In a revolutionary new book, a theoretical physicist attacks the foundations of modern scientific theory, including the notion of time, as he shares evidence of ...

Models are of central importance in many scientific contexts. The centrality of models such as inflationary models in cosmology, general-circulation models of the global climate, the double-helix model of DNA, evolutionary models in biology, agent-based models in the social sciences, and general-equilibrium models of markets in their respective domains is a case in point (the Other Internet Resources section at the end of this entry contains links to online resources that discuss these models). Scientists spend significant amounts of time building, (...) testing, comparing, and revising models, and much journal space is dedicated to interpreting and discussing the implications of models. In short, models are one of the principal instruments of modern science. (shrink)

During the last three decades, there has been a growing realization among physicists and cosmologists that the relation between particle physics and cosmology may constitute yet another successful example of the unity of science. However, there are important conceptual problems in the unification of the two disciplines, e.g. in connection with the cosmological constant and the conjecture of inflation. The present article will outline some of these problems, and argue that the victory for the unity of science in the context (...) of cosmology and particle physics is still far from obvious. (shrink)

During the last three decades, there has been a growing realization among physicists and cosmologists that the relation between particle physics and cosmology may constitute yet another successful example of the unity of science. However, there are important conceptual problems in the unification of the two disciplines, e.g. in connection with the cosmological constant and the conjecture of inflation. The present article will outline some of these problems, and argue that the victory for the unity of science in the context (...) of cosmology and particle physics is still far from obvious. (shrink)

By analyzing the meaning of time I argue, without endorsing operationalism, that time is necessarily related to physical systems which can serve as clocks. This leads to a version of relationism about time which entails that there is no time 'before' the universe. Three notions of metaphysical 'time' (associated, respectively, with time as a mathematical concept, substantivalism, and modal relationism) which might support the idea of time 'before' the universe are discussed. I argue that there are no good reasons to (...) believe that metaphysical 'time' can be identified with what we ordinarily call time. I also briefly review and criticize the idea of time 'before' the big bang, associated with some recent speculative models in modern cosmology, and I argue that if the big bang model is a (roughly) correct description of our universe, then the best current answer to the question in the title is that time did have a beginning. (shrink)

The cosmological constant problem arises at the intersection between general relativity and quantum field theory, and is regarded as a fundamental problem in modern physics. In this paper we describe the historical and conceptual origin of the cosmological constant problem which is intimately connected to the vacuum concept in quantum field theory. We critically discuss how the problem rests on the notion of physically real vacuum energy, and which relations between general relativity and quantum field theory are assumed in order (...) to make the problem well-defined. (shrink)

The cosmological constant problem arises at the intersection between general relativity and quantum field theory, and is regarded as a fundamental problem in modern physics. In this paper we describe the historical and conceptual origin of the cosmological constant problem which is intimately connected to the vacuum concept in quantum field theory. We critically discuss how the problem rests on the notion of physically real vacuum energy, and which relations between general relativity and quantum field theory are assumed in order (...) to make the problem well-defined. (shrink)

Spacetime substantivalism leads to a radical form of indeterminism within a very broad class of spacetime theories which include our best spacetime theory, general relativity. Extending an argument from Einstein, we show that spacetime substantivalists are committed to very many more distinct physical states than these theories' equations can determine, even with the most extensive boundary conditions.

Relativity is the most important scientific idea of the twentieth century. Albert Einstein is the unquestioned founder of modern physics. His Special and General theories of Relativity introduced the idea to the world. In this classic short book he explains clearly, using the minimum amount of mathematical terms, the basic ideas and principles of his theory of Relativity. Unsurpassed by any subsequent books on Relativity, this remains the most popular and useful exposition of Einstein's immense contribution to human knowledge.

Just what is Einstein's Theory of Relativity? The Big Bang Theory? Curvature of Spacetime? What do astronomers mean when they talk of a 'flat universe'? This approachable and authoritative guide to the cosmos answers these questions, and more. Taking advantage of the distinctive Companion format, readers can use the extensive, cross-referenced background chapters as a fascinating and accessible introduction to the current state of cosmological knowledge - or, they can use the convenient A-Z body of entries as a quick reference (...) to a wide range of terms and concepts. Entries include topics such as: Black Hole; Doppler Effect; Fermi, Enrico; Heat Death of the Universe; Life in the Universe; Olber's Paradox; Quantum Field Theory; Supernova; and much more. (shrink)

Just what is Einstein's Theory of Relativity? The Big Bang Theory? Curvature of Spacetime? What do astronomers mean when they talk of a 'flat universe'? This approachable and authoritative guide to the cosmos answers these questions, and more. Taking advantage of the distinctive Companion format, readers can use the extensive, cross-referenced background chapters as a fascinating and accessible introduction to the current state of cosmological knowledge - or, they can use the convenient A-Z body of entries as a quick reference (...) to a wide range of terms and concepts. Entries include topics such as: Black Hole; Doppler Effect; Fermi, Enrico; Heat Death of the Universe; Life in the Universe; Olber's Paradox; Quantum Field Theory; Supernova; and much more. (shrink)

Weinberg's 1972 work, in his description, had two purposes. The first was practical to bring together and assess the wealth of data provided over the previous decade while realizing that newer data would come in even as the book was being printed. He hoped the comprehensive picture would prepare the reader and himself to that new data as it emerged. The second was to produce a textbook about general relativity in which geometric ideas were not given a starring role for (...) (in his words) too great an emphasis on geometry can only obscure the deep connections between gravitation and the rest of physics. (shrink)

Just what is Einstein's Theory of Relativity? The Big Bang Theory? Curvature of Spacetime? What do astronomers mean when they talk of a 'flat universe'? This approachable and authoritative guide to the cosmos answers these questions, and more. Taking advantage of the distinctive Companion format, readers can use the extensive, cross-referenced background chapters as a fascinating and accessible introduction to the current state of cosmological knowledge - or, they can use the convenient A-Z body of entries as a quick reference (...) to a wide range of terms and concepts. Entries include topics such as: Black Hole; Doppler Effect; Fermi, Enrico; Heat Death of the Universe; Life in the Universe; Olber's Paradox; Quantum Field Theory; Supernova; and much more. (shrink)

linear time is inadequate to account for all events in our world. In particular, the idea that time may have more than one dimension has been invoked by J. W. Dunne, in his well-known book An Experiment with Time, to justify his claim that ...

This is a contribution to a book on quantum gravity and philosophy. I discuss nature and origin of the problem of quantum gravity. I examine the knowledge that may guide us in addressing this problem, and the reliability of such knowledge. In particular, I discuss the subtle modification of the notions of space and time engendered by general relativity, and how these might merge into quantum theory. I also present some reflections on methodological questions, and on some general issues in (...) philosophy of science which are are raised by, or a relevant for, the research on quantum gravity. (shrink)