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  2. Cosmic distance ladder - Wikipedia

    en.wikipedia.org/wiki/Cosmic_distance_ladder

    Kepler's laws provide precise ratios of the orbit sizes of objects orbiting the Sun, but provide no measurement of the overall scale of the orbit system. Radar is used to measure the distance between the orbits of the Earth and of a second body. From that measurement and the ratio of the two orbit sizes, the size of Earth's orbit is calculated.

  3. Corrective Optics Space Telescope Axial Replacement

    en.wikipedia.org/wiki/Corrective_Optics_Space...

    The Corrective Optics Space Telescope Axial Replacement (COSTAR) is an optical correction instrument designed and built by NASA. It was created to correct the spherical aberration of the Hubble Space Telescope ' s primary mirror , which incorrectly focused light upon the Faint Object Camera (FOC), Faint Object Spectrograph (FOS), and Goddard ...

  4. System of units of measurement - Wikipedia

    en.wikipedia.org/wiki/System_of_units_of_measurement

    The British imperial system uses a stone of 14 lb, a long hundredweight of 112 lb and a long ton of 2,240 lb. The stone is not a measurement of weight used in the US. The US customary system uses the short hundredweight of 100 lb and short ton of 2,000 lb. Where these systems most notably differ is in their units of volume.

  5. Astronomical system of units - Wikipedia

    en.wikipedia.org/wiki/Astronomical_system_of_units

    The astronomical system of units, formerly called the IAU (1976) System of Astronomical Constants, is a system of measurement developed for use in astronomy.It was adopted by the International Astronomical Union (IAU) in 1976 via Resolution No. 1, [1] and has been significantly updated in 1994 and 2009 (see Astronomical constant).

  6. SI base unit - Wikipedia

    en.wikipedia.org/wiki/SI_base_unit

    The SI system after 1983, but before the 2019 revision: Dependence of base unit definitions on other base units (for example, the metre is defined as the distance travelled by light in a specific fraction of a second), with the constants of nature and artefacts used to define them (such as the mass of the IPK for the kilogram).

  7. Slug (unit) - Wikipedia

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

    The slug is a derived unit of mass in a weight-based system of measures, most notably within the British Imperial measurement system and the United States customary measures system. Systems of measure either define mass and derive a force unit or define a base force and derive a mass unit [ 1 ] (cf. poundal , a derived unit of force in a mass ...

  8. Birdcage - Wikipedia

    en.wikipedia.org/wiki/Birdcage

    A birdcage (or bird cage) is a cage designed to house birds as pets. Antique (or antique-style) birdcages are often popular as collectors' items or as household decor but most are not suitable for housing live birds, being too small, improper shape, using unsafe materials or construction. [ 1 ]

  9. Photometry (optics) - Wikipedia

    en.wikipedia.org/wiki/Photometry_(optics)

    This is sometimes also confusingly called "spectral intensity". J e,λ [nb 7] watt per square metre, per metre W/m 3: M⋅L −1 ⋅T −3: Radiant exitance: M e [nb 5] watt per square metre W/m 2: M⋅T −3: Radiant flux emitted by a surface per unit area. This is the emitted component of radiosity. "Radiant emittance" is an old term for this ...