Oxygen can also be a marker in the search for signs of extraterrestrial life. Oxygen is relatively reactive in nature and quickly combines with other substances. It is photosynthesis that leads to higher concentrations of oxygen in the Earth's atmosphere, which 1 billion years ago was less than half as high as it is now. Astronomers can use spectroscopic analysis to measure the oxygen content of a traveling star's atmosphere. If a planet has an unusually high level of oxygen, then there may be life there. Similarly, carbon dioxide and water are of interest.

The search for extraterrestrial civilizations is a serious scientific study, and when will we get the answer? Maybe tomorrow, maybe 10,000 years. Since life on Earth can arise from inanimate matter, a similar story is likely to happen elsewhere in the universe.

Drake proposed a famous formula for calculating the number of Chinese in the Milky Way, known as the Drake formula. There is an important factor in this formula, which is how long a civilization can sustain. As a species, it is important to be able to safely survive the initial stages of mastering dangerous technology (e.g., can humanity not be destroyed by nuclear weapons that it has created?) and become rational. Different people have different opinions about how long civilizations last, with optimists coming to the conclusion that there are 10 million civilizations in the galaxy, while pessimists have no more than one.

Many people in history have had their own opinions on this topic:

The search for planetary systems beyond the solar system is another direction to explore extraterrestrial civilizations. – Carl Sagan

The exploration of extraterrestrial civilizations is not only a part of the exploration of the universe, but also has a profound impact on the evolution of human beings and the development of science and technology. - Zhou Haizhong

SETI explores the universe for signals across a variety of spectrums, hoping to discover intentional or unintentional broadcasts by extraterrestrial civilizations. The probability of success of such a project is difficult to determine. —Seth Shostark

In recent years, funding for the search for extraterrestrial civilizations has become increasingly difficult to raise, and as the recession continues, we have had to push back the timeline for the expected discovery of extraterrestrial civilizations. - Frank Drake

In addition, what surprised Hua Feng the most was the white hole, which is different from a black hole:

A white hole is a strong gravitational source, and its external gravitational properties are the same as those of a black hole, and the white hole can accretion the material around it to the boundary to form a layer of matter. The white hole theory can mainly be used to explain some high-energy celestial phenomena.

A white hole is a jet source in the universe that can provide matter and energy to the outer region, but cannot absorb any matter and radiation from the outer region, so a white hole is a special cosmic object that only emits and does not absorb, which is the opposite of a black hole.

A special celestial body predicted by general relativity with properties that are exactly the opposite of black holes. White holes are still only a theoretical model, but they have not been confirmed by observations.

According to the white hole theory, a white hole is similar to a black hole in that it also has a closed boundary. The matter that gathers in the white hole can only move outward through the boundary, not the opposite direction. Therefore, the material outside this celestial body cannot enter.

According to the white hole theory, it has been suggested that the core of the quasar may be a white hole. When the ultra-dense matter in the white hole is ejected outward, it will violently collide with the material around it, thus releasing a huge amount of energy. It can be inferred that some phenomena such as X-rays, cosmic rays, radio bursts, and radio dual sources may be related to this effect of white holes. The force of the white hole is the force of repulsion that opposes the attraction of the black hole.

Due to the strong gravitational field around the white hole, it attracts nearby dust, gas and radiation to the boundary, producing a high acceleration, which collides with the material particles ejected outward from the white hole at high speed, producing huge energy radiation. High-energy phenomena such as X-rays, cosmic rays, radio bursts, and dual radio sources can all be seen as the result of the interaction between the white hole and the accretive material around it. Using the white hole model to explain the source of cosmic background X-rays and γ-rays, we also obtained energy spectra similar to the observations.

The radiation emitted by the expansive material in the white hole has the characteristic of purple shift, especially in the initial expansion stage, which is particularly obvious. As for the origin of the white hole, one view is that the superdense matter in the white hole was obtained by the gravitational collapse to form the black hole, and they underwent some internal contradictory movement, transformed into an expanding state, and then ejected outward from the central singularity; The popular belief is that white holes originated from the Big Bang of the entire universe.

When the universe explodes from an ultra-dense state, due to the inhomogeneity of the explosion, some ultra-dense substances are still in a singularity state after being thrown, and they can wait for a certain period of time before they begin to expand and explode, and become new local expansion cores. Some cores have been delayed by about 1010 years (100000000000 years, or 10 billion years), and once they erupted, they formed quasars or other high-energy objects that can be observed today, hence the name "delayed core". As cosmology develops, its mysteries will be further revealed.

