Theories of the Universe

Theories Of The Universe

Since the universe of galaxies is expanding in all directions, how did it all begin? According to one theory, proposed in 1927 by the Belgian mathematician Georges Lemaitre, all the material in the universe was once concentrated in a giant atom. The atom exploded some 10,000 million years ago, and the fragments, now galaxies, moved outward and away from each other forever. According to another theory the expansion will be followed by contraction to an extremely dense state. Another explosion will then bring about expansion, and so on ad infinitu, In yet another theory the universe is supposed to be in a steady-state, in the sense that as the galaxies move further away from each other new galaxies are constantly being formed to fill the gaps.

That each of these and other theories of the universe has its supporters indicates the great uncertainty of our knowledge. Science thrives on well-ordered speculation, but all the theorizing in the world is useless unless it is based on the facts of observation. In the next few years, many of our present theories will probably have to be revised or discarded, and a whole crop of new problems will arise. But this is as it should be if our knowledge, like the universe in which we live, is to remain in as a state of expansion.

Quasars

Astronomers have been studying star-like objects whose velocities of recession, judges from the red-shifts of the lines in their spectra, indicate that they out among the galaxies. These objects are called quasi-stellar radio sources or quasars. They are far too large and luminous to be stars. The lines in their spectra show that they are composed of intensely hot gases. They are intense source of radio emission. Some of them vary in their energy output and some are associated with one or more bright jets. Their precise nature remains a mystery and until this is solved we cannot be sure where they are comparatively near to us or extremely distant.

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Four quasi-stellar radio sources photographed with the 200-inch Hale telescope