How old is the universe now?

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.

[Edit this paragraph] 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 1 125 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 planet. When a planet dies, substances containing heavy elements will be scattered into the surrounding space and then combined with the next generation of planets; 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] Age will increase.

On August 7, 2006, the American magazine Science published an article saying that an international team of astronomers published a new report, saying that the age of the universe may be 2 billion years earlier than originally thought. Scientists have discovered a neighboring galaxy that is 15% farther than originally expected, which means that the age of the universe may be underestimated 15%. But other experts think it is too early to draw a conclusion.

Astronomers have successfully measured the relative distances of many distant galaxies by observing a special planet whose brightness changes in stages. But in order to know how many light-years these galaxies are from humans, scientists need to directly calculate the distance between the Milky Way and some galaxies. This kind of measurement is difficult to make. For many years, the only reliable measurement distance was the nearby Large Magellanic Cloud, but some astronomers worried that its unusual chemical composition would affect the calculation.

Now, Chester Bonans of the Carnegie Institution in Washington and his colleagues have observed a faded eclipsing binary star in the "neighbor" triangle galaxy of the Milky Way. The two stars in this system cross each other in orbit, and observing the process of the two stars darkening each other can make astronomers ignore the size of the two stars and the energy they release. By comparing the observed brightness, we can see the distance between the planet and the earth.

This result was published in the American Journal of Astrophysics. It is estimated that the triangle galaxy (also known as M33) is 3 million light years away from the Earth, which is 2.6 million light years away 15% from the commonly thought, which is measured by other indirect techniques. If the data of 3 million years are confirmed, the new distance implies that galaxies farther away will be 15% farther than before, because the relative distance will not change. And because the size and age of the universe are based on the distance between galaxies, the age of the universe has increased from 65.438+0.37 billion years to 65.438+0.57 billion years.

[Edit this paragraph] The universe may be older.

German scientists have found that the iron content in a quasar deep in the universe far exceeds that of any other star in the solar system. Because it takes a long time for iron to form in celestial bodies, on the basis of comparing with the iron content in celestial bodies in the solar system, scientists suggest that the age of the universe may be older than people had previously speculated.

Scientists from the Max Planck Institute for Extraterrestrial Physics and the European Space Agency analyzed the composition of this quasar with XMM- Newton Space Ray Telescope, and found that although there seems to be no oxygen in this quasar, its iron content is about three times that of a single star in the solar system.

Scientists said that according to the existing knowledge, quasars and their iron-containing substances were gradually formed about 65.438+0.5 billion years after the Big Bang, and the iron substances in celestial bodies were formed by the fusion reaction after the burning and explosion of stars in the universe, that is, the iron substances on a celestial body can only be gradually accumulated in billions of years. According to the existing research, the age of the universe is at least 65.438+025 billion years, and the solar system was formed about 9 billion years ago. Therefore, comparing the iron content in celestial bodies in the solar system, scientists believe that this new discovery either indicates that there is an iron-rich star in the universe that people have not known so far, or indicates that the age of the universe is older than previously speculated.

Quasars are a kind of celestial bodies with relatively small volume but huge energy in the universe. This celestial body is similar to a star in general optical observation, but its spectral line has a great red shift in spectral observation, which is different from a star, so it is called a quasar. China scientist Cai Xingyu once speculated that the universe is at least 1 100 million years old.

[Edit this paragraph] Determined

Wendy Friedman, a cosmologist at the Carnegie Observatory in California, said that Bonans' team had done "very solid work". Since 1990s, she has been leading the large Hubble Space Telescope to measure the range of cosmic distance. However, she also believes that it is necessary to find another pair of "dim binary stars" in a galaxy to change people's current thinking about the age of the universe.

Edward shian, an astrophysicist at Villanova University in Virginia, agrees. He pioneered the technology of testing dim binary stars in the nearby large Magellanic galaxy. He said. It is not enough to have only one star to explain the conclusion. At the same time, he is also worried that the Bonans team used a shining planet instead of a dim binary star, because he thinks their theoretical model is not very solid. "My assumption is that the triangle galaxy should not be too far away," he said. "It may move to the earth again."

[Edit this paragraph] Research theory

When did the universe begin? When will it end? This is the most mysterious and difficult puzzle left by the universe to mankind. Although the Big Bang theory has been deeply rooted in people's hearts, people have acquiesced that the universe was born in the Big Bang nearly 654.38+0.4 billion years ago, and everything about the universe, galaxies, the earth and life was gradually formed after the Big Bang. However, after the birth of this theory, many people also raised another question: What happened before BIGBANG? On May 5th, a research paper published in the journal Science claimed that it had solved the problem that scientists were debating. Bohr Steingard of Princeton University in the United States and Neil Turk of Cambridge University in the United Kingdom jointly put forward a theory in this paper, that is, the Big Bang happened more than once, and the universe has been experiencing the process of "rebirth". People think that the Big Bang 65.438+04 billion years ago was not the absolute starting point of the birth of the universe, but only a rebirth of the universe.

