cuneiform characters
The Bible says: God created the universe.
Contemporary physicists say that the universe was born in the Big Bang.
Vatican says: The Big Bang theory is in line with the Bible.
Stephen Hawking said: The Big Bang and black holes are inevitable cosmic singularities.
Stephen Hawking said: Black holes are not black. It is not only visible, but also incandescent.
Stephen Hawking said: In the framework of classical physics, black holes become bigger and bigger, but in the framework of quantum physics, black holes become smaller and smaller due to radiation.
Stephen Hawking said: The cycle from BIGBANG to a black hole is a process of creation, destruction and rebirth of the universe. So God's contribution to the universe disappears.
Stephen Hawking divorced his wife who took care of him for more than ten years and deeply believed in Catholicism.
Some people say that Stephen Hawking is the greatest genius after Einstein, while others say that he is crazy.
Who is Stephen Hawking?
(2) Stephen Hawking
Stephen Hawking is a British theoretical physicist. His birthday is 1942 1.8, which happens to be the anniversary of Galileo's 300th anniversary. 1959, 17-year-old Hawking began to study in Oxford and did a doctoral thesis with his tutor Dennis Siama in Cambridge.
However, Hawking was diagnosed with a disease called amyotrophic lateral sclerosis at this time, which is still incurable or even uncontrollable. Stephen Hawking ended up in a wheelchair forever and lost his language ability. His life depends entirely on his wife, Jane Wald. However, this disabled person, who is said to have only three fingers moving all over his body, has completed a series of amazing theories about BIGBANG and black holes with amazing perseverance, making great contributions to quantum physics and showing the world the great and mysterious background of the universe. He is generally regarded as the most outstanding scientist after Einstein. From 65438 to 0974, Hawking was awarded the position of Lucas Professor of Mathematics in Cambridge.
At the inauguration ceremony, Hawking made great efforts to sign his name on the roster, and the first page of the roster was signed by isaac newton.
Hawking's lifelong contribution to physics proves that under the framework of classical physics, the Big Bang and black holes are inevitable, and black holes will become bigger and bigger. Under the framework of quantum physics, black holes become smaller and smaller because of radiation. The singularity of the Big Bang and the black hole was not only erased by quantum effect, but also the origin of the universe. Hawking's contribution to popular science is that he wrote a very popular book, A Brief History of Time, which has been on the bestseller list for more than 100 weeks, translated into 33 languages and sold more than 5.5 million copies.
This paper will introduce Stephen Hawking's theory with a brief history of time as the main line.
(3) Our universe
The universe is so mysterious that when everyone looks up at the starry sky, they can't help wondering what is hidden behind the stars. Our ancestors thought that "the sky is like the sky and the earth is like a chess scale", while the ancestors of ancient Indians thought that the earth was carried on the back of an elephant.
In 340 BC, Aristotle, an ancient Greek philosopher, expounded the following points in his book On Heaven: First, the solar eclipse was caused by the shadow of the earth cast on the moon.
Secondly, because the shadow of the earth seen during an eclipse is always round, it can be inferred that the earth should be a sphere, not a disk. Third, the earth is the center of the universe. The sun, the moon, planets and other stars are attached to the eight celestial spheres respectively, and revolve around the earth in a perfect circular orbit.
Christianity fully accepts Aristotle's theory, which is consistent with the biblical worldview and God's creationism. The biggest advantage of this cosmic model is that there is room for heaven and hell outside the outermost star celestial sphere.
15 14, pastor mikolaj kopernik put forward the "Heliocentrism", which holds that the sun is stationary in the center of the universe, while the earth and other planets move around the sun in a circle. For fear of persecution by the church, Copernicus could only spread his theory in secret. Later, when Galileo observed Jupiter, he found that several planets of Jupiter revolve around Jupiter, which shows that other planets do not necessarily revolve around the earth. Then Kepler revised Copernicus' theory and replaced the circular orbit with an elliptical orbit, which was in good agreement with the observation results. Their public support finally declared the end of Aristotle's theory.
