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Cosmology and Earth Science
The doctrine that the earth is not the centre of the universe, that it is not immovable but moves with a daily rotation, is absurd and both philosophically and theologically false.
The Congregation of the Inquisition against Galileo
The trouble with the word `cosmology' is that it means different things to different people. To the philosopher and the theologian, cosmology is a speculative study of the meaning of the universe. To the historian of science, the term refers to a particular account of the universe as dreamed up by various imaginative people in the past. To the astronomer, it means the study of what we can find out about the structure of the universe. To the astrophysicist, cosmology is concerned with the theories of the origins and evolution of the universe.
There are not too many professional cosmologists, and scientific cosmologists as distinct from philosophers, theologians and historians -- have to know a lot. As well as covering the whole of astronomy, they also need a thorough grasp of mathematics and physics. But in a sense we are all cosmologists. From the earliest times people have wondered about the origin and nature of the universe, and since people first put down their thoughts in writing, many of these speculations have been documented and preserved.
Before we get to the stage of scientific blundering, we need a brief review of what went before. Therewere plenty of blunders, but they were not scientific. Early cosmology came before science and had its origins in the age of magic when the best explanation people could come up with was that the world was run by ghosts or spirits sometimes friendly, but more often evil and malign. These ideas were necessarily based on human experience, and the spirits were credited with the same emotions and motivation as those of people but, of course, with a great deal more power. Even today, none of us is capable of envisaging anything totally different from what we know: we are the prisoners of our experience. This is why the word `anthropomorphic' (human-shaped) is so often used in connection with accounts of this kind. It also explains why any attempt to account for matters outside our experience will usually produce statements that may sound significant but are actually meaningless.
Like most things on earth, the sun, moon and stars were the abode of spirits, and all natural phenomena were attributed to the ill-will, or approval, of these spirits. In The Golden Bough (1890), the Scottish anthropologist James Frazer (1854-1941) describes how, as knowledge of the world grew, magic gradually evolved into myth and religion. Early people shared our need for explanations and their writings are full of accounts of creation myths. The earliest known are those of the Sumerians, who lived in the fertile region between the great Tigris and Euphrates rivers, the area occupied by modern-day Iraq. They decided that everything began in an `encircling watery abyss' which was acted on by a blind force to produce the gods and goddesses that created the universe. The ancient Egyptian myths also involve a watery abyss in which lived a formless spirit that carried within it the source of all existence, which created the gods and goddesses and the universe.
In fact, these statements don't actually explain anything. Oddly enough, people's desire for `explanations' are readily satisfied by firm statements, especially if delivered in an authoritative tone, even if they don't mean a thing. This characteristic of humans has not changed since the time of the Sumerians, six thousand years ago. You can come across examples of this every day, and not only in the case of simple-minded and ignorant people. One of the responsibilities of science is to distinguish between meaningful statements and merely emotionally gratifying noises.
The Indian myths did rather better than those of the Sumerians. Although they contained an immensely complicated history of gods, they were more sophisticated in acknowledging that the ultimate origin must remain unknown. The Rig-Veda asks: `Who can speak of the origins of creation? Did he who controls this world make it? Does he know?' Later documents, commenting on the beginning, state: `All was darkness, without form, beyond reason and perception, like sleep.' From this arose the all-creating Lord.
Chinese ideas began almost to border on science. They were complex and subtle and incorporated the concept that creation was based on earth, air, fire and water a completely wrong idea which was also later adopted by the Greeks but, at least, an attempt at a unifying explanation. They also incorporated the principle of the opposing but complementary qualities of yin and yang. This is an elegant concept, but there is no objective evidence that it is anything more than that. The early Greeks decided that the universe was made from four things, or, in more impressive language, primordial entities -- the void or Chaos; the earth or Gaea; the lower world, known as Tartarus; and love or Eros. These somehow worked together to give rise to a whole collection, or pantheon, of gods, including Uranus, the sky god. In the Christian tradition, creation, as recounted in the book of Genesis, was the work of a single God.
All early cosmological ideas quite naturally put humans at the centre of the universe. Aristotle's cosmology of the fourth century BC placed the earth at the middle of the universe, and this idea, which was also held by the second century Greek astronomer Claudius Ptolemaeus (c.90-168), better known as Ptolemy, actually persisted until the beginning of the sixteenth century. Ptolemy's great compendium of astronomy, the Almagest, contained a star map and a treatise on the fixed stars; this was based on the work of an earlier Greek astronomer called Hipparchus (fl. second century BC), who had set forth the basic principle of astronomy and compiled a catalogue of same 850 fixed stars. Ptolemy was less interested in science than in putting across his cosmological ideas. The fact is that the Greeks were not very keen on real experimental science, which they considered to be beneath their dignity. They considered that knowledge should be obtained by pure thought. Philosophy was the proper activity of a gentleman; finding out by looking and trying was strictly for slaves and other inferiors. This was a major blunder.
