Paul Davies

Much of the modern period was dominated by a `reductionist' theory of science. On this view, to explain any event in the world is to reduce it down to fundamental particles, laws, and forces. In recent years reductionism has been dramatically challenged by a radically new paradigm called `emergence'. According to this new theory, natural history reveals the continuous emergence of novel phenomena: new structures and new organisms with new causal powers. Consciousness is yet one more emergent level in the natural hierarchy. Many theologians and religious scholars believe that this new paradigm may offer new insights into the nature of God and God's relation to the world. This volume introduces readers to emergence theory, outlines the major arguments in its defence, and summarizes the most powerful objections against it. Written by experts but suitable as an introductory text, these essays provide the best available presentation of this exciting new field and its potentially momentous implications.

It is commonly assumed that low-mass primordial black holes cannot constitute a significant fraction of the dark matter in our universe due to their predicted short lifetimes from the conventional Hawking radiation and evaporation process. Assuming physical black holes are nonsingular--likely due to quantum gravity or other high-energy physics--we demonstrate that a large class of nonsingular black holes have finite evaporation temperatures. This can lead to slowly evaporating low-mass black holes or to remnant mass states that circumvent traditional evaporation constraints. As a proof of concept, we explore the limiting curvature hypothesis and the evaporation process of a nonsingular black hole solution in two-dimensional dilaton gravity. We identify generic features of the radiation profile and compare them with known regular black holes, such as the Bardeen solution in four dimensions. Remnant masses are proportional to the fundamental length scale, and we argue that slowly evaporating low-mass nonsingular black holes, or remnants, are viable dark matter candidates.

Many scientists regard mass and energy as the primary currency of nature. In recent years, however, the concept of information has gained importance. In this book, eminent scientists, philosophers, and theologians chart various aspects of information, from quantum information to biological and digital information, in order to understand how nature works. Beginning with a historical treatment of the topic, the book also examines physical and biological approaches to information, and the philosophical, theological, and ethical implications.

The hypothesis that life’s rapid appearance on Earth justifies the belief that life is widespread in the universe has been investigated mathematically by Lineweaver and Davis (Astrobiol- ogy 2002;2:293–304). However, a rapid appearance could also be interpreted as evidence for a nonterrestrial origin. I attempt to quantify the relative probabilities for a non-indigenous ver- sus indigenous origin, on the assumption that biogenesis involves one or more highly im- probable steps, using a generalization of Carter’s well-known observer-selection argument. The analysis is specifically applied to a Martian origin of life, with subsequent transfer to Earth within impact ejecta. My main result is that the relatively greater probability of a Mar- tian origin rises sharply as a function of the number of difficult steps involved in biogene- sis. The actual numerical factor depends on what is assumed about conditions on early Mars, but for a wide range of assumptions a Martian origin of life is decisively favored. By con- trast, an extrasolar origin seems unlikely using the same analysis. These results complement those of Lineweaver and Davis. Key Words: Origin of life—Mars—Probability theory— Carter—Transpermia. Astrobiology 3, 673–679.

Astrobiologists are aware that extraterrestrial life might differ from known life, and considerable thought has been given to possible signatures associated with weird forms of life on other planets. So far, however, very little attention has been paid to the possibility that our own planet might also host communities of weird life. If life arises readily in Earth-like conditions, as many astrobiologists contend, then it may well have formed many times on Earth itself, which raises the question whether one or more shadow biospheres have existed in the past or still exist today. In this paper, we discuss possible signatures of weird life and outline some simple strategies for seeking evidence of a shadow biosphere. Key Words: Weird life—Multiple origins of life—Biogenesis—Biomarkers—Extremophiles—Alternative biochemistry. Astrobiology 9, 241–249.

