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. In most of the cases, Charlie horses are the late responses of overstraining a muscle during exercise, or otherwise. 2  Charley horse might be the result of an electrolyte or mineral imbalance in the body. 3  In some of the cases, Charlie horses have been found to be a signal of the onset of a vascular disease.