4
Units of Scientific Measurements
PREFIXES
Scientific measurements range from fantastically large to incredibly small numbers, and units that are appropriate for one measurement may be entirely inappropriate for another. To avoid the creation of many different sets of units, it is
common practice to vary the size of a fundamental unit by attaching a suitable
prefix to it. Table 4-1 shows common metric prefixes and the multiples they
indicate for any given unit of measurement. Thus a kilometer is 1000 meters, a
microgram is 10~
6 gram, and a nanosecond is 10~
9 second.
SI UNITS
Except for temperature and time, nearly all scientific measurements are based
on the metric system. In recent years, there has been a concerted international
effort to persuade scientists to express all metric measurements in terms of just
seven basic units, called SI units (for Systeme International). In addition to the
seven basic SI units, there are seventeen other common units derived from
them that have special names. However, despite the logical arguments that
have been put forth for undeviating adherence to SI units, there has not been a
strong popular move in this direction. For one thing, each scientist must cope
Units of Scientific Measurements
PREFIXES
Scientific measurements range from fantastically large to incredibly small numbers, and units that are appropriate for one measurement may be entirely inappropriate for another. To avoid the creation of many different sets of units, it is
common practice to vary the size of a fundamental unit by attaching a suitable
prefix to it. Table 4-1 shows common metric prefixes and the multiples they
indicate for any given unit of measurement. Thus a kilometer is 1000 meters, a
microgram is 10~
6 gram, and a nanosecond is 10~
9 second.
SI UNITS
Except for temperature and time, nearly all scientific measurements are based
on the metric system. In recent years, there has been a concerted international
effort to persuade scientists to express all metric measurements in terms of just
seven basic units, called SI units (for Systeme International). In addition to the
seven basic SI units, there are seventeen other common units derived from
them that have special names. However, despite the logical arguments that
have been put forth for undeviating adherence to SI units, there has not been a
strong popular move in this direction. For one thing, each scientist must cope