Universe :-
In the universe, there are so many stars, Galaxies, Nebulas and Celestial objects. Earth is a negligible part of this universe. In olden days it was said that the Earth is situated at the center of the universe.
- There are so many theories about the origination of the Universe. But none of the theories are away from the criticism.
- To understand theses theories of Astro - nomical Phenomenon, which is known as "Red Shift" and "Doppler Effect", to knowledge is necessary. According to Doppler Effect, when source move towards supervisor then the frequency of wave feels increasing and when source moves away from the supervisor, then frequency decrease.
- In visible wave soectspe, frequency of red colors is minimum and wavelength is maximum whereas for violet, frequency is maximum and wavelength is minimum. It is seen that the livhl soectrsp from the Galaxy shift towards red colors. It is said to be the red shift.
- It is said that all the Galaxies are moving away from us, or the universe is in the position of the expansion. The fast expansion of the universe the centre of all the Modern theories of the origination if the Universe.
- Sun and revolving planets, secondary planets, meteors, comets, discursive planets etc. together are called the Solar system.
Planets :-
- They are the celestial objects, which revolve around the sun. They do not have their own light. They get heat and light from the Sun.
Secondary Planets :-
- They revolves around the planets. These are said to be the third generation of the celestial objects.
Outer and Inner Planets :-
- Mercury, Venus, Earth and Mars are called the inner planets, which are of the small size and high density. Jupiter, Saturn, Uranus and Neptune are called the outer planets and which are of large size and law density.
- Mercury is the nearest planets to sun and then comes Venus, Earth, Mars, Jupiter, Saturn, Uranus and then Neptune. Venus is nearest to Earth and then comes Mars, Mercury and Neptune.
