QUANTUM UNIVERSE, THE

As physics has progressed, its most fundamental theories have become more distant from everyday experience posing challenges for understanding, notably with quantum mechanics. This volume contains twenty-nine essays written to address such challenges. The essays address issues in quantum mechanics, quantum cosmology and physics in general. Examples include: How do we apply quantum mechanics to the whole universe when all observers are inside? What do we mean by past, present, and future in a four-dimensional universe? What is the origin of classical predictability in a quantum universe? Could physics predict non-computable numbers? Short personal recollections of Murray Gell-Mann and Stephen Hawking are included.The essays vary in length, style, and level but should be accessible to most physicists.Contents:

• Computability and Physical Theories (R Geroch and J B Hartle)
• Excess Baggage (J B Hartle)
• Sources of Predictability (J B Hartle)
• Theories of Everything and Hawking's Wave Function of the Universe (J B Hartle)
• Scientific Knowledge from the Perspective of Quantum Cosmology (J B Hartle)
• The Physics of 'Now' (J B Hartle)
• The Quantum Mechanics of Closed Systems (J B Hartle)
• The Spacetime Approach to Quantum Mechanics (J B Hartle)
• Quantum Physics and Human Language (J B Hartle)
• Quantum Pasts and the Utility of History (J B Hartle)
• The Quasiclassical Realms of this Quantum Universe (J B Hartle)
• Living in a Superposition (J B Hartle)
• The Quantum Mechanical Arrows of Time (J B Hartle)
• Why Our Universe is Comprehensible (J B Hartle)
• Quantum Cosmology: Problems for the 21st Century (J B Hartle)
• Anthropic Reasoning and Quantum Cosmology (J B Hartle)
• Are We Typical? (J B Hartle and M Srednicki)
• Science in a Very Large Universe (M Srednicki and J B Hartle)
• The Observer Strikes Back (J B Hartle and T Hertog)
• Quantum Multiverses (J B Hartle)
• Quantum Mechanics at the Planck Scale (J B Hartle)
• The State of the Universe (J B Hartle)
• The Impact of Cosmology on Quantum Mechanics (J B Hartle)
• Murray Gell-Mann: A Short Appreciation (J B Hartle)
• Working with Stephen Hawking (J B Hartle)

• Addresses questions that arise naturally and frequently in physics and cosmology in a clear and concise manner