Text 2 Measuring.

Vocabulary:

1. ascertain-устанавливать

2. to defineө - определять

3. wavelength - волна

4. to preserve - сохранить

5. to verify - проверять

6. imprecise - неточный

7. supersede - сменять

8. solid - твердый

Measuring a quantity means ascertaining its ratio to some other fixed quantity of the same kind, known as the unit of that kind of quantity. A unit is an abstract conception, defined either by reference to some arbitrary material standard or to natural phenomena. For example, the standard of length in the metric system was defined (1889–1960) by the separation of two lines on a particular metal bar, but it is now defined as equal to a certain number of wavelengths of light produced by a particular kind of atom under given conditions.

French Bureau International des Poids et Mesures (BIPM) international organization founded to bring about the unification of systems of measurement, to establish and preserve fundamental international standards and prototypes, to verify national standards, and to determine fundamental physical constants. The bureau was established by a convention signed in Paris on May 20, 1875, effective January 1876. In 1921 a modified convention was signed.

The convention provides for a General Conference that meets every four years to consider required improvements or modifications in standards, an International Committee of Weights and Measures composed of 18 scientists elected by the Conference (meets annually), and several consultative committees. The bureau headquarters at Sèvres, France, serves as a depository for the primary international standards and as a laboratory for certification and inter comparison of national standard copies.

Basic metric unit of mass, equal to the mass of the international prototype of the kilogram, a platinum-iridium cylinder kept at the International Bureau of Weights and Measures laboratory at Sèvres, near Paris. A kilogram is very nearly equal (it was originally intended to be exactly equal) to the mass of 1,000cubic centimetres of water. The pound is now defined as equal to 0.45359237 kilogram, exactly. As originally defined, the kilogram was represented in the late 18th century as a solid cylinder of platinum. Measurements of the mass of a volume of water proved to be imprecise and inconvenient to make, however, and the platinum artifact itself became the standard. It was superseded in 1889 by the present standard kilogram, also a solid cylinder, of height equal to its diameter, made of the same alloy as the standard metre bar then in use.

1. Complete the sentences from the text:

1. Basic metric unit of mass, equal to the mass of the international …… of the kilogram.

2. The bureau …. as a depository for the primary international standards and as a laboratory for certification and inter comparison of national standard copies.

3. A kilogram is very nearly equal (it was originally intended to be exactly equal) to the mass of 1,000 …. of water.

4. The kilogram was represented in the late 18th century as ….

5. The standard of …. in the metric system was defined (1889–1960)