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Cosmology: 2Cosmology: 2 Reviews of papers/articles/books etc on aspects of cosmology relevant to life and onsciousness. 1.) The Goldilocks Enigma - Paul Davies - Good discussion of examples of fine tuning, and argues for a law-like trend towards life in the universe. 2.) In the multiverse - stars burn black - Argument that the universe is less fine tuned that normally understood. 3.) Three Roads to Quantum Gravity - Lee Smolin - Close to Penrose in his view of the structure of spacetime The Goldilocks Enigma Paul Davies Penguin (2006) ISBN 978-0-141-0236-7 Davies’s book deals with the apparent ‘fine-tuning’ of the universe to render it suitable for organic life, and the problems that this produces for understanding the origin of the universe itself. In his preface, he discusses the anthropic principle, which is essentially the view that the structure of the universe is such as to make it suitable for life. Strictly, this proposition is the weak anthropic principle. The strong anthropic principle is more controversial in suggesting that the universe has to be like that, rather than just being like it by chance. Davies remarks on the way in which the scientific establishment has gradually gone from viewing the anthropic principle as semi-mystical mumbo-jumbo, to seeing it as a life line alternative to intelligent design, in the face the apparent fine-tuning of the universe. Much of the book is taken up by the discussion of various versions of the multiverse, a concept now widely promoted as an alternative to intelligent design. In respect of the multiverse idea, Davies discusses the question of the observable universe. Present technology can see about 10bn light years out from Earth, but in principle it should be possible to see 13.7bn light years out. That is the limit of the observable universe, because light would not have had time to reach Earth from more distant regions. Davies points out that galaxies at the limit of the observable universe having been moving away from Earth since the light we are now seeing left them, and would now be nearly 28bn light years away. Further to this, we can see out in all directions from Earth, so the width of the observable universe is twice whichever of the above figures is chosen. Davies points out that these distant regions in opposite directions from Earth would not have any contact with one another, because light or anything else would not have had time to pass between them. They are effectively part of different universes. The same rule applies to parts of the universe that are a long way out from Earth. They would be in contact with parts of the universe that could not be in contact with Earth. All this appears relevant to one version of the multiverse discussed at some length in this book. This idea is not so much a multiverse, as a single universe split into a huge or even infinite number of domains with different laws of physics. The different laws arise by chance out of the initial Big Bang, and the huge number of domains brought into existence makes it quite probable that one or even a few of them would have laws of physics suitable for the emergence of organic life. However, this proposition seems to give rise to significant problems. In the first place, it appears to violate Occam’s Razor, a scientific principle that favours the selection of the simplest or the most established theories. As far as we can tell the same physical laws operate throughout the observable universe even near its boundaries, and the simplest assumption is that those laws continue to apply throughout the universe that lies beyond the observable boundaries. Occam’s Razor is not the only problem faced by the multiple domain idea. Although Davies does not discuss this, it would seem to be necessary to look at what happens at the boundary between domains. What would happen if neighbouring galaxies to the Milky Way had different laws of physics? It might be argued that a huge area of empty space would be inserted between galaxies with different laws, but this looks much too convenient and orderly given that the whole system is supposed to have arisen by chance rather than design. The problem has echoes of the argument against dualism. Dualism is the view that spirit is a separate stuff from matter and accounts for mind, God and possibly other entities. It is ridiculed by most scientists, and the core of their argument against it is that it would be difficult for spirit to interact with matter without sharing some of the physical properties of matter. There seems to be hints of the same problem in the idea of domains with different laws of physics co-existing within the same universe. Examples of fine tuning Some of the best parts of this book are those in which Davies discusses the extent of fine tuning in the universe. The actual power of the Big Bang itself proves to be fine tuned to be favourable to life. A more powerful bang would have dispersed the cosmic gases too widely for them to subsequently aggregate into the stars and galaxies necessary for life. A less powerful Big Bang, however would have allowed the universe to fall back into a black hole. Another convenient circumstance arose in the first few minutes after the Big Bang, with the weak nuclear force being set at just the right level to give a favourable balance of hydrogen and helium atoms. Later on when stars form, helium atoms become important for life, because they are able to fuse together to produce carbon atoms. However, hydrogen is also vital as the basis of stars, which are also essential for life. Davies moves on to look at what