A Brief History of Time Chapter 3 Summary

In this chapter, Hawking begins by describing the night sky. Proxima Centauri, our nearest star, is 4 light years away. It would take a mere 8 light minutes to reach our sun, much less than Proxima Centauri. Knowing how separated our solar system is from the others is a kind of despairing thought, but we, as the curious minded humans that we are, carried on to discover more. Sir William Herschel would confirm the idea that all our stars are in a collection of stars that is now known as the Milky Way. But Hubble suggested the idea that our galaxy was not the only one and that there were many more galaxies in the universe out there. He decided that he must find a way to prove that there are many, many galaxies with little periods of space in between them. So he used the star's luminosity and distance to determine this. Eventually, he came up with a conclusion: Our universe is expanding.

A Brief History of Time Chapter 2 Summary

In this chapter, he explains about the birth of our ideas of motion of bodies. He begins with Aristotle, who said a body was at rest unless driven by a force or impulse. BUT he went on to say that heavier bodies fell faster than lighter bodies because the pull should be greater on the heavier object than the lighter one. Galileo eventually looked back on this and disproved his theory of the heavy and the light objects having different velocities. He rolled balls of different weight down a smooth slope (this method was equivalent to that of dropping two objects of different weight) and proved that "each body increased its speed at the same rate, no matter what its weight [was]".
Newton took this idea and used it to found his laws of motion. These famous three laws of motions are still widely used today. Newton also discovered another very famous concept in science: Gravity. This is what Stephen Hawking will use in the novel in order to explain more theories and answer some of the questions that there are.

A Brief History of Time Chapter 1 Summary

Stephen Hawkings, a brilliant mind of today, begins his book with a series of questions that are very important to us: Where did the universe come from? What is the nature of time? Will the universe come to an end? For those expecting him to give a final answer to these gigantic questions, they best look elsewhere. He, as the mortal human being that he is, cannot give us a final answer, but can only suggest an answer. They are very good answers, however.
He goes on to explain how Aristotle made an argument that the Earth was round but thought that it was at its center. Then Ptolemy advanced this and came up with a model for the planets and the sun, but it was still a geocentric model. Finally, Copernicus invents the heliocentric model but it was not taken up until Galileo publicly supported it. Kepler then proceeded to complete the model by saying that the planets did not move in circles but rather in ellipses.