: The oft-repeated claim that life is ‘ written into ’ the laws of nature is examined and criticised. Arguments are given in favour of life spreading between near-neighbour planets in rocky impact ejecta (transpermia), but against panspermia, leading to the conclusion that if life is indeed found to be widespread in the universe, some form of life principle or biological determinism must be at work in the process of biogenesis. Criteria for what would constitute a credible life principle are elucidated. I argue that the key property of life is its information content, and speculate that the emergence of the requisite information-processing machinery might require quantum information theory for a satisfactory explanation. Some clues about how decoherence might be evaded are discussed. The implications of some of these ideas for ‘ fine-tuning ’ are discussed.

Available from UMI in association with The British Library. ;The thesis considers the work of Maurice Blanchot: first, by noting four 'steps' in its gradual clarification of what we might call literature's question to philosophy; second, by reading it alongside the works of Heidegger and Levinas. The aim is to formulate a question from Blanchot to Heidegger and Levinas respectively. ;Heidegger and Levinas both write from, and to, a time in which philosophy itself is called into question. How are we to continue thinking in such a time? How are we to address the future when the very means of relating the future to the present have been undermined? Heidegger and Levinas insist on a radical openness or response. Confronted by an extreme discontinuity, philosophy continues, but differently. I am not to think of the future as mine, not to ground it in the present. The relation into which philosophy is called is one that cannot be thought in terms of a traditional logic of relation. It alters the way in which we talk of nearness and distance. To what does philosophy respond? What brings about this new relation? ;For Heidegger, that which has always concealed itself in the history of the tradition. Not that it is now to to be revealed, for it has concealed itself in and from the dialectic of presence and absence that defines 'revelation'. Neither present nor absent nor on its way to being either, what has been concealed is a more originary concealment. It is this concealment that first provoked the questions of philosophy and it is this concealment, concealed in the answer philosophy has given, that now calls philosophy into question. For Levinas, the alterity of the other person: an alterity always violated when the other is deemed analogous to the same, the self or 'I', or when myself and the other are thought from out of a common ground. My relation with another, however 'symmetrical', is always already vulnerable to the claims of the other as Other.

There have been many claims that quantum mechanics plays a key role in the origin and/or operation of biological organisms, beyond merely providing the basis for the shapes and sizes of biological molecules and their chemical affinities. These range from Schr¨odinger’s suggestion that quantum fluctuations produce mutations, to Hameroff and Penrose’s conjecture that quantum coherence in microtubules is linked to consciousness. I review some of these claims in this paper, and discuss the serious problem of decoherence. I advance some further conjectures about quantum information processing in bio-systems. Some possible experiments are suggested. © 2004 Elsevier Ireland Ltd. All rights reserved.

The quantum vacuum may in certain circumstances be regarded as a type of fluid medium, or aether, exhibiting energy density, pressure, stress and friction. Vacuum friction may be thought of as being responsible for the spontaneous creation of particles from the vacuum state when the system is non-stationary. Examples include the expanding universe, rotating black holes, moving mirrors, atoms passing close to surfaces, and the activities of sub-cellular biosystems. The concept of vacuum friction will be reviewed and illustrated, and some suggestions for future experiments made.

It is widely accepted that EinstcinRi7;s general theory of relativity is an satisfactory description of gravity 0nly in the macroscopic limit, where quantum eiTcc1;s may be neglected. Presumably this theory is inapplicable at the Planck length, but recently much attention has been devoted to gravitational theory at intermediate length scales where quantum affects 0f matter are inescapable, but where there is an general assumption that the gravitational Held may bc treated as a classical background, augmented if necessary by quamtizcd linearized pertur-