happens inside stars, which also proves to be a crucial area for making the universe suitable for life. A lot of helium atoms were created in the aftermath of the Big Bang, but another tranche of helium was created inside stars. In fact, stars derive most of their energy from the fusion of hydrogen into helium. However, the fusion of helium in stars uses a slower route than in the aftermath of the Big Bang. This latter process is controlled by the weak nuclear force. This makes the process slower than in the Big Bang, and this in turn allows stars to burn for sometimes billions of years giving organic life the time to emerge and evolve on neighbouring planet(s), another convenient circumstance for organic life. Another remarkable convenient (for organic life) circumstance emerges when higher-mass stars start to run out of hydrogen. They have sufficient internal temperature to fuse atoms larger than the hydrogen atom, but the next two atoms in weight, lithium and beryllium would not be stable under these circumstances. The next heaviest atom is carbon, but for this to be fused inside a star three helium nuclei have to come together, and at first sight the odds against this look high. However, it has been found that carbon has a resonance that is just right to allow the fusion of three helium nuclei. This resonance is determined by the interplay between the strong nuclear force and the electromagnetic force. It is this that allows carbon, fundamental to living organisms to be plentiful in the universe. If the strong force were only 1% weaker, this resonance would not work, and carbon would not be plentiful. Again this is another piece of fine tuning that is extraordinarily convenient for organic life. The weak nuclear force becomes important for organic life again when larger stars explode in super nova. These are important for disseminating carbon and the other heavier atoms into space, from whence they can eventually come to be present on a planet suitable for life. In this process, the weak nuclear force has to have very close to the strength it actually has for the neutrinos released in the process to not have sufficient strength to react with the stellar core, but to have sufficient strength to explode outwards from the star. Again this is a very convenient piece of fine tuning. Davies also looks at the convenient relationship of the strengths of the electromagnetic and gravitational forces. The electromagnetic force is 1040 times stronger than the gravitational force. A child’s toy magnet can lift a paper clip, and when it does, it outweighs the gravitational force of an entire planet. It turns out that this relationship is necessary to allow smaller stars to run on heat convection, which appears to aid the formation of planets, while large stars rely on radiating energy, which in turn creates conditions suitable for super nova. Both planets and super nova are essential for organic life. The structure of the universe appears to be littered with yet more convenient coincidences. The neutron has a slightly greater mass than the proton. If the tables were turned, it would be the proton that decayed into a neutron, and there would be no atoms, no chemistry and no life. The cosmic microwave background radiation contains ripples that probably originated in quantum fluctuations, and were the basis for the later formation of galaxies. If the size of these ripples were even slightly larger or smaller the formation of life bearing galaxies would be disrupted. The Multiverse In discussing the multiverse, Davies feels that this concept has only been partly successful in getting rid of the need for intelligent design. He suggests that it has simply shifted the problem from explaining the universe to explaining the multiverse. Inflation, originally thought up to explain the thermal equilibrium of the early universe, is the basis for presupposing the creation of many universes out of quantum fluctuations during the process of inflation. The problems come with inflation itself. This pre-supposes something that generates a universe in the Big Bang, plus the quantum laws and the laws governing gravitation and spacetime, which needed to be fine tuned themselves to produce inflation. Life, Consciousness and the Cosmos Davies feels that much of mainstream cosmology is too dismissive of both life and with it consciousness, as something happening on the surface of an obscure planet, with no great importance for the universe as a whole. However, Davies passes over the chance to explain the origin of life as something related to the laws of physics. He argues that life is 1% physics and 99% environment. However, while the evolution of organisms as a function of their environment is quite well understood, the actual origin of life is not, because of the enormous chances against a soup of organic molecules turning into a basic replicator, the start point of life. Despite this, Davies still toys with the idea of a law-like trend towards life in the universe. Davies’s seeks a quantum route to this. He goes back to the most basic of quantum experiments, the two slit experiment. Here a beam of light passes through two slits in a screen, before falling onto a second screen. The image will appear in the form of light and dark bands. This demonstrates the wave-like nature of light, because the pattern shows that waves from the two slits interfere with one another. As technology advanced this experiment was refined. Instead of a beam of light containing countless photons, photons were fired one at a time. The really surprising thing was that an interference pattern still gradually formed, although the