The term ‘Geography’ is derived from the Greek word ‘Geographia’ which means ‘description of Earth’
It deals with the study of Earth’s landscapes, phenomena of Earth, people,the inhabitants, places , environments,maps etc.
Geography is subdivided into human geography and physical geography.
Human geography concerns with the understanding the dynamics of cultures, societies and economies.
Physical geography deals with the understanding the dynamics of physical landscapes and the environment.
Father of Geography is ‘Eratosthenes.’
Astronomy is the study of celestial objects – Stars,Galaxies ,Planets Comets etc.
Astrophysics deals with concepts of physics to understand astronomy.
The study of universe known as cosmology.
Universe and Big Bang Theory
Universe refers to everything that exist and includes all the physical matter and energy, the planets, stars, galaxies and all interstellar spaces.
Origin of the universe is explained by the Big Bang Theory.
Big bang theory suggests that some 15 billion years ago, a massive blast allowed all the universe’s known matter and energy—even space and time themselves—to spring from some ancient and unknown type of energy.
Initially , all the matter in the universe was originally one concentrated lump called ‘primeval atom’.
A galaxy refers to a large system of stars, stellar, interstellar, remnants, gas dust , and dark matter.
Earth’s Galaxy is ‘milky way.’
The Milky way is a large spiral shaped galaxy.
It is also known as ‘akash ganga’.
The nearest galaxy to milky way is ‘Andromeda’.
Andromeda is also spiral in shape.
Nebulae are huge interstellar cloud of dust, hydrogen, helium and other ionized gases.
They appear either as bright luminous clouds or as dark patches.
Stars are the most widely recognized astronomical objects, and represent the most fundamental building blocks of galaxies.
Sun is also a star.
After sun, the nearest star to earth is ‘alpha centauri’(Also known as Proxima Centauri).It is about 4.3 light years away from us.
A constellation is a traditional or recognizable group of stars.
For instances- Capricorn, Sagittarius, Scorpius , Libra etc.
The Solar System
The Sun, Nine Planets (Now 8), the satellite of planets, the comets , the asteroids , the meteoroids and the interplanetary dust constitutes the solar system.
The planets names are mercury, Venus ,Earth ,Mars , Jupiter, Saturn , Uranus and Neptune.
Pluto is known as Dwarf planet.
Pluto lost the status of planet in year 2006 as announced by International astronomical union (IAU).
In the solar system the planet nearest to the sun is mercury the farthest planet from the sun is Neptune.
The size of the solar system has been estimated to about 105 astronomical units.
Note: To remember the sequence of planets ,follow this-
“My Very Elegant Mother Just Show Us Nine Planets”
Mercury Venus Earth Mars Jupiter Saturn Uranus Neptune Pluto (Not Planet)
Sun is the source of energy of solar system.
It is the nearest star to the earth.
Its size is 1300000 times as that of Earth.
It is at the center of the solar system.
Its diameter is about 1400000 kilometers.
It is composed of 71% hydrogen , 26.5 percent helium and 2.5 % other elements .
The surface temperature of sun is about 6000 degree Celsius.
The temperature at the center are the inner temperature is about 150 lac degree Celsius.
Shiny surface of the sun is called ‘photo sphere.’
The outermost layer of Sun’s atmosphere is made up of thin hot gases Called ‘Corona.’
Light takes about 8.5 minutes to reach the earth from the sun.
The sun is about 150 million kilometers away from the Earth.
The planets have no light of their own.
They take light from the Sun.
All planets move on their axes From west to east except Venus and Uranus which move on their axes from east to west.
The planets revolve around the sun in an elliptical orbit.
Satellites are the celestial bodies which revolve around the planet.
Jupiter has 63 satellites whereas Venus and mercury does not have any satellite.
Mercury and Venus are also known as inferior planets.
Mercury ,Venus ,Earth & Mars are known as ‘Terrestrial planets’ and the rest of the planets of the solar system are known as ‘Gaseous planets.’
The 4 outermost planets Saturn ,Jupiter ,Uranus and Neptune are also known as ‘Jovian planets’.
Mercury is the closest planet to the sun.
Mercury is the extremely hot planet.
The surface temperature of mercury is about 450 degree celsius in daytime and about several degrees below the zero degree celsius at night.
The orbital period of mercury is about 88 Earth days but it takes around 116 earth days to rotate on its axis.
The planet has no water.
Mercury planet has no life building gases is like carbon dioxide , Nitrogen oxide,oxygen and hydrogen which can build life.
Mercury has no protective layer like earth.
Venus is a second planet from the sun.
It is the nearest planet to the earth.
Venus is known as ‘evening star’ as well as ‘morning star.’
Venus is also known as ‘Earth’s twin’ as it is very much like the earth in size and mass.
It is the hottest planet of the solar system.
Venus also does not have any water.
It rotates from east to west.
Earth is the largest of the inner planets.
The earth is tilted 23.5 degrees on its axis.
The axial tilt is also known as obliquity.
It takes 365 days 5 hours and 48 minutes to revolve around the sun.
It takes 23 hours 56 minutes and 4 seconds to rotate on its axis.
Earth is the only planet which provide sustenance of life on it
It has large quantity of oxygen which supports life.
Earth is also known as watery Planet or the blue planet.
The earth has all the essential elements like carbon hydrogen nitrogen and oxygen which act as building blocks of the origin of life.
The earth is neither too hot or nor too cold it has Goldilocks zone
Goldilocks zone is a small habitable zone near star which has life sustainability.
Mars is also known as Red Planet.
It is the fourth planet from the sun.
Iron rich red soil of mass give it the name red planet and also it has pink Sky.
Mars to satellites ‘phobos’ and ‘Demos’.
It is the largest planet of the solar system.
Jupiter is as big as 1300 Earths put together.
It is also known as winter planet because of its low average temperature.
Jupiter has highest number of satellites in the solar system.
It is the second largest planet in the solar system .
Saturn has bright concentric rings which are made up of ice and ice covered dust particles which revolve around it.
Titan the satellite of Saturn is the largest satellite in the solar system.
Uranus is the seventh planet from the sun.
It appears greenish in color because of Methane Gas present in its atmosphere/
Uranus is about 4 times the size of the earth.
It is the first planet to have been discovered by the use of telescope
It is the third biggest planet of the solar system.
It rotates from east to west.
Neptune is a planet of the solar system
Neptune has very low average temperature
Neptune and Uranus can be considered as twin planet as they look similar
Pluto is classified as a dwarf planet and is also a member of a group of objects that orbit in a disc-like zone beyond the orbit of Neptune called the Kipper Belt.
Pluto is about two-thirds the diameter of Earth’s moon and probably has a rocky core surrounded by a mantle of water ice.
According to International Astronomical Union (IAU) the Pluto is not considered as the planet now as the planet must be big and round and also planet must orbit the sun.
On August 24 2006 it was declared that route of Pluto would no longer remain as that of planet.
Therefore now the solar system have only 8 planets.
The moon is the only satellite of the earth .
Its diameter is about 3475 km.
It takes 27 days 7 hours and 43 minutes to rotate on its axis and this period of 27 and half days is called sidereal month.
Moon takes approximately the same period of time review all around the earth and to rotate around the earth
The temperature during daytime is about 100 degree Celsius and in night it drops about -180 degree Celsius.
The size of the moon is one fourth of the size of the earth
Moon is also known as Fossil planet.
The study of moon is called selenography.
A small body made up of small amount of dust and rock
the main body of the Comet is called nucleus.
The chief constituent of nucleus is water, Methane ,nitrogen and ice.