One of the most influential physics books of the twentieth century was actually about biology. In a series of lectures, Erwin Schrödinger described how he believed that quantum mechanics, or some variant of it, would soon solve the riddle of life. These lectures were published in 1944 under the title What is life? and are credited by some as ushering in the age of molecular biology. In the nineteenth century, many scientists thought they knew the answer to Schrödinger’s rhetorical question. Life, they maintained, was some sort of magic matter. The continued use of the term ‘organic chemistry’ is a hangover from that era. The belief that there is a chemical recipe for life led to the hope that, if only we knew what it was, we could mix up the right stuff in a test tube and make life in the lab. Most research on biogenesis has followed that tradition, by assuming that chemistry was a bridge — and a long one at that — linking matter with life. Elucidating this chemical pathway has been a tantalizing goal, spurred on by the famous Miller–Urey experiment of 1952, in which amino acids were made by sparking electricity through a mixture of water and common gases. But the concept has turned out to be something of a blind alley, and further progress with prebiotic chemical synthesis has been frustratingly slow. The origin of life remains one of the great outstanding mysteries of science. To take up Schrödinger’s suggestion, a radical solution to the problem, ‘What is life?’ could be that quantum mechanics enabled life to emerge directly from the atomic world, without the need for complex intermediate chemistry. Life must have a chemical basis: organic molecules provide the hardware for biology. But what about the software? When Schrödinger asked, ‘What is life?’ he could already glimpse the central significance of the cell’s information storage and replication processes, even though the role of DNA and the genetic code was yet to be discovered..

Using a model quantum clock, I evaluate an expression for the time of a nonrelativistic quantum particle to transit a piecewise geodesic path in a background gravitational field with small spacetime curvature (gravity gradient), in the case that the apparatus is in free fall. This calculation complements and extends an earlier one (Davies 2004) in which the apparatus is fixed to the surface of the Earth. The result confirms that, for particle velocities not too low, the quantum and classical transit times coincide, in conformity with the principle of equivalence. I also calculate the quantum corrections to the transit time when the de Broglie wavelengths are long enough to probe the spacetime curvature. The results are compared with the calculation of Chiao and Speliotopoulos (2003), who propose an experiment to measure the foregoing effects.

The finite age of the universe and the existence of cosmological horizons provides a strong argument that the observable universe represents a finite causal region with finite material and informational resources. A similar conclusion follows from the holographic principle. In this paper I address the question of whether the cosmological information bound has implications for fundamental physics. Orthodox physics is based on Platonism: the laws are treated as infinitely precise, perfect, immutable mathematical relationships that transcend the physical universe and remain totally unchanged by physical processes, however extreme. If instead the laws of physics are regarded as akin to computer software, with the physical universe as the corresponding hardware, then the finite computational capacity of the universe imposes a fundamental limit on the precision of the laws and the specifiability of physical states. That limit depends on the age of the universe. I examine how the imprecision of the laws impacts on the evolution of highly entangled states and on the problem of dark energy.

A quantum particle moving in a gravitational field may penetrate the classically forbidden region of the gravitational potential. This raises the question of whether the time of flight of a quantum particle in a gravitational field might deviate systematically from that of a classical particle due to tunnelling delay, representing a violation of the weak equivalence principle. I investigate this using a model quantum clock to measure the time of flight of a quantum particle in a uniform gravitational field, and show that a violation of the equivalence principle does not occur when the measurement is made far from the turning point of the classical trajectory. The results are then confirmed using the so-called dwell time definition of quantum tunnelling. I conclude with some remarks about the strong equivalence principle in quantum mechanics.

The problem of how a mixture of chemicals can spontaneously transform themselves into even a simple living organism remains one of the great outstanding challenges to science. Various primordial soup theories have been proposed in which chemical self- organization brings about the required level of complexity. Major conceptual obstacles remain, however, such as the emergence of the genetic code, and the “chicken-and-egg” problem concerning which came first: nucleic acids or proteins. Currently fashionable is the so-called RNA world theory, which casts RNA in the role of both chicken and egg. Other theories assume that protein chemistry and even clay crystal life came before nucleic acids. To be fully successful, a theory of biogenesis has to explain not merely the emergence of molecular replication and chemical complexity, but the crucial information content and information processing capabilities of the living cell.