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light

(Encyclopedia)light, visible electromagnetic radiation. Of the entire electromagnetic spectrum, the human eye is sensitive to only a tiny part, the part that is called light. The wavelengths of visible light range ...

speed

(Encyclopedia)speed, change in distance with respect to time. Speed is a scalar rather than a vector quantity; i.e., the speed of a body tells one how fast the body is moving but not the direction of the motion. If...

polarization of light

(Encyclopedia)polarization of light, orientation of the vibration pattern of light waves in a singular plane. Unpolarized light can be converted into a single polarized beam by means of the Nicol prism, a device ...

hypersonic speed

(Encyclopedia)hypersonic speed: see aerodynamics. ...

supersonic speed

(Encyclopedia)supersonic speed: see aerodynamics. ...

Speed, John

(Encyclopedia)Speed, John, 1552?–1629, English historian and cartographer. He abandoned his trade as a tailor to engage in mapmaking. Many of his maps of parts of England and Wales were published in The Theatre o...

ground speed indicator

(Encyclopedia)ground speed indicator: see air navigation. ...

zodiacal light

(Encyclopedia)zodiacal light or zodiacal band, a faint band of light sometimes seen in the western sky just after sunset in the spring, extending up from the horizon at the point where the sun has just set, or in t...

light-year

(Encyclopedia)light-year, in astronomy, unit of length equal to the distance light travels in one sidereal year. It is 9.461 × 1012 km (about 6 million million mi). Alpha Centauri and Proxima Centauri, the stars n...

light horse

(Encyclopedia)light horse, any breed of horse that is used primarily for riding or for light work such as pulling buggies. Light horses have their origin in the Middle East and N Africa. All modern breeds of light ...