Where is the end of the universe
Before the 19th century, people thought that the solar system was almost everything, and did not believe that there were other planets beyond the solar system. By 1900, it was believed that the Milky Way to which the solar system belonged was the entire universe. As for the size of the Milky Way, the boldest estimate at the time was about 20,000 light-years wide (light-years, the distance light travels in a year, about 9,460.5 billion kilometers), containing about 2 to 3 billion sun-like stars.
In 1920, astronomer Harlow Shapley et al. based on a new method of measuring the distance of stars that were available at the time,
It was calculated that the true width of the Milky Way is 100,000 light-years, and the total number of stars contained in it is 200-300 billion. Compared with the view of 20 years ago, the Milky Way has "expanded" 100 times, and it is concluded that this extremely enlarged Milky Way is not the entire universe.
At the same time, astronomers discovered that the universe is made up of many galaxies like the Milky Way, each consisting of about billions to trillions of stars. And it proves that the universe is dynamic, and that hordes of galaxies are separated from each other, and the distance between them is getting wider and wider, as if the universe is also expanding.
In 1929, American astronomer Edwin P. Hubble and others devised a variety of methods to determine the distance of galaxies, showing that even galaxies that are relatively close to us (such as the Andromeda constellation system) are 2.3 million light-years away. In the 1960s, it was discovered that some of the matte stars that were once thought to be in our own galaxy were actually very far away from our galaxy and were known as "quasars." These "quasars" are the closest 1 billion light-years away from us, and the farthest ones are more than 12 billion light-years away.
According to the model of the universe that expanded rapidly since its birth, the age of the universe can be calculated to be 13 billion years. That is to say, the distance from The Earth to the "end" of the universe should theoretically be 13 billion light-years.
As for how big the universe really is, and where its "end" lies, it may always be a mystery.
Conjectures arising from the universe
How did the universe come into being? This is the biggest mystery today. Currently, most scientists accept the "Big Bang cosmology." The theory holds that the universe originated from a primordial fireball with extremely high temperatures and small positivity. Between 15 and 20 billion years ago, for physical reasons we don't know yet, this fireball exploded. With the expansion of space, the temperature decreases, the density of matter also gradually decreases, the original protons, neutrons and other elementary particles combined into deuterium, helium, lithium and other elements, and then gradually formed galaxies, galaxy clusters, and gradually formed stars, planets, and in some celestial bodies there are also life phenomena, and finally the birth of human beings, the initial formation of the universe.
The Big Bang doctrine is constantly being confirmed. On April 23, 1991, George Smoot, an astrophysicist at the University of California, announced at the Meeting of the American Physical Society that the scientific team he led had discovered clouds of matter at the beginning of the universe, strongly supporting the Big Bang theory.
Their discovery has attracted great attention from the world's scientific community, and is considered to be the most outstanding theoretical physicist after Einstein, Stephen Hawking, issued a statement on April 24, saying: "This is the most important discovery of this century." ”
The Big Bang theory can explain more observational phenomena. For example, astronomers observe that distant objects are always moving away from Earth, which proves that the universe is still expanding; the ages of various objects are less than 20 billion years, which is also consistent with the theory's theory that various objects formed after the Big Bang. In addition, the Big Bang theory successfully predicted the existence of background radiation in the universe. The Big Bang doctrine predicts that after the Big Bang, the structure of the universe before galaxies formed should be clouds. The discovery of this massive cloud confirms the predictions of the Big Bang doctrine, and by observing this cloud, scientists can further speculate about the early universe.
And, the discovery of this massive cloud also confirms another prediction by scientists that 90 percent of the universe's mass resides in "dark matter." The total mass of the universe observed by astronomers in the past is much smaller than the total mass of the universe calculated in theory. These "disappearing" substances are called "dark matter." The amount of "dark matter" directly affects the future of the universe, and if the total mass of the universe is less than a certain value, then it will continue to expand as it is now; if its total mass is greater than this value, then the gravitational force between celestial bodies will stop expanding the universe and begin to contract under the action of this huge gravitational force, forming the "big collapse" of the universe until the state before the Big Bang.
Is the universe harmonious?
The regularity and harmony of the movement of the universe seems to have become an immutable creed. Since the ancient Greek period, the famous Pythagorean school has proposed that "beauty is harmony and proportion", and then pointed out that it is precisely because of this harmony that the universe in which human beings live has evolved to this day and is orderly. It is precisely because of this harmony that celestial bodies should be spherical, and their movements should also be circular motions.
In the 16th century, Copernicus, through his own observations, rejected the traditional "geocentric theory" and proposed the "heliocentric theory". He believes that this model of the universe centered on the sun is both in line with the laws of celestial motion and embodies a "wonderful harmony." Later German astronomer Kepler also highly admired the aesthetic principles of Pythagoras, linking celestial motion to musical scales. Newton explored the motion of celestial bodies in greater depth from a mechanical point of view, proposing the law of universal gravitation, which not only proposed a more scientific explanation for the changes in motion, but also guided astronomers in discovering Neptune. Newton's law of universal gravitation reflects how harmonious the order of the universe is.
