63 pages • 2 hours read
Stephen HawkingA Brief History Of Time
Nonfiction | Book | Adult | Published in 1988A modern alternative to SparkNotes and CliffsNotes, SuperSummary offers high-quality Study Guides with detailed chapter summaries and analysis of major themes, characters, and more.
Themes
Humanity’s Shift from Philosophy to Science
Since ancient times, people have searched for explanations of how the world works, and why. Many accept the idea that a divine, external force created and maintains the cosmos, and ancient humans personified the natural world and its behaviors in anthropomorphic deities. In recent centuries, science has developed the tools to answer many of the old questions—why the seasons change, or why the sun rises and sets—with precise, provable answers. As a result, Hawking argues that the need for mythological or religious explanations for the forces in the universe decreases as science improves. By tracing the history of theoretical physics, Hawking explores how new and increasingly more accurate theories and experimentation brought old religious philosophies into question.
Aristotle argued that human reason alone could figure out how the cosmos works. He assumed that all matter was infinitely divisible, that the world was made of five essences, that objects tend to come to rest unless pushed, and that heavy objects fall faster than light ones. Galileo showed, with simple experiments, that heavy and light objects fall at the same rate: he “rolled balls of different weights down a smooth slope,” and “each body increased its speed at the same rate, no matter what its weight” (15). Where Aristotle asserted that bodies tended naturally to stop moving unless constantly pushed, Newton proved, with data carefully collected by astronomers, that heavenly bodies tend to stay in motion unless pulled by other bodies’ force of gravity, and that they do so at a specific rate that depends on their mass and distance. Using scientific techniques, physicists in recent centuries also found that matter is made of atoms. Their careful approach to gathering data, testing theories against evidence, and reaching cautious conclusions proved far more powerful than Aristotle’s somewhat arbitrary conclusions.
Hawking argued that, throughout this process, science overtook philosophy as the chief means of human thought for learning about the world around us:
[I]n the nineteenth and twentieth centuries, science became too technical and mathematical for the philosophers, or anyone else except a few specialists. Philosophers reduced the scope of their inquiries (191).
Where science and philosophy were once complementary fields of study, today the two fields are largely pursued separately. However, as Hawking is careful to emphasize, the scientific pursuit of explanations for how the universe began, what it’s made of, and where it may be headed have major philosophical and ideological implications. Hawking believes that advancements in science supplanted the insights of religion and philosophy concerning the universe with the careful techniques of experimentation, mathematical reasoning, and skeptical questioning of all data and theories. Hawking’s conclusions are reciprocally informed by his atheistic worldview, but he does use the concept of God as an intelligent creator throughout the book as an analogy for the inevitable, inherent, yet unknown conditions and rules of the universe. Other scientists, like evolutionary biologist Stephen Jay Gould, propose that science and religion exist to answer fundamentally different questions of facts and values, respectively, a theory referred to as Non-Overlapping Magisteria (NOMA). However, because of the historical relationship between scientific revelation and shifts in theology and philosophy, Hawking posits that science can sufficiently explain why anything exists, in addition to describing the conditions of that existence.
The Search for the Ultimate Answer
Hawking describes the major goal of science as the establishment of a single theory or equation that describes how the universe works, thus revealing how it began and how it might end. Hawking was a major contributor to this challenging effort, and his book A Brief History of Time summarizes that work. Hawking writes that science wants nothing less than a complete explanation of the cosmos, that scientists have pursued this goal relentlessly for millennia, and that humans may be close to finding an answer.
Hawking notes that curiosity about the nature of the universe drives scientific inquiry: “We want to make sense of what we see around us and to ask: What is the nature of the universe? What is our place in it and where did it and we come from? Why is it the way it is?” (187). These questions drive Hawking’s research as well. Parts of the answer to these questions came during the 20th century when two landmark intellectual achievements, the theory of relativity and quantum mechanics, proved able to explain the macrocosmic and microcosmic aspects of the universe, respectively. Studies of the stars showed that the universe is made up of billions of galaxies separated by vast spaces of emptiness, and relativity proposed that all of it must have started at a single, infinitely dense point and then spread out rapidly to form a universe that’s still expanding today. Quantum mechanics provided clues to how that tiny point must have evolved as it expanded.