Simply on the grounds of `a sense of the fitness of things', Ptolemy assumed that the earth was the central pivot around which the sun and stars revolved. Surrounding the earth, he stated, were eight concentric transparent spheres that could rotate around each other. Each of the first seven carried a single heavenly body the moon, sun and five planets while the eighth carried all the fixed stars. Beyond were the heavens, the abode of the blessed. Ptolemy was perfectly aware that there were unequivocal observations that did not fit into this scheme, but he was more interested in expounding his imaginary theories than in accounting for undeniable facts. So he had to produce some wildly elaborate explanations to account for such things as the apparent irregularity of the movement of the planets.
So far, we are at a fairly primitive stage of science the stage of bold assertion without proof. Ptolemy's speculations were pure imagination and were not based on observation. No one knows when the first serious astronomical observations were made. Some people think they go back to the times when the ancient stone circles and other megalithic structures were set up. Stonehenge, for instance, which probably dates from around 3000 BC, may possibly have been intended as some kind of astronomical instrument. It is impossible to be sure about this. We have to come to much more recent times to see the dawning of true scientific observation.
Much reliable astronomical information was derived from naked eye observation, long before the telescope was invented. This observation was not always as careful as it might have been and, for instance, many tables of the movements of the planets, relative to the fixed stars, were published with misleading data. Some of the early observations were, however, remarkable, notably those of the great Polish astronomer Nicolas Copernik (1473-1543), better known as Copernicus, the latinized form which it was then fashionable to use, who, incidentally, spent many years correcting old tables. Among many other things, Copernicus was actually able, simply by careful observation and record-keeping, to show that if you imagine the earth's axis extended out into space, it will be found to move in a circle and will eventually generate a cone. This was the explanation of the slow movement of the position in the year of the two points at which the day and night are equal (the precession of the equinoxes). This phenomenon had in fact been described by the above-mentioned Greek astronomer Hipparchus some sixteen hundred years before.
After naked eye observation came the dawn of scientific astronomical instruments. The first important one was the quadrant a simple form of protractor with a sighting rule, or alidade, used to measure the angle between a star, or the sun, and the horizontal. A plumb line was used to ensure that the instrument was kept horizontal. With a quadrant, you could measure the altitude of the North Star and then, by checking the time from the altitude of the sun and consulting a table, establish the latitude of the point from which the observation was made. This was a matter of some importance to ocean-going stalwarts.
The astrolabe a term meaning `star finder' was a more refined form of quadrant and was made in various models. One popular and portable form consisted of two flat metal discs, 7.5 to 25 centimetres (3 to 10 inches) in diameter, capable of being rotated on a common centre. One side of one disc had degrees around its edge and was equipped with an alidade for sighting the star or the sun. The other side was engraved with a star map and lines to show the horizon, the zenith and the lines of azimuth and altitude for particular latitudes. The most important treatise on the astrolabe a book that was studied for centuries by navigators and astronomers was, surprisingly, written by the English poet and humorist Geoffrey Chaucer (1340-1400) of Canterbury Pilgrims fame. In the eighteenth century, the astrolabe was replaced by the more accurate sextant, invented by Isaac Newton.
The most notable earliest exponent of the quadrant was the Danish pioneer of astronomy Tycho Brahe (1546-1601) whose work marked the real beginning of scientific astronomical research. Tycho did not have the benefit of a telescope, which had not yet been invented, and had to develop new instruments for himself. Among other things, he designed and had constructed an enormous but rather crude astronomical quadrant of radius fourteen cubits (about 7 metres), divided into minutes. This quadrant enabled him to locate the position of hundreds of fixed stats with remarkable accuracy, and made him famous.
Tycho's enthusiasm for science and insistence on exactness paved the way for future advances and inspired his assistant Johannes Kepler to even greater efforts. In November 1572 Tycho observed a new star in the constellation Cassiopeia, where no star had previously been observed. This star was brighter than Venus but faded away in 17 months. Tycho's observations recorded all its changes, and proved that it lay beyond the moon at an immeasurable distance away. He published an account of this in the book De nova stella in 1573 and soon had an international reputation as an astronomer. Since that time, such exploding stars have been called `novas'.
