Stephen Hawking's worldwide bestseller, A Brief History of Time, has been a landmark volume in scientific writing. Its author's engaging voice is one reason, and the compelling subjects he addresses is another: the nature of space and time, the role of God in creation, the history and future of the universe. But it is also true that in the years since its publication, readers have repeatedly told Professor Hawking of their great difficulty in understanding some of the book's most important concepts.
This is the origin of and the reason for A Briefer History of Time: its author's wish to make its content more accessible to readers -as well as to bring it up-to-date with the latest scientific observations and findings.
Although this book is literally somewhat "briefer," it actually expands on the great subjects of the original. Purely technical concepts, such as the mathematics of chaotic boundary conditions, are gone. Conversely, subjects of wide interest that were difficult to follow because they were interspersed throughout the book have now been given entire chapters of their own, including relativity, curved space, and quantum theory.
This reorganization has allowed the authors to expand areas of special interest and recent progress, from the latest developments in string theory to exciting developments in the search for a complete unified theory of all the forces of physics. Like prior editions of the book-but even more so-A Briefer History of Time will guide nonscientists everywhere in the ongoing search for the tantalizing secrets at the heart of time and space.
Starred Review. In the 17 years since the publication of A Brief History of Time, Dr. Hawking's bestselling exposition of physics, new data from particle physics and observational astronomy have shed light on efforts to find a Grand Unified Theory of Everything that Hawking and Mlodinow use to enhance and update their answers to basic questions about the universe: where it's going and how it began. Discussed at length are the mysterious dark matter and dark energy-both of which can only be observed by their gravitational effects and are believed to make up 90 percent of the universe. Another area of research that has exploded in the past 20 years is string theory. Hawking and Mlodinow provide one of the most lucid discussions of this complex topic ever written for a general audience. Readers will come away with an excellent understanding of the apparent contradictions and conundrums at the forefront of contemporary physics. Recognizing that much of their audience will also be science fiction buffs, they include a chapter on the possibility of time travel. "Don't bet on it," the authors advise. Throughout these discussions, the authors maintain the same wry, lively tone that made the original Brief History such a delight. They close with a discussion of where physics ends and philosophy begins, "Why does the universe exist at all?" They cannot provide the answer, but they do provide an immense amount of food for thought. Highly recommended.
Copyright (c) Reed Business Information, a division of Reed Elsevier Inc. All rights reserved. -- PUBLISHERS WEEKLY.
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September 26, 2005
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Excerpt from A Briefer History of Time by Stephen Hawking
Thinking About the Universe
WE LIVE IN A STRANGE AND wonderful universe. Its age, size, violence, and beauty require extraordinary imagination to appreciate. The place we humans hold within this vast cosmos can seem pretty insignificant. And so we try to make sense of it all and to see how we fit in. Some decades ago, a well-known scientist (some say it was Bertrand Russell) gave a public lecture on astronomy. He described how the earth orbits around the sun and how the sun, in turn, orbits around the center of a vast collection of stars called our galaxy. At the end of the lecture, a little old lady at the back of the room got up and said: "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant turtle." The scientist gave a superior smile before replying, "What is the turtle standing on?" "You're very clever, young man, very clever," said the old lady. "But it's turtles all the way down!"
Most people nowadays would find the picture of our universe as an infinite tower of turtles rather ridiculous. But why should we think we know better? Forget for a minute what you know-or think you know-about space. Then gaze upward at the night sky. What would you make of all those points of light? Are they tiny fires? It can be hard to imagine what they really are, for what they really are is far beyond our ordinary experience. If you are a regular stargazer, you have probably seen an elusive light hovering near the horizon at twilight. It is a planet, Mercury, but it is nothing like our own planet. A day on Mercury lasts for two-thirds of the planet's year. Its surface reaches temperatures of over 400 degrees Celsius when the sun is out, then falls to almost -200 degrees Celsius in the dead of night. Yet as different as Mercury is from our own planet, it is not nearly as hard to imagine as a typical star, which is a huge furnace that burns billions of pounds of matter each second and reaches temperatures of tens of millions of degrees at its core.
Another thing that is hard to imagine is how far away the planets and stars really are. The ancient Chinese built stone towers so they could have a closer look at the stars. It's natural to think the stars and planets are much closer than they really are-after all, in everyday life we have no experience of the huge distances of space. Those distances are so large that it doesn't even make sense to measure them in feet or miles, the way we measure most lengths. Instead we use the light-year, which is the distance light travels in a year. In one second, a beam of light will travel 186,000 miles, so a light-year is a very long distance. The nearest star, other than our sun, is called Proxima Centauri (also known as Alpha Centauri C), which is about four light-years away. That is so far that even with the fastest spaceship on the drawing boards today, a trip to it would take about ten thousand years.
Ancient people tried hard to understand the universe, but they hadn't yet developed our mathematics and science. Today we have powerful tools: mental tools such as mathematics and the scientific method, and technological tools like computers and telescopes. With the help of these tools, scientists have pieced together a lot of knowledge about space. But what do we really know about the universe, and how do we know it? Where did the universe come from? Where is it going? Did the universe have a beginning, and if so, what happened before then? What is the nature of time? Will it ever come to an end? Can we go backward in time? Recent breakthroughs in physics, made possible in part by new technology, suggest answers to some of these long-standing questions. Someday these answers may seem as obvious to us as the earth orbiting the sun-or perhaps as ridiculous as a tower of turtles. Only time (whatever that may be) will tell.
Our Evolving Picture of the Universe
ALTHOUGH AS LATE AS THE TIME of Christopher Columbus it was common to find people who thought the earth was flat (and you can even find a few such people today), we can trace the roots of modern astronomy back to the ancient Greeks. Around 340 B.C., the Greek philosopher Aristotle wrote a book called On the Heavens. In that book, Aristotle made good arguments for believing that the earth was a sphere rather than flat like a plate.