The density of water .... 1.00 kg/li ... or ... 1000 kg/m³

The diameter of an atom ... wavelength of X-rays ... and the separation of atoms in a crystal ~ 10^-10 meters

The diameter of the atomic nucleus ... ~ 10^-14 meters

The number of light years in one parsec ... 3.26

Wavelength of green light ... 5x10^-7 meters

The weight of one kg is 9.8 Newtons

Speed of light ... 3x10⁸ m/s

Temperature of the Sun ... 6000 K

Solar constant (at ground level) ... 1000 W/m²

To convert angular frequency to rotations ... x by 2p

To convert square cm to square meters ... x by 10⁴

To convert energy in eV to Joules ... x by 1.6x10^-19

Convert frequency to period ... T = 1/f

Convert half life to the decay constant (l) ... l = ^0.69/_T(half)