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  2. Geopotential height - Wikipedia

    en.wikipedia.org/wiki/Geopotential_height

    Geopotential height differs from geometric height (as given by a tape measure) because Earth's gravity is not constant, varying markedly with altitude and latitude; thus, a 1-m geopotential height difference implies a different vertical distance in physical space: "the unit-mass must be lifted higher at the equator than at the pole, if the same ...

  3. Null hypothesis - Wikipedia

    en.wikipedia.org/wiki/Null_hypothesis

    In scientific research, the null hypothesis (often denoted H 0) [1] is the claim that the effect being studied does not exist. [note 1] The null hypothesis can also be described as the hypothesis in which no relationship exists between two sets of data or variables being analyzed.

  4. Knudsen number - Wikipedia

    en.wikipedia.org/wiki/Knudsen_number

    The Knudsen number is a dimensionless number defined as =, where = mean free path [L 1], = representative physical length scale [L 1].. The representative length scale considered, , may correspond to various physical traits of a system, but most commonly relates to a gap length over which thermal transport or mass transport occurs through a gas phase.

  5. Scale height - Wikipedia

    en.wikipedia.org/wiki/Scale_height

    The earth atmosphere's scale height is about 8.5 km, as can be confirmed from this diagram of air pressure p by altitude h: At an altitude of 0, 8.5, and 17 km, the pressure is about 1000, 370, and 140 hPa, respectively.

  6. Effects of high altitude on humans - Wikipedia

    en.wikipedia.org/wiki/Effects_of_high_altitude...

    The medical problems that are direct consequence of high altitude are caused by the low inspired partial pressure of oxygen, which is caused by the reduced atmospheric pressure, and the constant gas fraction of oxygen in atmospheric air over the range in which humans can survive. [1]

  7. Hammond's postulate - Wikipedia

    en.wikipedia.org/wiki/Hammond's_postulate

    The relationship between Hammond's postulate and the BEP principle can be understood by considering a S N 1 reaction. Although two transition states occur during a S N 1 reaction (dissociation of the leaving group and then attack by the nucleophile), the dissociation of the leaving group is almost always the rate-determining step. Hence, the ...

  8. Duhem–Quine thesis - Wikipedia

    en.wikipedia.org/wiki/Duhem–Quine_thesis

    In philosophy of science, the Duhem–Quine thesis, also called the Duhem–Quine problem, says that unambiguous falsifications of a scientific hypothesis are impossible, because an empirical test of the hypothesis requires one or more background assumptions. Rather than disproving the main hypothesis, the blame can be placed on one of the ...

  9. Theoretical gravity - Wikipedia

    en.wikipedia.org/wiki/Theoretical_gravity

    For many problems such as aircraft simulation, it may be sufficient to consider gravity to be a constant, defined as: [2] g = g 45 = {\displaystyle g=g_{45}=} 9.80665 m/s 2 (32.1740 ft/s 2 ) based upon data from World Geodetic System 1984 ( WGS-84 ), where g {\displaystyle g} is understood to be pointing 'down' in the local frame of reference.