Since the distance between the Zeeman sub-levels is a function of the magnetic field, this effect can be used to measure the magnetic field, e.g. that of the Sun and other stars or in laboratory plasmas.
Charley horse: Slang for a cramp in a muscle in the leg, usually caused by a strain or injury. A charley horse can last anywhere from a few seconds to over a quarter of an hour. It is not uncommon for one to recur before it finally resolves.
What Causes Charlie Horses. Charlie horse is the name given to a muscle spasm or cramp experienced by an individual, especially in the leg. The most probable area where Charlie horse strikes is the calf region and that too, at night, lasting for a few seconds to few hours, thus awakening the patient. At times, kidney dialysis has lead to the occurrence of Charley horse in the muscles. 2  Low levels of minerals, such as sodium, magnesium or potassium, in the body can be one of the reasons for Charlie horses. 3  Deficiency of calcium in pregnant women can also be another reason for the onset of Charley horse.