A Brief History Of Time Summary

Stephen Hawking

A Brief History Of Time

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A Brief History Of Time Summary

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The notion that a book about cosmology (the study of the universe), a book including topics such as elementary particles and the unification of physics, could become a widespread bestseller was a long shot at best. Its author, however, British physicist Stephen Hawking, has proven himself capable of defying the odds: though he was given a life expectancy of two years in 1963, when at age twenty-one he was diagnosed with a form of amyotrophic lateral sclerosis, he continues his work today. In A Brief History of Time, Hawking writes about the origin and composition of the universe in accessible terminology for the masses. By explaining complex topics such as relativity and quantum mechanics, and phenomena such as the big bang and black holes, Hawking expanded general interest in cosmology and sold more than twenty million copies of the book along the way. What distinguishes Hawking’s bestseller from traditional scientific textbooks is his ability to be clear, without the use of intimidating equations. Indeed, only one equation appears in the entire book: E=mc2.

Hawking begins with an account of the historical studies of astronomy by ancients such as Aristotle and Ptolemy. The concept of a round-shaped Earth that was held by Aristotle was contrary to most others of his time. He came to this conclusion via his observations of lunar eclipses and by considering the altitude of the North Star from various observational points. He, like Ptolemy, believed the sun and stars orbited the Earth. This hypothesis was later disproven by the work of Copernicus, Galileo, and Kepler. As studies of the origin of the universe progressed, two opposing viewpoints become the most common: philosophers believed that the universe had always existed, while theologians generally contended that the universe was created at a specific point in time. The dominant name among the theologians, St. Augustine, held this belief, coupled with the idea that time itself was a concept that did not exist until the creation of the universe.  By the twentieth century, Edwin Hubble discovered that galaxies are moving away from each other, meaning that at one time they were all in one place. Scientists continue to seek a theory that would encompass everything in the universe and be able to explain it all.

Space and time are examined in Chapter Two, especially with respect to Albert Einstein’s theory of relativity. The big bang, which grew to be the dominant theory of the creation of the universe, is the basis for the third chapter. This concept of an expanding universe is explained by Hawking via the Doppler shift, which occurs when something moves toward or away from something else.  The uncertainty principle, which indicates that the speed and the position of particles cannot both be found at the same time, is the concept of Chapter Four. This chapter considers the behaviors of light and serves to undermine the concept of deterministic theories, which were said to be able to predict everything in the future. The next chapter explains the building blocks of the universe.  These are the smallest things from which all matter is made, and are called quarks. Nuclear forces unite the quarks into neutrons and protons and keep the neutrons and protons together in atoms. Hawking goes on to describe what is known as a “grand unified theory” in which some scientists attempt to explain weak and strong nuclear forces and electromagnetic forces in a unified manner.

Black holes are the central focus of the next chapter. Black holes are stars that have collapsed into one very small point called a singularity. They have a very strong gravitational force, thus are able to pull things, including light and stars, to their centers. Black holes are almost impossible to locate because they do not let light out. However, they can be seen by telescopes when they suck in other stars, thus emitting x-rays. Subsequent chapters explain topics in cosmology including entropy, which concerns disorder in the universe, and the big bang explosion, which is commonly believed to have been the birth of the universe. Worm holes and time travel are discussed as well. A worm hole is, in theory, a passage that could serve as a shortcut through the universe by collapsing space and time.

What sets A Brief History of Time apart from other texts on cosmology is, according to the New York Times Book Review, that it provides readers “with a jaunty overview of key cosmological ideas, past and present” and is at its best when Hawking “allows us a peek at his impish humor, inner motivations, theoretical goofs and scientific prejudices.” By injecting his personality into what previously had been staid accounts of ancient theories, “Mr. Hawking is bravely taking some of the first, though tentative, steps toward quantizing the early universe, and he offers us a provocative glimpse of the work in progress.”