metrisch/approximate.html
Approximately powers of ten in the S.I.
(roughly in order of decreasing accuracy)
- density of water at room temperature and pressure = 1000 kg/m3
- temperature difference between boiling and freezing water at atmospheric pressure = 100 K
- mass of 1 mole of hydrogen atoms (or 0.5 mole of hydrogen molecules) = 1 g
- distance from the equator to the north pole over the earth surface = 10 042 km
- half-period of a pendulum with a length of one metre = 1 s (exact if g = π2 m/s2)
- gravitational constant g = 9.8 m/s2
- atmospheric pressure at sea level (wmo.asu.edu) = 870 - 1083 hPa