photons had no conventional information about the photons that had gone before them, or the ones that would come after them. However, if a photon counter is placed at one of the slits, the quantum wave function collapses, the waves become particles and the interference pattern disappears. Possibly the most common explanation of this puzzling behaviour is that as a wave the single photon passes through both slits and interferes with itself. Davies discusses a further refinement to this experiment devised by the physicist, John Wheeler. He changed the second screen into a Venetian blind and placed detectors behind this blind, and pointing at the slits in the first screen. If the Venetian blind is closed, the experiment is seen to proceed in the normal way. However, if the blind is open, light photons pass through it, and the detectors can find which slit in the first screen the photons went through. As a result of this observation the photons become particles. The experimenter can choose whether or not to direct the detector at the slits, and thus whether or not to get waves or particles. However, the final stage is to delay the decision whether or not to detect the particle until it has reached the Venetian blind. In this case, the particle does not ‘decide’ on whether to take the wave or the particle form until it ‘sees’ the detector, but this is after it has already passed through either two slits as a wave or one slit as a particle. Backward Causation in Time The experiment thus delivers an apparent backward causation in time. To makes matters still worse, Wheeler extended this actual experiment to a thought experiment. Supposing the photons came not from a lamp in a laboratory but from a distant star, with photons in a superposition of passing round both sides of an intervening galaxy. If these photons eventually arrived at Wheeler’s Venetian blind contraption, the decision as to whether to pass on one side of the galaxy as a particle or both sides as a superposition could be referred back in time by billions of years to a period before the Earth even existed. Wheeler and Davies with him seem to favour the idea that conscious life now could have a backward causation effect stretching to the Big Bang, and creating a closed loop of cosmos–life–cosmos. I have to say that I am not very taken by Wheeler’s proposition in terms of explanatory power. While it might be arguable that existing life forms could exert some backward causation, this does not explain how the first life forms intelligent enough to exert backward causation came into being. On the basis of the rest of the book, these first backward causers would never appear without the whole paraphernalia of fine tuning, which backward causation is supposed to explain. The main virtue of Davies’s approach may be to open the door just a crack to the involvement of mind in the development of the universe. It would seem possible to do without a thunderbolt throwing type of God, but still allow some involvement of mind in the laws of physics. (See, Mind-Like Universe) In the multiverse ... stars burn black New Scientist, 2nd August 2008 This article refers to proposals by Fred Adams of the University of Michigan in Ann Arbor. These read as another attempt to deal with the fine-tuning problem, by which only very specific conditions, such as the existing forces of nature can produce a universe that is suitable for life. Adams points out that discussions of fine tuning usually revolve round what would happen if one characteristic of the universe, such as one of the forces of nature, was different from what it is in our universe. This thought experiment usually produces a universe that is completely unsuitable for life. Adams, however, works from the basis of generating models in which all the forces etc. are adjusted. He claims that calculations for the multiverse that he has generated suggest that up to 25% of the possible universes could support stars, or at least starlike radiating objects, the first step on the road to life. Beyond this point, the proposals get more doubtful. Many of the stars in these possible universes do not produce carbon. It is suggested that if the strength of the electromagnetic force was different from what it is in our universe, it would be possible to have universes with non-carbon life forms. This seems to go well beyond Occam’s razor in proposing something that has never been considered possible, in order to substantiate the theory. Even if we are prepared to go along with the idea, it seems likely that the odds against getting everything just right for the putative non-carbon life form might also be very high. Three Roads to Quantum Gravity Lee Smolin Weidenfeld & Nicolson (2000) ISBN 0 297 64301 0 This book highlights the argument that space or spacetime is not continuous but comes in discrete units, and further that these discrete units represent an organised structure. At the beginning of the book, Smolin stresses the different and conflicting natures of general relativity and quantum theory. Relativity changed the scientific concept of spacetime, but quantum theory, although conceived in the same period as relativity, based itself on earlier Newtonian concepts of spacetime. The author sees a theory of quantum gravity as being necessary to reconcile these two basic theories of physics. In relativity, gravity is a manifestation of the structure of spacetime, which is curved by massive objects. A quantum theory of gravity is looked to, to provide answers about the nature of spacetime, and also about the origin of the universe. Smolin goes on to discuss the actual concept of space. He points out