Constants library

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

Electromagnetic 2

c_{\mathrm{H_2O}} = 224,900,000\ \text{m/s}

m/sLight travels through water at about 225,000 km/s, or c/1.333 — the slowing that bends a straw at the waterline and lets Cherenkov detectors work.

c_{\mathrm{glass}} = 197,230,000\ \text{m/s}

m/sTypical propagation speed in crown glass, c/1.52 or about 197,000 km/s — the delay that makes lenses focus and optical fibres carry data.