(Metric) numbers to remember

This table contains numbers that people often memorize. Many of these are nicer round numbers, and easier to remember, in metric units than in old-fashioned units.

Quantity	Value in Metric units	Value in old-fashioned units
Speed of Light (Note 1)	300 000 km/s	186 000 miles/s
Speed of Sound	330 m/s	1090 feet/s
Acceleration due to Earth's gravity	10 m/s²	32 feet/s²
Distance between Earth and Sun	150 000 000 km	93 000 000 miles
Distance between Earth and Moon	385 000 km	240 000 miles
Circumference of Earth (Note 2)	40 000 km	25 000 miles
Geostationary Satellite Altitude (Note 3)	36 000 km	22 000 miles
Freezing Point of Water	0 °C	32 °F
Standard Human Body Temperature	37 °C	98.6 °F
Boiling Point of Water	100 °C	212 °F
Atmospheric pressure	100 kPa	30 inches
Density of Water	1 g/mL or 1 kg/L 1 g/cm³ or 1000 kg/m³ or 1 t/m³	8.35 lb/gal 0.58 oz/in³
Height of Mount Everest	8850 m	29 035 feet
Length of Marathon Footrace (Note 4)	42.195 km	26 miles 385 yd
World Long Jump Record (Note 5)	8.95 m	29 feet 4.5 in

Notes:

The speed of light is exactly 299 792 458 m/s (or 299 792.458 km/s), as specified in the current definition of the meter, established by the 17th General Conference on Weights and Measures in 1983.
When the metric system was created in the 1790s, the meter was originally specified as 1/10 000 000 of the distance between the Equator and the North Pole, so the Earth's (polar) circumference was exactly 40 000 000 m (or 40 000 km). The meter has been redefined several times, most recently in terms of the second (i.e., the unit of time) and a defined value for the speed of light (Note 1). But the Earth's circumference is still remarkably close to 40 000 km.
The geostationary satellite altitude is the distance above the earth's surface, whereas the earth-sun and earth-moon distances are between the centers of the bodies.
The first marathon race was an even metric 40 km, run during the first Modern Olympics, Athens 1896. The distance fluctuated in subsequent years, until it was standardized in 1924 at 42.195 km, the length first run during the 1908 Olympics in London. This is not an even distance in either kilometers or miles.
The current long jump record is 8.95 m by Mike Powell, Tokyo 1991. Previous record was 8.90 m by Bob Beamon, Mexico City 1968. Measurements of long jumps, discus throws, etc. and bar heights for high jumps, pole vaults, etc. are always whole numbers of centimeters, although they are often translated to approximate feet/inch equivalents for US audiences.

Much of the above information was provided by Bob Baumel (bobbau@earthlink.net) for the USMA Website. Dr. Baumel also provided improved graphics for several of the original images used on the USMA web site.

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