that position in space can only be defined in relation to other objects in space. Following this line of reasoning, it is the objects that create space. If there were no objects or only one object in the universe, there would be nothing that could be identified as space. Similarly, the motion of objects in space can be defined only in relation to other objects. The geometry of space, or the measurement of its areas and volumes, is seen as changing, when the position of objects alters relative to one another. Newton had viewed space as something fixed and absolute, but the experiments that confirm the general theory of relativity demonstrate that this is not the case. This view effectively refutes the instinctive concept of space as a stage on which objects may appear and move around, but which can at other times be empty. This approach is also seen as applying to time, which is described only in terms of evolving relationships between things in space. In fact, Smolin argues that the universe should be seen as a network of evolving relationships. Physicists refer to this approach as ‘background independence’, with objects evolving and creating their own spacetime, rather than operating in relation to a fixed background spacetime. In practise, it had proved difficult to construct a background independent version of quantum theory making no reference to points within such a background spacetime, but only to points that are defined by a network of relationships. In this book, Smolin advocates loop quantum gravity as a background independent theory. Most of the information needed to construct the geometry of spacetime comprises information about its causal structure. The fact that the universe is a causal structure means that even terms such as ‘things’ or ‘objects’ or ‘objects in space’ are not strictly correct, because causal structure means that things or objects are constantly developing, so that they are really processes rather than things, and as such causal structures that are creating space or spacetime geometry through their dynamic change. Smolin argues that we must get away from the view of either objects or space as being static, and accept the idea of a dynamic evolving universe. He views the extreme conditions of black holes as a way of examining the physics necessary to an understanding of quantum gravity. A black hole has a horizon from within which even light cannot escape, because of the strength of the hole’s gravitational force. This creates a region that is hidden from observers anywhere outside of the horizon of the black hole. In fact, quite apart from conditions around black holes, all observers have hidden regions, which are comprised of all those regions of the universe from which they will never receive light signals, because of their existing distance and the continuing expansion of the universe. The boundary between the part of the universe an observer can see and the part they cannot see is called an horizon. This horizon is observer dependent, but at the same time objective rather than subjective, because many observers can all agree on the existence of the same horizon. Smolin also looks at the similar but not identical situation of an observer in a spaceship constantly accelerating towards but never reaching the speed of light. Smolin assures his readers that it is consistent with relativity that as long as the ship continues to accelerate, there will be a region behind it from which light does not catch up with the ship, and that this will constitute a hidden region for an observer on the ship. Uncertainty principle, a key concept within quantum theory, prevents quantum particles from having a precisely defined position and momentum at the same time. The consequence of this is that even when a system is cooled to a point at which it has no energy, it will still have an intrinsic random motion, because if this ceased its position and momentum would both be precisely defined. This is known as zero point energy. Because of the lack of ordinary energy in the system, detectors do not register this motion. However, if the detector is accelerating, as would be the case of detectors placed on our observer’s spaceship, the accelerated ship/detector is itself a source of energy that allows the zero point energy to be detected. Smolin further indicates that uncertainty principle does not only apply to position and momentum, but also to the electric and magnetic fields that permeate space. One cannot simultaneously know the precise position of both the electric and the magnetic field in a particular region of space. Even when a region is cooled so as to contain zero energy, there will be randomly fluctuating electric and magnetic fields, referred to as quantum fluctuations of the vacuum. These, however, would also be detected by the accelerating detector on our observer’s spaceship. Smolin goes a step further to try and explain where the randomness in the fluctuations of the electric and magnetic fields come from. It is claimed that the photons that constitute the electric and magnetic fields are non-locally correlated, with each photon detected by the ship non-locally correlated with a photon in the ship’s hidden region. The observed randomness is a measure of the observer’s lack of information about the hidden region. The entropy represented by this randomness is related to the size of the hidden region. In turns out that the entropy of the particles detected by the ship is proportional to the area of the horizon of the ship’s hidden region. This is referred to as Bekenstein’s law, after the physicist of that name, stating that with the horizon of a hidden