Monday, May 20, 2013

A Planet Orbiting Around Sun


There are 2 theories about the center of the solar system stated by two astronomers. Geocentric model presented by Ptolemy states that earth is the center of the solar system and the revolution takes place around it. Heliocentric model presented by Nicolaus Copernicus states that sun is the center of the universe and planets rotate around it.

There are two hemispheres of earth, one is North and second is South which are divided by an imaginary like called equator.

All planets revolve on their orbits. Earth's shape is ellipse and its axis is tilted.  Earth reaches the state of perihelion when it is nearest to sun and reaches aphelion when it is furthest from the sun. Earth’s shape is ellipse, not circle. A star which always stays in North and is seen is known as Polaris.

Earth is divided in 24 time zones. Each time zone is divided by its position on longitude and is 1 hour different from the time zone next to it. A town situated on 0 longitude known as Greenwich is the place where time starts, which separates West and East by 12 times zones on each side, this is known as GMT (Greenwich Mean Time). An imaginary line moving from north to south on 0 longitude is known as International date line which divides the East and West by one day. Similarly a line moving from North to South but on 0 latitude is known as Prime meridian.

Earth's tilted axis plays an important role in the division of the seasons. Regions where direct sunlight falls have summer where as regions where sunlight falls indirectly have winter. Equator plays an important role in distribution of seasons because regions near or on the equator have summer all year because sunlight falls on the equator directly all year long.

There are 9 phases of the moon. First quarter moon has sunlight on half of the moon and other side is dark. Waxing crescent is the moon’s light is going away, where as new moon is totally dark that is why we can’t see the moon sometimes. Waning moon is shown when the moon start getting sunlight after fully dark. Full moon is shown when the whole moon is lightened by sunlight. Gibbous moon is the moon, which consists light more than quarter moon and less then full moon. 

Water Waves raise and fall on daily basis known as tides. Moon has a great effect on the water level while it raises and falls. When sun, moon and Earth are in a single straight line, the tides at the moment are known as Spring tides. When moon, sun and earth are in a 90degree angle or a right triangle, Neap tides are formed.

When Earth is in the middle of sun and moon, lunar eclipse is formed. And when moon is between sun and earth, solar eclipse is formed. There are 2 types of solar eclipses. First is total solar eclipse which takes place when the moon covers the whole sun, where as when moon covers a part of sun, partial solar eclipse takes