Is the Universe Expanding?

In 1929, the American astronomer Hubble concluded that the entire universe is constantly expanding based on the observations that "all nebulae are far away from each other, and the farther they are away, the faster they leave." The separation of galaxies from each other is also part of the expansion, not due to any repulsive force.

Universe expansion theory

On a clear autumn day and no clouds, the stars flashed red, blue, or white light, as if they were blinking at people. Occasionally one

The spots on the colorful balloons are as the balloons are inflated, and the spots on the balls go away. Many astronomy books use vivid illustrations of a man blowing a balloon to illustrate the theory of the expansion of the universe. But apart from this "

Correction: If the material ejects from the A pole at high speed, and then starts to get slower and slower after reaching the highest speed at the equator-the slowest speed at the B pole, then a problem will occur:

Three future destinies

Starting from Einstein's theory of relativity, Alexander Friedman studied the "dome" structure. He discovered that a space that does not change in time, that is, a static universe does not exist. Over time, space either grows larger or shrinks. Friedman distinguishes between the two situations. Obviously, the universe is expanding, and galaxies are moving away at a certain speed. The power to prevent this process comes from the gravitational attraction between galaxies. In the first case, when the density of the entire universe is high, the gravitational force is also very large, so the speed of galaxy regression will continue to slow down until the galaxy's regression stops, that is, the expansion of the universe stops. This process of cessation will not last long. The force that slows down the universe causes the universe to reverse its course. Just like putting a film on the reverse, the universe begins to shrink until it becomes a point. This model of the universe is called a closed model; at the beginning of the universe, the volume is zero, and once it begins to expand, it keeps expanding because the material density of the universe is not enough to provide the gravitational pull that stops it. These two models are like the scenario of a human launching a rocket. When the rocket runs out of fuel at a speed that is less than the first cosmic speed, the rocket's lift-off speed becomes slower and slower, and eventually falls back to the ground under the attraction of gravity; if the rocket reaches the first cosmic speed after the fuel is exhausted, it Fly into space and say goodbye to the ground permanently. The phenomenon we observe in the universe is that galaxies fly away from each other.

Regardless of whether it is a closed or open universe model, the speed of galaxy regression must be slowed down over time. However, humans living in the expanding universe cannot determine whether the model of the universe is closed or open, because both have periods of expansion. Let's let go of the imagination and imagine for the "humans" who live in the shrinking universe. They will also worry about choosing the model of the universe. Will the universe shrink forever or will it expand after shrinking? Every family has a difficult scripture.

Friedman also established a third model, called the flat type. At the beginning, the universe expanded like a closed, open type. After that, although the universe continued to expand, it always hovered around the shrinking edge. .

Difficult question

Scientists after Friedman tried to define the only way for the universe, so the material density and expansion rate of the universe became the focus of discussion. The speed of galaxy retrograde will not cause too much trouble, as long as the observation is more detailed and the calculation is more accurate. But the material density of the universe is a headache. If only the mass of matter within the range of human observation is calculated, the material density of the universe is very small, and the universe will expand forever. But don't forget, there are still many unknown fields in the universe. It is likely that there are substances that we can't see, and their masses should also be counted. Scientists refer to invisible matter as "dark matter" and distinguish between hot dark matter and cold dark matter. Hot dark matter refers to neutrinos with mass. We mentioned neutrinos in previous chapters and said that they have no mass. However, some scientists believe that neutrinos are of mass, but are so small that they are almost undetectable. In 1994, a scientist named White measured that the mass of a neutrino was between one and two billion to two billion. Cold dark matter is just like a stealthy person. Without giving humans a chance to discover it, humans can only guess its existence and believe that cold dark matter is of many varieties. Anyway, as long as there is dark matter, the material density of the universe has to be recalculated and influence the choice of the universe model by scientists.

It s up to scientists to choose the model of the universe. Let s just travel to the future and take a look at the future of the universe in different models. What kind of ending do you like? In the open universe, the universe will not change much in the next few billion years, and there will be new galaxies and stars, but they will become more and more dim. This is partly because the galaxy is getting farther and farther away from us. On the other hand, the nuclear reaction inside the star will gradually weaken until the star's fire goes out. At this time, the universe will be irresistibly darkened, the stars will die after exhausting limited fuel, and the final destination will be black holes. The black hole was the only watcher in the universe at that time.

refute

But the winner of the 2011 Nobel Prize in Physics found that the universe was accelerating, that is to say, contrary to Friedman's theory.

Theoretical challenge

Telescope observations show that most galaxies will exhibit "redshifts," and that as galaxies become more distant, the degree of redshift will increase. From the perspective of anyone who lives in these galaxies, let the neighbourhood of the Buddha Galaxy be moving away from you. (Ie the expansion of the universe)

Although this view sounds very monotonous, it marks the beginning of a revolutionary view of the nature, origin, and destiny of the universe, which implies that billions of years ago, the universe was dense and began with the Big Bang.

However, a new article published by Professor Christof Wetterich at the University of Heidelberg, Germany, challenges this traditional way of thinking. He pointed out that the light emitted by atoms is also governed by the mass of their constituent particles, the electrons. If the atomic mass increases, the absorbed and released light will move towards the blue part of the spectrum, and vice versa.

As the frequency of light, or "tone", increases with increasing mass, Professor Witridge argues that atomic masses could have been very low long ago. If the mass continued to increase, then the color of ancient galaxies would show a red shift -And the degree of redshift depends on how far they are from the earth. "My colleagues haven't found any flaws in this theory," Witridge said.

