Talking about the universe

Yu, Zhou ZHU, called Yu in all directions, has been called Zhou since ancient times. -Xinhua Dictionary

In Chinese, "Yu" stands for up and down four directions, that is, all the space, and "Zhou" stands for all the time, that is, all the time. Yu: infinite space, and Zhou: infinite time. So the word "universe" has the meaning of "all time and space". Linking the concept of "universe" with time and space embodies the wisdom of the ancient people in China.

The word "universe" comes from the book Zhuangzi. "Yu" refers to all spaces, including all places in the east, south, west and north, which are boundless; "Week" refers to all time, including past, present, day and night, with no beginning and no end.

In the west, the word universe is called universe, universe and space; In English; Russian name is кocMoc, German name is kosmos, and French name is cosmos. Are derived from the Greek κoσμoζ. The ancient Greeks believed that the universe was created to produce order from chaos, and the original meaning of κoσμoζ was order. But in English, the more commonly used word for "universe" is Universe. This word has something to do with universitas. In the Middle Ages, people called universities a group of people who acted in the same direction and goal. In the broadest sense, universitas also refers to a unified whole composed of all ready-made things, that is, the universe. The universe and the universe often express the same meaning, but the difference is that the former emphasizes the sum of material phenomena, while the latter emphasizes the structure or construction of the whole universe.

"Yu" refers to space and "Zhou" refers to time. The universe is a material world with infinite space, no beginning and no end of time, and moving according to objective laws.

Summary of the universe [1]

The universe is a unity composed of space, time, matter and energy. It is the synthesis of all space and time. Generally speaking, the universe refers to a space-time continuous system in which we exist, including all the matter, energy and events in it.

The universe is the general name of all things, and it is the unity of time and space. The universe is a material world, which exists objectively regardless of human will and is in constant movement and development. The universe is diverse and unified. It includes everything and is the unity of all time and space. There is no time and space, nothing. So it contains everything.

Hierarchical understanding of the universe

From a philosophical point of view. People think that the universe has no beginning, no end and no end. However, we are not going to discuss this abstruse concept in depth, so let's leave it to philosophers to study. We might as well squint and use our existing science and technology to talk about the universe that we can understand and observe. People call it "our universe" or "total galaxy".

According to the latest observation data, the farthest galaxy observed by people is 65.438+0.3 billion light years. That is to say, if a beam of light is emitted from a galaxy at a speed of 300,000 kilometers per second, it will take 654.38+03 billion years to reach the earth, which is of course 654.38+03 billion years ago. This distance of 65.438+0.3 billion light years is the universe we know today (2009). More specifically, the universe as we know it today, or its size, is a spherical space with the earth as the center and the distance of 65.438+0.3 billion light years as the radius. Of course, the earth is not really the center of the universe, and the universe is not necessarily a sphere. It's just limited to our current observation ability, and we can only know this extent.

In this spherical space with a radius of1300 million light years, there are about1250 million galaxies that have been discovered and observed, and each galaxy has hundreds to trillions of sun-like stars. So as long as you do a simple math problem, it is not difficult for you to know how many stars there are in the universe we have observed. In such a vast universe, the earth is really a drop in the ocean and insignificant.

Astronomers have always wondered how big the universe is, just like us. Recently, the American Space Network reported that after hard calculation, astronomers found that the universe is extremely huge, with a length of at least 65.438+056 billion light years. "Such a discovery about the size of the universe is obviously based on the premise that the universe is spherical and limited. This assumption was first put forward by Einstein. " Daming Chen, a researcher at the National Astronomical Observatory of China, said in an exclusive interview with reporters, "For a long time, there has been such a debate in the field of cosmology, whether the universe is spherical, saddle-shaped or flat." Zhang Yue, an associate professor at Beijing Normal University, said: "The international mainstream cosmology generally believes that the universe is flat and infinite." So, where does the debate around the universe come from? What makes sense? The most common view is that after the Big Bang, the universe was born. "According to the most influential Big Bang theory in modern cosmology, our universe was produced by a very small point explosion about 65.438+0.37 billion years ago, and the universe is still expanding." Researcher Daming Chen said, "This theory has been confirmed by a large number of astronomical observations." This theory holds that in the early days of the birth of the universe, the temperature was very high. With the expansion of the universe, the temperature began to drop, producing neutrons, protons and electrons. Since then, these elementary particles have formed various elements. These particles attract and fuse with each other, forming larger and larger clumps, and gradually evolving into galaxies, stars and planets. Life phenomena have appeared on individual celestial bodies, and finally human beings who can understand the universe have been born. Is the universe spherical and finite? "The idea that the universe is spherical has existed for a long time, although it is not the mainstream of the international cosmology community." Daming Chen said, "Every time it is mentioned, it will attract people's attention, because this view is very strange." One of the most obvious examples is the universe model established by American mathematician Jeffrey Wilkes not long ago: a mirror maze of limited size, shaped like a football. The model of "shaped like a football" shocked the scientific community, because this theory claimed that the universe produces an "illusion" without boundaries because this limited space reflects itself endlessly through the "circle" effect. Wilkes believes that people think that the universe is infinite because the universe is like a mirror maze, and light shuttles back and forth, giving people the illusion that the universe is infinitely extended. This amazing inference was later included in New Scientist magazine and widely circulated among the people as a kind of "strange talk".

