## Sunday, December 11, 2011

### How big is the universe?

Can any one guess how big is the universe?  The answer to this question can only be guessed because no one can exactly tell how big is the universe.

Our earth is only a small and tiny dot in space which is revolving around another bright and larger dot, the Sun.  The Sun revolves around the center of Milky Way galaxy.  Milky Way is one of the billions of galaxies that exist in this universe.  These galaxies form clusters and these clusters form super galactic clusters.  In this way it goes on increasing and there is no end.

Does the universe has an end or it is going on expanding? As per Big Bang theory, the universe formed with a big bang and is now expanding.  There is no way to understand how big is the universe.  The only unit for measuring distance of objects far away is the light year which is the distance travelled by light in one year (Light travels at speed of 3,00,000 Kilometers per second). One light year is approximately equal to 9.45 trillion kilometers ( A trillion is 1000 billions or 1 followed by 12 zeroes).  The nearest galaxy is Andromeda galaxy is about 2,500,000 light years away from us.

The only way we can understand how big is the universe is by observing the light from as far as we can.  The Hubble telescope is one eye that can see the farthest point from us.  Just by observing the light from a far off place is not enough.  We need to find a way in which we can estimate the distance from where the light started.  This is achieved by use of cosmic candles, which are objects for which astronomers have a calibrated relation between distance and the brightness.  By using such cosmic candles, the farthest points of our universe have been explored by scientists.  Even then we cannot say how big is the universe but we can safely assume that the diameter of universe is 93 billion light years!!.