Equations · equation
First Friedmann Equation
Cosmology · 1922
- Equation
- (ȧ/a)² = 8πGρ/3 − kc²/a² + Λc²/3
- Field
- Cosmology
- Named After
- Alexander Friedmann
- Year
- 1922
Symbols
a the scale factor of the universe · ȧ its rate of change · H = ȧ/a the Hubble parameter · G gravitational constant · ρ the total energy density, matter and radiation together · k spatial curvature (−1 open, 0 flat, +1 closed) · Λ the cosmological constant · c speed of light
Significance
How fast the universe expands, given what it contains — Einstein's field equations applied to a uniform cosmos. The Hubble parameter, the critical density, and the fate of the universe all fall out of this one line.
Referenced by
constant
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equation
event
instrument
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