In astronomy, the relative brightness of a celestial body. Originally a scale from 1 to 6, where 1 represented the brightest and 6 the faintest visible night sky objects. This scale has been expanded to include negative integers, integers greater than 6 and decimal values. A decrease of 1 in magnitude indicates an increase in brightness by a factor of 2.512 times. In mathematics, the magnitude of an object is often used to describe the size or length of that object. In optics, the magnitude is often associated with the amplitude or electric field strength of an electromagnetic wave vector.