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Doppler effect

(Encyclopedia)Doppler effect, change in the wavelength (or frequency) of energy in the form of waves, e.g., sound or light, as a result of motion of either the source or the receiver of the waves; the effect is nam...

infrared radiation

(Encyclopedia)infrared radiation, electromagnetic radiation having a wavelength in the range from c.75 × 10−6 cm to c.100,000 × 10−6 cm (0.000075–0.1 cm). Infrared rays thus occupy that part of the electrom...

Grosseteste, Robert

(Encyclopedia)Grosseteste, Robert grōsˈtĕst [key], c.1175–1253, English prelate. Educated at Oxford and probably also at Paris, he became one of the most learned men of his time. He taught at Oxford and later,...

brown dwarf

(Encyclopedia)brown dwarf, in astronomy, celestial body that is larger than a planet but does not have sufficient mass to convert hydrogen into helium via nuclear fusion as stars do. Also called “failed stars,”...

pulsar

(Encyclopedia)pulsar, in astronomy, a neutron star that emits brief, sharp pulses of energy instead of the steady radiation associated with other natural sources. The study of pulsars began when Antony Hewish and h...

Bernoulli

(Encyclopedia)Bernoulli or Bernouilli both: bĕrno͞oyēˈ [key], name of a family distinguished in scientific and mathematical history. The family, after leaving Antwerp, finally settled in Basel, Switzerland, whe...

Talmud

(Encyclopedia)Talmud tălˈməd [key] [Aramaic from Heb.,=learning], in Judaism, vast compilation of the Oral Law with rabbinical elucidations, elaborations, and commentaries, in contradistinction to the Scriptures...

interstellar matter

(Encyclopedia)interstellar matter, matter in a galaxy between the stars, known also as the interstellar medium. The interstellar gas, which constitutes about 99% of the interstellar matter, consists mostly of hyd...

measurement

(Encyclopedia)measurement, determination of the magnitude of a quantity by comparison with a standard for that quantity. Quantities frequently measured include time, length, area, volume, pressure, mass, force, and...

parallax

(Encyclopedia)CE5 The trigonometric parallax of a star, expressed by the angle θ, is a measure of its apparent motion against the background of more distant stars as a result of the earth's motions in its orbit...