Antimatter and positive matter have the same mass and number of charges, but the signs of the charges are different and opposite.

Typically, the nucleus is positively charged and the electrons are negatively charged.

Antimatter is the mirror image of normal matter, with positively charged electrons and negatively charged nuclei.

  Li Zuhao Researcher, Institute of High Energy Physics, Chinese Academy of Sciences

  For years, scientists have longed to find traces of antimatter in the universe.

Recently, according to media reports, based on data collected by the Alpha Magnetic Spectrometer particle detector carried on the International Space Station, scientists speculate that there may be more antimatter in the universe than we think.

Previously, some scientists believed that antimatter may exist in the universe in the form of antimatter stars.

  What is antimatter?

Are antimatter and matter mirror images of each other?

Do antimatter stars really exist?

With these questions, the reporter interviewed relevant experts.

  Antimatter goes from science fiction to reality

  Science writer Gordon Fraser writes in Antimatter: The Ultimate Mirror of the World: "Antimatter was decisive for the operation of the 'Enterprise' in Star Trek, and without antimatter, there would be no Star Trek." It is true that in the movie "Star Trek", antimatter is the basis of interstellar travel, and the "Enterprise" spacecraft uses the powerful energy generated by the annihilation of positive and negative matter as thrust to achieve superluminal flight.

  In novelist Dan Brown's novel "Angels and Demons", scientists at CERN have created antimatter in the laboratory, and only 0.25 grams of antimatter is enough to destroy the Vatican in an instant.

  Antimatter not only exists in movie plots and literary creations, but is also one of the important directions of scientific research.

Li Zuhao, a researcher at the Institute of High Energy Physics of the Chinese Academy of Sciences, believes that to understand antimatter, these names cannot be avoided:

  In 1928, Paul Dirac, the "father of antimatter", wrote an equation to describe electrons, which later became the famous "Dirac equation", which made Dirac, who was only 26 years old, famous in the scientific community. .

The Dirac equation theoretically predicts the existence of antimatter—an electron must have a corresponding particle of equal but opposite charge.

Dirac called these new particles "antiparticles."

  From 1929 to 1930, Chinese physicist Zhao Zhongyao observed traces of the existence of "anti-electrons" in his experiments, and his paper provided evidence for the study of the generation of "positive-negative" electron pairs. "Footprints" of scientists.

  It was Anderson, an American physicist, who made antiparticles go from theory to reality.

In 1932, Anderson announced the discovery of "antielectrons" in cosmic rays, confirming the existence of antiparticles.

In 1936, at the age of 31, Anderson shared the Nobel Prize in Physics with scientist Hess for this discovery.

  In 1955, scientists such as Chamberlain and Segre successfully "captured" antiprotons using the high-energy proton synchro-stable accelerator, and the two shared the Nobel Prize in Physics in 1959.

Subsequently, scientists have successively produced anti-particles such as anti-neutrons and anti-deuterons.

  In 1995, CERN physicist Orlert led the team to conduct the third experiment to create antimatter atoms. During the three-week collision experiment between antiprotons and xenon atoms, a total of 9 antihydrogens were produced. Atoms, with an average survival time of four millionths of a second, travel a dozen meters at close to the speed of light, and then annihilate with positive matter.

This means that the first batch of antimatter atoms, antihydrogen atoms, have been successfully produced in the laboratory.

  Antimatter was successfully created in the laboratory.

So, where does the antimatter in the universe live?

  In 1997, American astronomers announced that they used the Compton Gamma-ray Observatory to discover an antimatter source (the Galactic Center Antimatter Fountain) about 3,500 light-years above the Milky Way that continuously ejected antimatter.

Later studies have shown that there is indeed a large amount of antimatter of unknown origin at the center of the Milky Way, but not in the form of "geyser".

  In 2011, the Alpha Magnetic Spectrometer particle detector was launched.

At present, scientists have observed four candidate cases of anti-helium through this equipment.

"Anti-helium 4 is an anti-helium nucleus, which is considered unlikely to be produced by cosmic ray collisions." Li Zuhao explained, "So, if it can be confirmed that anti-helium 4 nuclei exist in cosmic rays, it will be strong evidence for the existence of antimatter celestial bodies."

  Positive and negative matter is originally "a mother compatriot"

  The existence of antimatter has been established, but a new question has arisen - what does antimatter look like?

How is it different from positive matter?

