A BRIEF HISTORY OF TIME PDF
A NOT-QUITE-SO BRIEF HISTORY OF TIME Many Times Its Original Size in a Very Short Period of Time. EXPANSION. 7. In Which the Universe Continues to. A BRIEFER HISTORY OF TIME The History of the Universe in Words or Less Quantum In the years since A Brief History of Time was published A Briefer. A Brief History of Time - Stephen Hawking Chapter 1 - Our Picture of the Universe Chapter 2 - Space and Time Chapter 3.
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I didn't write a foreword to the original edition of A Brief History of Time. A brief history of time/A Brief History in resourceone.info (1 of 2) [2/20/ A Brief History of Time - Stephen Hawking. Chapter 1 - Our Picture of the Universe Chapter 2 - Space and Time Chapter 3 - The Expanding. I didn't write a foreword to the original edition of A Brief History of Time. The success of A Brief History indicates that there is widespread interest in the big.
Secondly, the universe would expand and at sometime if the expansion rate and the density of the universe become equal, it would expand slowly and stop at infinite time, leading to a somewhat static universe. Thirdly, the universe would continue to expand forever if the density of the universe is less than the critical amount required to balance the expansion rate of the universe.
The first model depicts the space of universe to be curved inwards, a somewhat earth-like structure. In the second model, the space would lead to a flat structure, and the third model results in negative curvature, or saddle shaped.
Even if we calculate, the current expansion rate is more than the critical density of the universe including the dark matter and all the stellar masses. The first model included the beginning of the universe as a big-bang from a space of infinite density and zero volume known as ' singularity ', a point where General Theory of Relativity Friedmann's solutions are based in it also breaks down.
This concept of the beginning of time was against many religious beliefs, so a new theory was introduced. Its predictions also matched with the current Universe structure. But the fact that radiowave sources near us are far fewer than from the distant universe and there were numerous more radio sources than at present, resulted in failure of this theory and everybody finally supported the Big Bang theory.
Roger Penrose used light cones and General Relativity to prove that a collapsing star could result in a region of zero size and infinite density and curvature called a Black Hole. Hawking and Penrose proved together that the universe should have arisen from a singularity, which Hawking himself disproved once Quantum effects are taken into account.
Chapter 4: The Uncertainty Principle[ edit ] The uncertainty principle says that the speed and the position of a particle cannot be found at the same time. To find where a particle is, scientists shine light at the particle. If a high frequency light is used, the light can find the position more accurately but the particle's speed will be unknown because the light will change the speed of the particle. If a lower frequency light is used, the light can find the speed more accurately but the particle's position will be unknown.
The uncertainty principle disproved the idea of a theory that was deterministic, or something that would predict everything in the future. Here is a picture of a light wave. How light behaves is also talked more about in this chapter. Some theories say that light acts like particles even though it really is made of waves; one theory that says this is Planck's quantum hypothesis. A different theory also says that light waves also act like particles; a theory that says this is Heisenberg's uncertainty principle.
Light interference causes many colors to appear. Light waves have crests and troughs. The highest point of a wave is the crest, and the lowest part of the wave is a trough. Sometimes more than one of these waves can interfere with each other - the crests and the troughs line up. This is called light interference. When light waves interfere with each other, this can make many colors. An example of this is the colors in soap bubbles.
A Brief History of Time
Chapter 5: Elementary Particles and Forces of Nature[ edit ] Quarks and other elementary particles are the topic of this chapter. Quarks are very small things that make up everything we see matter. There are six different "flavors" of quarks: the up quark, down quark, strange quark, charmed quark, bottom quark, and top quark. Quarks also have three "colors": red, green, and blue. There are also anti-quarks, which are the opposite of the regular quarks.
In total, there are 18 different types of regular quarks, and 18 different types of anti quarks.
Quarks are known as the "building blocks of matter" because they are the smallest thing that make up all the matter in the universe. A particle of spin 1 needs to be turned around all the way to look the same again, like this arrow.
All particles for example, the quarks have something called spin. The spin of a particle shows us what a particle looks like from different directions. For example, a particle of spin 0 looks the same from every direction.
