The metric system is used by every country in the world except for Liberia, Myanmar, and the United States of America. In the metric system, you have a base<\/span><\/em>\u00a0unit that tells you what kind of quantity is being measured and a prefix<\/strong><\/span>\u00a0that tells you the scale. For example, a meter<\/em><\/span> is a measurement of distance, and\u00a0the prefix kilo<\/strong><\/span>\u00a0means thousand; so a kilometer (kilo<\/strong>meter<\/em><\/span><\/span>) is one thousand meters. The following table gives the common metric prefixes that we will be using in this book:<\/p>\n\n\n\n The scientific community uses a particular variety of the metric system called the Syst\u00e8me International d\u2019Unit\u00e9s<\/em>, or SI. The difference between SI and other varieties of the metric system lies in how the base units are defined. The base units in the SI system are the meter for length, the kilogram for mass, and the second for time (it is sometimes called the\u00a0mks<\/em>\u00a0system). This is summarized, with examples, in the following table. This is a very elegant system: whenever we see a prefix in front of a base unit, we automatically know the scale we’re dealing with, and the physical quantity being measured.\u00a0By convention, the prefix centi<\/strong>\u00a0is generally only used in length measurements with SI units.<\/p>\n\n\n\n The defining characteristic of any variety of the metric system is that units scale in multiples of ten. This makes calculations and conversions very straightforward, and lends itself to a system of notation called scientific notation<\/em>, which provides a convenient method of writing down very large and very small numbers.<\/p>\n\n\n\n A quantity is written in scientific notation by expressing it as a product of a number between 1 and 10, and a multiple of ten. For example, <\/p>\n\n\n \\[ 42\\thinspace000 = 4.2 \\times 10^4 \\]<\/p>\n\n\n\n For decimals, we use negative exponents:<\/p>\n\n\n \\[ 0.000\\thinspace42 = 4.2 \\times 10^{-4} \\]<\/p>\n\n\n\n Now we can write our metric prefixes as powers of ten, and each metric prefix means “multiply by 10 to some power.” For example, kilo-<\/em> means “multiply by 103<\/sup>.” So 42 km is 42\u00d7103<\/sup> m, or 42\u2009000 m. The table below gives the powers of ten associated with commonly-used metric prefixes.<\/p>\n\n\n\nPrefix<\/th> Abbreviation<\/th> Meaning<\/th><\/tr><\/thead> kilo-<\/td> k<\/td> 1\u2009000<\/td><\/tr> centi-<\/td> c<\/td> 1\/100<\/td><\/tr> milli-<\/td> m<\/td> 1\/1\u2009000<\/td><\/tr> micro-<\/td> \u03bc<\/td> 1\/1\u2009000\u2009000<\/td><\/tr><\/tbody><\/table> Measurement<\/th> Base unit<\/th> Abbreviation<\/th> Example<\/th><\/tr><\/thead> Length<\/td> meter<\/td> m<\/td> 65 m \u2248 width of a soccer field<\/td><\/tr> Mass<\/td> kilogram<\/td> kg<\/td> 65 kg \u2248 mass of an adult human<\/td><\/tr> Time<\/td> second<\/td> s<\/td> 60 s = 1 minute<\/td><\/tr><\/tbody><\/table> 3.3.1 Powers of ten<\/h3>\n\n\n\n