Author: Stephen Hawking
Translated by Xu Mingxian and Wu
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Translator's order
thank
introduce
Chapter One: Our Universe Image
Chapter II Space and Time
Chapter III The Expanding Universe
The fourth chapter uncertainty principle
Chapter V Fundamental Particles and Natural Forces
Chapter VI Black hole
Chapter 7 Black holes are not so black.
Chapter VIII The Origin and Destiny of the Universe
Chapter 9 Arrow of Time
Chapter 10 The Unity of Physics
Chapter 11 Conclusion
[Name] Albert Einstein (Jewish theoretical physicist)
Galileo Galilei
[Name] isaac newton (English physicist, mathematician, astronomer, natural philosopher and alchemist)
Small dictionary
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Chapter One: Our Universe Image
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A famous scientist (said to be Bertrand Russell) once gave a lecture on astronomy.
He described how the earth moves around the sun and how the sun moves around the huge stars we call galaxies.
The center of the group rotates. At the end of the speech, a short old lady sitting at the back of the classroom stood up and said, "What did you say?"
These are all nonsense. The world is actually a flat plate on the back of a turtle. "scientists are very
Educated smile and answer: "What is this turtle standing on?" "You are very clever, young man.
"Very clever indeed," said the old woman. However, this is a group of turtles that have been going on! "
Most people will think it is ridiculous to compare our universe to an infinite turtle tower, but why do we do this?
Think you know more? What do we know about the universe? How do we know? universe
Where did it come from and where will it go? Does the universe have a beginning? If so, what happened before that? time
What is the essence of space? Will there be an end? Some recent breakthroughs in physics have produced some wonderful new discoveries.
This technology has been realized, which is instructive to answer these long-standing unsolved problems. perhaps
One day, these answers will be as obvious as we think that the earth moves around the sun-of course, it may also be like the Turtle Tower.
That's ridiculous anyway, only time will tell.
As early as 340 BC, the Greek philosopher Aristotle was able to understand it in his book On Heaven.
The argument that the earth is a sphere rather than a flat plate puts forward two good arguments. First of all, he thinks that the solar eclipse is caused by
Caused by the earth moving between the sun and the moon. The earth's shadow on the moon is always round, which is unique to the earth.
It holds only if it is spherical. If the earth is a flat disk, unless the solar eclipse always happens on the sun.
When it is under the center of this disk, otherwise the shadow of the earth will be elongated and become an ellipse. Second, Greece.
People know from their travels that the farther south they look at the stars, the closer Polaris is to the horizon. (Because of Polaris
It is directly above the North Pole, so it appears on the head of the observer at the North Pole, and for the observer at the equator,
Polaris appears on the horizon. According to the position of Polaris in Egypt and Greece, Asia
Aristotle even estimated that the length of the great circle of the earth was 400 stidia. Now we can't know for sure, a Sturdee.
What is the length of Asia, but it may be about 200 yards, which makes Aristotle's estimate acceptable now.
Twice the value. The Greeks even provided a third argument for the fact that the earth is spherical, otherwise why would it come from beyond the horizon?
Ships always sail first, then the hull?
Aristotle thinks that the earth is motionless, and the sun, moon, planets and stars all move in circles around it.
Turn around. He believes this is for mysterious reasons. He thinks the earth is the center of the universe, with the most circles.
Perfect. In the second century, Ptolemy refined this idea into a complete cosmological model. The earth is positive.
In the center, there are eight celestial spheres around, which contain the sun, moon, stars and five at that time.
Known planets: Mercury, Venus, Mars, Jupiter and Saturn (Figure 1.5438+0). These planets are thought to be along the corresponding attachment
The smaller circular motion on the celestial sphere illustrates the rather complex trajectory they observe in the sky. outermost
The celestial sphere is inlaid with fixed stars, which always stay in the same relative position, but generally revolve around the sky. finally
What is beyond the celestial sphere has never been clear, but one thing is certain, it is not the universe that humans can observe.
Part.
Figure 1. 1 From the innermost to the outermost, the order is the moon, the water planet, the gold planet, the sun ball, the Mars ball, and the wood planet.
Earth, planets and stellar spheres. The center is the earth.
