Atmosphere of Earth surface. The refractive index of air depends on temperature, giving rise to refraction effects when the temperature gradient is large. An example of such effects is the mirage. "Atmospheric circulation" is the large-scale movement of air through the troposphere, and the means (with ocean circulation) by which heat is distributed around Earth. The large-scale structure of the atmospheric circulation varies from year to year, but the basic structure remains fairly constant because it is determined by Earth's rotation rate and the difference in solar radiation between the equator and poles. The first atmosphere consisted of gases in the solar nebula,
Before We Ruled the Earth Before We Ruled the Earth Before We Ruled the Earth is a two-part documentary television miniseries that premiered on February 9, 2003 on the Discovery Channel. The program featured early human history and the challenges human beings faced thousands of years ago. It also features animals examples such as: Woolly mammoth, "Megantereon", American buffalo, cave bear, and Irish elk ("Megaloceros giganteus"). The first episode was called "Hunt or Be Hunted" and the second called "Mastering the Beasts." "Hunt or Be Hunted" (narrated by Linda Hunt). The first part in the series shows how humans started out as prey for other