Summary of Stephen Hawking's A Brief History of Time

Everest Media

Description

Please note: This is a companion version & not the original book.
Sample Book Insights:
#1 The ancient Greek philosopher Aristotle believed that the earth was a round sphere rather than a flat plate. He knew that eclipses of the moon were caused by the earth coming between the sun and the moon, and that the North Star appeared lower in the sky when viewed in the south than it did in more northerly regions.
#2 Aristotle believed the earth was the center of the universe, and that circular motion was the most perfect. This idea was elaborated by Ptolemy in the second century AD into a complete cosmological model.
#3 The model proposed by Ptolemy in the second century AD was accepted by the Christian church as the picture of the universe that was in accordance with Scripture. However, a simpler model was proposed in 1514 by a Polish priest, Nicholas Copernicus.
#4 The Copernican model got rid of Ptolemy’s celestial spheres, and with them, the idea that the universe had a natural boundary. Since fixed stars did not appear to change their positions apart from a rotation across the sky caused by the earth spinning on its axis, it became natural to suppose that the fixed stars were objects like our sun but much farther away.

Sujets

• Astronomie
• Astrophysique
• Space science
• Cosmology

Informations

• Publié par: Everest Media LLC
• Date de parution: 24 mars 2022
• Nombre de lectures: 0
• EAN13: 9781669359753
• Langue: English
• Poids de l'ouvrage: 1 Mo

Extrait

Insights on Stephen Hawking's A Brief History of Time
Contents Insights from Chapter 1 Insights from Chapter 2 Insights from Chapter 3 Insights from Chapter 4 Insights from Chapter 5 Insights from Chapter 6 Insights from Chapter 7 Insights from Chapter 8 Insights from Chapter 9 Insights from Chapter 10 Insights from Chapter 11 Insights from Chapter 12
Insights from Chapter 1

#1

The ancient Greek philosopher Aristotle believed that the earth was a round sphere rather than a flat plate. He knew that eclipses of the moon were caused by the earth coming between the sun and the moon, and that the North Star appeared lower in the sky when viewed in the south than it did in more northerly regions.

#2

Aristotle believed the earth was the center of the universe, and that circular motion was the most perfect. This idea was elaborated by Ptolemy in the second century AD into a complete cosmological model.

#3

The model proposed by Ptolemy in the second century AD was accepted by the Christian church as the picture of the universe that was in accordance with Scripture. However, a simpler model was proposed in 1514 by a Polish priest, Nicholas Copernicus.

#4

The Copernican model got rid of Ptolemy’s celestial spheres, and with them, the idea that the universe had a natural boundary. Since fixed stars did not appear to change their positions apart from a rotation across the sky caused by the earth spinning on its axis, it became natural to suppose that the fixed stars were objects like our sun but much farther away.

#5

The idea that the universe is expanding was first suggested in the nineteenth century, but it was not well accepted. It was generally believed that the universe had existed forever in an unchanging state, or that it had been created at a finite time in the past.

#6

The beginning of the universe has been discussed by philosophers for a long time. The ancient Greeks believed that the human race and the world around it had existed forever, and that the universe had no beginning.

#7

When people believed in an essentially static and unchanging universe, the question of whether or not the universe had a beginning was largely a matter of metaphysics or theology. But in 1929, Edwin Hubble made the landmark observation that distant galaxies are moving away from us.

#8

A scientific theory is a model of the universe, or a restricted part of it, and a set of rules that relate quantities in the model to observations that we make. It exists only in our minds and does not have any other reality. A good theory is characterized by the fact that it makes a number of predictions that could be disproved or falsified by observation.

#9

The goal of science is to provide a single theory that describes the whole universe. However, the approach most scientists take is to separate the problem into two parts: the laws that describe how the universe changes with time, and the initial state of the universe.

#10

The search for a complete unified theory is difficult to justify on practical grounds. The discovery of a complete unified theory may not aid the survival of our species, but it may not even affect our life-style.
Insights from Chapter 2

#1

The Aristotelian tradition, which believed that bodies naturally existed in a state of rest, and that they moved only if driven by a force or impulse, was incorrect. Galileo showed that bodies of different weights fell at the same speed.

#2

Newton’s second law states that a body will accelerate at a rate that is proportional to the force. The acceleration is also smaller the greater the mass of the body. This law explains why all bodies fall at the same rate: a body of twice the weight will have twice the force of gravity pulling it down, but it will also have twice the mass.