1687, isaac newton published the world-famous Principles. In the book, the famous law of gravity is put forward. The book Principles solves the problem of how objects move in space and time.
People can even use his theory to accurately calculate the orbits of planets.
But the problem has arisen again. According to the law of universal gravitation, planets always attract each other. It seems impossible for them to remain relatively static in a large range, but they will eventually fall together. Newton also realized this, and he explained: If a limited number of planets are distributed in a limited area, this will indeed happen. But if there are infinite planets, evenly distributed in infinite space, this will not happen, because the gravity distribution is uniform at this time, and there is no center to gather them.
In fact, this is a theoretical trap that we often encounter. In fact, in an infinite universe, every star can be regarded as a center, because there are infinite stars in every direction. The correct method should be: first consider the limited space and the stars will collapse together. Add more stars evenly outside this area. According to Newton's law, these added stars have no effect on the original area, so the stars will still fall together. We add more stars at will, as many as we want, and they always collapse to a point. In other words, the local area of the universe is always uneven, and there should be local collapse, and this trend will gradually expand. The observed result is not the case.
So we have a big problem: the infinite static universe does not exist!
(D) Olbers Paradox
The idea of a static universe is so strong that scientists who realize that gravity theory makes the universe impossible to be static do not suggest that the universe is expanding, but try to revise their theory. Even when Einstein published his general theory of relativity in 19 15, he was quite sure that the universe was static. So he had to introduce a so-called cosmological constant into his equation to correct it. He introduced a kind of "anti-gravity", which is passive and inherent in the structure of time and space. He claimed that the internal expansion trend of space-time can just balance the mutual attraction of various substances in the universe, thus creating a static universe. This theory was later called "the most unforgivable mistake in life" by Einstein.
It is generally believed that the German philosopher Olbers first attacked the infinite static universe. 1823, he put forward the famous "Olbers paradox". He pointed out that if the universe is infinitely static and uniform, then the end of every line of sight of the observer will definitely end in a star. Then it is easy for us to imagine that even at night, the whole sky will be as bright as the sun. Some people retort that the light of a distant star is absorbed by the matter it passes through and weakened. In fact, this seemingly reasonable rebuttal is untenable, because the substance that absorbs light will eventually be heated until it emits light as strong as a star. In the infinite static universe, there is only one thing that can prevent the night sky from being as bright as during the day, that is, the stars did not start to shine infinitely long ago. In this case, the matter through which the light passes has not been heated, or the distant star light has not yet reached the earth. Then we face another question: what makes the stars shine for the first time? This is the question that human beings have explored for countless centuries-the origin of the universe.
178 1 year, the philosopher Immanuel Kant deeply analyzed the question of whether the universe has a beginning in time and a limit in space in his iconic work Critique of Pure Reason, which he called pure antinomy (that is, contradiction). He argues that if the universe has no beginning, there must be infinite time before any event happens, which is absurd; And if the universe has a beginning, what time is before the beginning of the universe? Kant believes that both sides have convincing arguments. In fact, his argument is based on an implicit assumption, that is, whether the universe exists indefinitely or not, time can go backwards indefinitely. But the big bang theory that will be talked about soon will make us understand that the concept of time before the beginning of the universe is meaningless.
(5) The universe is expanding.
Astronomers in the 20th century used the spectra of stars to study them. Since each element has its own specific absorption line, scientists can analyze the constituent elements and temperature of stars from their spectra. When studying these spectra, scientists found a strange phenomenon: all the line families of the spectrum moved to the red end of the spectrum by the same amount. What does this mean?
We all have the following experiences: when the car horns come towards us, the flute sounds loud and harsh; The pitch becomes lower when the car is far away, which is caused by the high and low frequency of the sound. This Doppler effect describing the relationship between speed and frequency is not difficult to understand. Light is electromagnetic wave, with low frequency at the red end and high frequency at the blue end of the spectrum. The spectrum moves to the blue end, which means that the light wave frequency of the star we receive becomes higher, which means that the star is coming towards us; If the spectrum is red-shifted, this star is far away from us.
