“magnitude”的概念、定义、翻译、参考文献-科学参考

magnitude

Physics

A measure of the relative brightness of a star or other celestial object. The apparent magnitude depends on the star’s luminosity, its distance, and the absorption of light between the object and the earth. In 1856 the astronomer Norman Robert Pogson (1829–91) devised a scale in which a difference of five magnitudes corresponds to a brightness ratio of 100 to 1. Two stars that differ by one magnitude therefore have a brightness ratio of (100)^0.2:1=2.512, known as the Pogson ratio. This scale is now universally adopted. Apparent magnitudes are not a measure of luminosity, which is defined in terms of the absolute magnitude. This is the apparent magnitude of a body if it were situated at a standard distance of 10 parsecs.

Mathematics

A statistically significant result is a function of both the sample size and of the magnitude of the difference being measured. With advances in technology, sample sizes now can be extremely large, and in these cases almost any difference will turn out to be significant. It becomes important in such cases to consider whether the difference is large enough to be of practical importance.

Astronomy

A measure of the brightness of a star. Ancient Greek astronomers defined the brightest stars as being of the first magnitude because they were the first to appear after sunset. The magnitude scale continued in steps of decreasing brightness down to sixth magnitude, for those stars which were visible only in total darkness. From its crude beginnings, the magnitude scale has been extended and is now on a strictly defined footing (see Pogson Scale) so that a difference of one magnitude corresponds to a difference in brightness of a factor of 2.512, and 5 magnitudes equals a brightness difference of exactly a hundredfold. Ancient magnitude estimates depended solely on the human eye, corresponding roughly to the modern V magnitude. The apparent magnitude of a star is its brightness as seen from Earth, whereas the absolute magnitude is a measure of its actual (i.e. intrinsic) brightness; the two differ because the intensity of light falls off with distance, and because of interstellar absorption. When the brightness is measured over all wavelengths, rather than just visible wavelengths, it is known as the bolometric magnitude.

Space Exploration

A measure of the brightness of a star or other celestial object. The larger the number denoting the magnitude, the fainter the object. Zero or first magnitude indicates some of the brightest stars. Still brighter are those of negative magnitude, such as Sirius, whose magnitude is −1.46.
Apparent magnitude is the brightness of an object as seen from the Earth; absolute magnitude is the brightness at a standard distance of 10 parsecs (32.616 light years).
Each magnitude step is equal to a brightness difference of 2.512 times. Thus a star of magnitude 1 is (2.512)⁵ or 100 times brighter than a sixth-magnitude star just visible to the naked eye. The apparent magnitude of the Sun is −26.8, its absolute magnitude +4.8.

Geography

Of an earthquake, an expression of the total energy released.

Philosophy

See measurement.

单词	magnitude
释义	magnitude Physics A measure of the relative brightness of a star or other celestial object. The apparent magnitude depends on the star’s luminosity, its distance, and the absorption of light between the object and the earth. In 1856 the astronomer Norman Robert Pogson (1829–91) devised a scale in which a difference of five magnitudes corresponds to a brightness ratio of 100 to 1. Two stars that differ by one magnitude therefore have a brightness ratio of (100)^0.2:1=2.512, known as the Pogson ratio. This scale is now universally adopted. Apparent magnitudes are not a measure of luminosity, which is defined in terms of the absolute magnitude. This is the apparent magnitude of a body if it were situated at a standard distance of 10 parsecs. Mathematics A statistically significant result is a function of both the sample size and of the magnitude of the difference being measured. With advances in technology, sample sizes now can be extremely large, and in these cases almost any difference will turn out to be significant. It becomes important in such cases to consider whether the difference is large enough to be of practical importance. Astronomy A measure of the brightness of a star. Ancient Greek astronomers defined the brightest stars as being of the first magnitude because they were the first to appear after sunset. The magnitude scale continued in steps of decreasing brightness down to sixth magnitude, for those stars which were visible only in total darkness. From its crude beginnings, the magnitude scale has been extended and is now on a strictly defined footing (see Pogson Scale) so that a difference of one magnitude corresponds to a difference in brightness of a factor of 2.512, and 5 magnitudes equals a brightness difference of exactly a hundredfold. Ancient magnitude estimates depended solely on the human eye, corresponding roughly to the modern V magnitude. The apparent magnitude of a star is its brightness as seen from Earth, whereas the absolute magnitude is a measure of its actual (i.e. intrinsic) brightness; the two differ because the intensity of light falls off with distance, and because of interstellar absorption. When the brightness is measured over all wavelengths, rather than just visible wavelengths, it is known as the bolometric magnitude. Space Exploration A measure of the brightness of a star or other celestial object. The larger the number denoting the magnitude, the fainter the object. Zero or first magnitude indicates some of the brightest stars. Still brighter are those of negative magnitude, such as Sirius, whose magnitude is −1.46. Apparent magnitude is the brightness of an object as seen from the Earth; absolute magnitude is the brightness at a standard distance of 10 parsecs (32.616 light years). Each magnitude step is equal to a brightness difference of 2.512 times. Thus a star of magnitude 1 is (2.512)⁵ or 100 times brighter than a sixth-magnitude star just visible to the naked eye. The apparent magnitude of the Sun is −26.8, its absolute magnitude +4.8. Geography Of an earthquake, an expression of the total energy released. Philosophy See measurement.
随便看	crucial experiment crucible crucible process crucifixion CRUD crude data crude distillation crude oil crude rate crude unit Crudinian cruise missile cruise phase crumb Crum Brown, Alexander Crum Brown’s rule crumb structure crura crus Crusades crusher crushing Crusius, Christian August (1715–75) crust Crustacea