Tycho was one of those characters, unusual but immensely important in the history of science, whose contribution consisted less in the advancement of knowledge than in the promotion of method and in the stimulation of enthusiasm. Regrettably, Tycho subscribed to the view of Ptolemy that the earth was the centre of the universe. Possibly to appease his many enemies at Court, he claimed to reject the then theologically heretical sun-centred theory of Copernicus (see below), and insisted that the sun with its train of planets circled around the earth. Fortunately, this rather weak compromise had no permanent influence on science.
Tycho carried astronomical observation as far as was possible with the quadrant only. His accuracy was remarkable, his readings being correct to about two minutes of arc. His tables of the motions of the planets and the sun were better than any that had gone before and he established the length of the year to less than a second. This showed the existing calendar to be causing a cumulative error and in 1582 Pope Gregory XIII agreed to a correction. Ten days were cut out of the calendar, producing an interesting and illuminating sidelight on human understanding. Thousands of people became convinced that their lives were being shortened and in their fury went on the rampage, rioting in the streets. It is easy for us to smile at this example of human folly, but these people were deadly serious and genuinely believed that ten days had been stolen from their lives. There are plenty of examples of similar irrationality, even today, among non-scientific people. Even the scientists are by no means entirely rational in their private lives, but any lapse of rationality in their work will be quickly detected and pointed out by their peers.
Other less major corrections to the calendar were also ordained and the Gregorian calendar is now in universal use. The respect with which Tycho's name was held by scientists was later shown when it was given to the most prominent crater on the moon. Ptolemy, and other astronomers, had to make do with smaller craters.
Ptolemy's book remained the sole scientific authority on astronomy until his beliefs were challenged by Copernicus, the real founder of modern astronomy. By careful observation he was able to compile accurate tables of the movement of the planets. These, together with his painstaking calculations, clearly indicated that, in defiance of Ptolemaic orthodoxy, the planets, including the earth, rotated around the sun. Copernicus incorporated his life's work into the book De revolutionibus orbitum coelestium (On the Revolutions of the Heavenly Spheres), completed in 1530 and published just before his death in 1543. A printed copy was put into his hands as he lay on his death-bed.
Copernicus's demonstration that the earth was a planet moving round the sun seemed to most people of the time, at best, foolish and perverse and, at worst, heretical and damnable. The earth was obviously stationary and the sun visibly moved round it, and, moreover, it said as much in the Scriptures. Where, in Copernicus's scheme, was Heaven? Ironically, Copernicus, who was an ecclesiastic, had dedicated the book to the Pope, and a Cardinal had actually paid the cost of printing it presumably without reading it.
It took the Church some little time to realize that it had been nurturing a viper in its bosom. At the time, few could understand the learned explanations in this book. But when its central conclusions finally became apparent, the Church hurled anathemas at its author and at anyone who believed him. Had he lived, it is probable that he would have been burned at the stake, as were others who insisted that he was right. The Copernican cosmology was a revolution not only in science but also in human thought, and it was not until the eighteenth century that it was fully assimilated.
Modern cosmology is largely concerned with the problem of the origin of the universe. It is only in the twentieth century that cosmological theory has advanced sufficiently beyond the realm of vague speculation to provide anything approaching a plausible account. Today's cosmologists are no longer the fanciful dreamers of the past but are hard-headed scientists whose hypotheses are made on the basis of known facts. Their work has become very complex, involving astronomy, mathematics, physics, and, for some, philosophic speculation. At the same time it has become far more plausible, because it is based on an increasing volume of established fact.
The finding that triggered off modern cosmological thought was the discovery in the 1930s, by the American astronomer Edwin P. Hubble (1889-1953), that the light from all distant galaxies is coming from a receding source. This is the only acceptable explanation of the fact that the light coming from these galaxies is observed to be shifted towards the red end of the visible spectrum. The cause of this is the Doppler effect. You will be more familiar with this in the context of sound than that of light, but the principle is the same. When a moving sound source approaches you hear the pitch of the sound rising, and when the source passes and retreats the pitch falls. You can consider that the sound waves from the approaching source are `compressed' so that more arrive in a given time, causing a raised pitch; and you can think of the waves from the retreating source as being `stretched out'.
In 1948 the Russian-born American physicist George Gamow (1904-68), in a theory concerned with the origin of the light elements, interpreted this Doppler effect as demonstrating that the universe was expanding. Nearly everyone now accepts this as a fact. This expansion, however, implied that it had originated in a single point billions of years ago. This idea received wide support but was not widely known outside scientific circles until the British cosmologist and science fiction writer Fred Hoyle (1915-), in a highly critical and would-be destructive account, referred to it, satirically, as the `Big Bang' hypothesis. Ironically, Hoyle's comment had quite the opposite effect to what he intended. Popular imagination and attention was caught by the phrase `Big Bang' and soon everyone had heard of the theory.
