# SI - metric system

## The SI System

• SI is the modernized version of the metric measurement system. (Système International d'Unités)
• The metric system is based on seven base units.
• SI measurements are expressed with decimals, not fractions (1.5 , not 1 ½)
• Other measures of length are based upon multiplying or dividing the meter by 10.
• A prefix is added to the word 'meter' to describe these other measures.

## The Meter

• The meter is the unit of length used in the SI measurement system.
• In 1793, the meter was defined as 1/10,000,000 of the distance from the pole to the equator.
• Over the years, standard meter length bars of brass, platinum, and platinum-iridium were used.
• In 1983, the length traveled by light in vacuum during 1/299,792,458 of a second was defined as one meter.

## SI Prefixes

• mega (M_): 1,000,000 of the base units (106).
Example 1,000,000 meters = 1 Mm
• kilo (k_): 1,000 of the base units (103).
Example 1000 meters = 1 km
• centi (c_): 1/100 of the base units (10-2).
Example .01 meters = 1 cm
• milli (m_): 1/1000 of the base units (10-3).
Example .001 meters = 1 mm
• micro (µ_):1/1,000,000 of the base units (10-6) .
Example .000001 meters = 1 µm
• nano (n_): 1/1,000,000,000 of the base units (10-9) .
Example .000000001 meters = 1 nm
• pico (p_): 1/1,000,000,000,000 of the base units (10-12).
Example .000000000001 meters = 1 pm

## Equivalent Measures

• 1 meter = 100 centimeters = 1000 millimeters
• 1 m = 100 cm = 1000 mm
• 1 cm = 10 mm

## Questions

Using a meter stick, answer these questions:

1. My hand span is ________ centimeters. (Measure outstretched hand between tip of thumb and tip of little finger)
2. The width of my _____________ fingernail is 1 cm. (Find the fingernail that is the closest)
3. The width of the back my hand is _________ cm. My height is _____________ m.
4. The width of my table is ___________ m.
5. The table length is ___________ m.
SI prefixes. Derived from Wikipedia Prefix Symbol 10n Decimal Short scale
exa E 1018 1000000000000000000 Quintillion