Editing A Brief History of Time (section)

=== Chapter 1: Our Picture of the Universe ===
[[File:Ptolemaic-geocentric-model.jpg|thumb|[[Ptolemy]]'s Earth-centric model about the location of the planets, stars, and Sun]]

Hawking begins with an anecdote about a scientist lecturing on the universe. An old woman got up and said, "What you have told us is rubbish. The world is really a flat plate supported on the back of a giant tortoise." The scientist asked what the tortoise was standing on. She replied, "You're very clever young man, very clever. But it's [[turtles all the way down]]!"{{Sfnp| Hawking| 1996| p=2}} Hawking goes on to explain why we know better.

He discusses the history of [[astronomy]], starting with [[Aristotle]]'s conclusions about a [[spherical Earth]] and a circular [[geocentric model]] of the universe, later elaborated upon by the second-century Greek astronomer [[Ptolemy]]. He discusses the development of the [[heliocentric model]] of the [[Solar System]] by the Polish astronomer [[Nicholas Copernicus]] in 1514. A century later, the Italian [[Galileo Galilei]] turned a Dutch spyglass to the heavens. His observations of [[Galilean satellites| Jupiter's moons]] provided support for Copernicus. The German astronomer [[Johannes Kepler]] formulated his [[Kepler's laws of planetary motion| laws of planetary motion]], in which planets move in [[ellipse|ellipses]]. Kepler's laws were explained by English physicist [[Isaac Newton]] in his ''[[Philosophiæ Naturalis Principia Mathematica|Principia Mathematica]]'' (1687). 

Hawking discusses how the subject of the origin of the universe has been debated over time: the perennial existence of the universe hypothesized by Aristotle and other early philosophers was opposed by [[St. Augustine]] and other theologians' belief in its creation at a specific time in the past. [[Immanuel Kant]] argued that time had no beginning. In our time, the discovery of the expanding universe implied that between 10 billion and 20 billion years ago, the entire universe was contained in one singular extremely dense place, and that it doesn't make sense to ask what happened before. He writes: "An expanding universe does not preclude a creator, but it does place limits on when he might have carried out his job!"<ref>{{cite book| last=Hawking| first=Stephen| title=The Illustrated A Brief History of Time| p=14-15| year=1996}}</ref>