Hoyle strenuously opposed the Big Bang idea. He pointed out that the original calculations of the age of the universe, based on Hubble's figures, indicated that it was younger than known geological evidence suggested. The theory also failed to account for the formation of elements heavier than helium. Hoyle and two other young Cambridge scientists, Hermann Bondi and Thomas Gold, had already, in 1946, proposed a completely different hypothesis for the origins of the universe the steady state theory. This, they claimed, could account for the expansion without involving an unrealistic time-scale. The steady state theory proposed that the universe had had no beginning and that matter is continuously created at exactly the rate required to compensate for the expansion. In this way the overall density of the universe would remain constant. Critics suggested that this theory contravened the law of conservation of mass and energy. Hoyle replied that so did Big Bang.
The steady state theory became linked to the idea of nucleosynthesis an explanation of how heavier elements might be made from hydrogen and helium. This theory soon commanded a great deal of support from many who found the Big Bang idea unpalatable. It received a severe setback, however, when observations at Mount Wilson observatory showed that the galaxies were much further away than had previously been supposed. This meant that the calculated age of the universe had to be increased to a minimum of 10 billion years a figure entirely consistent with known geology and the Big Bang hypothesis. The steady state theory had another major snag it predicted a zero temperature for space, which is absurd.
The final blow to the steady state theory came in May 1965. Two scientists working on radio astronomy at the Bell Laboratories, Arno A. Penzias (1933-) and Robert W. Wilson (1936-) were much troubled by microwave noise in their receiver. Initially attributed to pigeon droppings, every effort to discover the source of this interference failed. Eventually, careful tests showed that it was coming from everywhere in the universe. At this point it should be mentioned that radio waves, light, heat, X-rays, gamma rays and cosmic rays are all the same kind of radiation electromagnetic. They differ only in wavelength. So there is nothing odd about picking up heat radiation with a radio receiver. All you need is one that can tune to the right very short wavelength.
The noise that Penzias and Wilson were detecting has a wavelength corresponding to the radiation emitted by a black body at a temperature of 2.74 kelvin (K); this is a very low temperature; just a little above the lowest possible temperature, absolute zero (0 K, or -- 273.15°C). Penzias and Wilson went to see the physics professor Robert Dicke at Princeton University and were astonished to learn that Dicke had already predicted exactly such radiation. In fact, the people in his department were actually in the process of constructing a radio telescope to detect it.
Every body in the universe that is at a temperature above absolute zero emits electromagnetic radiation. These 2.74 K signals do not, however, come from cold bodies. They were actually emitted, a very long time ago, by white-hot matter moving rapidly outwards. On their way to us, travelling, like all electromagnetic radiation, at the speed of light, they have undergone so profound a red shift as to increase their wavelength to that corresponding to a microwave frequency. Calculations based on the parameters of the now standard model of the origins of the universe agree with numerous measurements made during and since the 1970s of the wavelength and uniformity of the 2.74 K radiation. When the news of the findings at the Bell Laboratories was published, support for the steady state theory collapsed. Today, no alternative theory to that of the Big Bang is seriously considered by the experts.
So now we have reached this stage of extraordinary sophistication in cosmology, can we congratulate ourselves that we have explained the origin of the universe? Certainly not. Explain all this to any bright child and he or she will say: `Yes, but what was there before the Big Bang started?' Don't expect to get an answer to this question, even from the most egg-headed astrophysicist. There is no answer, and, for a very good reason, there is no point in trying to look for one in science. Science is concerned with demonstrable fact and deals only in matters of which we can have direct or indirect experience. Its function is to describe how things are. This gives it plenty of scope, but it also imposes strict limits. Science has nothing to say on matters that lie outside any possible human physical interaction because such matters do not provide us with the essential data that science uses.
To the scientist, when acting as a scientist, questions such as `What was happening before the Big Bang?' actually have no meaning. You can ask them as often as you like, but you are just making pointless noises. As we have noted, scientists are, however, human beings and they share the human need for explanations. In contexts such as this, scientists, like anyone else, may fall back on non-scientific activity. They may experience religious faith, go in for spiritualism, propose elaborate theologies of their own, and so on. All this is fair enough but scientists are the first to recognize that such things have nothing to do with science.