The Law

candela; cd

The fundamental SI unit of luminous intensity defined as the luminous intensity in a given direction of a source that emits monochromatic photons of frequency 540 x 1012 Hz and has a radiant intensity in that direction of 1/683 W/sr.

Carnot's theorem (S. Carnot)

The theorem which states that no engine operating between two temperatures can be more efficient than a reversible engine.

Casimir effect (Casimir)

A quantum mechanical effect, where two very large plates placed close to each other will experience an attractive force, in the absence of other forces. The cause is virtual particle-antiparticle pair creation in the vicinity of the plates. Also, the speed of light will be increased in the region between the two plates, in the direction perpendicular to them.

causality principle

The principle that cause must always precede

effect. More formally, if an event A ("the cause") somehow influences an event B ("the effect") which occurs later in time, then event B cannot in turn have an influence on event A. That is, event B must occur at a later time t than event A, and further, all frames must agree upon this ordering.

The principle is best illustrated with an example. Say that event A constitutes a murderer making the decision to kill his victim, and that event B is the murderer actually committing the act. The principle of causality puts forth that the act of murder cannot have an influence on the murderer's decision to commit it. If the murderer were to somehow see himself committing the act and change his mind, then a murder would have been committed in the future without a prior cause (he changed his mind). This represents a causality violation. Both time travel and faster-than-light travel both imply violations of causality, which is why most physicists think they are impossible, or at least impossible in the general sense.

centrifugal pseudoforce

A pseudoforce that occurs when one is moving in uniform circular motion. One feels a "force" directed outward from the center of motion.

Chandrasekhar limit (S. Chandrasekhar; 1930)

A limit which mandates that no white dwarf (a collapsed, degenerate star) can be more massive than about 1.4 masses solar. Any degenerate mass more massive must inevitably collapse into a neutron star.

Charles' law (J.A.C. Charles; c. 1787)

The volume of an ideal gas at constant pressure is proportional to the thermodynamic temperature of that gas.

Cherenkov [Cerenkov] radiation (P.A. Cherenkov)

Radiation emitted by a massive particle which is moving faster than light in the medium through