magnitude

mag·ni·tude   (māg'nĭ-tōōd', -tyōōd')    n.   Greatness of rank or position: "such duties as were expected of a landowner of his magnitude" (Anthony Powell). Greatness in size or extent: The magnitude of the flood was impossible to comprehend. Greatness in significance or influence: was shocked by the magnitude of the crisis. A number assigned to a quantity so that it may be compared with other quantities. A property that can be described by a real number, such as the volume of a sphere or the length of a vector. Astronomy The degree of brightness of a celestial body designated on a numerical scale, on which the brightest star has magnitude -1.4 and the faintest visible star has magnitude 6, with the scale rule such that a decrease of one unit represents an increase in apparent brightness by a factor of 2.512. Also called apparent magnitude. Mathematics A number assigned to a quantity so that it may be compared with other quantities. A property that can be described by a real number, such as the volume of a sphere or the length of a vector. Geology A measure of the amount of energy released by an earthquake, as indicated on the Richter Scale. [Middle English, from Old French, size, from Latin magnitūdō, greatness, size, from magnus, great; see meg- in Indo-European roots.]

Magnitude

Mag"ni*tude\, n. [L. magnitudo, from magnus great. See Master, and cf. Maxim.]

1. Extent of dimensions; size; -- applied to things that have length, breath, and thickness.

Conceive those particles of bodies to be so disposed amongst themselves, that the intervals of empty spaces between them may be equal in magnitude to them all. --Sir I. Newton.

2. (Geom.) That which has one or more of the three dimensions, length, breadth, and thickness.

3. Anything of which greater or less can be predicated, as time, weight, force, and the like.

4. Greatness; grandeur. "With plain, heroic magnitude of mind." --Milton.

5. Greatness, in reference to influence or effect; importance; as, an affair of magnitude.

The magnitude of his designs. --Bp. Horsley.

Apparent magnitude (Opt.), the angular breadth of an object viewed as measured by the angle which it subtends at the eye of the observer; -- called also apparent diameter.

Magnitude of a star (Astron.), the rank of a star with respect to brightness. About twenty very bright stars are said to be of first magnitude, the stars of the sixth magnitude being just visible to the naked eye. Telescopic stars are classified down to the twelfth magnitude or lower. The scale of the magnitudes is quite arbitrary, but by means of photometers, the classification has been made to tenths of a magnitude.

magnitude 

Main Entry: mag·ni·tude
Pronunciation: 'mag-n&-"t(y)üd
Function: noun
: relative size or extent

magnitude   (māg'nĭ-td')  Pronunciation Key  The degree of brightness of a star or other celestial body, measured on a logarithmic scale in which lower numbers mean greater brightness, such that a decrease of one unit represents an increase in brightness by a factor of 2.512. An object that is 5 units less than another object on the magnitude scale is 100 times more luminous. Because of refinements in measurement after the zero point was assigned, very bright objects have negative magnitudes. ◇ The brightness of a celestial body as seen from Earth is called its apparent magnitude. (When unspecified, an object's magnitude is normally assumed to be its apparent magnitude.) The dimmest stars visible to the unaided eye have apparent magnitude 6, while the brightest star in the night sky, Sirius, has apparent magnitude -1.4. The full Moon and the Sun have apparent magnitudes of -12.7 and -26.8 respectively. ◇ The brightness of a celestial body computed as if viewed from a distance of 10 parsecs (32.6 light-years) is called its absolute magnitude. Absolute magnitude measures the intrinsic brightness of a celestial object rather than how bright it appears on Earth, using the same logarithmic scale as for apparent magnitude. Sirius has an absolute magnitude of 1.5, considerably dimmer than Rigel which, though its apparent magnitude is 0.12, has an absolute magnitude of -8.1. Stars that appear dim in the night sky but have bright absolute magnitudes are much farther from Earth than stars that shine brightly at night but have relatively dim absolute magnitudes. The Sun, a star of only medium brightness, has an absolute magnitude of 4.8. ◇ The degree of total radiation emitted by a celestial body, including all infrared and ultraviolet radiation in addition to visible light, is called its bolometric magnitude. Bolometric magnitude is generally measured by applying a standard correction to an object's absolute magnitude. A measure of the total amount of energy released by an earthquake, as indicated on the Richter scale. See more at Richter scale.