Evolution in the Matter Era
Discussion
Fred Spier:
The Big Bang and the Radiation Era
"According to our modern creation story, at the beginning of time and space there was a lot of undifferentiated energy/matter packed extremely close together. At the instant of creation, the Universe was infinitely dense and unimaginably hot. At that very moment, the Universe was entirely undifferentiated. In other words, the instant of the Big Bang was the most simple and basic regime imaginable.
The Radiation Era first witnessed the emergence of the three basic forces that organize matter: the nuclear force, electromagnetism and gravity. The first level of material complexity would later be reached as a result of the nuclear force – which acts by far the strongest on very short distances. This complexity consisted of the smallest, subatomic and atomic particles. Electromagnetism, the intermediate force, would take care of the second stage, in which atoms, molecules and complexes of molecules were formed. The effects of gravity, the weakest of the three forces but with the longest reach, would kick in the last and would bring about all the larger structures in the observable Universe.
During the first period of cosmic expansion, temperature differences were very small, if they existed at all. Yet as a result of the cosmic expansion, temperatures began to drop rapidly. Radiation dominated the early Universe, while any stable large-scale matter did not yet exist. Eric Chaisson calls, therefore, this early phase of cosmic history the Radiation Era. Yet during this period, as the Universe expanded while the temperature and the pressure dropped steeply, all the elementary particles emerged out of radiation, first the heavier hadrons, mostly protons and neutrons (within a fraction of the first second), followed by the lighter leptons, such as electrons and neutrinos. Their emergence took about 100 seconds. Yet according to the standard cosmological view, most of these subatomic and atomic particles that were originally formed soon annihilated one another and were reconverted into radiation. Only a tiny fraction of ordinary matter survived. This left-over stuff constituted the building blocks for all the known material complexity that followed.
This period was followed by the nucleosynthesis of some lighter elements, most notably helium and deuterium as well as a few heavier elements. Yet the expansion went so fast that most matter remained in the form of protons, which are the nuclei of hydrogen. This led to a primordial composition of the Universe of about 70 per cent hydrogen and 27 per cent helium, while the rest was made up by a few heavier chemical elements. This whole process took about fifteen minutes. Apparently, the expansion of the early Universe created Goldilocks circumstances for this sequence of events.
It is not completely clear whether radiation was completely uniformly distributed during this period. At that time, as Eric Chaisson emphasizes, entropy was at a maximum. Current measurements of the cosmic background radiation, which dates back to about 400,000 years after the Big Bang show minor fluctuations. I wonder whether this may also provide an indication of emerging complexity of the energy regime of the very early Universe.
The Matter Era
After about 50,000 years of cosmic expansion, the Radiation Era came to an end. By that time, the temperature of the early Universe radiation had dropped to around 16,000 Kelvin.
Since the Universe kept expanding, the temperature of the radiation kept dropping. As a result, the importance of radiation decreased. Cosmic expansion had, however, no similar effect on matter. Although, seen on the scale of the Universe, matter became more diluted, the particles themselves did not change in nature. As a consequence, relatively speaking, matter became increasingly important. According to Eric Chaisson, the Matter Era had begun. This transition marked the first formation of stable material complexity. During the early phase of the Matter Era only a few types of small building blocks of matter existed, mostly protons, neutrons and electrons. No heavy chemical elements were formed yet. The expansion would have gone so very quickly that the conditions of high temperatures and pressures needed to cook heavier elements did not prevail for long enough. As a result, the possibilities for greater complexity in the early Universe were limited.
Here we see a critical factor for the formation of complexity in operation, namely time. It takes time, often a great deal of time, for complexity to emerge. In certain situations the energy flows and levels may be right for the emergence of greater levels of complexity. Yet if such conditions prevail for only a short period of time, no substantial amounts of such complexity can form. The destruction of greater levels of complexity, by contrast, can take place very quickly indeed.
After about 400,000 years of expansion the Universe had cooled down to about 3000 Kelvin, while the pressures had been dropping also. These lower energy levels allowed negatively and positively charged particles to combine for the first time and form matter regimes of greater complexity, first atoms and later molecules. This process had a marked effect on radiation, since it is far less affected by neutral particles than by charged ones. Radiation could now suddenly travel throughout the Universe virtually unimpeded. As a result, the Universe became transparent. The cosmic background radiation of 2.73 K that can be observed today dates back to this monumental change.