I have to mention a great man here-Edwin Hubble. 1924, he proved through observation that our galaxy is not unique, and he also calculated the distance between galaxies.
After a lot of observation, he classified and counted the spectra of these galaxies. People expect to find as many blue shift spectra as red shift. However, Hubble's discovery made everyone lose their eyes-almost all galaxy spectra are red shift, and the amount of red shift is very regular, which is directly proportional to the square of the distance between galaxies and us. In other words, the speed at which galaxies leave us is directly proportional to the distance from us. The farther the galaxy is from us, the faster it is from us.
People are surprised to find that the universe is expanding!
The speed at which galaxies leave the earth is so perfect that the earth seems to be the center of the universe again. Are we going back to Aristotle's theory? Actually, it is not. First of all, we can draw that the density of matter has nothing to do with the scale of distance, and the distribution of celestial bodies on a large scale is very uniform, which is increasingly proved by astronomical observations. Secondly, through galilean transformation (motion transformation between different coordinate systems), we can easily draw the conclusion that at any point in the universe, other stars are far away from that point, and the speed of their departure is proportional to the square of the distance. This is like an inflated balloon. Any two points on the ball are moving away from each other. The greater the distance between the two points, the faster they move away from each other, but they can't be regarded as the center of expansion. In fact, the expansion is very uniform. So we come to the conclusion that "there is no special place in the universe. Every observer sees the same phenomenon. " This is called the Copernican principle.
(6) Three models of the universe
The expansion of the universe is one of the greatest discoveries of the 20th century. In less than half a century, this discovery has brought earth-shaking changes to the world outlook of mankind for thousands of years. The novelty of these changes is almost dumbfounded. To observe cosmology before the expansion of the universe with our present knowledge, we will find that the contrast between them is as strong as that between static cosmology and geocentric theory. People are surprised to find that this seemingly familiar universe is actually unfamiliar.
How will the universe expand? What will be the result of expansion?
1922, when Einstein was still trying to find the gravitational constant to balance the contraction trend of the universe in the general theory of relativity, Friedman, a mathematician and physicist in the former Soviet Union, put forward two viewpoints on the basis of the general theory of relativity, that is, the universe looks the same no matter where it is observed, no matter which direction it is observed. He pointed out that only from these two concepts, we should expect that the universe is not static. His model of the universe based on this is completely consistent with Hubble's later observations.
Friedman model has two solutions. One solution is that when the universe expands fast enough, gravity only slows it down, but it can't stop it, and the universe will expand forever; Another solution is that the expansion of the universe is slow enough that gravity finally stops expanding, and the universe will shrink and be squeezed under the action of interstellar gravity. It can also be considered that there is a third scheme, that is, the expansion speed of the universe is just fast enough to avoid collapse. It differs from the second solution in that the universe of the third solution is flat, while the universe of the second solution is curved, like an arch. The third solution is actually a special case of the second solution. The universe and model of these two solutions are infinite.
In the first solution, we see the singularity-the universe is not infinite in space and has no boundaries. Here, I didn't write it wrong. The situation of this universe can be understood by our earth. There is no boundary on the surface of the earth, but its volume is limited. Except that the surface of the earth is two-dimensional, the space of the universe is three-dimensional. The gravity of the first model of the universe was so strong that space was bent back to itself.
This is indeed a good science fiction theme. After a week of traveling around the universe, a person returns to the starting point. However, Hawking told us: "This actually doesn't make much sense, because before one can make a circle, the universe has collapsed to zero scale. You must travel faster than light waves to return to your starting point before the end of the universe-and this is not allowed! "
For time, this solution is also limited, it has a beginning and an end, such as the two ends of the same rope, that is, it has a boundary. In the future, we will see that when people combine general relativity with quantum mechanics, we can connect the two ends of this rope and make time and space finite and unbounded.
So what kind of solution does our universe conform to? This is determined by the average mass density of the universe we have observed so far. The total mass of all the stars we have observed now is less than 1% of the critical mass needed to stop expansion. Even considering the dark matter between galaxies that we can't observe, the total mass is less than one tenth of the density needed to stop expansion. These results mean that our universe may expand forever at the current almost critical speed.
