Constants library

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

Astronomical 5

M_{\mathrm{Moon}} = 7.3459 \times 10^{22}\ \text{kg}

kgMass of the Moon, 7.346 × 10²² kg — 1.23 per cent of Earth's, the largest satellite-to-planet mass ratio in the solar system.

R_{\mathrm{Moon}} = 1,737,400\ \text{m}

mVolumetric mean radius of the Moon, 1737.4 km — just over a quarter of Earth's radius, and barely 0.3 per cent from a perfect sphere.

a_{\mathrm{Moon}} = 384,400,000\ \text{m}

mSemi-major axis of the lunar orbit, 384 400 km centre to centre; the actual distance ranges from 356 500 to 406 700 km.

g_{\mathrm{Moon}} = 1.62\ \text{m/s}^{2}

m/s²Gravitational acceleration at the lunar surface, 1.62 m/s² — one sixth of Earth's, the value the Apollo crews had to learn to walk in.

v_{\mathrm{esc},\mathrm{Moon}} = 2380\ \text{m/s}

m/sSpeed needed to leave the Moon's gravity from its surface, about 2.38 km/s — roughly a fifth of Earth's escape velocity.