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A Brief History of Time: Summary & Quotes

Instructor: Krista Langlois

Krista has taught language arts for 14 years. She has a master's degree in teaching and loves researching, reading, and introducing others to the wonders of literature and language.

In 1988, Stephen Hawking tried and succeeded in making physics and how everything in the universe works much more understandable. This lesson gives a chapter by chapter overview of ''A Brief History of Time'' as well as important quotations from the book.

A Brief History of A Brief History of Time

When Stephen Hawking first published A Brief History in Time, he had no idea it would become a best seller. The book has sold over 10 million copies and spent more than 5 years on the London Sunday Times bestseller list. Written in layman's terms, the book aims to address the questions even the most non-scientifically minded of us ask: ''What are we doing here, where did we come from, and where are we going?''

Stephen Hawking
stephen hawking

Chapter Summaries

Chapters 1 and 2

Chapter 1 is a short history of physics, its impact on our relationship and location within our universe, and gravity. Hawking addresses Aristotle and Ptolemy, the theory of a round world, and how the stars and the sun work as part of our universe. He also looks into Copernicus, Galileo, Kepler, and Newton who worked to prove that the Earth goes around the sun.

In Chapter 2, readers are introduced to theories of how objects move in the universe. Hawking begins with Aristotle, who believed heavier things would fall faster than light things, and moved on to Galileo who proved this wrong showing all objects decreased and increased speed at the same rate. Hawking also introduces Einstein's theory of relativity and how light interacts with time.

Einstein is responsible for our most famous physics equation: E=mc^2
Albert Einstein

Chapters 3, 4, and 5

Here we learn the universe is expanding. Discussed is the Doppler shift, a phenomenon that occurs when something is moving towards (blue shifts) or away (red shifts) from something else. By studying blue and red shifting through wavelengths of visible light, Edwin Hubble discovered many stars were red shifting. Hawking describes our expanding universe through this lens.

Chapter 4 deals with the idea that we could understand the universe's future as long as we knew everything about it at any time during the past or present. This theory was debunked by quantum mechanics and the uncertainty principle that states you can't know the future of anything because we can't measure both velocity and position (which is needed to make the future prediction).

Chapter 5 delves into the quark, the smallest known bits in the universe that are thought to make up everything. Also discussed are electromagnetic forces, spin, and gluons.

Quarks are the smallest material in the universe
quarkssmall

Chapters 6 and 7

In chapters 6 and 7, we learn what happens when a star's fuel supply dries up. Its fate depends on Chandrasechar's limit which explains that if a star is a certain mass, it will either become a white dwarf, a neutron star, or, if it's heavy enough and gravity collapses within it, a black hole! Also discussed is the event horizon, that black holes aren't really black, how particles can escape black holes as x-rays and gamma rays, and that black holes are constantly shrinking.

Black Holes form when the gravity collapses inside of a star
black holes in space

Chapter 8

Chapter 8 covers both the origin and fate of our universe. How did we begin and where are we likely to end up? A number of theories concerning a big bang singularity event are discussed such as the hot big bang model, chaotic boundary conditions, anthropic principle, and the inflationary model.

Chapters 9 and 10

In this chapter, Hawking works to support a theory that he himself hypothesized. His theory states there are three types of time (for those of us who are late all the time, maybe there's hope!), thermodynamic time, psychological time, and cosmological time. He discusses the arrow of time and how the direction of time's arrows would and do affect us and our reality.

Chapter 10 and here's time travel! Here Hawking discusses two types of time travel that may be possible: traveling faster than the speed of light or discovering/creating a wormhole in space that closes the gap between parts of the universe.

Physicists theorize that humans may be able to create wormholes in space
worm holes

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