A particle of spin 1 looks different in every direction, unless the particle is spun completely around degrees. Hawking's example of a particle of spin 1 is an arrow.
A particle of spin two needs to be turned around halfway or degrees to look the same. The example given in the book is of a double-headed arrow. All of these particles follow the Pauli exclusion principle.
Pauli's exclusion principle says that particles cannot be in the same place or have the same speed. If Pauli's exclusion principle did not exist, then everything in the universe would look the same, like a roughly uniform and dense "soup". This is a proton. It is made up of three quarks. All the quarks are different colors because of confinement.
Particles with a spin of 0, 1, or 2 move force from one particle to another. Some examples of these particles are virtual gravitons and virtual photons. Virtual gravitons have a spin of 2 and they represent the force of gravity. This means that when gravity affects two things, gravitons move to and from the two things. Virtual photons have a spin of 1 and represent electromagnetic forces or the force that holds atoms together.
Besides the force of gravity and the electromagnetic forces, there are weak and strong nuclear forces.
Weak nuclear forces are the forces that cause radioactivity , or when matter emits energy. Strong nuclear forces are the forces that keep the quarks in a neutron and a proton together, and keeps the protons and neutrons together in an atom. The particle that carries the strong nuclear force is thought to be a gluon.
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The gluon is a particle with a spin of 1. The gluon holds together quarks to form protons and neutrons. However, the gluon only holds together quarks that are three different colors. This makes the end product have no color. This is called confinement. Some scientists have tried to make a theory that combines the electromagnetic force, the weak nuclear force, and the strong nuclear force.
This theory is called a grand unified theory or a GUT. This theory tries to explain these forces in one big unified way or theory. Chapter 6: Black Holes[ edit ] A picture of a black hole and how it changes light around it. Black holes are talked about in this chapter. Black holes are stars that have collapsed into one very small point. This small point is called a singularity. Black holes suck things into their center because they have very strong gravity.
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Some of the things it can suck in are light and stars. Only very large stars, called super-giants, are big enough to become a black hole. The star must be one and a half times the mass of the sun or larger to turn into a black hole. This number is called the Chandrasekhar limit.
If the mass of a star is less than the Chandrasekhar limit, it will not turn into a black hole; instead, it will turn into a different, smaller type of star. The boundary of the black hole is called the event horizon. If something is in the event horizon, it will never get out of the black hole. Black holes can be shaped differently.
Some black holes are perfectly spherical - like a ball. Other black holes bulge in the middle. Black holes will be spherical if they do not rotate. Black holes will bulge in the middle if they rotate.
Black holes are difficult to find because they do not let out any light. They can be found when black holes suck in other stars. When black holes suck in other stars, the black hole lets out X-rays , which can be seen by telescopes.
In this chapter, Hawking talks about his bet with another scientist, Kip Thorne. Hawking bet that black holes did not exist, because he did not want his work on black holes to be wasted. He lost the bet. Hawking realized that the event horizon of a black hole could only get bigger, not smaller.
The area of the event horizon of a black hole gets bigger whenever something falls into the black hole. He also realized that when two black holes combine, the size of the new event horizon is greater than or equal to the sum of the event horizons of the two original black holes.
This means that a black hole's event horizon can never get smaller. Disorder, also known as entropy , is related to black holes. There is a scientific law that has to do with entropy. This law is called the second law of thermodynamics , and it says that entropy or disorder will always increase in an isolated system for example, the universe. The relation between the amount of entropy in a black hole and the size of the black hole's event horizon was first thought of by a research student Jacob Bekenstein and proven by Hawking, whose calculations said that black holes emit radiation.
This was strange, because it was already said that nothing can escape from a black hole's event horizon. This problem was solved when the idea of pairs of "virtual particles" was thought of. One of the pair of particles would fall into the black hole, and the other would escape. This would look like the black hole was emitting particles.
This idea seemed strange at first, but many people accepted it after a while. Chapter 8: The Origin and Fate of the Universe[ edit ] The Big Bang and the evolution of the universe How the universe started and how it might end is discussed in this chapter. Most scientists agree that the universe started in an expansion called the Big Bang. The model for this is called the "hot big bang model". When the universe starts getting bigger, the things inside of it also begin to get cooler.
