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Brief Summary of "A Brief History of Time"

Stephen Hawking wrote "A Brief History of Time" in order to explain to the ordinary people who populate society how science works. But Hawking did not do so in a complicated fashion in which he fills it up with scientist jargon that would scare off most non-scientists. He finds a way to teach it to the non-scientist community in a way that makes sense. This is what has made his book so popular and well-known. Explaining the most complicated things we know of in science today, he simplified several theories such as the Theory of Relativity, the models of the universe, and the mind-boggling Quantum Mechanics field.
For the general theory of relativity, I learned from him that an object can never move at the speed of light because Einstein's famous equation, E=MC^2, says that it would take an infinite amount of energy and infinite mass in order to propel it that fast. I also learned that gravity travels at an infinite speed, but not at the speed of light.
I learned about the three models of the universe that scientists have come up with over the years. One model says that gravity will expand the universe until it collapses on itself. Another model says that space is curved and not infinite and gravity cannot prevent the inevitable expansion of our universe. the third model states that space is flat and infinite and the expansion of the universe is going fast enough to not collapse. Through Hawking's calculations, he says that the universe will continue to expand for infinity.
Quantum Mechanics is a field that is not fully realized yet, but is still credible enough to put faith in. Einstein once said "God does not play dice" in disdain towards this field. He did not know that this theory would soon become generally accepted. Quantum Mechanics says that energy must be produced in particles called quanta. To predict the location of a particle, you need to know its position and velocity. But in order to view the particle, you need to use at least one quantum of light which changes the velocity of the particle. This is what makes it hard to observe particles because by observing the particle more properly, you will disrupt the particle more.
Hawking's book did what my physics teacher struggles to achieve in class everyday: Make me understand the concept of physics. It is a very foreign field to people who use their right brain a lot more often like me, and it takes some simplification in order to get these concepts understood correctly. This is a book that does a good job in compressing physics down into one understandable format.

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.