Besaran dan satuan

Besaran-besaran Pokok :
- Panjang
- Massa
- Waktu
- Temperatur (Suhu)
- Kuat Arus Listrik
- Kuat Cahaya
- Jumlah Zat

Panjang Standar :
In 1799, the legal standard of length in France became the meter, defined as one ten millionth of the distance from the equator to the North Pole. Until 1960, the official length of the meter was the distance between two lines on a specific bar of platinum-iridium alloy stored under controlled conditions. This standard was abandoned for several reasons, the principal one being that measurements of the separation between the lines are not precise enough. In 1960, the meter was defined as 1 650 763.73 wavelengths of orange-red light emitted from a krypton-86 lamp. In October 1983, this definition was abandoned also, and the meter was redefined as the distance traveled by light in vacuum during a time interval of 1/299 792 458 second.



This latest definition establishes the speed of light at 299 792 458 meters per second.

Massa Standar

Satuan Massa standar adalah kilogram, massa standar terbuat dari senyawa Platina Iridium berbentuk silinder. Disimpan di Biro Internasional Berat dan Pengukuran, Sèvres, Perancis.
Massa adalah kuantitas yang digunakan untuk mengukur perubahan inersia (ketahanan suatu benda) saat benda tersebut dalam melakukan gerak atau dinamika.
Ada kalanya, massa adalah kuantitas jumlah zat yang dikandung suatu benda.

Waktu Standar

Before 1960, the time standard was defined in terms of the average length of a solar day in the year 1900. (A solar day is the time between successive appearances of the Sun at the highest point it reaches in the sky each day.) The basic unit of time, the second, was defined to be (1/60)(1/60)(1/24) 1/86 400 of the average solar day. In 1967, the second was redefined to take advantage of the high precision attainable with an atomic clock, which uses the characteristic frequency of the light emitted from the cesium-133 atom as its “reference clock.” The second is now defined as 9 192 631 700 times the period of oscillation of radiation from the cesium atom. The newest type of cesium atomic clock is shown below.