(7) Relativity theory
In view of the contents involved in the following chapters, it is necessary to spend some time here to introduce relativity.
It should be said that all the incredible changes later began with the principle of constant speed of light.
First of all, people realize that the speed of light is limited. 1676, Danish astronomer Orr christiansen Milo discovered that Jupiter's moons do not come out from behind Jupiter at equal intervals, and the farther Jupiter leaves the earth due to its revolution, the longer the time interval. He pointed out that the farther away Jupiter is from us, the longer it takes for light to reach the earth after it is emitted from Jupiter. This shows that light is not infinitely fast.
Nearly 200 years later, British physicist james maxwell put forward the famous Maxwell equation in 1865. This equation describing electromagnetic waves has become a real theory of light propagation. The theory predicts that electromagnetic waves should move at a fixed speed. But Newtonian mechanics got rid of the concept of absolute rest, and the speed is relative. So which reference is chosen to measure the speed of light? Therefore, it is proposed that there is an extremely elastic substance-"ether" in vacuum, through which light propagates. 1887 "Michelson-Morey experiment" broke this hypothesis. The two men accurately measured the speed of light in the tangential direction and vertical direction of the earth's rotation respectively. They predicted that the speed of light measured in the tangential direction would be greater than that measured in the normal direction, and the result was that the two speeds of light were exactly the same.
Later, Albert Einstein, an employee of the Swiss Patent Office, pointed out in one of his papers that if people are willing to abandon the concept of absolute time, then the whole concept of ether is completely redundant. The year is 1905, and this paper is the famous "Special Theory of Relativity". Einstein pointed out that when light is emitted from a light source, any observer with uniform motion will measure the same speed of light. The principle of constant light speed makes the absolute time that people have never doubted disappear, and then draws the inference that the ruler of motion becomes shorter and the clock of motion becomes slower.
In fact, the principle of constant light speed can be seen everywhere in life, but people have never realized it.
For example, if a person throws a stone at us, the stone will leave his hand as quickly as possible. If the speed of light and the speed of the light source can be superimposed, the speed of light when the stone is ejected should be higher than before, so we will see the stone ejected first and then see the throwing action. This is obviously inconsistent with our daily experience.
As for why the speed of light has this characteristic, Einstein thought for many years and said, "Light is very strange, but we don't need to delve into it, because it is such a substance."
However, there are some inconsistencies between special relativity and gravity theory. The theory of gravity points out that the attraction between objects depends on the mass and distance between them, which means that if we move an object, the gravity on another object will change immediately. In this case, the gravitational effect will be transmitted at infinite speed, not below the speed of light as required by special relativity.
After many failed attempts, Einstein finally put forward a revolutionary "general theory of relativity".
The general theory of relativity points out that gravity is different from other forces, "it is the distortion of time and space caused by the existence of mass of matter." For example, in the view of general relativity, our earth does not move along an elliptical orbit because of gravity, but along a trajectory called geodesic which is closest to a straight line in curved space. When we walk in a straight line on the ground, we actually walk an arc on the surface of the earth's sphere, and the plane of the arc passes through the center of the earth's sphere. This arc is called geodesic. This is the trajectory of a straight line closest to the earth's surface. This trajectory is the shortest distance that the earth has traveled in uneven time and space. Due to the curvature of spacetime caused by the mass of the sun, although the earth moves in a straight line in the four-dimensional space, we seem to travel along an ellipse in the three-dimensional space.
It's like a plane flying over a mountain area. Although it travels in a straight line in three-dimensional space, its projection on the rugged two-dimensional ground moves along a curved trajectory. Similarly, light must follow the geodesic line, and it cannot avoid being bent by the gravitational field. We will have a deeper understanding of this in later chapters on the Big Bang and the singularity of black holes.
