THE UNIVERSE
Universe means
unimaginably vast space which is unbounded with its dots of body's are by
definition, the universe includes everything that abounds in space, and space
is filled with matter which varies from the tiniest and cosmic particle to the
gigantic galaxies. The universe is known to composed of many types of
comparatively small and large dense Bo e.g., the galaxies, the constellations
(star groups), the stars, the planets other heavenly bodies.
The totality of the
heavenly bodies from grand galaxies down to the sm cosmic dust filling the
endless space describes the Universe w dimension is beyond our comprehension.
There are t divergent
theories on the mode of origin of the universe. These are the B Bang and the
Steady State theories. According to 'Big Bang' theory universe has a finite
beginning, through a tremendous explosive expansion superdense and very
condensed matter. The "steady state" theory states the universe
expands through a process of continuous creation of matt which (the process)
remains unchanged through eternity.
Galaxy: A galaxy is a
rotating stellar system (star system) consisting of a swarm of stars which are
held together by mutual gravitational attraction. In other words, a galaxy is
an enormously large cluster of stars. Our galaxy to which the sun along with
its planet families belong is an aggregate of aboii one hundred billion stars.
Ours is called "Milky way" galaxy which looks like a discuss (a
disc-shaped metal used in discus throw) when viewed through powerful optical
telescope.
It is a pancake
shaped whirling body which is gigantic in size. A part of the "Milky
way" is clearly seen with naked eye as a faint luminous broad band across
the sky during a clear autumn night. It takes about 100,000 years for the light
to go from one end of our galaxy to the other end. There are billions of
galaxies in the universe. The nearest galaxy comparable to our Milky Way in
size is the Andromeda galaxy.
Stars and Planets: A
star is a self-luminous and incandescent globe of hot gases. Stars produce
their own light and are seen twinkling in the sky. The stars vary in size,
temperature and constituent materials. Many stars occur in pairs (twins). They
may even occur in triplets or quadruplets.
Most of the stars
have their own systems of planets and satellites revolving round them. In such
cases, a star constitutes a star system. Our sun is a star having its own
planetary and satellite system called the "solar system".
Planets and
satellites are non-luminous heavenly bodies which shine only because of
reflection of star (sun) light from their surface. The planets whirl round
their stars in definite orbits.