This "predetermined harmony" also influences the study of modern astronomy. The famous "Big Bang" hypothesis, which reflects the expansion of the universe, embodies the principle of "harmony" very concretely, is based on Hubble's observations about the redshift of galaxies, and predicts the existence of microwave radiation in the cosmic background. These are reproductions of the harmonious picture of the universe on a large scale in space.
Modern physicist Albert Einstein pointed out that this predetermined harmony of the universe can give people beauty and pleasure, and is the source of all human literary and artistic creation, perseverance and patience.
The harmony of the universe has long been universally accepted, but in recent years it has been challenged. Some people, represented by Sars, a scientist at the Massachusetts Institute of Technology in the United States, and Wizdem, an astronomer, believe that the entire solar system cannot be predicted at all.
Perhaps 4 million years later, Newton's doctrine will be proven wrong. They believe that there is a phenomenon in the universe that is predicted according to some simple law, and that due to many accidental factors at work, it will lead to very complex and irregular phenomena, which is the phenomenon of chaos.
So, is the master of the universe harmony or chaos? It's really an unexplainable mystery.
Will the universe heat up?
In 1854, the German scientist Helmholtz proposed the theory of cosmic heat death, pointing out that the universe can only convert all the energy into heat, and eventually in a uniform state, which in turn makes the universe fall into an eternal state of rest. This hypothesis is also known as the heat death hypothesis or the thermodynamic hypothesis.
The heat death hypothesis caused panic in the world, because the dead and lifeless universe is equivalent to the world's imminent arrival, in order to eliminate this hypothesis, many scientists have tried this, the German physicist Clausius and the Austrian physicist Boltzmann have debated this, the latter believes that the universe does not change in one direction, but also in the opposite direction. Engels also disagreed with the view of the heat death fin, which he believed contradicted the principle of conservation of energy.
Since the heat death hypothesis contradicts the infinity of the universe, cosmologists who advocate the Big Bang theory have solved it from the point of view of the expansion of the universe. The Russian scientist Friedman once made precise calculations, and the results showed that the universe may contract and expand periodically, or it may expand indefinitely. Later, the American astronomer Hubble used the 1.5-meter telescope and the 2.5-meter telescope on Mount Wilson in California to find that the universe was expanding. According to this view, the universe is divided into particles and radiation (such as light, infrared, ultraviolet x-rays), due to the thermal expansion of the universe, particles are thermally balanced, radiation is also thermally balanced, but there is no thermal equilibrium between the two, it takes a certain amount of time to reach the thermal equilibrium, due to gravity, so they do not have enough time to reach the thermal equilibrium.
However, some scientists have questioned the thermal expansion of the universe, and it is unsatisfactory to attribute the explanation of certain physical properties to the situation at the beginning of the universe. People hope that the universe will not die of heat, and hope that life and the civilized world will continue, but there has been no solution to the hypothesis of heat death.
The most mysterious mystery in the universe
The so-called "black" of a black hole indicates that it does not emit and reflect any light to the outside world, so people cannot see it, it is "black"; the so-called "hole" is to indicate that anything enters its boundary and then refuses to go out again, so it lives like a real "bottomless pit". Why do black holes have such properties? This is because it has an extremely strong gravitational field that nothing, including light, can escape from it. Not only that, the black hole's powerful gravitational field is enough to destroy all the objects inside it, so the black hole does not have any type of material structure inside, which is the famous "black hole impermanence theorem". Black holes have strange, unimaginably bizarre properties.
Its density is amazing, if the sun becomes a black hole, its radius will be "compressed" from the current 700,000 kilometers to about 3 kilometers, that is, reduced to one hundred and thirty thousandths; if our earth becomes a black hole, then its radius will be "compressed" from the current more than 6,000 kilometers to only a few millimeters, equivalent to a small green bean. After astronomers have studied, there are three views on the source of black holes: first, the star in its later years of nuclear fuel is exhausted, the star in its own gravitational action began to shrink the depression, if the mass of the trapped material is greater than 3 times the mass of the sun, then the product of the contraction depression is the black hole; the second is that the central part of the galaxy or globular cluster of stars is very dense, and large-scale collisions are easy to occur between the stars, resulting in the collapse of supermassive objects, which can form a black hole with a mass of more than 100 million times that of the sun Third, according to the big bang cosmic model, the huge force of the big bang will squeeze some matter extremely tightly, thus forming a "proto-black hole".
Astronomers also cite many facts about the distortion of the orbits of stars to confirm the existence of black holes. But while astronomers have all assumed the existence of a black hole, no one has found one. Therefore, the existence of a black hole is still a mystery.