|
light-year
light-year in astronomy, unit of length equal to the distance light travels in one sidereal year . It is 9.461 × 10 12 km (about 6 million million mi). Alpha Centauri and Proxima Centauri, the stars nearest our solar system, are about 4.3 light-years distant. See also parsec .
...
Read more
|
|
|
refugee
refugee one who leaves one's native land either because of expulsion or to escape persecution. The legal problem of accepting refugees is discussed under asylum ; this article considers only mass dislocations and the organizations that help refugees.
The Rise of International Refugee Organiz...
Read more
|
|
|
Bantu languages
Bantu languages group of African languages forming a subdivision of the Benue-Niger division of the Niger-Congo branch of the Niger-Kordofanian language family (see African languages ). Bantu contains hundreds of languages that are spoken by 120 million Africans in the Congo Basin, Angola, the Rep...
Read more
|
|
Australopithecus
Australopithecus , an extinct genus of the hominid family found in Africa between about 4 and 1 million years ago. At least seven species of australopithecines are now generally recognized, including Australopithecus afarensis, A. africanus, A. bahrelghazali, A. anamensis, A. boisei, A. r...
Read more
|
|
|
wilderness
wilderness land retaining its primeval character with the imprint of humans minimal or unnoticeable. In the United States, the Wilderness Act of 1964 established the National Wilderness Preservation System with a nucleus of 9 million acres (3.6 million hectares) of land in 54 different areas, mostl...
Read more
|
|
|
migration
migration of people, geographical movements of individuals or groups for the purpose of permanently resettling.
Early History
Migrations have occurred throughout history and have played an important part in the peopling of all the areas of the earth. Primitive migrations were usually in s...
Read more
|
|
Earth
Earth The third planet in the solar system, outwards from the Sun. The mean distance of the Earth from the Sun is 149.6 × 106 km. This distance provides the standard ‘astronomical unit’ (AU) of measurement. The Earth has a mean radius of 6371 km, density of 5517 kg/m3, and a mass ...
Read more
|
|
Deep Sea Drilling Project
Deep Sea Drilling Project U.S. program designed to investigate the evolution of ocean basins by core drilling of ocean sediments and underlying oceanic crust. Funded by the National Science Foundation, the project was directed by the Joint Oceanographic Institution for Deep Earth Sampling (JOIDES),...
Read more
|
|
human evolution
human evolution theory of the origins of the human species, Homo sapiens. Modern understanding of human origins is derived largely from the findings of paleontology , anthropology , and genetics , and involves the process of natural selection (see Darwinism ). Although gaps in the fossil reco...
Read more
|
|
|
parsec
parsec [ par allax + sec ond], in astronomy, basic unit of length for measuring interstellar and intergalactic distances, equal to 206,265 times the distance from the earth to the sun, 3.26 light-years, or 3.08 × 10 13 km (about 19 million million mi). The distan...
Read more
|
