THE FAMED SCIENCE WRITER SUMMARIZES OUR PAST AND FUTURE KNOWLEDGE
Isaac Asimov (1920-1992) was a chemist who is best-known for his voluminous writings (he wrote or contributed to about 500 books) on science, science fiction, and even topics such as the Bible.
He wrote in the first chapter of this 1966 book, “Does the universe extend forever or is there an end somewhere? Does it expand and contract like an accordion, with each in and out motion lasting billions of years? Was there a time when it exploded once and for all and will the flying fragments separate until our own fragment is virtually alone in the universe? Does the universe renew itself and is it eternal, unborn, and undying? We are a fortunate generation, for we are watching a period of astronomy in which the answers to such questions and to many others equally intriguing may actually be at hand…
“[I]f we go back 2500 years to, say, 600 B.C., we will find that the entire Universe known to man was but a patch of flat ground, and not a very large patch either… By what process of reasoning, then, did the narrow surroundings visible to ourselves fade outward and outward and outward until no man’s mind can possibly grasp the size of the Universe we now speak of, or imagine the tiny insignificance of our physical surroundings in comparison with it? In this book I want to trace the steps by which man’s grasp of the Universe as a whole (‘cosmology’) and of its origin and development (‘cosmogony’) widened and deepened.” (Pg.13-14)
He points out, “Indeed, the flat Earth did not even appear to be commonsensical, if one used one’s eyes properly. If the Earth were really flat, then the same stars ought to be visible in the sky from all points… Yet it was the universal experience of travelers that if one traveled north, some stars disappeared beyond the southern horizon and new stars appeared from behind the northern horizon. If one traveled south, the situation was reversed. This could most easily be explained by supposing that the Earth curved in a north-south direction…
“Yet a cylindrical Earth was insufficient. It was the experience of men who lived on the seashore and dealt with ships that vessels heading out to sea did not merely grow smaller and smaller until they disappeared … Instead, they disappeared and did so hull-first as though they were moving beyond the top of a hill. This would be exactly what would be expected if the surface of the Earth were curved. What is more, ships disappeared in much the same fashion no matter toward which point of the compass they moved. Therefore the Earth was curved… in all directions equally; and the only surface that curves in all directions equally is a sphere.” (Pg. 16-17)
He states, “The celestial sphere appears to revolve about the Earth once in 24 hours... In so doing, it seems to carry the stars with it ‘all in one piece.’ … the stars do not shift position relative to one another but remain fixed in place year after year… It seemed natural to believe that the stars were attached to the vault of the sky… and until the 17th century that was, indeed, the common opinion. However, even prehistoric man must have noticed that some of the heavenly bodies moved in relation to the stars and were near one star at one time and near a different star at another. These bodies, therefore, could not be attached to the vault of the sky but must be closer to the Earth than was the sky itself. There were seven such bodies known to the ancients… These seven bodies were called 'planets’ ("wanderers’’) by the Greeks, because they wandered among the stars.” (Pg. 22-23)
He explains, “Once Copernicus had done his work, and the heliocentric theory was… slowly accepted, it became more difficult to attach the proper importance to man. After all, he inhabited only one planet of many, and man’s planet, moreover, was not the largest nor the most spectacular by far. Earth could not begin to compare with Jupiter for size or with Saturn for beauty.” (Pg. 62)
He states, “Isaac Newton was the first to study a man-made rainbow in detail. In 1666, Newton allowed a beam of light to enter a darkened room through a hole… and then pass through a triangular piece of glass or ‘prism.’ The light beam was bent, or ‘refracted’ … and fell on the wall opposite as a broadened spot of successive colors… Newton called the band of colors a ‘spectrum.’” (Pg. 75)
Harlow Shapley calculated the distances of the various 'globular clusters'. “By 1920, then, the position of man in the Universe had again been altered, drastically, and once again in the direction of increased humility. Copernicus had shown that the Earth was not the center of the universe, but he had been certain that the Sun was… Now Shapley showed, quite convincingly, that this was not so, that the Sun was on the far outskirts of the Galaxy.” (Pg. 84)
He asks, "Is it possible for the Sun to support this steady stream of mass at the rate of millions of tons per second? Yes, it certainly is, for the loss is infinitesimally small compared with the total vast mass of the Sun and trillions of years would have to pass before the loss at such a rate would consume even 1 percent of the mass of the Sun. Nor would the loss of mass seriously affect the nature of the Earth’s gravitational field.”(Pg. 121)
He argues, “If we ask… whether the Universe might not be eternal, we are essentially asking whether hydrogen fusion might not go on forever… For a finite Universe to be eternal… there must be some process that can reverse the fusion of hydrogen, restore the hydrogen and make it available for fusion once more… [A]t first glance this does not seem possible… the second law of thermodynamics… tells us that the amount of energy available for conversion to work decreases constantly… We could conclude, then, that … the energy of the Universe will be tied up irrevocably… and that will be the end of the Universe from our standpoint…Yet this conclusion rests on the assumption that the … laws of thermodynamics are really valid everywhere in the Universe… and that they are valid under all possible circumstances and not only those we have been able to witness.” (Pg. 185-186)
He concludes, “the salvation of the steady-state theory seems now a rather forlorn hope. Even [Fred] Hoyle, in 1965, finally gave up and accepts the Big Bang. He speculates, however, that the big bang may still be a local phenomenon; and that we are living in a big bang ‘bubble’ within a much larger Universe… There seems at present, however, no way of checking such a far-ranging supposition.” (Pg. 302)
Nearly sixty years old, this book is obviously ‘out-of-date’ in some aspects of its cosmology; but Asimov’s clear explanations of earlier matters remains very helpful to a general reader.