formula.expert

Constants library

3 values, each with its units, its uncertainty, and where it came from.

Astronomical 3

Hubble Constant measured

H0=67.4 km/(s⋅Mpc)H_0 = 67.4\ \text{km/(s}{\cdot}\text{Mpc)}

km/(s·Mpc)Present expansion rate of the universe, 67.4 km/(s·Mpc) from the cosmic microwave background — a galaxy 1 Mpc away recedes at 67 km/s.

Age of the Universe measured

t0=4.354×1017 st_0 = 4.354 \times 10^{17}\ \text{s}

sTime since the Big Bang, 13.797 billion years or 4.35 × 10¹⁷ seconds, from fitting the ΛCDM model to the microwave background.

Critical Density of the Universe measured

ρc=8.53×10−27 kg/m3\rho_c = 8.53 \times 10^{-27}\ \text{kg/m}^{3}

kg/m³Density 3H₀²/8πG that makes the universe spatially flat, about 8.5 × 10⁻²⁷ kg/m³ — some five hydrogen atoms per cubic metre.