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   Measurements and Units. Conversions. History Measurement is one way of knowing. It compares any quantity (for example, a line segment) with a homogeneous quantity (for example, a centimeter), taken as a unit of measure. The measurement result is expressed as a number showing how many times the selected unit is contained in the measured quantity.On the other hand, measurements are one of the most important information technologies. The development of science and technology is closely related to measurements. Scientific research is accompanied by measurements that allow us to establish quantitative relationships and patterns of properties of the phenomena being studied. The measurement of a physical quantity - length, area, volume, weight, temperature - is carried out empirically using various measuring instruments, such as scales and a thermometer. In the measurement process, the measured quantity's numerical value, such as length, weight, or temperature, is found empirically in the accepted units of measurement. The results of measuring any amount and the points of the number line are compared on a scale (lat.: scala - ladder). For example, we look at which division of the scale corresponds to the liquid level in the thermometer and thus convert the measured temperature into several degrees (for example, Celsius or Reaumur), that is, we encode it - we remember or write it down as a number. Some scientists wrote: "Science begins from the time they begin to measure: exact science is unthinkable without measure." In ancient times, at an early stage of development, man faced the need for measurements in practical life, agriculture, the construction of his own homes, the palaces of his rulers, temples, and trade. People needed to measure distances, areas, volumes, weights, and, of course, time. The first units of length were very approximate. They were associated with the sizes of parts of the human body. In England and the USA, the units of length "foot" - foot (31 cm), "thumb" - inch (25.4 mm), and yard (91 cm) are still used. It was equal to the distance from the tip of King Henry I's nose to the end of his outstretched fingers. 1 foot = 12 inches. These are also the old Russian units of length: a fathom was equal to the distance from the end of the fingers of one hand to the end of the fingers of the other, an elbow was equal to the distance from the elbow joint to the end of the outstretched middle finger of the hand, and a span was equal to the distance between the ends of the outstretched fingers of the hand—the thumb and index finger. The concept of area is known to people from everyday experience. Everyone understands the meaning of the words: the area of a room is equal to 25 square meters, the area of a summer cottage is twelve hundred square meters, etc. Area is the size of that part of the plane occupied by a polygon. Areas are measured using a selected unit of measurement, similar to measuring the lengths of segments. A square is taken as a unit of area measurement, the side of which is equal to the unit of measurement of segments. So, if a square with a side of 1 cm is taken as a unit of area measurement, such a square is called a square centimeter and is denoted by a square centimeter. A square meter, a square millimeter, etc., are defined similarly. A volume is defined similarly - a cubic centimeter, a cubic meter, etc. The volume of a liquid is measured in liters - the volume of a fluid in the volume of one cubic decimeter, or more precisely, the volume of 1 kg of pure water at normal atmospheric pressure (760 mm Hg) and the temperature of the highest density of water (4 °C). Thus, the volume of 1 liter in 1901 was taken as 1.000028 dm3. Very early, in the process of bartering, man needed to measure weight—the force of the body's impact on a support or suspension. Scales are one of the most ancient devices. They arose and improved with trade, production, and science development. The entire development of society, first of all, the emergence of trade, urgently required the invention of a device capable of weighing goods intended for sale. The first simple scales in the form of an equal-arm beam with suspended bowls began to be used in ancient Babylon two and a half thousand years BC and Egypt two thousand years BC. This is a beam with suspended bowls, where the goods are placed on one, and weights are placed on the other.
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ShareJim: 2025-05-09 11:34:55 It is impossible to describe the length of something without comparing it to the length of something else. Think of money: something might be valuable without it, but it would have no price. We use centimeters and inches as our standards in the modern world, but this was not always the case.Going back to the beginning of human history, to the times of nomads and hunter-gatherers, there was no need to measure lengths. Phrases like "twice as long as I am tall" and "a little longer than a cow" were enough. But when man began to settle down and plant fields, descriptions like "my land is seven times as long as I am tall and ten cows wide" were no longer enough.
Many ancient measurement systems used parts of the human body. At the time, this seemed logical: people were everywhere where measurements were needed, and there was nothing more suitable for measurements than people themselves. The ancient Greek philosopher Protagoras said: "Man is the measure of all things." Problems arose when people realized that different people had different-sized body parts.
They chose one person to use as a standard: the ruler (the king or queen). Thus, the problem was solved by measuring different objects in terms of one person's arm length. Variations of such measurement standards included special wooden rods used in ancient Egypt and Mesopotamia and pieces of ivory in the Indus Valley.
Soon, a system was developed to divide larger units into smaller lengths. For example, Egypt used a basic unit of length called the meg nejes, or common cubit, the distance from the elbow to the tip of the middle finger, about 45 centimeters. The meg nejes could be divided into six shesps (the width of a palm without the thumb), consisting of four jebs (thickness of fingers).
Other states also created their systems of measurement. Typically, a set of lengths was selected based on needs and convenience, and then a master copy of the standard was made. These master length standards were kept in public places so that people could use them to make copies for their measurements.
In Ancient Greece, Rome, and Egypt, units of length measurement based on parts of the human body were used. Thus, the length equal to the width of a finger was called "dactyl" in Ancient Greece and "digit" (digitus in Latin) in Rome. Incidentally, the latter later gave its name to numbers (digits).
And in England, for example, the inch (25.4 mm) was the main unit of length for a long time. It is still used as a measure of length in the USA. Initially, an inch was defined as the thickness of an adult male thumb. Longer segments were measured in feet (12 inches). Some metrologists believe that the foot was borrowed from the Egyptian system of measures. Three feet make a "yard". In turn, the yard itself is equal to approximately two ancient Egyptian "meg nejes".
A unified international system of measures was needed. The first attempt to create one was during the French Revolution. In 1799, the first two standards were made in France—for the unit of length (meter) and for the unit of mass (kilogram). This system is now known as the metric system. It had a decimal conversion of multiple length measures: 10 millimeters = 1 centimeter, 10 centimeters = 1 decimeter, and so on.
Initially, the meter was defined as one forty-millionth (1/40,000,000) of the length of the Paris meridian. A specially made platinum bar became the standard. Platinum was chosen for this purpose because products made from it retain their shape and size for a long time.
The platinum standard of the metre was used from 1889 to 1960.
Subsequently, the metric system developed, adding a unit of time - the second, and the base units of length - a hundredth of a metre - a centimeter, and mass - a thousandth of a kilogram - a gram. Based on the first letters of these units, the system was called CGS (centimeter-gram-second).
In 1875, seventeen countries, including Russia, Germany, the USA, France, Italy, and others, signed the Metre Convention, which created the International Committee for Weights and Measures and the International Bureau for Weights and Measures.
In 1960, the General Conference on Weights and Measures (CGPM) adopted a standard called the International System of Units (Le Système International d'Unités), also known as SI. This system's basic units were the meter, kilogram, second, ampere, degree Celsius, and candela.
Nowadays, length is measured by something that remains constant: the speed of light. One meter is the distance light travels in a vacuum in 1/299792458 of a second. |
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