A Brief History of Time

The book opens with a famous anecdote: as the story goes, Bertrand Russell was once giving a lecture on astronomy when an elderly woman at the back of the hall stood up and said the world actually rests on the back of a giant turtle. When Russell asked, mockingly, what the turtle stands on, she replied: "You're very clever, young man, but it's turtles all the way down!" With this joke, Hawking prepares the reader for the possibility that the question of how the universe "stands" might seem just as naive as the turtle's answer.

Hawking then returns to the beginning of the history of science: as early as 340 BCE, Aristotle had already proven with two solid arguments that the Earth was a sphere rather than a flat disk — the roundness of the shadow cast during a lunar eclipse, and the fact that the North Star appears at different angles at different latitudes. Hawking also notes that Aristotle calculated the Earth's circumference as 400,000 stadia — roughly twice today's accepted value.

The chapter then moves from Ptolemy's Earth-centered model to Copernicus's sun-centered proposal — Copernicus first circulated his idea anonymously, out of fear of the Church. Kepler and Galileo went on to defend the theory, and in 1609, Galileo's telescopic observations (of Jupiter's moons) dealt a fatal blow to the Aristotelian-Ptolemaic model.

Hawking then turns to Newton's law of gravity and explains how it relates to Einstein's general theory of relativity — Newton's theory still works fine in everyday life, since the difference between the two theories is negligible under ordinary conditions, but subtle anomalies in Mercury's orbit confirm Einstein's theory instead.

The chapter's central argument is this: modern physics describes the universe with two "partial theories" — general relativity for large scales, quantum (particle) mechanics for very small scales — and these two theories contradict each other; both cannot be correct at once. Hawking announces the search for a "quantum theory of gravity" that would resolve this contradiction as the book's main subject.

The chapter closes on a philosophical question: if the universe is entirely governed by laws, can human reasoning actually reach true conclusions, or is even that predetermined? Hawking answers with Darwin's principle of natural selection — since organisms that reason correctly gain an advantage in the struggle for survival and reproduce, it's no accident that human intelligence is capable of correctly understanding the universe; it's a result of evolution.

What comes after this is the work of the book's remaining ten chapters — space and time, the expanding universe, black holes, and the nature of time. So we're stopping here, and we recommend you get the book and read it yourself. But if what you've read so far interests you, you can check the brief overview of the remaining chapters in the section below.

• Hawking deliberately avoids mathematical formulas (the book contains just one equation — E=mc²), relying instead on analogies and everyday examples.
• The history of science is presented as a chronological narrative — it reads as one continuous story from Aristotle to Einstein.
• The chapters build on one another thematically — it becomes harder to follow a later chapter without having read the ones before it.
• The book opens with a foreword by Carl Sagan, underscoring its place in the popular-science canon.
• The translation (Sabit Say, Murat Uraz) is precise, though some terminology differs from modern Azerbaijani scientific vocabulary.