(8) BIGBANG
Let's go back to Lidman's model of the universe. All Lidman's solutions have a common feature, that is, about150 ~ 20 billion years ago, all the galaxies in the universe gathered at one point, which is the so-called "Big Bang". The density and curvature of spacetime of the universe at this moment are infinite. In other words, Lidman's model of the universe is based on general relativity, which predicts the existence of the Big Bang singularity in the universe, and all scientific laws fail-because it is impossible to deal with infinite numbers mathematically. If there is an event before the big bang, it will have no influence on the event after the big bang, and there is no scientific foresight to judge the situation after the big bang according to the event before the big bang. In other words, the time before the Big Bang formed the universe is meaningless, or the events before the Big Bang can't have consequences, so they don't form part of our current universe model.
This conclusion was difficult for most people to accept at first. Both the universe and time have a starting point, which inevitably bears the color of God's intervention. Just as Newton attributed the "first driving force" that originally made the stars move to God, Catholicism seized this opportunity and declared that the "Big Bang" theory conformed to the Bible.
In order to avoid the creation of the universe, many people keep trying to find a theory to stabilize the universe, but almost every new explanation has fatal problems. More and more evidence shows that the "steady state theory" must be abandoned!
If the matter in the early universe is very close to each other, then the early universe should be extremely hot. 1965, American physicists Robert Dick and James Pi pars suggested that we should still be able to see the white heat in the early universe. It was 20 billion years ago, and the blazing radiation of the universe had traveled for a long time. Just now, it reached the earth. However, due to the expansion of the universe, these light waves have been redshifted and can only be observed as microwave radiation. At the same time, Arnold Panchia and robert wilson of Bell Telephone Laboratory in New Jersey, USA are doing a precise microwave measurement experiment. The noise they received was much louder than expected. They carefully ruled out possible interference-including bird droppings on the antenna. They predict that when the detector is tilted to the sky, it will be more disturbed, because the light passes through a thicker atmosphere and the noise should be stronger than when the detector is pointed vertically to the sky.
However, we found that no matter which direction the detector faces, the extra noise is the same. This shows that the noise comes from outside the atmosphere. Two scientists inadvertently proved Lidman's hypothesis that the universe is isotropic and extremely uniform on a large scale, and more surprises are still waiting for them. They heard about Dick and Pi pars' work on early cosmic radiation, and immediately realized that they had found-2.7K (absolute temperature) cosmic background radiation!
They also won the Nobel Prize in 1978.
Also in 1965, Stephen Hawking's later collaborator, roger penrose, a British physicist, proved that on the basis of general relativity, the surface area and volume of a star that collapses due to its own gravity will eventually shrink to zero, and at this time, the density of matter and curvature of spacetime are infinite, which is another singularity we will talk about later-black hole.
Penrose's results only involve stars, not the singularity of the Big Bang. Hawking, who is studying for a doctorate, read Penrose's theorem that "when any object collapses under the action of gravity, it will eventually form a singularity" and soon realized that if the time arrow of the theorem is reversed, he should come to the following conclusion: "Any Friedmann expansion model similar to Freund's must start from the singularity". 1970, Hawking and Penrose finally proved that if the general theory of relativity is correct, then there must be a big explosion singularity in our expanding universe!
Their work met with considerable opposition. Scientists don't like the conclusion that singularity and the beginning of cosmic time. However, after all, emotion cannot transcend mathematical theorems. With the accumulation of experimental and observational data, it is becoming increasingly clear that the universe must have a beginning in time.
Hawking and Penrose's research shows that general relativity is only an incomplete partial theory, which can't tell us how the universe started and what it looked like before it started. The singularity theorem further shows that at a moment in the very early universe, the scale of the universe was so small that people had to consider another great partial theory-quantum mechanics, which described the small-scale effect. As Hawking himself said: "Now almost everyone believes that the universe started from the singularity of the Big Bang, but I changed my mind and tried to convince other scientists that there is no singularity at the beginning of the universe-as long as we consider quantum effects, the singularity will disappear!"
(9) Black holes
Before considering the singularity of the Big Bang with quantum mechanics, let's take a look at another singularity under the framework of general relativity-a black hole.
