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The air mass coefficient defines the direct optical path length through the Earth's atmosphere, expressed as a ratio relative to the path length vertically upwards, i.e. at the zenith. The air mass coefficient can be used to help characterize the solar spectrum after solar radiation has traveled through the atmosphere.
In astronomy, air mass or airmass is a measure of the amount of air along the line of sight when observing a star or other celestial source from below Earth's atmosphere . It is formulated as the integral of air density along the light ray .
Mass–energy equivalence states that all objects having mass, or massive objects, have a corresponding intrinsic energy, even when they are stationary.In the rest frame of an object, where by definition it is motionless and so has no momentum, the mass and energy are equal or they differ only by a constant factor, the speed of light squared (c 2).
An air mass originating over northern Siberia in winter may be indicated as "cA". [3] The stability of an air mass may be shown using a third letter, either "k" (air mass colder than the surface below it) or "w" (air mass warmer than the surface below it). [3] An example of this might be a polar air mass blowing over the Gulf Stream, denoted as ...
Conventional mass is defined as follows: "For a mass at 20 °C, ‘conventional mass’ is the mass of a reference standard of density 8,000 kg/m 3 which it balances in air with a density of 1.2 kg/m 3."
The cosine of the hour angle (cos(h)) is used to calculate the solar zenith angle. At solar noon, h = 0.000 so cos( h ) = 1 , and before and after solar noon the cos(± h ) term = the same value for morning (negative hour angle) or afternoon (positive hour angle), so that the Sun is at the same altitude in the sky at 11:00AM and 1:00PM solar time.
The solar mass (M ☉) is a standard unit of mass in astronomy, equal to approximately 2 × 10 30 kg (2 nonillion kilograms in US short scale). It is approximately equal to the mass of the Sun. It is often used to indicate the masses of other stars, as well as stellar clusters, nebulae, galaxies and black holes. More precisely, the mass of the ...
is the molar mass of dry air, approximately 0.028 9652 in kg⋅mol −1. [note 1] is the Boltzmann constant, 1.380 649 × 10 −23 in J⋅K −1 [note 1] is the molecular mass of dry air, approximately 4.81 × 10 −26 in kg. [note 1]