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  2. Light-year - Wikipedia

    en.wikipedia.org/wiki/Light-year

    The product of Simon Newcomb's J1900.0 mean tropical year of 31 556 925.9747 ephemeris seconds and a speed of light of 299 792.5 km/s produced a light-year of 9.460 530 × 10 15 m (rounded to the seven significant digits in the speed of light) found in several modern sources [10] [11] [12] was probably derived from an old source such as C. W ...

  3. List of common astronomy symbols - Wikipedia

    en.wikipedia.org/wiki/List_of_common_astronomy...

    d - in km = kilometer; d - in mi = mile; d - in AU = astronomical unit; d - in ly = light-year; d - in pc = parsec; d - in kpc = kiloparsec (1000 pc) D L - luminosity distance, obtaining an objects distance using only visual aspects

  4. Squaregraph - Wikipedia

    en.wikipedia.org/wiki/Squaregraph

    The squaregraphs include as special cases trees, grid graphs, gear graphs, and the graphs of polyominos. As well as being planar graphs , squaregraphs are median graphs , meaning that for every three vertices u , v , and w there is a unique median vertex m ( u , v , w ) that lies on shortest paths between each pair of the three vertices. [ 1 ]

  5. Langley (unit) - Wikipedia

    en.wikipedia.org/wiki/Langley_(unit)

    41 840 J/m 2 The langley (Ly) is a unit of heat transmission, especially used to express the rate of solar radiation (or insolation ) received by the earth. The unit was proposed by Franz Linke in 1942 [ 1 ] and named after Samuel Langley (1834–1906) in 1947.

  6. Square kilometre - Wikipedia

    en.wikipedia.org/wiki/Square_kilometre

    The square kilometre (square kilometer in American spelling; symbol: km 2) is a multiple of the square metre, the SI unit of area or surface area. 1 km 2 is equal to: 1,000,000 square metres (m 2) 100 hectares (ha) It is also approximately equal to: 0.3861 square miles [2] 247.1 acres [3] Conversely: 1 m 2 = 0.000001 (10 −6) km 2; 1 hectare ...

  7. Speed of light - Wikipedia

    en.wikipedia.org/wiki/Speed_of_Light

    For example, for visible light, the refractive index of glass is typically around 1.5, meaning that light in glass travels at ⁠ c / 1.5 ⁠ ≈ 200 000 km/s (124 000 mi/s); the refractive index of air for visible light is about 1.0003, so the speed of light in air is about 90 km/s (56 mi/s) slower than c.

  8. Jansky - Wikipedia

    en.wikipedia.org/wiki/Jansky

    To calculate the flux density in janskys, the total power detected (in watts) is divided by the receiver collecting area (in square meters), and then divided by the detector bandwidth (in hertz). The flux density of astronomical sources is many orders of magnitude below 1m −2 ·Hz −1 , so the result is multiplied by 10 26 to get a more ...

  9. List of mathematical abbreviations - Wikipedia

    en.wikipedia.org/wiki/List_of_mathematical...

    sqrt – square root. s.t. – such that or so that or subject to. st – standard part function. STP – [it is] sufficient to prove. SU – special unitary group. sup – supremum of a set. [1] (Also written as lub, which stands for least upper bound.) supp – support of a function. swish – swish function, an activation function in data ...