c

   1. see cycle

   2. see cup

   3. see carat

   4. a symbol for the speed of light. One of the fundamental principles of physics is that light always travels at the same speed ina vacuum, exactly 299 792 458 meters per second or about 670 617 300 milesper hour. Another fundamental principle is that no object can travel fasterthan light. At speeds that are large fractions of the speed of light,the theory of relativity predicts a variety of strange physical effects.In calculations involving relativity, speeds are customarily expressed asfractions of the speed of light, such as 0.95 c.