For thousands of years, scientists have been exploring when and how the universe was formed. Until today, scientists are convinced that the universe was formed by a big bang about 654.38+03.7 billion years ago. The matter and energy stored in the universe gather together and condense into a very small volume, with extremely high temperature and density, which instantly produces great pressure, and then there is the Big Bang. The reaction principle of this big bang is called quantum physics by physicists.
Research experience
What is the essence of space and time? This is a question that ancient philosophers and modern astronomers have been thinking hard for more than two thousand years. After Copernicus, Herschel and Hubble's trilogy of exploring the universe from solar system, milky way and extragalactic galaxy, cosmology is no longer an abstract philosophical speculation, but a modern science based on astronomical observation and physical experiments.
Until the 20th century, two more influential "cosmological models" appeared. One is the steady-state theory and the other is the big bang theory. In the late 1920s, Edwin Hubble discovered the phenomenon of redshift, indicating that the universe is expanding. In the mid-1960s, arno penzias and robert wilson discovered "cosmic microwave background radiation". These two findings strongly support the big bang theory.
Related theory
explosion
The most influential picture of Big Bang Cosmology in the modern cosmic system is a theory, also called Big Bang Cosmology. Compared with other models of the universe, it can explain more observational facts. Its main idea is that our universe once had an evolutionary process from hot to cold. During this period, the cosmic system is not static, but constantly expanding, which makes the density of matter evolve from dense to sparse. This process from hot to cold, from dense to thin, is like a huge explosion. According to BIGBANG's cosmology, the whole process of BIGBANG was in the early universe, and the temperature was extremely high, above 1000 billion degrees. The density of matter is also quite large, and the whole universe system is in equilibrium. There are only some elementary particles in the universe, such as neutrons, protons, electrons, photons and neutrinos. But because the whole system is expanding, the temperature drops rapidly. When the temperature drops to about1000 billion degrees, neutrons begin to lose the condition of free existence, and they either decay or combine with protons to form heavy hydrogen, helium and other elements. It was from this period that chemical elements began to form. When the temperature further drops to 6.5438+0 million degrees, the early process of forming chemical elements ends (see the theory of element synthesis). The substances in the universe are mainly protons, electrons, photons and some lighter nuclei. When the temperature drops to several thousand degrees, the radiation decreases, and the universe is mainly gaseous. Gas gradually condenses into gas clouds, and then further forms various star systems, becoming the universe we see today. The Big Bang model can uniformly explain the following observations:
(1) According to the Big Bang theory, all stars were born after the temperature dropped, so the age of any celestial body should be shorter than the period when the temperature dropped to today, that is, less than 20 billion years. The measurement of the ages of various celestial bodies proves this.
(2) It is observed that the celestial bodies outside the river have a systematic red shift of spectral lines, and the red shift is roughly proportional to the distance. If it is explained by Doppler effect, then the red shift is a reflection of the expansion of the universe.
(3) Helium is abundant in various celestial bodies, most of which are 30%. The mechanism of stellar nuclear reaction is not enough to explain why there is so much helium. According to the Big Bang theory, the early temperature was very high, and the efficiency of helium production was also very high, which can be illustrated by WMAP's image of BIGBANG's post-cosmic microwave background.
(4) According to the expansion speed and helium abundance of the universe, we can calculate the temperature of the universe in each historical period. Gamov, one of the founders of the Big Bang theory, predicted that today's universe is already very cold, and the absolute temperature is only a few degrees. 1965 detected microwave background radiation with thermal radiation spectrum in microwave band, and the temperature was about 3K.
The Big Bang theory holds that the universe originated from a single dimensionless point, that is, a singularity without time and space scale but containing all the substances in the universe. At least120 ~1500 million years ago, the universe and space itself were formed by this point explosion.
Split into countless pieces in an unparalleled big bang, forming today's universe. 1948, Russian-American physicist Gamov and others drew a detailed picture of the whole expansion and evolution process of planets and galaxies after a big explosion/kloc-0.5 billion years ago. But there are many puzzles in this theory.
The macro universe is relatively infinite. The "Big Bang Cosmology" assumes that the universe is just a point at first, but there is a blank around it, that is, the universe whose scope and quality have not been determined by human beings so far is compressed in a very small space, which is just a guess. Moreover, considering that energy is directly proportional to mass, where does the energy of a small point suddenly burst into the vast universe for no reason come from?
Humans set the revolution of the earth around the sun as the standard for measuring time-year. But the speed of motion of all celestial bodies in the universe is different, and there is no measure of time in the universe. For example, the concept of east, west, north and south on the earth has no meaning in the universe. Since the concept of year does not exist for the universe, how can Big Bang cosmology use the concept of year to calculate the exact age of the universe?