We all know the speed of escape. The greater the gravitational field generated by a star (related to its mass and density), the greater the limit speed required to escape from its surface. If this gravitational field is so large that objects moving at the speed of light cannot escape its bondage, then we will not be able to observe this star, but only feel its gravitational effect. . This is the original definition of a black hole 200 years ago.
In fact, light can't be regarded as the same as ordinary objects, because the speed of ordinary objects gradually slows down in the process of being thrown on the floor, and finally falls back to the ground, while light advances at a constant speed. Therefore, we must reinterpret the phenomenon of black holes from the viewpoint of general relativity, namely:
Due to the distortion of time and space caused by strong gravitational field, light is strongly bent and returns to the surface of the star, and it cannot escape from its surface.
A black hole is a space-time region, and its outermost layer is the farthest distance that light can reach from a black hole. This boundary is called "horizon". It is like a one-way movie, which only allows matter to pass through the horizon and fall into a black hole, but nothing can come out!
So how did black holes form? Let's talk about the life cycle of stars first. Nebular matter in the early universe-extremely thin gas, mainly hydrogen-contracted into stars due to its own gravity. Due to the increasing frequency and speed of gas atoms colliding with each other in the process of contraction, the temperature of gas rises, and finally the star shines. When the temperature is so high that hydrogen atoms do not leave after collision and polymerize into helium, it is called "thermonuclear fusion". The huge energy released by fusion further increases the pressure of the star gas to a level sufficient to balance the internal gravity of the star, so the contraction of the star stops and the star burns stably for a long time. When the star's hydrogen is exhausted, it begins to cool due to the weakening of nuclear reaction, and the pressure of the star gas is not enough to resist its own gravity, which causes the star to contract again. Helium in stars fuses to form heavier elements such as carbon or oxygen. But this process did not release too much energy, and the stars continued to shrink.
Chandraseka, a Nobel Prize winner and Indian-American scientist, pointed out in 1928 that due to the Pauli exclusion principle (there are no two particles in the same motion state in the same orbit), when the star shrinks further, the material particles get close together and must strictly abide by the exclusion principle, so the divergence trend between particles balances the gravity of the star itself and makes the star stop shrinking. If the repulsive force caused by this incompatibility principle is generated between electrons, then the star will collapse into a cold star with a radius of thousands of miles and a density of several hundred tons per cubic inch-a "white dwarf". Scientists have observed a large number of white dwarfs. Another form of collapse is a "neutron star"-the electrons on it have already been pulled to protons by gravity, so this star is all composed of neutrons. It relies on the repulsive force generated by the neutron incompatibility principle to counter its own gravity to maintain its "shape". Their radius is only about 10 mile, and their density is several hundred million tons per cubic inch. Neutron stars have also been confirmed by observation.
At the same time, Chandraseka calculated that when the mass of a star is more than 1.5 times that of the sun, even the principle of incompatibility cannot prevent the star from continuing to collapse, and the star will shrink endlessly until its volume is zero! At this time, the density of matter and curvature of spacetime will be infinite. All the laws of science will fail here. This is the "black hole singularity" we mentioned earlier.
In fact, in one case, when stars exceeding the strong Draseka limit run out of fuel, they may throw a lot of matter in a huge explosion called "supernova explosion", thus reducing themselves below the limit mass and avoiding collapse. But this can't always happen. Even so, what happens if a white dwarf or neutron star adds extra matter?
Scientists were shocked. They can't believe this theory and are hostile to it. They all wrote articles to prove that the volume of stars will not shrink to zero, including Einstein.
However, Stephen Hawking and roger penrose's research in 1965 and 1970 pointed out that if the general theory of relativity is correct, there must be infinite density and curvature of spacetime singularity in black holes. Similar to BIGBANG, this singularity is the end of all events, and the predictability of scientific laws will be invalid.
We use general relativity to describe and understand black holes. When the star collapses, the light waves emitted by the star have a strong red shift. When a star shrinks to a critical radius, its gravitational field is so strong that light waves are scattered into infinite time intervals. Observers outside the black hole will see that the light emitted by this star is getting redder and darker, and finally the star will never be seen again. This is a veritable black "hole"!