Although Witridge's research has not been published in peer-reviewed publications, the journal Nature has claimed that the universe has not expanded at alland may even be contracted with the attention of some experts, such as the University of St Andrews, UK Cosmologist HongSheng Zhao, who studies gravitational substitution theory.

"I did not find any flaws in Professor Mathematics's mathematical processing. A preliminary version of this view appeared 20 years ago. I think the alternative view of exploring the expansion of the universe is very fascinating. The evolution of the universe is like playing the piano. The low tones gradually transition to the high tones. "

Professor Wittridge has shown a transcendent and even humorous attitude towards his own research that marked a change in two different perspectives. These two perspectives represent different perspectives on reality: Either the distance between galaxies is increasing, as described in traditional perspectives, or the size of atoms is shrinking to increase their own mass; or both Complex combination. One of the advantages of Witrich's view is that it can abandon the singularity at the beginning of time, that is, the turning point of the collapse of physical principles, a physical phenomenon. The Big Bang has become obscure in the distant past: the first note of the "Cosmic Piano" is too long and too low.

According to Harry Cliff, a physicist at the European Nuclear Research Council (CERN) and modern science at the British Science Museum, the effect of increasing particle mass is similar to the expansion of space-time , which is very incredible and shocking. "Thinking about the same problem in two different ways often leads to new insights," Cliff said. "For example, string theories are 'binary' like this, which allows theorists to choose the point that makes calculations easier."

If Professor Wittridge's point is correct, it will pave the way for a new way of thinking about the universe. If we are lucky, we may get revolutionary new ideas, just as Hubble put forward a century ago. ^[4]

Hawking's answer

Even then, the evolution of the universe has not stopped, because the life of a black hole is not eternal. When people first started to study black holes, they thought that they were extremely greedy guys who would eat anything that fell into their claws, and they would not be able to escape any form of energy and matter. Later researchers changed this view.

Talking about the nature of black holes can not help but talk about Hawking. Stephen Hawking was born on January 8, 1942 in Oxford, England, and January 8, 300 years ago, happened to be the day Galileo died. After graduating from Oxford University, Hawking went to graduate school at Cambridge University, another famous university in the UK. One afternoon in the spring of 1962, he suddenly found it difficult to tie his shoes. After the doctor's diagnosis, he had amyotrophic lateral sclerosis, in other words, an incurable disease, and the doctor regretfully told him that his life was two years away. Hawking was very upset at first, and like everyone else who was terminally ill, he borrowed alcohol to relieve his sorrow. Soon Hawking got out of this state, and his attention to the fate of the universe made him forget how much time he had left. And God seems to have forgotten the length of Hawking's time in the world, and let his mind travel in the universe. By the early 1970s, Hawking's hands were basically paralyzed, and he could not draw pictures or write calculations. So he created a research method, using thinking to draw pictures and calculate. He imagined formulas as various figures, and in his thinking world, he used pen changes instead of calculating with figures. This unique way of thinking helped him discover the nature of black holes: the surface area of a black hole will never shrink. Soon, he discovered that the black hole is not completely "black". The huge gravity of the black hole can suck the negative energy particle in the pair of particles (particles with negative energy and positive energy respectively) into the black hole, so that The black hole's mass decreases; the other escapes in the form of radiation and is found by outside observers. This is the mechanism of black hole radiation.

Hawking's model of the universe is a closed, unbounded, finite four-dimensional spacetime that does not leave a place for God. However, the Holy See still elected him as a member of the Holy See Academy, because he supported the Big Bang theory, and "the people who support the Big Bang theory are all friends of the church." The church even awarded Hawking a medal. However, Hawking was still very concerned about the trial of Galileo in the church, insisting that he should take a look at the record of trial of Galileo in the church library before receiving the prize. In the end, the church conceded. Galileo was acquitted.

Cosmic expansion rate

For the first time, astronomers in the United States directly observed the diameter change of a Cepheid variable star, so they could directly calculate the distance between it and the earth. This will help more accurately measure the distance of each galaxy from the earth and "calibrate" the expansion rate of the universe.

Cosmic expansion rate

Cepheid variable stars are a class of stars whose brightness changes periodically. Polaris is one of them. It is thought that such stars will expand and contract constantly like a "deep breath", producing light changes. Observation found that the light-changing period of Cepheid variable stars is related to their true brightness (absolute luminosity), so the brightness (observed magnitude) observed from the earth is related to their distance from the earth. If you know the exact distance between a Cepheid variable star and the earth, using the apparent magnitude and absolute luminosity data of other Cepheid variable stars, you can calculate the distance of these variable stars to determine the distance of the galaxy they are located from. The galaxy distance is the basis for calculating the expansion rate of the universe. But the nearest Cepheid variable star to the earth, Polaris, is also hundreds of light years away from the earth, and it is difficult to directly measure its distance using traditional parallax methods. In the past, scientists could only use indirect methods to estimate the distance of constellations containing Cepheid variable stars, and then infer the distances of other galaxies. Scientists at the Palomar Observatory at the California Institute of Technology reported in the latest issue of the British journal Nature that they used "optical interferometry" technology to make two small telescopes work like a large telescope and directly observed the "Gemini The expansion and contraction of the Zeta Cepheid variable star. Zeta Gemini is one of the brightest Cepheid variable stars ever discovered, about 1,000 light years from Earth. Using its size changes and brightness data, it can directly calculate its exact distance from the earth. Based on this, scientists can more accurately calculate the distances between other galaxies containing Cepheid variable stars and Earth.