Ptolemy model provides a very accurate system for predicting the position of celestial bodies in the sky. But in order to predict this correctly
Ptolemy must assume that the moon's orbit is sometimes twice as close to the earth as at other times, which means that the moon sometimes
It looks twice as big as other times. Ptolemy admitted this defect, but his model was not universal.
Slowly but widely accepted. It is accepted by Christianity as a universal image consistent with the Bible. This is because of it.
It has a great advantage, that is, it leaves a lot of places for heaven and hell outside the celestial sphere.
However, in 15 14, a priest named mikolaj kopernik proposed a simpler model. (At first,
Perhaps fearing that the church would persecute heresy, Copernicus could only circulate his model anonymously. ) His idea is that,
The sun is at rest in the center, while the earth and other planets revolve around the sun. Nearly a century later,
His idea was seriously accepted. Later, two astronomers-johannes kepler of Germany and Italy.
Galileo galilei began to openly support Copernicus' theory, although its predicted orbit could not be completely observed.
Meet. It was not until 1609 that Aristotle-Ptolemy's theory was declared dead. That year, Galileo used only his hair.
Bright telescopes observe the night sky. When he observed Jupiter, he found several small satellites or satellites revolving around it. This watch
Unlike Aristotle and Ptolemy, not everything has to revolve around the earth directly.
Of course, it is still possible to believe that the earth is still the center of the universe, and Jupiter's satellites follow an extremely complicated.
Their orbits go around the earth. Obviously, they surround Jupiter. However, Copernicus' theory is much simpler. )
At the same time, Kepler revised Copernicus' theory that planets are not along the circumference but along the ellipse (an ellipse is an elongated circle).
Movement, so that the prediction and observation are finally consistent with each other.
As far as Kepler is concerned, the elliptical orbit is just taken for granted, which is a rather annoying assumption, because the ellipse is obvious.
The ground is not as perfect as a circle. Although he almost unexpectedly found that the elliptical orbit can be well consistent with the observation, it is not the case.
It can be explained from another point of view that his planet revolves around the sun because of magnetic force. Get ready for all this.
The explanation was much later, because Sir isaac newton published his book Natural Philosophy of Mathematics in 1687.
Richard, perhaps the most important book in the history of physical science. In this book, Newton not only mentioned
The theory of how objects move in space and time is developed, and the complex mathematics needed to analyze these movements is developed.
In addition, Newton put forward the law of universal gravitation, according to which any object in the universe is attracted by another object.
The greater the mass of objects, the closer they are, and the greater the attraction between them. This is to let the object fall to the ground.
Force. The story that Newton was inspired by an apple that fell on his head is almost certainly unreliable.
Newton himself said that when he was lost in thought, the fall of an apple gave him gravity.
Thought. Newton went on to point out that according to his law, gravity makes the moon orbit the earth in an elliptical orbit, and the earth
The ball and other planets revolve around the sun in elliptical orbits.
Copernicus' model got rid of the concept that Ptolemy's celestial sphere and the universe related to it had natural boundaries.
The "fixed star" does not change its orbit except the rotation across the sky caused by the rotation of the earth around its own axis.
The position will naturally make people feel that the fixed star is a celestial body similar to our sun, but farther away from us than the sun.
It's much farther.
Newton, according to his theory of universal gravitation, realized that stars should be attracted to each other, and it seems impossible to basically stand still.
So will they fall together somewhere? 169 1 To Richard Bent, another most important thinker at that time.
In a letter from the library, he believes that it is correct if only a limited number of stars are distributed in a limited space area.
It will happen. On the other hand, he concluded that if there are infinite stars, they are more or less evenly distributed in infinity.
Space, this will not happen, because there is no central point where they fall.
When people talk about infinity, this argument is a trap you will encounter. In the infinite universe, every one.
It can be completely regarded as the center, because there are infinite stars on each side of it. The correct way is to wait for a long time.
What is achieved is to consider the limited situation first, when all the stars fall together, and then in this area.
In addition, add more stars roughly evenly and see how things will change. According to Newton's law, this extra star
On average, it has no effect on the original stars, so these stars will get together quickly. we
You can add as many stars as you want, but they always collapse together. Now we know
Gravity is always attractive, and there can be no infinite static model of the universe.