1929, American astronomer Hubble put forward Hubble's law that the redshift of galaxies is directly proportional to the distance between galaxies, and deduced that in the theory of galaxy inflation universe, American astronomer Hubble is far away from each other. Hubble's law only states that the farther away from the earth, the faster the galaxy moves-the redshift of the galaxy is proportional to the distance of the galaxy. But he failed to find another important point-the redshift of galaxies is also directly proportional to the mass of galaxies.
The distance between galaxies in the universe is very, very far, and the propagation of light will gradually weaken because of the absorption and blocking of space materials. Those galaxies that move faster are galaxies with higher mass. Large mass, strong energy radiation. Therefore, the galaxy with a large red shift we observed is of course a galaxy with a large mass. This is why distant galaxies called quasars have huge redshifts because of their huge mass. In addition, those galaxies with small mass and weak energy radiation (except a few galaxies close to the Milky Way, such as large and small Magellanic galaxies) are difficult to observe, and all stars can see them, so the number of red shifts and purple shifts of stars is roughly the same.
Another reason for the galaxy's red shift and less purple shift is that all the material structures in the universe move in circular orbits around a center within a certain range, rather than moving radially from a center to the periphery as described in the Big Bang cosmology. Therefore, the purple shift galaxies seen from the earth are very narrow and few in number. They can only be galaxies moving in the same direction as the Milky Way, and the front is smaller than the Milky Way. A galaxy whose rear is larger than the Milky Way. Only by developing astronomical observation instruments with higher resolution can we see more purple-shifted galaxies in the future.
When the distribution of matter in the universe is unbalanced, the local material structure will continue to expand and contract, but the relative balance of the overall structure of the universe will not change. It cannot be said that the universe as a whole is expanding or contracting only by partially (but not completely) observing the distance between galaxies and the earth. Just like the tidal phenomenon that the oceans on the earth are constantly rising and falling under the action of gravity, it does not mean that the total amount of seawater is increasing or decreasing.
1994, Friedman and others of Carnegie Institution of the United States calculated the age of the universe by estimating the expansion rate of the universe, and obtained the age calculation value of 80 ~1200 million years. However, according to the analysis of stellar spectra, the oldest star in the universe is140 ~1600 million years old. Stars are older than the universe.
1964, American engineers penzias and Wilson detected the microwave background radiation, which was due to the energy transfer effect between various substances that filled the space. The radiation of matter in the universe is all the time, and the temperature of 3K or 5K is only a measure designed by human beings according to their own judgment. This energy radiation phenomenon can only show that the matter in the universe is attracted by gravity.
As for the abundance of helium in the Big Bang cosmology, helium is an extremely rich atomic structure in the universe, second only to hydrogen. Its percentage content in space and the percentage content of other elements are also common physical phenomena in the distribution law of material structure. In the large-scale scope of the universe, not only the abundance of helium is similar, but also the abundance of other elements such as hydrogen and oxygen. Moreover, various elements are constantly changing with different temperatures and environments, and do not always keep the same face, so microwave background radiation and helium abundance are not necessarily related to the origin of the universe.
Big bang cosmology faces another problem. If the universe expands infinitely, what will be the final outcome? Clausius, a German physicist, pointed out that the changing process of energy from non-uniform distribution to uniform distribution is applicable to all energy forms and events in the universe. In any given object, there is a physical quantity based on the ratio of its total energy to temperature. He named this physical quantity "entropy", and the "entropy" in isolated systems often increases forever. But in the universe, there will always be areas with high entropy and low entropy, and there can be no absolute unity. Therefore, when the level of "entropy" keeps rising and reaches the maximum, the universe will enter an eternal dead state and eventually die of "thermal silence". When the universe expands to a certain extent, all galaxies and planets will be alienated, and molecules will be broken down into quarks or even smaller. The whole universe continues to expand and become a lifeless state. This prediction is based on the brightness of hundreds of A 1 supernovae.
According to astronomical observation data and physical theory, describe the specific form of the universe. The morphological characteristics of galaxies are very important for studying the structure of the universe, and the structural morphology of the whole universe can be inferred from the motion law of galaxies. The circular vortex structure shared by galaxies is the epitome of the whole universe, and those different galaxy shapes such as ellipse and rod spiral are just visual effects caused by different galaxy ages and observation angles.