Where does antimatter come from and where does it go?

  In layman's terms, the antimatter world is a mirror image of our existing world, and its constituent elements, appearance, and even spectral structure look exactly the same as the physical world, with only some differences in physical properties.

  "The mass and charge of antimatter and positive matter are the same, but the sign of the charge is different, which is opposite." Li Zuhao said, "Usually, the nucleus is positively charged, and the electron is negatively charged. Antimatter is the mirror image of normal matter, and they have Positively charged electrons and negatively charged nuclei."

  A study by CERN shows that the spectral structures of hydrogen and antihydrogen atoms look the same.

CERN also said that until now, antimatter looks like ordinary matter as we know it.

  According to Li Zuhao, the scientific community generally believes that a considerable amount of matter and antimatter were produced in the early days of the Big Bang, and it can be said that the two are "one mother".

But today almost no naturally occurring antimatter can be seen near Earth, which has been dubbed the "antimatter-missing mystery."

  Theoretically, the number of particles and antiparticles produced at the Big Bang should be the same, but why are all the positive particles we see today?

Where did the antiparticles go?

  Li Zuhao introduced: "There are currently two hypotheses: one is that due to the different properties of positive and negative matter produced by the Big Bang in the evolution of the universe, antimatter gradually disappears, leaving only positive matter, but the current experimental results do not support this. One conclusion; another that the matter and antimatter created by the Big Bang were located in different regions of the universe."

  In other words, antimatter either "leaves without saying goodbye" or disappears into the depths of the universe.

  Can only wait for antimatter "self-injection"

  The "mystery of the absence of antimatter" has long puzzled scientists, and hypotheses about antimatter have emerged one after another.

One hypothesis is that antimatter may exist in the universe in the form of antimatter stars.

This hypothesis means that if antimatter stars exist, antimatter could potentially make up the "other half of the universe."

  To test this hypothesis, how do we look for antimatter stars?

  Li Zuhao said that, strictly speaking, existing research cannot find antimatter stars.

At present, the only magnetic spectrometer in the world to detect antimatter in space, the Alpha Magnetic Spectrometer, has been working on the International Space Station for more than 10 years. Its main task is to search for antimatter and dark matter, and to accurately measure the composition and energy spectrum of cosmic rays to study the universe. line origin.

However, the Alpha Magnetic Spectrometer is anchored to the International Space Station.

Therefore, strictly speaking, under the existing research conditions, we can only wait for antimatter to enter the detection range of the magnetic spectrometer, but cannot actively search for antimatter and antimatter stars.

  At present, there are two main methods to detect antimatter particles in the universe. One is to directly detect antimatter through a magnetic spectrometer, and the other is to detect the existence of antimatter by using high-energy detectors to detect the high-energy photons generated by the annihilation of positive matter and antimatter.

The difficulty in detecting and verifying the existence of antimatter stars is that judging the existence of antimatter and even antimatter stars needs to be based on observations of charged particles in the universe.

But unlike directional light, charged particles are not directional.

Because in the process of propagation, the charged particles are susceptible to the influence of the magnetic field and constantly change direction.

Therefore, even if an antimatter particle is detected, it is impossible to determine its source, and scientists cannot "find the root" of the antimatter particle with a "travel history" of millions of years and trace its source.

Therefore, the detection and verification of antimatter stars has become particularly difficult.

  Still, many scientists are enthusiastic about finding antimatter and the existence of antimatter stars.

  Li Zuhao said that if antimatter stars exist, it will be completely composed of antimatter, in which all elementary particles have the same mass and lifespan as the particles in our present world, but the basic physical properties such as the sign of charge are opposite, which is very important to us. The effects of all known physical laws have yet to be verified by theorists' calculations and experiments.

  French scientists have calculated the maximum number of antimatter stars that may be lurking in the universe.

Scientists believe that antimatter stars will shine like normal stars, and there may be one antimatter star in every 400,000 ordinary stars.

However, whether this hypothesis holds or not remains to be further verified.

  "Today's people do not see the ancient moon, but this month once illuminated the ancients." Compared with the 13.8 billion-year-old deep universe, the human beings who have changed from generation to generation are extremely small. Many questions about the universe can only be answered by time.

Perhaps in the corners that high-energy detectors and magnetic spectrometers have never looked at, there is light from antimatter stars, just waiting for a glimpse of mankind.