Second sound travels about 343 meters in one second in air; light takes 1.3 seconds to reach Earth from the surface of the Moon, a distance of 384,400 kilometers. A second is part of other units, such as frequency measured in hertz (inverse seconds or second), speed (meters per second) and acceleration (meters per second squared). The metric system unit becquerel, a measure of radioactive decay, is measured in inverse seconds. The meter is defined in terms of the speed of light and the second; definitions of the metric base units ampere and candela also depend on the second. Of the
Gram per cubic centimetre Gram per cubic centimetre Gram per cubic centimetre is a unit of density in the CGS system, commonly used in chemistry, defined as mass in grams divided by volume in cubic centimetres. The official SI symbols are g/cm, g·cm, or g cm. It is equivalent to the units gram per millilitre (g/mL) and kilogram per litre (kg/L). The density of water is about 1 g/cm, since the gram was originally defined as the mass of one cubic centimetre of water at its maximum density at 4 °C. 1 g/cm is equivalent to: 1 kg/m = 0.001 g/cm(exactly) 1 lb/ft ≈