©If one looks at the sky on a clear,moonless night,the brightest objects one sees are likely to be the planets Venus,Jupiter,Mars and Saturn.There will also be a very large no. of stars ,which are just like our own sun but much farther from us.Some of these fixed stars do ,infact,appear to change very slightly their positions relative to each other as the earth orbits around the sun:the are not really fixed at all!This is because they are comparatively near to us.As the Earth goes around the Sun,we see them from different positions against the background of more distant stars.This is fortunate,because it enables us to measure directly the distance of these stars from us:the nearer they are,the more they appear to move.
The nearest star ,called Proxima Centauri,is found to be about four light-years away that is light from it take 4 years to reach our Earth that is 23000000000000 miles[23 million million miles].Most of the other stars that are visible to the naked eye lie with in a few hundred light years of us.Our sun,for comparison is a mare 8 light-minutes away!The visible stars appear spread all over the night sky,but are particularily concentrated in one band,which we call the Milky Way.As long ago as 1750,Some astronomers were suggesting that the appearance of the Milky Way could be explained if most of the visible stars lie in a single disclike configuration,one example of what we now call a spiral galaxy .Only a few decades later,The astronomer,Sir William Herschel confirmed his idea by painstakingly cataloguing the positions and distances of vast no. of stars.Even so the idea gained complete acceptance only early his century.
Our modern picture of the Universe dates back to only 1924,when the American astronomer Edvin Hubble demonstrated that ours was not the only galaxy.There were infact many others,with vast tracts of empty space between them.In order to proove this,he needed to determine the distances to these other galaxies,which are so far away that ,unlike nearby stars,they really do appear fixed.
We live in a galaxy that is about one hundred thousand light-years across and is slowly rotating;the stars in its spiral arms orbit around its centre about once every several hundred million years.Our Sun is just an ordinary average-sized yellow star,near the inner edge of one of the spiral arms.We have certainly come a long way since Aristotle and Ptolemy,when we thought that the Earth was the centre of the Universe!
Stars are just the pinpoints of the light They are so far from us. Due to their point size,whenever the intensity of light increases or decreases due to large distance between us,it appears to be blinking or fluctuating.When ever we see a huge no. of stars in the night sky,it always create 100% possibility of life existence some where else.
Earlier,Most People expected the galaxies to be moving around quite randomly,and so expected to find as many blue-shifted spectra as red-shifted ones.Nearlly all were moving away from us !The farther the galaxy, the faster it is moving away!This is great witness for Big Bang supporters.It means the gravitational attraction of the bodies cannot contract the universe or we can say that gravity was unable to hold all the matter togather after the early beginning of time.
The assumption that the universe looks the same in every direction is clearly not true in reality.As we have seen,the other stars in our galaxy from a distinct band of light across the night sky, called the Milky Way.But if we look at distant galaxies,Their seems to be more or less the same number of them.So the universe does seem to be roughly the same in every direction, provided one views it on a large scale compared to the distance between galaxies,and ignores the diferences on small scale.
In short, any point of the universe can be reguarded as centre of the Universe which is expanding equally in every direction having radius’∞’ infinity!
Mr Universe 
Very nice
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