The standard measurement system used by the scientists is called International System of Units, or SI. The units of measurement of a few physical quantities are considered to be base units; the units of measurement of all other quantities can be expressed through these. The base units are

- Meter - a unit of length....

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The standard measurement system used by the scientists is called International System of Units, or SI. The units of measurement of a few physical quantities are considered to be base units; the units of measurement of all other quantities can be expressed through these. The base units are

- Meter - a unit of length. It is defined, interestingly enough, as the length that the light traverses in 1/299,792,458 of a second.
- Second - a unit of time.
- Kilogram - a unit of mass. The prototype for kilogram - that is, an object that has a mass of 1 kilogram with a very high level accuracy - is made of platinum-iridium alloy and is kept in the International Bureau of Weights and Measures in France.
- Ampere - a unit of electric current, defined by the magnetic force between the two parallel conductors.
- Kelvin - a unit of temperature.
- Mole - a unit of measuring amount of substance (containing a certain number of particles.)
- Candela - a unit of luminous intensity (of radiation.)

The units of measurements of other physical quantities are related to these base units. For example, the unit of volume is a `m^3` , cubic meter, the unit of energy is a Joule, equal to `kg*m^2/s^2` , the unit of measuring electric charge is a Coulomb, equal to `A*s` .

Please see the reference link for the history of development of SI, and how the definitions and prototypes for various units evolved with time so that their maximum accuracy is assured.

**Further Reading**

Measurements in science are made in Système International (SI) units. The use of SI units was agreed upon by an international association of scientists in 1960.

The SI system is a base 10 system. This means that units in the SI system vary by multiples of ten. Base units are established and prefixes are used to indicate smaller and larger units.

**Base Units**:

length: meter (m)

volume: cubic meter (`~m^3` )

mass: kilogram (kg)

temperature: Kelvin (K)

energy: Joule (J)

**Prefixes**:

mega (M) - multiply base unit by `~10^6`

kilo (k) - multiply base unit by `~10^3`

deci (d) - multiply base unit by `~10^-^1`

centi (c) - multiply base unit by `~10^-^2`

milli (m) - multiply base unit by `~10^-^3`

micro (`mu` ) - multiply base unit by `~10^-^6` ` `

nano (n) - multiply base unit by `~10^-^9`

pico (p) - multiply base unit by `~10^-^12`