This ‘neutralization’ of the Universe also marked an important transition for the factors which determine the levels of material complexity that can be attained. Before that time, only the energy levels limited the levels of material complexity. Yet after about 400,000 years of cosmic expansion, the formation of complexity would come as a result of the interplay between energy levels and energy flows. Since that time, all subatomic complexity has been determined by the nuclear force (in some conjunction with the ‘weak force’, now thought to be part of electromagnetism). The intermediate scales of complexity, from atoms and molecules up to stars and planets have come as a result of the electromagnetic force and of gravity, while all the large-scale complexity, ranging from our solar system to galaxy clusters, has been shaped by gravity.
According to Eric Chaisson, cosmic expansion has been vital for the formation of complexity (2001: 126). Because in the early Universe entropy was at a maximum, for complexity to form, some sort of entropy trash can was needed, since the formation of local or regional order requires the formation of more disorder somewhere else. The continuing expansion of the Universe provided increasing room for entropy, and thus functioned as a huge entropy trash can, which can take up low level energy, most notably heat. And as long as the Universe keeps expanding, the cosmic entropy trash can will get bigger. As a result, it can store increasing amounts of low level energy. This – and this alone – allows energy levels to keep flowing and greater complexity to exist.
While the cosmic trash can was getting bigger, another major trend started: energy differences began to level out. Both these processes have made possible the rise of complexity. Since the energy supplies of the Universe as a whole are not being replenished, and assuming that the Universe will keep expanding for the foreseeable future, the long-term effect of all these effects will be the overall increase of entropy everywhere. In other words, in the very long run the Universe will become a rather dull place.
Galaxy Formation
The unrelenting expansion of the Universe led to a further decrease of the temperature levels. As a result, gravity began to shape the ways in which matter clung together. Since that time gravitational energy has driven the formation of larger structures, ranging from asteroid-sized clumps of matter to clusters of galaxies. Only during the first two billion years or so were the conditions right for galaxy formation. Even while they were being formed, most galaxies began to fly away from one another. This defines, in fact, the expansion of the Universe. In a number of cases, however, gravity kept galaxies close together, while some galaxies actually merged with others. Yet with the passage of time, these occurrences diminished in importance.
It is now thought that the rather mysterious ‘dark matter’ may well have played a major role in the process of galaxy formation. The existence of dark matter is inferred by its gravitational effects on galaxies, which cannot be sufficiently explained with the aid of the established theory of gravity. Today, astronomers think that there is a great deal more dark matter in the Universe than ordinary matter. Yet other than through gravity, dark matter would not, or only very weakly, interact with the matter and radiation we are familiar with. According to this model, large amounts of dark matter would have begun to clump well before the neutralization of the Universe, thus forming ever larger gravitational structures, which subsequently attracted the baryonic matter we are familiar with, which coalesced into galaxies. This would have been the major mechanisms causing galaxy formation.
While the Universe kept expanding, the galaxies appear to have retained their original sizes more or less. As a result, the Universe became more differentiated. Over the course of time within galaxies greater levels of complexity would arise. The expanding intergalactic space, by contrast, was mostly empty and would therefore never become very complex. Yet intergalactic space did provide a cosmic trash can for low level energy produced in galaxies. This made possible the rise of greater complexity within galaxies.
The cores of newly forming stars within galaxies began to produce circumstances that were similar to the early stages of the Matter Era. Temperatures rose to 107 Kelvin and above, while pressures would go up to 1011 atmospheres and higher. The major difference with the early Matter Era was that stars last far longer than the period in which the first elements were cooked. This means that there was far more time available to produce heavier chemical elements. As a result, stars would become the major furnaces for producing greater levels of nuclear complexity.
The mechanism which drove this process was nuclear fusion. After enough hydrogen nuclei had gathered under the influence of gravity, temperatures and pressures would rise to the extent that nuclear chain reactions could ignite, forging one helium nucleus out of four hydrogen nuclei. During this process some matter was converted into energy, which was subsequently radiated out into the Universe. Over the course of time, this radiation would drive the formation of most biological and cultural complexity.
All stars came into being by gathering matter and energy from their surroundings through the action of gravity. Yet after their initial formation, harnessing external matter was no longer needed for their continued existence. In fact, stars shine thanks to the generation of energy within themselves (under the pressure of gravity) and not through a continuous extraction of matter from their environment. In contrast to living beings, which continuously have to extract both matter and energy from their surroundings in order to maintain their complexity, stars do not need any new matter in order to shine.
During the early period of galaxy formation many huge stars formed that burned very quickly and subsequently exploded. This released gigantic energy flows, which would have destroyed most, if not all, nearby levels of intermediate complexity that might have formed, such as planets or perhaps even life. In other words, a great deal of energy ultimately derived from the Big Bang was spent without creating any such complexity. Yet these explosions did create the right circumstances for heavier chemical elements to form.
