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  2. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    A light-year, alternatively spelled light year (ly or lyr[3]), is a unit of length used to express astronomical distances and is equal to exactly 9,460,730,472,580.8 km (Scientific notation: 9.4607304725808 × 10 12 km), which is approximately 5.88 trillion mi.

  3. Mass versus weight - Wikipedia

    en.wikipedia.org/wiki/Mass_versus_weight

    The mass of an object is a measure of the object’s inertial property, or the amount of matter it contains. The weight of an object is a measure of the force exerted on the object by gravity, or the force needed to support it. The pull of gravity on the earth gives an object a downward acceleration of about 9.8 m/s 2.

  4. Weight - Wikipedia

    en.wikipedia.org/wiki/Weight

    In science and engineering, the weight of an object, is the force acting on the object due to acceleration of gravity. [1][2][3] Some standard textbooks [4] define weight as a vector quantity, the gravitational force acting on the object. Others [5][6] define weight as a scalar quantity, the magnitude of the gravitational force.

  5. Weber–Fechner law - Wikipedia

    en.wikipedia.org/wiki/Weber–Fechner_law

    Weber's law. Ernst Heinrich Weber (1795–1878) was one of the first persons to approach the study of the human response to a physical stimulus in a quantitative fashion. Fechner was a student of Weber and named his first law in honor of his mentor, since it was Weber who had conducted the experiments needed to formulate the law.

  6. Fluorescent-lamp formats - Wikipedia

    en.wikipedia.org/wiki/Fluorescent-lamp_formats

    G5 bi-pin. 2GX13 quad-pin. G10q quad-pin. Original 4–13 W miniature fluorescent range from 1950s or earlier. [1] Two newer ranges, high-efficiency (HE) 14–35 W, and high-output (HO) 24–80 W, introduced in the 1990s. [2] Panasonic's range of FHL fluorescent tubes in 18W, 27W, and 36W varieties for the Japanese market.

  7. Observable universe - Wikipedia

    en.wikipedia.org/wiki/Observable_universe

    So if the matter that originally emitted the oldest CMBR photons has a present distance of 46 billion light-years, then the distance would have been only about 42 million light-years at the time of decoupling. The light-travel distance to the edge of the observable universe is the age of the universe times the speed of light, 13.8 billion light ...

  8. Weight class (boxing) - Wikipedia

    en.wikipedia.org/wiki/Weight_class_(boxing)

    A boxing match in 1914 between Freddie Welsh and Joe Rivers in Vernon, California. In the early nineteenth century, there were no standard weight classes. In 1823, the Dictionary of the Vulgar Tongue said the limit for a "light weight" was 12 stone (168 lb, 76.2 kg) while Sportsman's Slang the same year gave 11 stone (154 lb, 69.9 kg) as the ...

  9. System of units of measurement - Wikipedia

    en.wikipedia.org/wiki/System_of_units_of_measurement

    A system of units of measurement, also known as a system of units or system of measurement, is a collection of units of measurement and rules relating them to each other. Systems of measurement have historically been important, regulated and defined for the purposes of science and commerce. Instances in use include the International System of ...