The Universe
People's concepts of what constitutes the Universe have changed drastically over the ages . At first the Earth was put at the centre of the universe. Then Earth was found to be just a planet, and thought Sun as the centre. Soon Sun was found to be an ordinary star, which was part of Galaxy and man began to think that galaxy was the universe. Now scientists believe that there are many galaxies and that clusters of many galaxies make our Universe . Continuing this trend of astronomical upsizing, the latest speculation among Astronomers is that maybe the universe we know is only of the many -and that there may be many universe, making a vast Superuniverse.
The Universe was called COSMOS, as opposed to chaos, when it was first conceived of as an ordely unit, and the studies relating to the Cosmos were known as Cosmogony or Cosmology. Today we speak of them as Space Sciences.
(Click to read about Ancient Cosmology)
They had different ideas about what the universe was like. But obviously, people started stargazing long before the early civilizations grew up. When they learned how to write and read they started recording what interested them.
(Click to read about Astronomy)
The word astronomy is from the Greek astron meaning stars. Astronomy is the scientific study of the heavens and all that in therein. In it is not to be confused with astrology which lacks any kind of scientific basis and encompasses the belief that heavenly bodies affect human lives.
Galaxies are huge congregation all stars held Together by force of gravity. They are so big that they are also called Island Universe. Studies of distant spaces with optical and radio telescope indicate that there may be about 1.3 trillion galaxies in the visible Universe. Galaxies seems to be scattered in space. Galaxies tend to be grouped together into clusters, and some clusters appear to be grouped into superclusters all the galaxies will look at all display red shift in their Spectra indicating they are moving from from us.
There are millions of starts in the sky. We see only a few thousands of them with the naked eye. In the whole heavens, fewer than 6000 starts are bright enough to be visible; and at any one time , less than 2500 stars are visible above the horizon.
(Click to read about size of Universe)
No one knows whether the universe is finite or infinite in size. Albert Einstein described unbound the universe as 'finite but unbound' meaning that the frontiers cannot be observed even though they are definitely there.
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