Chapter 1

We each exist for but a short time, and in that time explore but a small part of the whole universe. But humans are a curious species. We wonder, we seek answers. Living in this vast world that is by turns kind and cruel, and gazing at the immense heavens above, people have always asked a multitude of questions: How can we understand the world in which we find ourselves? How does the universe behave? What is the nature of reality? Where did all this come from? Did the universe need a creator? Most of us do not spend most of our time worrying about these questions, but almost all of us worry about them some of the time.

Traditionally these are questions for philosophy, but philosophy is dead. Philosophy has not kept up with modern developments in science, particularly physics. Scientists have become the bearers of the torch of discovery in our quest for knowledge. The purpose of this book is to give the answers that are suggested by recent discoveries and theoretical advances. They lead us to a new picture of the universe and our place in it that is very different from the traditional one, and different even from the picture we might have painted just a decade or two ago. Still, the first sketches of the new concept can be traced back almost a century.

According to the traditional conception of the universe, objects move on well-defined paths and have definite histories. We can specify their precise position at each moment in time. Although that account is successful enough for everyday purposes, it was found in the 1920s that this "classical" picture could not account for the seemingly bizarre behavior observed on the atomic and subatomic scales of existence. Instead it was necessary to adopt a different framework, called quantum physics. Quantum theories have turned out to be remarkably accurate at predicting events on those scales, while also reproducing the predictions of the old classical theories when applied to the macroscopic world of daily life. But quantum and classical physics are based on very different conceptions of physical reality.

Quantum theories can be formulated in many different ways, but what is probably the most intuitive description was given by Richard (Dick) Feynman, a colorful character who worked at the California Institute of Technology and played the bongo drums at a strip joint down the road. According to Feynman, a system has not just one history but every possible history. As we seek our answers, we will explain Feynman's approach in detail, and employ it to explore the idea that the universe itself has no single history, nor even an independent existence. That seems like a radical idea, even to many physicists. Indeed, like many notions in today's science, it appears to violate common sense. But common sense is based upon everyday experience, not upon the universe as it is revealed through the marvels of technologies such as those that allow us to gaze deep into the atom or back to the early universe.

Until the advent of modern physics it was generally thought that all knowledge of the world could be obtained through direct observation, that things are what they seem, as perceived through our senses. But the spectacular success of modern physics, which is based upon concepts such as Feynman's that clash with everyday experience, has shown that that is not the case. The naive view of reality therefore is not compatible with modern physics. To deal with such paradoxes we shall adopt an approach that we call model-dependent realism. It is based on the idea that our brains interpret the input from our sensory organs by making a model of the world. When such a model...

Author: Leonard Mlodinow
Bio:  

Stephen Hawking was the Lucasian Professor of Mathematics at the University of Cambridge for thirty years, and has been the recipient of numerous awards and honors including, most recently, the Presidential Medal of Freedom. His books for the general reader include the classic A Brief History of Time, Black Holes and Baby Universes and Other Essays, The Universe in a Nutshell, and A Briefer History of Time. He lives in Cambridge, England.

www.hawking.org.uk

Leonard Mlodinow is a physicist at Caltech and the bestselling author of The Drunkard's Walk: How Randomness Rules our Lives, Euclid's Window: The Story of Geometry from Parallel Lines to Hyperspace, and Feynman's Rainbow: A Search for Beauty in Physics and in Life. He also wrote for Star Trek: The Next Generation. He lives in South Pasadena, California.

www.its.caltech.edu/~len

Author: Stephen Hawking
Bio:  

Stephen Hawking was the Lucasian Professor of Mathematics at the University of Cambridge for thirty years, and has been the recipient of numerous awards and honors including, most recently, the Presidential Medal of Freedom. His books for the general reader include the classic A Brief History of Time, Black Holes and Baby Universes and Other Essays, The Universe in a Nutshell, and A Briefer History of Time. He lives in Cambridge, England.

www.hawking.org.uk

Leonard Mlodinow is a physicist at Caltech and the bestselling author of The Drunkard's Walk: How Randomness Rules our Lives, Euclid's Window: The Story of Geometry from Parallel Lines to Hyperspace, and Feynman's Rainbow: A Search for Beauty in Physics and in Life. He also wrote for Star Trek: The Next Generation. He lives in South Pasadena, California.

www.its.caltech.edu/~len

"In this short and sprightly book, Messrs. Hawking and Mlodinow take the reader through a whirlwind tour of fundamental physics and cosmology." - The Wall Street Journal

"Fascinating . . . a wealth of ideas [that] leave us with a clearer understanding of modern physics in all its invigorating complexity." - Los Angeles Times

"Groundbreaking." - The Washington Post