World Geography: Universe

World Geography

Universe:-

The Universe is generally defined as the sum of everything that exists that includes all physical matter and energy, stars, galaxies, the planets, and the contents of intergalactic space.

World Geography and Universe

Cosmology: 

The study of the Universe is called as Cosmology.

Galaxy: 

A galaxy is a vast system of billion of stars, dust and light gases bound by their own gravity. There are 100 billion galaxies in the universe and each galaxy has an average of 100 billion stars. Our galaxy is Milky Way Galaxy or it is called Akash Ganga. It is formed after the Big Bang. Andromeda is that the nearest galaxy to the Milky Way.

The Big Bang Theory: 

Big Bang was an explosion of concentrated matter in the universe that occurred 15 billion years ago, leading to the formation of galaxies of stars and other heavenly bodies.

It is believed that universe should be filled with the radiation called the cosmic microwave background. NASA has launched two missions to study these radiations. One is The Cosmic Background Explorer (COBE) and other is The Wilkinson Microwave Anistropy Probe (WMAP).

Stars: 

Stars are the heavenly bodies made up of hot burning gases and they shine by emitting their own light.

What is Black Hole?

Star having mass greater than three times that of the sun, and having a very high gravitational power, so that even light cannot escape from its gravity and it is called Black Hole.

Comets: 

Comets is made up of frozen gases. They move round the Sun in an elongated elliptical orbit with the tail that is always pointing away from the Sun.

Constellations:  

The sky is divided into units to enable the astronomers to identify the position of the stars. These units are called Constellations. These are also known as 88 known constellations.

Satellites:  

Satellites are the heavenly bodies that revolve around the planets. Moon is the natural satellite of the Earth. Time taken by moonlight to reach the Earth is about 1.3 seconds.

What is Solar System?

The Solar System consists of the Sun, eight planets and their satellites and thousands of other smaller heavenly bodies such as asteroids, comets and meteors.

Sun: 

The Sun is placed at the center of the solar system. It is nearest to the Earth. Time taken by the sunlight to reach the Earth is about 8 minute and 16.6 seconds.

Earth: 

The Earth is an oblate spheroid. It is nearly spherical, stroked a little at the poles with a sight bulge at the center or equator. The Earth’s interior is composed of three important layers – first is the crust, second is the mantle and the last is the core. 

Earth spins on its imaginary axis from West to East in one day that is result in causation of day and night and also tides.

Earth’s motion in elliptical orbit around the sun is called one year that is results in the change of seasons. Earth’s rotation speed is 23 hour, 56 minutes and 4.10 seconds. Earth’s revolution speed is 365 days, 5 hours and 45.51 seconds. Escape velocity of Earth is 11.2 km/sec. 

The Longest day on Earth is 21^st June when Sun is vertically overhead at the Tropic of Cancer. The shortest day on Earth is 22^nd December when Sun is vertically overhead at the Tropic of Capricorn. Total land area on Earth is 29.2% and total water area is 70.8%.