Scientists are relentless about getting answers. Once they theorized that the universe began as a point source, they wondered what the conditions were inside that point. Others considered “the question of the initial situation as a matter for metaphysics or religion” (11)—that is, a matter of theoretical religious or philosophical thought, and not the province of physical science. Yet understanding the initial conditions of the universe would go a long way toward helping cosmologists discover an ultimate answer to the puzzle of existence, which in turn would create radical new scientific possibilities. Hawking, however, believes that the singular, infinitely dense point that contained all matter and energy is itself an impenetrable barrier: “Under such conditions all the laws of science, and therefore all ability to predict the future, would break down” (9). Hawking characterizes the search as incrementally more and more complete, and also as potentially futile by current methodologies. The “Theory of Everything” has never been closer, yet remains unsolvable.
So far, a Grand Unified Theory remains elusive because no one has found a way to unite the force of gravity with the quantum mechanics of the other three forces. Lacking such a unification, a single, all-encompassing law of matter and energy remains elusive. New data from studies of the cosmic background radiation, and from gravitational waves caused by colliding black holes and neutron stars, are helping scientists draw ever closer to an answer. It’s in scientists’ nature never to rest until a great puzzle is solved; Hawking believes humanity may truly be close to unraveling this greatest of all mysteries.
The Need for Humility in the Process of Scientific Discovery
Several times in the book, Hawking relates stories of scientists who believed in something that they later discovered was incorrect. Fallibility despite high intelligence and plentiful resources is a hard reality for scientists, whose pride and career opportunities sometimes depend on the answers they produce. Hawking posits that it is nevertheless vital to the progress of science that theorists admit when they’re wrong so that everyone can move forward and find the correct—or even just a better—solution.
Sir Arthur Eddington was the physicist who helped prove Einstein’s theory of general relativity during a voyage to witness a total eclipse. Starlight from behind the sun could be seen next to it because of the sun’s gravitational warpage of space-time around it. Eddington and most physicists of the time, including Einstein, believed black holes weren’t possible, even though they were implied by Einstein’s theory. Eddington’s student, Subrahmanyan Chandrasekhar, showed that the Pauli Exclusion Principle, which prevents matter particles from occupying the same space, breaks down in situations of extremely high density, so that particles can be squished together into a single point in space. Eddington discouraged Chandrasekhar from pursuing this research, but later developments proved Chandrasekhar was right. Eddington still refused to believe it; Chandrasekhar later won the Nobel Prize, in part for his discovery confirming black holes. Studies have since confirmed the existence of billions of black holes in the universe.
Even Einstein contradicted or rejected his own ideas occasionally. He proposed a cosmological constant that regulated the expansion of the universe, but he later decided this was wrong and called the idea “the biggest mistake of his life” (155). Ironically, in the 1990s, astronomical surveys supported the notion that a cosmological constant is, in fact, a part of the universe. Einstein disavowed his concept based on what was known at the time; had he lived to hear of the recent discoveries, he might have learned that his original intuition was correct. The fallibility—and uncertainty—of one of science’s most revered thinkers emphasizes the collaborative nature of science. Many minds and ideas are needed to interrogate problems and consider questions from different perspectives.
Hawking argued for many decades that the universe began as a “singularity” that contained all the contents of the universe in a single point of infinite density. His later research suggested that such points may not exist, and he found himself in the position of arguing against his own theory. Hawking’s willingness to change his mind, based on the latest knowledge, is a testament to his honesty and desire to find the truth at whatever cost to his reputation. Science makes progress in part because its greatest theorists are willing to be wrong and to improve their theories. Hawking posits that for the best scientists, what’s actually true is superior to what feels right.
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