the frequency of occurrence is 1 cycle at an angular velocity of 27 days, 7 hours and 43 minutes.