Increasing Complexity of the Elementary Building Blocks
During the early phase of galaxy development, stars consisted of only very few elements, mostly hydrogen and helium. This severely limited the level of complexity the early Universe could attain. Over the course of time, however, an increasing variety of building blocks came into being. This was the result of nucleosynthesis, the forging of new elements within stars. Stellar nuclear fusion processes gradually but inevitably lead to the depletion of the main fuel supply, hydrogen. In larger stars under the continuing impact of gravity the core then heats up to temperatures higher than 108 Kelvin. New nuclear fusion processes begin, in which helium is converted into ever heavier chemical elements, up to iron. Also, this situation is a relatively stable steady state. In contrast to the circumstances prevailing right after the Big Bang, when expansion went so very quickly that the formation of heavier chemical elements was not possible, in stars approaching the end of their lives there is sufficient time for more complex atomic nuclei to form. As a result, these chemical elements are comparatively abundant.
After these processes are completed and no further nuclear fusion is possible within stellar cores, a star may first implode under the action of gravity and then explode as a result of sudden further nucleosynthesis. During these short-lived yet very violent circumstances even heavier chemical elements are formed, up to uranium. Since these circumstances last only a very short time, heavy chemical elements such as gold and uranium are rare. Over the course of time, these so-called nova and supernova events began seeding the surrounding space with these new forms of complexity. In other words, they enriched nature's construction kit with an increasingly large assortment of building blocks. As a result, more complex toys could be built. These chemical elements were sometimes dispersed to areas where the circumstances were favorable for the rise of further complexity. When close to the outer edges of galaxies new stars and planets formed from galactic dust clouds and assimilated these new chemical elements, new levels of complexity could emerge. On the surface of one such well-positioned planet, these chemical elements would become the essential building blocks for biological and, much later, for cultural complexity.
Stars and Planets
Most complexity within stars exists thanks to the fact that there is a continuous supply of energy released inside by fusing nuclei that are tightly packed under the action of gravity. This energy then flows down the energy gradient towards the surface. The complexity of stars is, therefore, the result of a balance between gravity and nuclear fusion. The situation for planets is more complicated. Their complexity is caused by gravity, by energy released inside – mostly through nuclear fission under the effect of gravity – as well as by external energy received in the form of radiation from their central stars. This radiation mostly influences the planetary surfaces. Like stars, planets do not need to continuously extract new matter from their environment in order to exhibit certain levels of complexity.
Because of this comparatively simple situation, most stellar and planetary complexity is rather basic. In the words of Philip and Phylis Morrison: ‘Astro-nomy is thus the regime of the sphere; no such thing as a teacup the diameter of Jupiter is possible in our world’ (Morrison and Eames 1994: 7). In other words, in the physical Universe, spheres, and clusters of spheres, rule. Since most matter in the Universe rotates, the resulting centrifugal force causes these spheres to flatten. This explains why the sky is dominated by more or less flattened spheres or by constellations of such spheres in various shapes. Only comparatively small objects such as asteroids can attain more complex forms. Teacups were, however, the invention of culturally endowed life forms.
Since stars and planets mostly rely on energy sources from within that ignite spontaneously and maintain themselves without any form of active control, the possibilities for complexity within such bodies are rather limited. Especially deep inside big spheres and at the centers of galaxies, the power densities may be small, but the temperatures and pressures are elevated. These circumstances do not allow for the rise of more complex matter regimes.
The Formation of Complexity at the Edges
Near the edges of galaxies, or on the surfaces of stars and planets, greater levels of complexity can emerge. This is because the energy differentials between the surfaces of stars and planets and the surrounding space are large, while the energy levels may be more moderate. On the surfaces of stars, of course, the energy levels are still way too high for any great molecular complexity to exist. On the surfaces of small planets, by contrast, the energy levels may be more moderate. As a result, mountains and oceans can form, while chemical evolution might take place. In addition, the comparatively mild energy flow from a central star may significantly contribute to the rise of planetary complexity. Below the surfaces of planets towards the center, however, the chances for greater complexity are dimmer. Very soon the energy levels become too high and the energy differentials too small. On planets, therefore, only the surfaces and atmospheres can exhibit significant complexity.
As a result, biological and cultural complexity are marginal phenomena. They can only exist on the outer edges of planets circling stars which, more likely than not, find themselves on the outer edges of galaxies. Only in such places are the conditions right. The energy flows and levels are neither too big, which would destroy the greater forms of complexity, nor too small, which would not allow their formation."