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  2. International Terrestrial Reference System and Frame

    en.wikipedia.org/wiki/International_Terrestrial...

    An International Terrestrial Reference Frame ( ITRF) is a realization of the ITRS. Its origin is at the center of mass of the whole earth including the oceans and atmosphere. New ITRF solutions are produced every few years, using the latest mathematical and surveying techniques to attempt to realize the ITRS as precisely as possible.

  3. Rotating reference frame - Wikipedia

    en.wikipedia.org/wiki/Rotating_reference_frame

    A rotating frame of reference is a special case of a non-inertial reference frame that is rotating relative to an inertial reference frame. An everyday example of a rotating reference frame is the surface of the Earth. (This article considers only frames rotating about a fixed axis. For more general rotations, see Euler angles .)

  4. Alternative approaches to redefining the kilogram - Wikipedia

    en.wikipedia.org/wiki/Alternative_approaches_to...

    Single-pan scales, which measure weight relative to an invariant of nature, are not precise to the necessary long-term uncertainty of 10–20 parts per billion. Another issue to be overcome is that silicon oxidises and forms a thin layer (equivalent to 5–20 silicon atoms deep) of silicon dioxide ( quartz ) and silicon monoxide .

  5. Terrestrial reference frame - Wikipedia

    en.wikipedia.org/wiki/Terrestrial_reference_frame

    A terrestrial reference frame ( TRF) is the reference frame as one views from Earth, or from the surface of another Earth-like planet. A TRF affects the way humans perceive almost everything from day to day because as they live on the Earth an Earth-based point of view was the only viewpoint from which the rest of the universe could be observed ...

  6. Gravity Probe B - Wikipedia

    en.wikipedia.org/wiki/Gravity_Probe_B

    Gravity Probe B. Gravity Probe B ( GP-B) was a satellite -based experiment to test two unverified predictions of general relativity: the geodetic effect and frame-dragging. This was to be accomplished by measuring, very precisely, tiny changes in the direction of spin of four gyroscopes contained in an Earth-orbiting satellite at 650 km (400 mi ...

  7. Cavendish experiment - Wikipedia

    en.wikipedia.org/wiki/Cavendish_experiment

    Cavendish's result provided additional evidence for a planetary core made of metal, an idea first proposed by Charles Hutton based on his analysis of the 1774 Schiehallion experiment. [18] Cavendish's result of 5.4 g·cm −3, 23% bigger than Hutton's, is close to 80% of the density of liquid iron, and 80% higher than the density of the Earth's ...

  8. Earth-centered, Earth-fixed coordinate system - Wikipedia

    en.wikipedia.org/wiki/Earth-centered,_Earth...

    The Earth-centered, Earth-fixed coordinate system (acronym ECEF ), also known as the geocentric coordinate system, is a cartesian spatial reference system that represents locations in the vicinity of the Earth (including its surface, interior, atmosphere, and surrounding outer space) as X, Y, and Z measurements from its center of mass.

  9. Space Shuttle external tank - Wikipedia

    en.wikipedia.org/wiki/Space_Shuttle_external_tank

    The Space Shuttle external tank ( ET) was the component of the Space Shuttle launch vehicle that contained the liquid hydrogen fuel and liquid oxygen oxidizer. During lift-off and ascent it supplied the fuel and oxidizer under pressure to the three RS-25 main engines in the orbiter. The ET was jettisoned just over 10 seconds after main engine ...