Mass refers to the basic properties of matter. It exists by itself and does not depend on other parameters, such as temperature, pressure and the location of an object in space. Being a physical quantity, mass is determined by the amount of matter (substance) contained in the object, and is an internal characteristic of this body, allowing you to find other parameters depending on it. In Newtonian mechanics, mass is responsible for gravitational attraction to other bodies and resistance to acceleration due to inertia.
Who has more talents, or what "people" measured in antiquity
All these scientific terms associated with space technology, in fact, have their roots in ancient times. From ancient times, the rational person was faced with the question of determining the mass of various objects. Agriculture, logistics, construction, absolutely any field of activity required knowledge of weight, and over time, only the requirements for measurement accuracy changed. Initially to this day, all units of mass measurement are based on a comparison with the selected reference sample. In the deep past, the objects of the surrounding world served as a measure, although many of them are used as a reference in our time. For example, the weight of jewelry since the XV century is considered to be the mass of seeds of a bean plant (carob) carats (about 0.2 g).
In ancient Rome, the unit of mass measurement was talent, determined by the amount of water contained in an amphora of a certain volume. Copies of weights made according to accepted reference units were reliably guarded by rulers, elders or clergy.
Old Russian measures of weight
The first known weight measure in Ancient Russia is considered to be the hryvnia, named the same as a precious jewelry for the neck. These were silver ingots of a special form of two types: northern Novgorod, which weighed 204 g, and southern (160 g) Kiev hryvnia. The big hryvnia was obtained from a pair, it was subsequently called the pound, which weighed about 409.5 g.
The pound was divided into smaller units - 32 lots, 96 spools, and the share was considered the tiniest measure (1 spool included 96 shares weighing 0.44 grams). To determine the large masses, a pound of 16.38 kg and a Berkovets consisting of 10 pounds were used.
How did we get to such a life
With the development of interstate commodity-money relations, the need arose for a single quantitative definition of the concept of "mass." The unit of mass in the metric system (SI) was originally adopted a gram, determined by the amount of distilled water at an ice melting point (0 ° C) in a cubic tank with sides of 0.01 m (1 cm). Later, they determined a value more convenient for practical use - 1 kilogram, corresponding to the amount of purified water in a volume of 1 dm 3 at the temperature of its maximum density (at normal atmospheric pressure it is +4 ° C). The prefix "kilo" is adopted to indicate the number of measured units multiplied by 10 3 , in the Russian version "k", the international designation is "k", and this unit of mass measurement is the only one of the main units in SI that is used with the prefix.
Since the density of water strongly depends on atmospheric pressure, this was a very risky method for determining the unit of measure of mass, which could cause an error in the value of a kilogram. At low values, this could lead to serious errors. Therefore, in 1889, in France, after accurate measurements, the International Kilogram prototype (kilogram) was created, which is an ingot of noble platinum (90%) and a material with a very high density - iridium (10%) in the form of a cylinder of 39.17 mm in height and in diameter. From 1878 to 1983, 43 copies were created in the image and composition of a kilogram from the archive.
The most accurate of them was taken as the international standard, which currently determines the value of the unit of mass for the member states of the Metric Convention. It is safely stored in the suburbs of Paris, in the commune of Sevres, and the remaining countries have acquired the parties to the agreement. Russia got two copies - No. 12, approved as a standard, and No. 26, which became the secondary standard of a kilogram. A prototype is stored in St. Petersburg, at the Institute of Metrology. D.I. Mendeleev.
To infinity and beyond
A kilogram is perfectly applicable for everyday use, but it becomes inconvenient as a unit of measure for the mass of extremely large and extremely small objects.
Let's start with the ancient Latin - centum "hundred", which defines 100 kg in the metric system with a single word - centner, by it (Latin) and continue - a ton (from Latin tunna "barrel") gave the name to the mass of 1000 kg. Further simpler, prefixes are added to grams, centners and tons, increasing or decreasing the value of these values by a factor of 10 to some extent. In the direction of increasing 10 to a positive degree: deck - in the 1st order, hecto - in the 2nd, kilo - in the 3rd, mega - has the order of 6, giga - 9, tera - 12, peta - 15, exa - 18, zeta - 21, iotta - 24.
Now let's go towards infinitely small quantities. There is some compromise caused by the presence of the prefix kilo in the main unit, therefore, the fraction of it is taken as the base value - gram: deci - 10 to the power of -1, centi - 2, milli - 3, micro - 6, nano - 9, pico - 12, femto - 15, atto - 18, zepto - 21, iokto - 24.
With the advent of molecular chemistry, the need arose to determine the mass of atoms and molecules. For this, the concept of atomic mass unit (daltons) was introduced, which is approximately 1.66 times 10 -27 kg. Due to the complexity of the calculations, the daltons were replaced by the relative atomic mass, calculated by dividing the mass of the atom of the element by the twelfth of the carbon atom, this quantity has no dimension.
The last of the Mohicans
Alas, this is far from all the units of mass measurement existing in the world. In addition to metric, many countries often use historically established national systems of measures (ounce, pound, sy, tribute, livre, drachma, etc.), and three small developing states still have not switched to the SI system at all. These metric outcasts are Liberia, Myanmar (Burma) and ... USA.