Universe of Galaxies

The Universe of Galaxies

The discovery that our Galaxy is one among millions of other galaxies was one of the great scientific events in the first quarter of the 20th century. These other systems of stars extend in their number to the very limits of observation with the giant photographic telescope of modern times. Some 2,000 million are thought to be within reach of one of the world’s largest optical telescopes, the 200-inch reflector of the Mount Wilson and Palomar Observatories. One extremely distant galaxy, photographed with this telescope, has an estimated distance of 5,000 million light-years. If we represented the Galaxy by a dime, this remote object would be over two miles away.

Other galaxies have a remarkable range in form, size, and structure. Some are much larger than our Galaxy, others are considerably smaller. Some, like our Galaxy, are disk-shaped systems, others are almost spheroidal. In the former we find a great deal of gas and dust, but the latter contain little, if any, interstellar material. Recently astronomers have discovered galaxies which are apparently interacting one with another; also galaxies whose nuclei or central parts are presumably exploding. All told, it is now reasonably clear that galaxies, like stars, evolve at different rates towards final dissolution. There is no permanence even among galaxies.

Universe and Galaxies : Deep Space Ships. The Man’s knowledge of the universe is very small, but the quest is endless. Illustration: Elena

The history of astronomy from the time of Newton to the present day is one of great interest, but the main threads of early enquiry become more difficult to trace as we approach the modern period. One present problem is the almost overwhelming rate at which new knowledge is being acquired. If the rate increases, which is more than likely, our picture of the universe in, say, one, two or three hundred years will be completely different from that at present. As different perhaps, as the present one is from the picture drawn by Aristotle.

Another sobering thought is that the more we discover, the more we find awaits discovery. The quest is endless. So, in the last analysis, Man’s knowledge of the universe will always be small compared with what he has still to discover.