Friday, 6 April 2018

Revisiting Hawking's A Brief History of Time

A Brief History of Time: From the Big Bang to Black Holes is arguably the most popular-science book on cosmology (the study of the universe) by the legendary British physicist Stephen Hawking who passed away recently.

It was first published in 1988. Hawking wrote the book for nonspecialist readers with no prior knowledge of scientific theories.

In A Brief History of Time, Hawking writes in non-technical terms about the structure, origin, development and eventual fate of the universe, which is the object of study of astronomy and modern physics. He talks about basic concepts like space and time, basic building blocks that make up the universe (such as quarks) and the fundamental forces that govern it (such as gravity). He writes about cosmological phenomena such as the Big Bang and black holes. He discusses two major theories, general relativity and quantum mechanics, that modern scientists use to describe the universe. Finally, he talks about the search for a unifying theory that describes everything in the universe in a coherent manner.

The book became a bestseller and sold more than 10 million copies in 20 years. It was also on the London Sunday Times bestseller list for more than five years and was translated into 35 languages.

In A Brief History of Time, Stephen Hawking attempts to explain a range of subjects in cosmology, including the Big Bang, black holes and light cones, to the nonspecialist reader. His main goal is to give an overview of the subject, but he also attempts to explain some complex mathematics. In the 1996 edition of the book and subsequent editions, Hawking discusses the possibility of time travel and wormholes and explores the possibility of having a universe without a quantum singularity at the beginning of time.

In the first chapter, Hawking discusses the history of astronomical studies, including the ideas of Aristotle and Ptolemy. Aristotle, unlike many other people of his time, thought that the Earth was round. He came to this conclusion by observing lunar eclipses, which he thought were caused by the earth's round shadow, and also by observing an increase in altitude of the North Star from the perspective of observers situated further to the north.

Aristotle also thought that the sun and stars went around the Earth in perfect circles, because of "mystical reasons". Second-century Greek astronomer Ptolemy also pondered the positions of the sun and stars in the universe and made a planetary model that described Aristotle's thinking in more detail.

How the universe started and how it might end is discussed in a chapter.

Most scientists agree that the universe started in an expansion called the Big Bang. The model for this is called the "hot big bang model". When the universe starts getting bigger, the things inside of it also begin to get cooler. When the universe was first beginning, it was infinitely hot. The temperature of the universe cooled and the things inside the universe began to clump together.

Hawking also discusses how the universe could have been. For example, if the universe formed and then collapsed quickly, there would not be enough time for life to form. Another example would be a universe that expanded too quickly. If a universe expanded too quickly, it would become almost empty. The idea of many universes is called the many-worlds interpretation..

Conclusion

Humans have always wanted to make sense of the universe and their place in it. At first, events were considered random and controlled by human-like emotional spirits. But in astronomy and in some other situations, regularities were observed. With the advancement of the human civilization in the modern age, more regularities and laws were discovered.

Laplace suggested at the beginning of the nineteenth century that the universe’s structure and evolution could eventually be precisely explained by a set of laws. However, the origin of these laws was left in God’s domain. In the twentieth century, quantum theory introduced the uncertainty principle, which set limits to the predictive accuracy of laws to be discovered.

The big bang implied by the general theory of relativity indicates that a creator of the universe or God has the freedom to choose the origin and the laws of the universe. When one combines theory of relativity with quantum mechanics, however, a unified and completely self-contained theory may emerge, in which God has little or no role to play. So the search of a unified theory may shed light on the nature of God. However, most scientists today are working on the theories themselves than asking such philosophical questions.

On the other hand, these physical theories are so mathematical and technical that philosophers are not discussing them like they used to do, let alone ordinary people. Hawking would like to see that eventually everybody would one day talk about these theories in order to understand the true origin and nature of the universe, accomplishing the ultimate triumph of human reasoning.

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