By definition, a white hole and a black hole are "imaginary" objects, or mathematical models, proposed by physicists based on Einstein's general theory of relativity. Physics

The astronomical community defines a white hole as a super-dense object with the exact opposite of its properties. The white hole does not absorb external matter, but continuously sprays various interstellar matter and cosmic energy to the periphery, which is a kind of ejection source in the universe. To put it simply, a white hole can be said to be a black hole with a reversal of time, and the matter that enters the black hole should eventually come out of the white hole and appear in another universe.

Because it has the opposite property of a "black" hole, it is called a "white" hole, and because the gravitational pull of a black hole makes it impossible for light to escape, and a white hole and a black hole are completely opposite (even light will be repelled), so it appears white, called a white hole. It has a closed border, and the matter that gathers inside the white hole can only move outward, not inward. Thus, a white hole can provide matter and energy to the outer area, but cannot absorb any matter and radiation from the outer area. A white hole is a source of strong gravity, and its external gravitational properties are the same as those of a black hole.

In quantum mechanics, black holes emit Hawking radiation, so thermal equilibrium can be reached by radiating gases (not mandatory). Since the thermal equilibrium state is a time reversal invariant, Stephe

Hawki

g argues that the time reversal of a thermal equilibrium black hole is still a black hole in thermal equilibrium, which may mean that the black hole and the white hole are the same object. Hawking radiation emitted from an ordinary black hole can be confirmed by radiation from a white hole.

A white hole can accretion its surrounding material to the boundary to form a layer of matter. The White Hole Theory is mainly used to explain some high-energy celestial phenomena. At present, astronomers have not actually found a white hole, and it is still only a theoretical term. The white hole is a very "scholarly" theoretical product obtained through the analogy of black holes, which is more of a mathematical model.

Unlike black holes, white holes do not absorb any objects, instead, they continuously release matter, including elementary particles and fields.

White holes, like black holes, have a closed "event horizon". However, unlike a black hole, the curvature of space-time here is negative infinity, that is, here, the repulsion of the white hole to the outside world reaches infinity, and even if the light rushes straight towards the singularity of the white hole, it will bounce back, so it is impossible for it to enter the white hole for a single step.

Theoretically, white holes can also be classified according to whether they rotate or not, but theoretical physicists believe that the infinite repulsion of white holes forces white holes to have no charge, because the charge can easily be driven out of the event horizon. And rotation, too, is considered impossible.

However, it seems that the white hole can only be an imaginary product. Because if the white hole does not absorb any objects but only ejects matter (energy), then no matter how massive the white hole is, its matter will be ejected very quickly.

Of course, physicists have also offered several ideas for the existence of white holes, some of which believe that white holes and black holes are connected through wormholes, thus making a connection between the mother universe and the baby universe. For an overview of this mechanism, see the overview of the "wormhole of time" (see Stephen Hawking's The Universe in a Shell).

The white hole is actually the inversion of the black hole, and there is a channel of more than three dimensions between the black hole and the white hole, which enters from the black hole and comes out of the white hole, because these substances have a great velocity when they are sucked in from the black hole, so they erupt from the white hole also have a great velocity, but their velocities are generally equal. As the ultimate development of things, black holes will inevitably lead to another end, which is white holes. In fact, in the theory of the expansive explosion cosmology, the primordial fireball has long been encountered

The singularity problem, in fact, has been bothering scientists for a long time. The maximum mass of this singularity is similar to the singularity of density and black holes, but the mechanism of their activity is quite the opposite. The discovery of high-energy ultra-dense matter shows the possibility of black holes, and naturally also shows the possibility of white holes.

If the matter of the universe goes to the end according to different paths and times, then it is also possible to start from the primitive according to different times and paths, that is, after the occurrence of the great white hole at the beginning of the big explosion, there may still be a small white hole with a small explosion. And what is the fate of the matter that flows into the black hole? will it accumulate forever in the infinitesimal singularity until the universe is destroyed, or will it emerge in another universe?

Since 1960, due to the wide application of space exploration technology in astronomical observations, many high-energy astrophysical phenomena have been discovered, such as cosmic X-ray bursts, cosmic γ-ray bursts, supernova bursts, galactic nuclei and explosions, quasars, pulsars, etc.

These high-energy astrophysical phenomena are no longer explained by the laws of physics that people know. Take quasars, for example, which are about the same apparent size as ordinary stars, but they are tens of thousands of times brighter than ordinary galaxies.

The unique property of a quasar, which is extremely small and extremely bright, has never been seen before, which has led scientists to think that the quasar is likely to be a strange object that is very different from any other known celestial body.

How do you explain the quasar phenomenon? Scientists have come up with a variety of theoretical models. In 1964, the former Soviet cosmologist Igo

Novikov proposed the possibility of the existence of white holes, and the white hole model proposed by Israel's Niyeman, which attracted everyone's attention. This is how the concept of white holes was born.