as the volume of one cubic decimeter, and the kilogram was the weight of a liter of
pure water.
The standards metamorphosed over the years. For example, the first physical stan-
dard meter was in the form of a bar defined as a meter in length. By 1889 the Interna-
tional Bureau of Weights and Measures (BIPM, or Bureau International des Poids et
Mesures) replaced the original meter bar. The new bar not only became a standard in
France, but copies of the newest bar were distributed to the 17 countries that signed
the Convention of the Meter (Convention du Mètre) in Paris in 1875. The accepted dis-
tance became two lines marked on a bar measuring 2 centimeters by 2 centimeters in
cross-section and slightly longer than one meter; the bar itself was composed of 90
percent platinum and 10 percent iridium. But it was only a “standard meter” when it
was at the temperature of melting ice.
By 1960 the BIPM decided to make a more accurate standard; mostly, this was done
to satisfy the scientific community’s need for precision. The new standard meter was
based on the wavelength of light emitted by the krypton-86 atom (or 1,650,763.73 wave-
lengths of the atom’s orange-red line in a vacuum). An even more precise measurement
of the meter came about in 1983, when it became defined as the distance light travels in
a vacuum in 1/299,792,458 second. This is the currently accepted standard.What is scientific notation?
Scientific notation is a way of making larger and smaller numbers used in the scientif-
ic field easier to write, read, and take up less space in calculations. Scientists generally
pick the power of ten that is multiplied by a number between 1 and 10 to express these
numbers. For example, it is easier to write 0.00023334522 as 2.3334522 10 ^4. (For
more about scientific notation and power of ten, see “Math Basics.”)How is temperature measured?
Temperature is measured using a thermometer (thermomeaning “heat” and meter
meaning “to measure”). The inventor of the thermometer was probably Galileo Galilei
(1564–1642), who used a device called the thermoscope to measure hot and cold.
Temperatures are determined using various scales, the most popular being Cel-
sius, Fahrenheit,and Kelvin.Invented by Swedish astronomer, mathematician, and
physicist Anders Celsius (1701–1744) in 1742, Celsiusused to be called the Centigrade
scale (it can be capitalized or not; centigrade means “divided into 100 degrees”). He
used 0 degrees Celsius to mark the freezing point of water; the point where water boils
was marked as 100 degrees Celsius. Because of its ease of use (mainly because it is
based on an even 100 degrees), it is the scale most used by scientists; it is also the
scale most associated with the metric system.
Fahrenheitis the scale invented by Polish-born German physicist Daniel Gabriel
54 Fahrenheit (1686–1736) in 1724. His thermometer contained mercury in a long, thin