[Edit this paragraph] Cosmic Age

Definition of cosmic age

The time interval between a certain moment and the present. For some cosmological models, such as Newton's cosmological model, hierarchical model and steady-state model, the age of the universe is meaningless. In the usual evolutionary universe model, the age of the universe refers to the time interval from the zero scale factor of the universe to the present. Generally, Hubble age is the upper limit of the age of the universe and can be used as a measure of the age of the universe. According to the Big Bang model, the age of the universe is about 20 billion years.

Age calculation

The age of the universe is 125 billion years.

Scientists use telescopes to observe the uranium spectrum on the oldest planet, thus estimating the age of the universe as 125 billion years. Scientists have different estimates of the age of the universe. According to different cosmological models, scientists estimate that the age of the universe is between10 billion and16 billion years. In 200 1 year, scientists observed a planet named CS3 1082-00 1 using the telescope of the European Southern Observatory. By measuring the spectrum of the radioactive isotope uranium -238 on the planet, the age of the planet is calculated as 125 billion years, and the error of this estimation is about 3 billion years, that is to say, the age of the universe is at least 125 billion years. This is the first time that scientists have measured the uranium content outside the solar system.

Scientists explained that this method is the same as using carbon-14 isotope to measure the age of matter in archaeology, and the half-life of uranium -238 isotope is 4.45 billion years. Half-life is the automatic transformation of a radioactive element into other elements until the remaining half of the time.

Scientists pointed out that at the beginning of the universe, the Big Bang produced elements such as hydrogen, helium and lithium, while the heavier elements were produced inside the stars. When a massive star dies, substances containing heavy elements will be scattered into the surrounding space and then combined with the next generation of stars; In fact, the gold on the earth also comes from the exploding planet.

So the older the planet, the less heavy elements there will be. Scientists believe that the content of heavy elements in some older planets is only 1% of that of the sun. Scientists try to estimate the age of the universe by thorium -232 isotope. Thorium is a radioactive metal element. Contact with neutrons will cause nuclear fission and produce atomic energy. However, the half-life of thorium is1410.5 billion years, which is longer than that of uranium -238, so the estimation error is relatively large.

[Edit this paragraph] [BIGBANG]

The Big Bang is just a theory, an idea based on astronomical observation and research. About 654.38+0.5 billion years ago, all the substances in the universe were highly concentrated at one point, with extremely high temperature, which led to a huge explosion. After the big bang, matter began to expand outward, forming the universe we see today. The whole process of the Big Bang is complicated, and now we can only describe the history of the development of the ancient universe on the basis of theoretical research. In this/kloc-0.5 billion year, galaxy clusters, galaxies, our galaxies, stars, solar systems, planets, satellites and so on were born one after another. Now all the celestial bodies and cosmic substances we see and can't see have formed today's cosmic form, and human beings were born in this cosmic evolution.

The constant expansion of the universe

Scientists believe that it originated from an incredible explosion 654.38+03.7 billion years ago. This is an unimaginable energy explosion. It takes 654.38+0.2 billion years for the light at the edge of the universe to reach the earth. The material emitted by the Big Bang drifted in space, and a huge galaxy composed of many stars was made of these materials. Our sun is one of countless stars. Originally, people imagined that the universe would not expand due to gravity, but scientists found that there is a kind of "dark energy" in the universe, which will produce a repulsive force and accelerate the expansion of the universe.

The expansion process after the big bang is a struggle between gravity and repulsion, and the power generated by the explosion is a repulsion, which keeps the celestial bodies in the universe away. There is gravity between celestial bodies, which will prevent them from moving away and even try to make them close to each other. Gravity is related to the mass of celestial bodies, so whether the universe eventually expands or stops expanding and then contracts after the Big Bang depends entirely on the density of matter in the universe.

