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  2. Friedmann equations - Wikipedia

    en.wikipedia.org/wiki/Friedmann_equations

    For example, w = 0 describes a matter-dominated universe, where the pressure is negligible with respect to the mass density. From the generic solution one easily sees that in a matter-dominated universe the scale factor goes as a ( t ) ∝ t 2 / 3 {\displaystyle a(t)\propto t^{2/3}} matter-dominated Another important example is the case of a ...

  3. Earth mass - Wikipedia

    en.wikipedia.org/wiki/Earth_mass

    An Earth mass (denoted as M 🜨, M ♁ or M E, where 🜨 and ♁ are the astronomical symbols for Earth), is a unit of mass equal to the mass of the planet Earth. The current best estimate for the mass of Earth is M 🜨 = 5.9722 × 10 24 kg, with a relative uncertainty of 10 −4. [2] It is equivalent to an average density of 5515 kg/m 3.

  4. Birch–Murnaghan equation of state - Wikipedia

    en.wikipedia.org/wiki/Birch–Murnaghan_equation...

    The third-order Birch–Murnaghan isothermal equation of state is given by = [() / /] {+ (′) [() /]}. where P is the pressure, V 0 is the reference volume, V is the deformed volume, B 0 is the bulk modulus, and B 0 ' is the derivative of the bulk modulus with respect to pressure.

  5. Curved space - Wikipedia

    en.wikipedia.org/wiki/Curved_space

    The surface of a sphere can be completely described by two dimensions, since no matter how rough the surface may appear to be, it is still only a surface, which is the two-dimensional outside border of a volume. Even the surface of the Earth, which is fractal in complexity, is still only a two-dimensional boundary along the outside of a volume. [3]

  6. Stefan–Boltzmann law - Wikipedia

    en.wikipedia.org/wiki/Stefan–Boltzmann_law

    At Earth, this energy is passing through a sphere with a radius of a 0, the distance between the Earth and the Sun, and the irradiance (received power per unit area) is given by = The Earth has a radius of R ⊕ , and therefore has a cross-section of π R ⊕ 2 {\displaystyle \pi R_{\oplus }^{2}} .

  7. Planck's law - Wikipedia

    en.wikipedia.org/wiki/Planck's_law

    The "mass emission coefficient" j ν is equal to the radiance per unit volume of a small volume element divided by its mass (since, as for the mass absorption coefficient, the emission is proportional to the emitting mass) and has units of power⋅solid angle −1 ⋅frequency −1 ⋅density −1. Like the mass absorption coefficient, it too ...

  8. Center of mass - Wikipedia

    en.wikipedia.org/wiki/Center_of_mass

    This toy uses the principles of center of mass to keep balance when sitting on a finger. In physics, the center of mass of a distribution of mass in space (sometimes referred to as the barycenter or balance point) is the unique point at any given time where the weighted relative position of the distributed mass sums to zero.

  9. Gravity of Earth - Wikipedia

    en.wikipedia.org/wiki/Gravity_of_Earth

    The density at the center is the same as in the PREM, but the surface density is chosen so that the mass of the sphere equals the mass of the real Earth. See also: Shell theorem An approximate value for gravity at a distance r from the center of the Earth can be obtained by assuming that the Earth's density is spherically symmetric.