Astrophysics (index)about

mass density

(density of a volume of space)

Mass density is a measure of the amount of matter in a unit volume of space. Some examples:

Medium equivalent hydrogen atoms/meter³
Earth rock 1030
Earth atmosphere at sea level 1026
Typical interstellar medium 1 to 1012
Typical intergalactic medium 1 to 50
Apparent baryonic density of the universe .2-.25
critical density 5
Apparent density w/dark matter etc. same

(astrophysics,measure,mass)
http://en.wikipedia.org/wiki/Outer_space
http://en.wikipedia.org/wiki/Density_of_air

Referenced by:
astronomical quantities
cluster radius
column density
critical density (ρc)
free-fall time
Jeans length
number density
vortensity (PV)

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