There is a critical density in theory. If the average density of matter in the universe is less than the critical density, the universe will continue to expand, which is called opening the universe; If the average density of matter is greater than the critical density, the expansion process will stop sooner or later, and then it will shrink. This is the so-called closed universe.

The problem seems simple, but it is not. The theoretical critical density is 5× 10-30g/cm3. But it is not so easy to determine the average density of matter in the universe. There is a vast intergalactic space between galaxies. If the mass of all luminescent substances observed at present is evenly distributed in the whole universe, the average density is only 2× 10-3 1g/cm3, which is far lower than the above critical density.

However, all kinds of evidence show that there are still so-called dark matter that has not been observed in the universe, and its quantity may far exceed that of visible matter, which brings great uncertainty to the determination of average density. Therefore, whether the average density of the universe is really less than the critical density is still a controversial issue. However, at present, it is more likely to open the universe.

When a star evolves to a later stage, it will throw some substances (gases) into interstellar space, which can be used to form the next generation of stars. This process will consume less and less gas, so that new stars cannot be formed in the end. 10 14 years later, all the stars will lose their luster and the universe will become dark. At the same time, stars will escape from galaxies because of interaction, and galaxies will shrink because of energy loss. In this way, the central part will produce a black hole, which will devour the stars passing by it and grow up.

After1017 ~10/8 years, only black holes and some scattered death stars remain in a galaxy. At this point, the protons that make up the star are no longer stable. When the age of the universe reaches 10 24, protons begin to decay into photons and various leptons. 10 At the age of 32, this decay process was completed, leaving only photons, leptons and some huge black holes in the universe.

10 100 years later, through evaporation, high-energy particles will escape from the huge black hole and eventually disappear completely, and the universe will return to darkness. This may be the scene at the end of the universe, but it is still expanding constantly and slowly.

What will happen if the universe is closed? In a closed universe, the end time of the expansion process depends on the average density of the universe. If the average density is assumed to be twice the critical density, then according to a simple theoretical model, after 40-50 billion years, when the radius of the universe expands to about twice its current size, gravity will begin to prevail, the expansion will stop, and then the universe will begin to shrink.

In the future, the situation is almost like a cosmic movie that is shown backwards. All the major changes in the universe after the Big Bang will be reversed. After shrinking for tens of billions of years, the average density of the universe has roughly returned to its present state. However, the retrogression of galaxies far away from the earth will be replaced by the movement closer to the earth. In a few billion years, the background radiation of the universe will rise to 400 kHz and continue to rise, so the universe will become very hot, dense and shrinking faster and faster.

In the process of collapse, galaxies will merge with each other and stars will collide frequently. Once the temperature of the universe rises to 4000 kHz, electrons will be dissociated from atoms; When the temperature reaches several million degrees, all neutrons and protons are separated from the nucleus. Soon, the universe entered the stage of "big collapse", and all matter and radiation were swallowed into an infinitely high-density and infinitely small space very quickly, returning to the state when the Big Bang occurred.

[Edit this paragraph] The paradox of the origin of the universe

At present, the familiar "theory of the origin of the universe", such as the Big Bang and string theory, are all based on the existence of vacuum.

Because if there is no vacuum, then there is no "big bang singularity" and "string"

Paradox/contradiction lies in:

Vacuum is also a part of the universe.

Since the current theory is the theory of the origin of the universe,

But it doesn't talk about the origin and composition of vacuum.

So this is a contradiction.

Therefore, the best word to describe the current theory of the origin of the universe is the theory of the origin of stars.

From the complete works of civilization x archives

[Edit this paragraph] Paradox of Parallel Universe

Parallel universes, also known as multiverses, say: There may be more than one universe in this world, but there are many different, parallel and non-interfering universes; Sometimes things in these different universes can come to another universe through certain channels (namely "wormholes").

Paradox/contradiction lies in:

The word universe includes: everything in the world.

If there is another universe in this world,

Then the word universe can't include: everything in the world.

So this is a contradiction.

In fact, the parallel universe/multiverse describes "different time and space"

Or: there may be different time and space in this universe, but there is no different universe (because it has fundamental contradiction with the concept of the universe)

So the most accurate description should be: this universe may have many parallel spacetimes.

From the complete works of civilization x archives

[Edit this paragraph] The development of the concept of the universe