Stephen Hawking’s central mission in A Brief History of Time is to find a unifying scientific theory that will explain the universe itself. This one definitive theory would pull together all the separate theories that scientists have already, under one set of rules that illuminates and predicts how everything in existence works. The book is a chronology of humankind’s efforts so far to determine this unifying theory, as well as ongoing work to find the answer to how everything in the universe works. This is a mission Hawking undertakes on the basis of fulfilling humanity’s “deepest desire for knowledge,” hinting that his quest to find a unifying theory of physics is no less than a quest to find the meaning of life itself.
Hawking argues there is most likely a unified theory of everything because scientists find that strict rules, for example the law of gravity, govern the universe’s makeup and movement. If everything is ordered, it follows there is one central key that determines the nature of the entire universe. Hawking writes, “Now, if you believe that the universe is not arbitrary, but is governed by definite laws, you ultimately have to combine the partial theories into a complete unified theory that will describe everything in the universe.” The observable world follows strict, predictable rules, meaning all the accurate scientific theories developed should fit together; any contradiction would imply chaos.
So far, scientists have found four forces that relate to and govern all force-particles in the universe. These are: gravitational force, electromagnetic force, the weak nuclear force, and the strong nuclear force. Yet scientists have not found a singular theory that ties these forces together, meaning this unification quest is ongoing. “Ultimately,” Hawking writes, “most physicists hope to find a unified theory that will explain all four forces as different aspects of a single force. Indeed, many would say this is the prime goal of physics today.” Hawking, then, is not alone in his quest. Rather, hoped-for, central theories motivate scientists around the world.
While finding such a unifying theory might excite physicists, Hawking is not oblivious to the fact this question does not usually occupy a place close to the average person’s heart. Hawking admits: “The discovery of a complete unified theory […] may not aid the survival of our species. It may not even affect our life-style.” The average person’s everyday life might not change after the conclusion of this epic quest, even if scientists find their long-sought-after goal. This raises the question of whether physicists’ efforts and intellect are well-placed or a waste of time in that they don’t immediately affect the practical realities of human existence.
Yet Hawking asserts that seeking such answers represents the deepest longing of the human heart. Since ancient times, people have looked to the stars and asked the “big, basic questions” about how and why we exist, and that still hasn’t changed. “Today we still yearn to know why we are here and where we came from,” Hawking writes. “Humanity’s deepest desire for knowledge is justification enough for our continuing quest.” Hawking represents his mission as a service to humankind’s perpetual longing to know where we come from. Although the lay person might not phrase their inner longing for meaning as the search for the unification of physics, Hawking says that, in fact, both searches are more or less the same.
He further suggests that by finding how we came to be here, we might start to understand why. Hawking states, “Then we shall all […] be able to take part in the discussion of the question of why it is that we and the universe exist.” In finding a unified theory of physics, then, humankind would give itself the ability to perceive and understand the entirety of the universe and to perhaps answer the deepest question of all: the meaning of life. In seeking the key rules that govern the activity of the entire universe, Hawking’s quest is essentially to find the tools with which to answer the big questions asked by every person who ever lived, although they perhaps did not realize the answer could be found via theoretical physics. For Hawking, uncovering the secrets of the universe is searching for the meaning of life. But, without the unified theory of everything, that reality feels cosmically distant.
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The Search for a Unifying Theory of the Universe Quotes in A Brief History of Time
Our sun is just an ordinary, average-sized, yellow star, near the inner edge of one of the spiral arms [of a galaxy that is 100,000 light-years across]. We have certainly come a long way since Aristotle and Ptolemy, when we thought that the earth was the center of the universe!
The success of scientific theories […] led the French scientist the Marquis de Laplace […] to argue that the universe was completely deterministic. Laplace suggested that there should be a set of scientific laws that would allow us to predict everything that would happen in the universe.
We now know that neither the atoms nor the protons and neutrons within them are indivisible. So the question is: what are the truly elementary particles, the basic building blocks from which everything is made?
The whole history of science has been the gradual realization that events do not happen in an arbitrary manner […] they reflect a certain underlying order, which may or may not be divinely inspired. […] There ought to be some principle that picks out […] one model, to represent our universe.
Must we turn to the anthropic principle for an explanation? Was it all just a lucky chance? That would seem a counsel of despair, a negation of all our hopes of understanding the underlying order of the universe.
We don’t yet have a complete and consistent theory that combines quantum mechanics and gravity. However, we are fairly certain of some features that such a unified theory should have.
The progress of the human race in understanding the universe has established a small corner of order in an increasingly disordered universe.
A complete, consistent, unified theory is only the first step: our goal is a complete understanding of the events around us, and of our own existence.
Even if there is only one possible unified theory, it is just a set of rules and equations. What is it that breathes fire into the equations and makes a universe for them to describe? […] Why does the universe go to all the bother of existing?
[…] if we do discover a complete theory […] Then we shall all […] be able to [discuss] why it is that we and the universe exist. If we find the answer to that, it would be the ultimate triumph of human reason—for then we would know the mind of God.