The wonderful spiral is the most common and basic form of material movement in nature. This spiral phenomenon has an important enlightening effect on understanding the shape of the universe. As large as spiral galaxies and as small as DNA molecules, they are all produced in this vortex. Nature does not recognize the linear form, and the basic structure of all substances in nature is a circle with curved motion. From atoms and molecules to planets and galaxies, to galaxy clusters and superclusters, there is no doubt that the vast universe is a big vortex. Therefore, establishing a "spiral motion model of the universe" can better reflect the real structure of the universe than the "big bang model" in which the universe is the sum of all substances, which is separated from the curve motion model and stretches infinitely from a center in all directions with a straight line.
One more thing, the big bang is periodic. Some scientists claim that the universe will become a sphere with high density and small volume. After shrinking to a certain extent, there will be another big outbreak. According to the law of conservation of energy, the energy of the universe has not died out. However, no one can explain whether the time, space and molecular structure of each cycle of the Big Bang are the same as last time (hundreds of billions of years later, there are solar system, earth, China and you) or rearranged (light can be bent out of thin air).
Steady state theory
The question of the origin of the universe is a bit like this old question: which came first, the chicken or the egg? In other words, what created the universe and what created the universe? Maybe the universe, or what created it, has existed for infinite time and does not need to be created. Until recently, scientists have been trying to avoid such problems, thinking that they belong to metaphysics or religion rather than science. However, in the past few years, people have found that the laws of science are valid even at the beginning of the universe. In that case, the universe can be self-sufficient and completely determined by scientific laws.
The debate about whether and how the universe began runs through the whole recorded history. There are basically two schools of thought. Many early traditions, as well as Judaism, Christianity and Islam, believe that the universe was created in the fairly recent past. /kloc-in the 7th century, Bishop Wu Schell calculated that the date of the birth of the universe was 4004 BC, which was obtained by adding up the ages of the characters in the Old Testament. It is a fact that there has been an obvious evolution of human culture and technology since modern times to support the above viewpoint. We remember the founder of that performance or the developer of this technology. It can be said that we can't exist that long; Because otherwise, the date of creation of the Bible is similar to the end of the last ice age, which seems to be the earliest time for modern humans to appear.
On the other hand, some people, such as the Greek philosopher Aristotle, don't like the idea that the universe has a beginning. They think this means god's intervention. They prefer to believe that the universe already exists and will continue to exist indefinitely. Immortal things are more perfect than things that must be created. Their answer to the above questions about human progress is that periodic floods or other natural disasters repeatedly bring human beings back to their original state.
Theoretical comparison
Both schools believe that the universe will basically not change with time. Because human life-the whole recorded history is so short, the universe has never changed significantly during this period. In a stable cosmic framework, whether it exists in infinite time or was born in limited time is really a metaphysical or religious question: any theory explains it. 178 1 year, the philosopher Immanuel Kant wrote a landmark and very vague work, Critique of Pure Reason. In this book, he concludes that there are equally valid arguments to support the belief that the universe has a beginning or that the universe has no beginning. As the title of his book implies, he simply draws a conclusion by reasoning, in other words, he simply ignores the observation of the universe. After all, what is there to observe in an unchanging universe?
However, in the nineteenth century, evidence began to accumulate, indicating that the earth system and the universe are other parts and actually change with time. Geologists realize that the formation of rocks and fossils in them takes hundreds of millions or even billions of years. This is much longer than the age of the earth calculated by creationists. The so-called second law of thermodynamics put forward by German physicist ludwig boltzmann also provides further evidence that the total amount of disorder in the universe (measured by a quantity called entropy) always increases with time, just as the argument about human progress implies that it can only run for a limited time, otherwise.
Another difficulty with the idea of stabilizing the universe is that according to Newton's law of gravity, every star in the universe must attract each other. If Newton's fruits are like this, how can they keep a constant distance and stand still?
Newton knew the problem. In a letter to Richard Bentley, a famous philosopher at that time, he agreed with the view that a limited group of stars could not stand still, and they would all fall on a central point. However, he concluded that an infinite number of stars would not fall together because there was no central point for them to fall. This argument is an example of the trap people will encounter when talking about infinite systems. Adding up the forces of infinite stars in the universe acting on each star in different ways will give different answers to whether the stars keep a constant distance. Then add more stars that are roughly evenly distributed outside the region. Stars in a limited area will collapse together. According to Newton's law, adding more stars outside this area can't stop them from collapsing. In this way, an infinite number of stars cannot be at rest. If they don't move relative to each other at a certain moment, the attraction between them will make them start to fall in each other's direction. In another case, they may be moving away from each other, and gravity slows down this return.