Paul Davies

Recent attempts to explain the dark matter and energy content of the universe have involved some radical extensions of standard physics, including quintessence, phantom energy, additional space dimensions, and variations in the speed of light. In this paper I consider the possibility that some dark matter might be in the form of tachyons. I show that, subject to some reasonable assumptions, a tachyonic cosmological fluid would produce distinctive effects, such as a surge in quantum vacuum energy and particle creation, and a change in the conventional temperature–time relation for the normal cosmological material. Possible observational consequences are discussed.

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.

A simple model of a quantum clock is applied to the old and controversial problem of how long a particle takes to tunnel through a quantum barrier. The model has the advantage of yielding sensible results for energy eigenstates and does not require the use of time-dependent wave packets. Although the treatment does not forbid superluminal tunneling velocities, there is no implication of faster-than-light signaling because only the transit duration is measurable, not the absolute time of transit. A comparison is given with the weak-measurement post-selection calculations of Steinberg.

We study the response of switched particle detectors to static negative energy densities and negative energy fluxes. It is demonstrated how the switching leads to excitation even in the vacuum and how negative energy can lead to a suppression of this excitation. We obtain quantum inequalities on the detection similar to those obtained for the energy density by Ford and co-workers and in an ‘‘operational’’ context by Helfer. We reexamine the question ‘‘Is there a quantum equivalence principle?’’ in terms of our model. Finally, we briefly address the issue of negative energy and the second law of thermodynamics.

T he term emergence is used to describe the appearance of new properties that arise when a system exceeds a certain level of size or complexity, properties that are absent from the constituents of the system. It is a concept often summed up by the phrase that “the whole is greater than the sum of its parts,” and it is a key notion in the burgeoning field of complexity science. Life is often cited as a classic example of an emergent phenomenon: no atoms of my body are living, yet I am living (see, for example, Morowitz [1]). Biological organisms depend on the processes of their constituent parts, yet they nevertheless exhibit a degree of autonomy from their parts (see, for example, Kauffman [2]). How can this be? These seem to be contradictory properties.

This two-volume collection of cutting edge thinking about science and religion shows how scientific and religious practices of inquiry can be viewed as logically compatible, complementary, and mutually supportive. Features submissions by world-leading scientists and philosophers Discusses a wide range of hotly debated issues, including Big Bang cosmology, evolution, intelligent design, dinosaurs and creation, general and special theories of relativity, dark energy, the Multiverse Hypothesis, and Super String Theory Includes articles on stem cell research and Bioethics by William Hurlbut, who served on President Bush's Bioethics Committee.

This chapter contains sections titled: * 1 The Universe Is Weirdly Fine-Tuned for Life * 2 The Cosmic Code * 3 The Concept of Laws * 4 Are the Laws Real? * 5 Does a Multiverse Explain the Goldilocks Enigma? * 6 Many Scientists Hate the Multiverse Idea * 7 Who Designed the Multiverse? * 8 If There Were a Unique Final Theory, God Would Be Redundant * 9 What Exists and What Doesn’t: Who or What Gets to Decide? * 10 The Origin of the Rule That Separates What Exists From What Doesn’t * 11 Why Mind Matters * 12 The Universe as a Finite Computer Exposes the Fiction of Idealized Laws * 13 Quantum Mechanics Could Permit the Feedback Loop Between Mind and the Laws Of Physics * Notes.

The paper reflects on the experience of reading Levinas’s ‘God and Philosophy’ paying particular attention to the ways in which it would have us read the word ‘God.’ Levinas refuses to let the word become the property of even the most radical treatment of religious faith. The word, the biblical word, must never serve the self-consolation of philosophy. Many of Levinas’s readers regret this aspect of his writing, but the paper argues that ‘God and Philosophy’ offers an exemplary introduction to Levinas’s most developed style of writing and thinking, and it does so while bringing to mind the question of the relation between Levinas’s philosophy and their religion. The second part of the essay considers possible contexts in which this question and ‘God and Philosophy’ itself can perhaps best be understood.

In attempting to re-think the notion of asymmetry and its relations with 'first philosophy' and to see how that notion is tracked by the provocation of scepticism, the paper demonstrates something about the implications of Levinas' ethical asymmetry. The paper considers Levinas' tendency to introduce the topic of scepticism when confronted by the logical and textual difficulties that necessarily befall his account of the ethical relation. It argues that such an introduction commits Levinas to the claim: first philosophy entails a fundamental (first person) asymmetry and its attendant scepticism. If, for Levinas, scepticism and first person asymmetry are implicated in all attempts at first philosophy, the paper suggests that an intriguing place to set it to work is those pages of Being and Time which prioritize being-towards-death, the polemical focus of Levinas' being-for-beyond-my-death.