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.
If a spasm is forcefully sustained and doesnât relax, then it ripens into a cramp. A charlie (charley) horse is a common term many use to indicate they either have a muscle spasm or cramp, typically in a thigh or leg muscle. This charlie of a horse is very often caused by dehydration and/or lack of potassium. A muscle spasm can occur in any muscle and you may be able to see or feel the hardened muscle, like a knot. Sometimes, muscle spasms will occur with such force that theyâll leave a bruise behind.