Before the 20th century, it was never suggested that the universe was expanding or contracting, which reflected that era interestingly.
Thinking atmosphere. It is generally believed that the universe has existed in an unchanging state for an infinite time, more or less.
As we can see today, it is even less created in a limited past. Part of the reason may be that people tend to
Believe in eternal truth, but also because people will live and die, but the universe must be immortal.
It's comforting.
Even those who realized that Newton's gravity theory made it impossible for the universe to stand still did not think of proposing that the universe could stand still.
The energy is expanding. Instead, they try to modify the theory so that gravity is repulsive at a great distance. This is not right.
The prediction of planetary motion has great influence, but it allows the distribution of infinite stars to keep balance-one of the neighboring stars.
The attraction between stars is balanced by the repulsion between distant stars. However, now we know that this balance is unstable.
Yes: if the stars in a certain area are a little closer to each other, the gravity will increase and exceed the repulsive force, so that,
These stars will continue to fall together. On the other hand, if the stars in a certain area are slightly away from each other, the repulsion will
Play a leading role and pull them further and further.
Another objection to the infinite static universe is usually considered by the German philosopher Henrich Olbers, 1823.
He published this theory. In fact, this question was also raised by Newton's contemporaries. Even Obers.
This article is not the first article to refute this model reasonably. Anyway, this is the first article that has been widely concerned.
Articles. The difficulty of this infinite static model is that almost every line of sight must end at the surface of the star. In this way,
People can expect that the whole sky will be as bright as the sun even at night. Olbers retorted that the stars in the distance
Light is absorbed by the substance through which it passes and weakened. However, if this is the case, the matter will eventually
Heat it until it emits light as strong as a star. The only way to avoid the conclusion that the whole sky is as bright as the sun.
However, suppose that the stars are not always so bright, but only start to shine in a limited time. In this case, light absorption
Matter has not been heated, or light from distant planets has not reached us. This makes us face what made it for the first time.
The problem of stars shining.
Of course, the question of the origin of the universe has been discussed before. According to some early cosmology and Jews
/Christian/Muslim tradition, the universe began in a limited and not too distant time in the past. over here
There is a discussion at the beginning that there must be a "first reason" to explain the existence of the universe. (In the universe,
You can always interpret an event as being caused by another earlier event, but the universe itself only exists.
You can only explain it if you have a beginning. ) Another argument is saint augustinus's City of God.
Put it forward at work. He pointed out that civilization is progressing, and we will remember those who created these achievements and developed technology. such
People, maybe the universe, can't exist for long. So according to St. Augustine in Genesis,
By the time the universe was born in 5000 BC. (Interestingly, this is the same as the end of the last ice age.
About BC 1, not far apart. Archaeologists tell us that civilization actually began at that time. )
On the other hand, Aristotle and most other Greek philosophers don't like the idea of creation because it is too
The smell of theological intervention. So they believe that human beings and the world around them have existed and will exist forever.
The ancients once considered the above argument of civilization progress and used the recurrence of periodic floods or other disasters.
It is difficult to answer the above words by bringing mankind back to the beginning of civilization.
178 1 year, the philosopher Immanuel Kant published a landmark (and very vague) book-
Critique of Pure Reason, in which he made an in-depth investigation on whether the universe has a beginning and space in time.
Whether the world has a limit. He called these problems the antinomy of pure reason. Because he thinks
There are also convincing arguments to prove that the universe has a beginning, and the universe has existed for an infinite time.
His argument for the positive proposition is that if the universe has no beginning, there must be an infinite time before any event.
Between. He thinks it's ridiculous. His argument for the counter-proposition is that if the universe has a beginning, there must be infinity before it.
Why does the universe have to start at some point? In fact, he used the same method for affirmative and negative propositions.
An argument. Is based on his implicit assumption that the universe is infinite and there is no time.
Return to the limited land. We will see that the concept of time is meaningless before the beginning of the universe. This is St.
Augustine first pointed out. When he was asked: What did God do before he created the universe? Augustine didn't do this.
Answer: He is preparing hell for people who ask such questions. On the contrary, time is an attribute of the universe created by God.
It didn't exist before the beginning of the universe.
When most people believe in an essentially static universe, the question about whether it has a beginning is actually a question
Metaphysical or theological problems. According to the theory that the universe is infinite, or according to the theory that the universe exists in a finite time.
