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balance

(Encyclopedia)balance, instrument used in laboratories and pharmacies to measure the mass or weight of a body. A balance functions by measuring the force of gravity that the earth exerts on an object, i.e., its wei...

air navigation

(Encyclopedia)air navigation, science and technology of determining the position of an aircraft with respect to the surface of the earth and accurately maintaining a desired course (see navigation). Basic to air ...

Carboniferous period

(Encyclopedia)Carboniferous period kärbənĭfˈərəs [key], fifth period of the Paleozoic era of geologic time (see Geologic Timescale, tablegeologic timescale, table), from 350 to 290 million years ago. The pl...

Permian period

(Encyclopedia)Permian period pûrˈmēən [key] [from Perm, Russia], sixth and last period of the Paleozoic era (see Geologic Timescale, tablegeologic timescale, table) from 250 to 290 million years ago. Many ma...

Islam

(Encyclopedia)Islam ĭslämˈ, ĭsˈläm [key], [Arab.,=submission to God], world religion founded by the Prophet Muhammad. Founded in the 7th cent., Islam is the youngest of the three monotheistic world religions ...

global warming

(Encyclopedia)global warming, the gradual increase of the temperature of the earth's lower atmosphere as a result of the increase in greenhouse gases since the Industrial Revolution. Global warming and its effects,...

birth control

(Encyclopedia)birth control, practice of contraception for the purpose of limiting reproduction. Although contraceptive techniques had been known in ancient Egypt, Greece, and Rome, the modern movement for birth ...

diplomatic service

(Encyclopedia)diplomatic service, organized body of agents maintained by governments to communicate with one another. In the 20th and 21st cent. there have been numerous meetings of heads of state and foreign min...

conservation laws

(Encyclopedia)conservation laws, in physics, basic laws that together determine which processes can or cannot occur in nature; each law maintains that the total value of the quantity governed by that law, e.g., mas...

mutation

(Encyclopedia)mutation, in biology, a sudden, random change in a gene, or unit of hereditary material, that can alter an inheritable characteristic. Most mutations are not beneficial, since any change in the delica...