Introduction
The moon completes one rotation around its axis in 29 days and the same time it takes to complete one revolution around the earth. Hence, we never see the other side of the moon. The Pole star doesn’t move from its position as it’s located on the earth’s axis.
Mercury is the smallest planet and closest to the sun. It has no satellites. Venus [Earth’s twin] is closest to the earth and rotates east to west. Saturn is less dense than water. Uranus has a highly tilted axis; it appears to be rolling on its side. It also rotates from east to west. The first four planets are rocky with few satellites or no. But outer planets are gaseous and with many satellites.
Asteroids are found between Mars and Jupiter. largest asteroid is cereus. Comets have an elliptical orbit around the sun and have a long period of revolution. Their tail is always away from the sun. Meteors are objects that enter the earth’s atmosphere, usually, they burn in the atmosphere but sometimes they fall on the earth. This fallen body is called a meteorite. The atmosphere regulates the temperature of the planet by allowing it to cool slowly in the daytime and during the night time trapping the heat and preventing it from escaping.
The ozone layer absorbs the harmful UV-B radiations of the sun. But due to CFCs, it is thinning and this leads to a hole in the ozone layer above Antarctica. Ozone [O3] is the product of UV radiation. UV rays split the O2 molecule into free atoms which combine with the O2 molecule to form an ozone molecule. Depletion of the ozone layer above Antarctica is seen and is called the ozone hole. This is due to the formation of polar stratospheric clouds in summer which causes depletion. In winter chlorine sinks are present which prevent ozone depletion.
The greenhouse effect is seen when the long wave radiation of the earth is absorbed by the greenhouse gases causing heating of the atmosphere.
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