Sculpture, which gives people the feeling that there seems to be infinite time, can also be well understood.
Explain the observed facts. But in 1929, Edwin Hubble made an epoch-making observation, namely
But no matter which direction you look, distant galaxies are rapidly leaving us. In other words, the universe is expanding.
This means that the distance between early stars is closer. In fact, it seems to be 10 billion years ago to about 20 billion years ago.
At a certain moment, they happened to be in the same place, so the density of the universe at that time was infinite. This discovery finally changed the universe.
The initial problem has been brought into the kingdom of science.
Hubble's discovery implies the existence of a moment called the Big Bang, when the universe was infinitely small and infinitely tight.
Secret. Under this condition, all scientific laws and all the ability to foresee the future are invalid. If at this moment,
There have been some events before, which will not affect what is happening now. So we can ignore them because
They have no obvious consequences. Since there is no definition of earlier time at all, in this sense, people can
Said time began with the big bang. It must be emphasized that the beginning of this time is quite different from what was thought before.
Same. In an unchanging universe, the endpoint of time must be given by something outside the universe; The origin of the universe did not
There is no physiological necessity. People can imagine that God created the universe at any time in the past. On the other hand, if
The universe is expanding, and there seems to be a physical reason why the universe has a beginning. People can still imagine that god is
The universe was created at the moment of the Big Bang, or even later, so it looks like the Big Bang.
The way to create, but it is meaningless to imagine creating the universe before the big bang. The big bang model does not exclude creation.
Lord, this is just a time limit for when he will do the work!
In order to talk about the nature of the universe and whether the universe has a beginning and an end, you must know what it is.
Scientific theory. I will adopt the simple-minded view that theory is only a model of the universe or its limited parts.
Types, some rules that relate this model to the quantities we observe. It only exists in our minds.
There is no longer any other reality. If it meets the following two requirements, it is a good theory:
It must accurately describe a large number of observations and predict the future on the basis of a model that only contains some arbitrary elements.
Make a clear prediction according to the observation results. For example, Aristotle said that everything is made up of four elements, earth, air,
The fire-water theory is simple enough, but it doesn't make any definite predictions. On the other hand, Newton's
The theory of gravity is based on a simpler model, in which two objects attract each other and what they call gravity.
The size of the mass is directly proportional to the square of the distance between them, and inversely proportional. However, its prediction accuracy is very high.
The motions of the sun, the moon and the planets are analyzed.
Any physical theory is temporary, because it is only a hypothesis: you can never prove it.
No matter how many times the experimental results are consistent with a certain theory, you can never be sure that the next result will not contradict it.
On the other hand, even if you find that an observed fact is inconsistent with the theoretical prediction, you can falsify it. Just like science.
The philosopher Karl Popper emphasized that the characteristic of a good theory is that it can give many things that can be observed in principle.
A denied or forged prophecy. This theory exists and develops whenever a new experiment consistent with this prediction is observed.
Increased our credibility; However, if a new observation is inconsistent with it, we have to give up or correct this principle.
Open. At least some people think it's a matter of time. The question is whether people have the talent to make such observations.
In fact, what often happens is that the new theory designed is really a generalization of the original theory. For example, for mercury.
Usually accurate observation reveals a slight difference between its motion and Newton's theoretical prediction. Einstein's general theory of relativity
The predicted motion is slightly different from Newton's theory. Einstein's prediction is consistent with observation, while Newton's prediction is consistent with observation.
This fact is the key evidence of this new theory. However, in most practical cases, we still use cattle.
Newton's theory, because in the case we usually deal with, the difference between the two is very small. Another great theory of Newton.
The advantage is that it is much easier to deal with than Einstein's theory! )
The ultimate goal of science is to provide a simple theory to describe the whole universe. However, most scientists follow.
The method to be followed is to divide the problem into two parts. First of all, there are some laws that tell us how the universe changes with time;
If we know what the universe looks like at any moment, these laws can tell us at any time in the future.
Carve out the appearance of the universe. Second, about the initial state of the universe. Some people think that science should only ask the first question.
Some of them think that the problem of initial state should be a metaphysical or religious category. They will say, Almighty God.
