Universe

 The Universe and Beyond

Universe consist of everything from atoms to giant Galaxies. The observable Universe is estimated about 93 billion light years in Diameter, the most widely accepted theory about the origin of universe is the Big Bang Theory. At first universe consisted of very hot, dense fireball of expanding, cooling gas. After many years the gases began to condense into localized clumps called the Protogalaxies. After a long span of time these protogalaxies began cooling, condensing, forming galaxies in which first stars were born. Thus, giving rise to universe as we know it. Universe is still Expanding, although there are localized areas in which objects are held together by gravity for example, many galaxies are found in cluster. The Big Bang Theory is supported by the discovery of faint, cool background radiation coming evenly from all directions. This radiation is believed to be the remnant of the radiation produced by the Big Bang. Small "ripples" in the temperature of the Cosmic Background Radiation are thought to be evidence of slight fluctuation in the density of early Universe, which resulted in the formation of Galaxies.

• Astronomers still don't know whether the Universe is Finite or Infinite? 
• Will it stop or continue expanding forever? 
• Is there some kind of Multiverse?

You can find more information on Universe by these PBS videos.