measurement summary

Written and fact-checked by The Editors of Encyclopaedia Britannica

Below is the article summary. For the full article, see measurement.

measurement, Association of numbers with physical quantities and natural phenomena by comparing an unknown quantity with a known quantity of the same kind. Weights and measures are standard quantities with which such comparisons are made. The earliest ones measured mass (weight), volume (liquid or dry measure), length, and area using units mostly based on dimensions of the human body. The cubit, representing the distance from elbow to fingertips, was the most widespread unit of measure in the ancient world. As such units were standardized, more were added, including units of temperature, luminosity, pressure, and electric current. Measurements made by the senses instead of by measurement devices are called estimates (see estimation).

Ramadan Summary

Ramadan, in Islam, the ninth month of the Muslim calendar and the holy month of fasting. It begins and ends with the appearance of the crescent moon. Because the Muslim calendar year is shorter than the Gregorian calendar year, Ramadan begins 10–12 days earlier each year, allowing it to fall in

Anderson-Wood torsion pendulum seismograph

Richter scale Summary

Richter scale (ML), quantitative measure of an earthquake’s magnitude (size), devised in 1935 by American seismologists Charles F. Richter and Beno Gutenberg. The earthquake’s magnitude is determined using the logarithm of the amplitude (height) of the largest seismic wave calibrated to a scale by

Understanding the International System of Units in science

International System of Units Summary

International System of Units (SI), international decimal system of weights and measures derived from and extending the metric system of units. Adopted by the 11th General Conference on Weights and Measures (CGPM) in 1960, it is abbreviated SI in all languages. Rapid advances in science and

astronomical unit Summary

Astronomical unit (AU, or au), a unit of length effectively equal to the average, or mean, distance between Earth and the Sun, defined as 149,597,870.7 km (92,955,807.3 miles). Alternately, it can be considered the length of the semimajor axis—i.e., the length of half of the maximum diameter—of