Who accelerated the expansion of the universe made scientists notice that BIGBANG was not only a "cosmological constant" abandoned by scientists, but also picked up again. The so-called cosmological constant is a mathematical expression of energy in vacuum, which is expressed by the letter 1 1 of the Greek alphabet. This kind of energy is also considered as mysterious "dark energy", which is accelerating the expansion of the universe.

In a report on this study by British and American scientists on May 8, American Space Network said that when Einstein first proposed the cosmological constant, he wanted to prove that there was an energy in the universe to counteract the gravity between stars, so that the stars would not attract each other, and eventually the whole universe would be integrated, so he also wanted to prove that the universe was static, without growth or contraction. But it didn't take long for Einstein to give up this theory, saying that he had made the "biggest mistake" in his life. Because the universe is expanding according to his own general relativity formula, and astronomer Edwin Hubble has confirmed through observation that the universe is indeed expanding.

In the late 1990s, "Ramda" was picked up by scientists again. At this time, some astronomers found that the universe is not only expanding, but also accelerating. Scientists don't know what mysterious force led to this result, so the word "dark energy" came into being. Scientists believe that "dark energy" is the cosmological constant "lambda". "Ramda" after BIGBANG did not share the world with gravity to keep the balance of the universe, but seized power from gravity, making the stars farther and farther away and the universe expanding.

Cosmic constants should be geometric.

How big should the cosmological constant be? This is the key to the number of big explosions. American and British scientists Bohr Stangard and Neil Turk found that the Big Bang should not happen only once in the calculation of the size of the cosmological constant.

One question that the scientific community has been trying to explain is why so many constants in nature are just right for life. If "Ramda" is too big, then the universe will expand and burst immediately after the Big Bang, just like a balloon blown up, so life will cease to exist after 10 billion years. Professor Bohr said in an interview with Space Network: "The value of' λ' is one of the most mysterious things in physics. This makes us very confused. " Even the "anthropic principle" has appeared in the scientific community, that is, the cosmological constant properly chose human survival, and human beings just chose to appear under such constant conditions, and human beings went back to study why the cosmological constant just allowed human survival. This sounds really incredible. Professor Neil said: "This is simply too bad and should really be abandoned. This theory is to show that human beings can never understand the mystery of the universe, which is our way of survival. "

In order to find a reasonable explanation beyond the "anthropic principle", two scientists used the BIGBANG model to calculate the cosmological constant, but the result was much larger than the actually observed cosmological constant, which was 100 times of the actual value, that is, it was not suitable for life in the universe at all. The big novel of cosmological constant is still related to human survival. Therefore, Professor Bohr and Professor Neil think that the cosmological constant (that is, "dark energy") will weaken with the passage of time after BIGBANG. However, after further calculation, they found that 654.38+04 billion years was not enough to weaken the value after the explosion to the present value. Professor Neil of Cambridge University said: "People think that time started with that big bang, but there has never been a reasonable explanation. And our inference seems very radical: there was time before the big bang. "

The Big Bang happened more than once, and the age of the universe is beyond the imagination of scientists. The theories of two scientists have subverted people's "common sense". When people often want to know when time will end, they tell people that time has no beginning. Because the value of "Lambda" has weakened to the value suitable for life in the past 654.38+0.4 billion years, the two scientists believe that the Big Bang may have happened more than once, and each big bang weakened the cosmological constant. Before the formation of the universe we are now in, it probably happened many times in the big bang of trillions of years. Professor Neil said: "I think the age of the universe may be much older than one trillion years. Time has no beginning. According to theory, the age of the universe is infinite, and the scope of the universe is infinite. "

In 2002, the two scientists put forward the view that the evolution of the universe is going through a "cycle of life and death". The universe was born again and again after the big bang. In every "reincarnation", the universe consumes the original matter in the expansion, and at the same time, some new particles are produced when the cosmological constant is weakened, until another big bang comes, and then the new particles form new matter, celestial bodies and even life.

If the hypothesis of these two scientists is correct, when will the next big bang come? Professor Neil said: "No matter how accurate the calculation is, people can't predict the time of the next big bang, but it can be said that the next big bang will not happen in the next 654.38 billion years."