When the universe was first beginning, it was infinitely hot. The temperature of the universe cooled and the things inside the universe began to clump together.
Hawking also discusses how the universe could have been. For example, if the universe formed and then collapsed quickly, there would not be enough time for life to form. Another example would be a universe that expanded too quickly.
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If a universe expanded too quickly, it would become almost empty. The idea of many universes is called the many-worlds interpretation. Inflationary models and the idea of a theory that unifies quantum mechanics and gravity also are discussed in this chapter.
Each particle has many histories. This idea is known as Feynman's theory of sum over histories. A theory that unifies quantum mechanics and gravity should have Feynman's theory in it. To find the chance that a particle will pass through a point, the waves of each particle needs to be added up. These waves happen in imaginary time. Imaginary numbers, when multiplied by themselves, make a negative number. Chapter 9: The Arrow of Time[ edit ] In this chapter Hawking talks about why "real time" as humans observe and experience it in contrast to the "imaginary time" in the laws of science seems to have a certain direction, notably from the past towards the future.
The things that give time this property are the arrows of time. Firstly, there is the thermodynamic arrow of time. According to this, starting from any higher order organized state, the overall disorderliness in the world always increases as time passes.
This is why we never see the broken pieces of a cup gather themselves together to form a whole cup. Even though human civilizations have tried to make things more orderly, the energy dissipated in this process has created more overall disorder in the universe.
The second arrow is the psychological arrow of time. Our subjective sense of time seems to flow in one direction, which is why we remember the past and not the future. Hawking claims that our brain measures time in a way where disorder increases in the direction of time. We never observe it working in the opposite direction. In other words, the psychological arrow of time is intertwined with the thermodynamic arrow of time.
Thirdly there is the cosmological arrow of time, the direction of time in which our universe is expanding and not contracting. Hawking believes that in order for us to observe and experience the first two arrows of time, the universe would have to begin in a very smooth and orderly state.
We believe that this book is suited for all individuals willing to expand their knowledge in various fields. Despite the insights of the processes in the universe, it presents numerous studies and analysis that question religion, our daily habits and much more. Probably many people consider him as the righteous successor of Albert Einstein in the field of physics, philosophy, and evolution.
He was given the honors to hold the Isaac Newton chair at the University of Cambridge and received the presidential medal of freedom, the highest award a civilian can get in the U. His leading theories on evolution confused many theoreticians and scientists who taught that the chapter of human development is closed. What about our knowledge? In fact, the vast universe offers plenty of room for surprise visits, meaning that our discoveries can be twisted in a second.
According to many, he is already an icon, in various scientific fields due to its contribution to the global culture. The rise of science and its branches: Long before the Christ, an ancient civilization out of curiosity launched a philosophical campaign to satisfy their thirst for answers. We are referring to the Greek countries. Aristotle, a prominent philosopher, theoretician, and scientist of his time, embarked on a journey to resolve the dilemma of human existence.
Probably that was the official date, from where it all began. Imagine this, without any evidence, years ago Aristotle wrote — The planet is round and probably we are not alone in this vast space. A contradictory statement at the time, because according to many, the Earth was still a flat plate, or the center of the universe, while other elements were orbiting around it.
This claim or theory was not acknowledged nor accepted until the arrival of Galileo Galilei in the 17th century.
Stay tuned for more: Sir Isaac Newton, is linked to his book called Principia — the most exciting, breathtaking masterpiece, or classic ever published in the realm of physical sciences. What power is pulling them in, or out? What was the end result? The analysis required time and effort, something Newton had in abundance, the only thing missing was support. Every body in the universe attracts other entities and is attracted by force emerging from a different one. As the distance reduces, the link becomes more evident.
What is happening behind closed doors?They persisted, despite many battles, and continue, to this day, to distribute things in a Robin Hood sort of manner.
In fact, the vast universe offers plenty of room for surprise visits, meaning that our discoveries can be twisted in a second. Theoretical Physics. Enter Elvenar. The book does employ a number of complex models, diagrams, and other illustrations to detail some of the concepts it explores. Aristotle, unlike many other people of his time, thought that the Earth was round.
What was the end result? Where can I download the book "Doing Justice" for free?