region there is an associated entropy that indicates the amount of information hidden by the region. This rule can be applied to black holes. The entropy of the horizon of a black hole is given as a quarter of the area of the horizon divided by h bar times the gravitational constant. Perhaps more helpfully, the horizon can be conceived as a computer screen with one pixel for every four Planck areas. The amount of information hidden in the black hole is equivalent to the number of notional pixels. This brings us to the argument for spacetime being discrete rather than continuous. This is connected to the author’s concept of the universe as a network of evolving events, processes and relationships. It is easiest to view such things or processes as being finite in number, and therefore discrete from one another. Given that it is these events and processes that create space, it is therefore also possible to view spacetime as discrete. By contrast, a smooth continuous space would require an infinite number of relationships. The discreteness of space is one of the few areas in speculative physics where there appears to be something of a consensus among physicists. Smolin claims loop quantum gravity as the theory that allows a detailed description of the discrete structure of spacetime. The scale at which the continuity of spacetime breaks up is thought to be the Planck scale of 10-35m. This is the scale at which the influence of gravity and quantum effects are calculated to be equally important. The behaviour of larger things can be described by gravity without reference to quantum theory. The Planck scale has been calculated with reference to three fundamental constants, Planck’s constant, the speed of light and the gravitational constant. The Planck time of 10-43 seconds is defined as the time it takes for something to happen at the Planck scale. Loop quantum gravity proposes that space is made of discrete units each carrying a unit of volume. The volume must be one of a finite set of numbers, in a manner that is analogous to quantum theory, in which only certain values can apply to the energy of an electron or to electric charge. There is similarly a smallest possible unit of area in loop quantum gravity. The jumps between the possible areas and volumes relate to the square and cube of the Planck length. Smolin also discusses the phenomena of superconducting in which magnetic field lines become quantised. This is taken to indicate that fields that carry force can become quantised. Protons are known to be composed of quarks. The quarks within the proton are bound together by a force known as the colour force that is comparable to the electric and magnetic fields. However, unlike the electromagnetic forces that fall off with distance, the colour force binding the quarks is weak at closer quarters, but rise to a constant value if the quarks are pulled apart. The metaphor of a piece of string is successful in describing the behaviour of this force. It is also noted that force behaves like the quantised magnetic flux in a superconductor. The hypothesis is that space is a colour force superconductor. There are three ways of looking at this proposition. The colour field could be the fundamental entity, the stretched strings could be fundamental, or in a third option the string and the field could be different aspects of the same thing. Loop quantum gravity emerged out of this thinking with the geometry of spacetime expressed in terms of loops, as a set of elementary objects. These are the loops of colour force flux identified by some earlier researchers, but instead of being related to any fixed background, it is their interrelations that define space. The theory depends on the particular connections between the loops. It allows the area of any surface to come in discrete multiples of units. The smallest units is about the Planck area, which is the square of the Planck length. Surfaces are made of discrete parts each of which comprises a finite amount and similarly for volumes. Areas and volumes cannot take any value but come in multiples of fixed units. It was subsequently found that the discrete units of the theory related to the spin network theory developed by Roger Penrose a generation earlier. Penrose had also considered that space was purely relational. The spin network was the version of quantum geometry that Penrose came up with. The spin network is a graph labelled with integers, with the spins that particles have in quantum theory. The spin networks provide a possible quantum state for the geometry of space. The edges of the network correspond to units of area. The nodes, where edges of the spin network meet, correspond to units of volume. Further study suggested that the spin network picture follows from combining quantum theory with relativity. The spin networks are not set in space, they generate space, with relationships in space determined by how the edges come together at the nodes. The spin networks can evolve in time in response to changes. Each event in spacetime is seen as a change in the quantum geometry of space. The causal evolution of the spin networks can be described by the development of light cones through time. Even Penrose appears to leave it to his readers to speculate how his proposition that non-computable consciousness is embedded in the geometry of spacetime relates to these spin network and related theories. However, it appears at least plausible that the fundamental and discrete structures proposed here could provide a code for the consciousness that is suggested to be embedded in spacetime. |
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