You can start the universe at will. Maybe so. But, in that case, he can also make the universe.
Any form of evolution. However, it seems that he chose the universe to play in a very regular and regular way.
Change. Therefore, it seems reasonable to assume that there are laws that limit the initial state.
It seems very difficult to design a theory that can describe the whole universe in one battle. On the contrary, we
Is to divide the problem into many small pieces and invent many partial theories. Every part of theoretical description and prediction must be limited.
Observe the surroundings, ignore the influence of other quantities or express them with a set of simple numbers. Maybe this method is all wrong.
If everything in the universe depends on everything else in a very basic way, probably not.
Study a part of the problem by isolation method to approach its complete answer. However, this is definitely the progress we have made in the past.
The methods used in the exhibition. Newton's theory of gravity is another classic example, which tells us that the gravity between two objects only
It depends on a number associated with each object-its mass; This has nothing to do with what an object is made of. In this way, people
The orbits of the sun and planets can be calculated without their structure and composition theory.
Today, scientists describe the universe according to two basic partial theories-general relativity and quantum mechanics. they
This is a great intellectual achievement in the first half of this century. General relativity describes gravity and the large-scale structure of the universe, that is,
It is the scale of hubble volume, ranging from just a few miles to 65438+ 10 billion miles (1 followed by 24 zeros).
The structure of. On the other hand, quantum mechanics deals with phenomena on a very small scale, such as a trillionth of an inch. Unfortunately, however,
The point is that these two theories are incompatible-they can't both be right. One of the major achievements of contemporary physics,
The theme of this book is to seek a theory that can combine them-quantum gravity theory. We didn't.
With this theory, we may still have a long way to go to get it, but we already know it.
Many properties that this theory should possess. In the next chapter, people will see that we already know quite a lot.
Prediction of quantum gravity theory.
Now, if you believe that the universe is not arbitrary, but limited by some laws, you must finally put this
These theories are combined into a complete and unified theory, which can describe anything in the universe. However, when looking for such an ending.
There is a basic contradiction in the theory of integration and unity. In the previous summary of scientific theory, suppose we
It is a rational creature, and can freely observe the universe and draw logical inferences from the observation. such
It is reasonable to assume that we can get closer and closer to finding the laws governing our universe. However, if
If there is a complete and unified theory, it will also determine our actions. In this way, the theory itself will determine our understanding of
The result of exploration! So, why does it have to ensure that we get the correct conclusion from the evidence? Isn't it the same?
Will we draw the wrong conclusion? Or is there no conclusion at all?
The answer I can give is based on Darwin's principle of natural selection. The idea is,
In any self-propagating population, the genetic material and development of different individuals are different. These differences indicate that some kind of
Some people can draw correct conclusions about the world around them better than others and adapt to it. These individuals are more likely to survive.
Life and reproduction, so their behavior and thinking mode will play a leading role more and more. This must have been true in the past.
Yes, our so-called wisdom and scientific discoveries have brought us the benefits of survival. Will this happen again?
It is not clear whether our scientific discovery can also destroy everything. Even if it's not, it's over.
The unified theory of integration will not have a great impact on our chances of survival. However, suppose that the universe has been running regularly.
So far, we can expect that the reasoning ability endowed by natural selection still exists when exploring a complete and unified theory.
Effect, so it won't lead us to the wrong conclusion.
Because except for the most extreme cases, we have a partial theory, which is enough to give an accurate prediction of everything.
In theory, it seems difficult to defend the ultimate theory of exploring the universe with realistic reasons. (it is worth pointing out that although similar ones can be used.
Attack the arguments of relativity and quantum mechanics, but these theories have brought us revolutions in nuclear energy and microelectronics! )
Therefore, the discovery of a complete unified theory may not help the survival of our race, or even affect us.
Lifestyle. However, since the beginning of civilization, people have been reluctant to regard events as insignificant and incomprehensible. he
Children are eager to know the basic order of the world. Today we are still eager to know, why are we here? Where do we come from?
The deepest human thirst for knowledge is enough to prove the legitimacy of our continuous exploration. And our purpose.
The Gospel of Kyle is a complete description of the universe in which we live.
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Wang Yifan sweeps schools in piles.
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See for yourself. . .