"Spaceships can do this kind of yo-yo movement," Damur said, "[but] if you use your own fuel, you can escape from the gravitational pull of the wormhole" and explore the universe on the other side.

But your friends on this side of the universe may have to wait billions of years to see you again, because it will be a long time to travel through the wormhole. Such a delay makes effective communication on both sides of the wormhole nearly impossible. If microscopic wormholes can be discovered or constructed, this delay can be as short as a few seconds, says Sorodugin, potentially supporting bilateral communication.

Stephen Hsu of the University of Oregon at Eugene, who studies the formation and properties of black holes, agrees that it is almost impossible to distinguish between black holes and wormholes using observations, at least not with current technology.

"The most important property of a black hole is the tipping point at which an object that falls into a black hole has no return, and we can't test it yet. Stephen said.

But it is not impossible that objects that are currently considered black holes are indeed black holes rather than wormholes. There are many possible scenarios for the formation of black holes, such as the collapse of massive stars, but how wormholes are formed is still unknown.

A wormhole may be different from a macroscopic black hole in that it needs some foreign matter to stabilize itself, and it is unknown whether this foreign matter actually exists.

Sorodukin thinks wormholes may be formed in a similar way to black holes, for example, from collapsing stars. In this scenario, physicists generally believe that black holes are created, but Sorodugin thinks that quantum effects may prevent the process of collapsing to form black holes, and instead form wormholes.

Sorodukin said this mechanism would be inevitable under a more complete theory of physics, which unifies the theories of gravity and quantum mechanics, which has long been the dream and goal of the physics community. If this theory is correct, then wormholes may form where we thought black holes would form.

And this conjecture is not without a way to test it, and some physicists believe that future particle accelerator experiments will be able to produce microscopic black holes. It is possible that such microscopic black holes emit calculable Hawking radiation to prove that black holes are being created rather than wormholes. But if Sorodugin's conjecture is correct, then a microscopic wormhole will be formed, so no radiation will be generated. "With such a simple test, you can tell if a black hole or a wormhole is generated. ”

Another advantage of wormholes is their ability to solve the so-called black hole information paradox. The only thing a black hole is capable of releasing is Hawking radiation, but it is unclear how this Hawking radiation will carry the original information that originally fell into the black hole object. This chaotic effect conflicts with quantum mechanics, which prohibits the loss of such information.

"Theoretically, a wormhole is much better than a black hole, so it doesn't lose information. Sorodugin said. Since wormholes have no horizon, objects can automatically leave the wormhole without being converted into Hawking radiation, so there is no problem of information loss.

"Students should study hard in private to consolidate their knowledge and get out of class!" said Professor Sorodugin.

"Goodbye Professor!" the students responded, and then a large group of people packed up their things and left the classroom in an orderly manner, such days have become the norm for this group of elite students who have been selected from all over the world.

After a while, there were three more people in the corridor of the classroom, Hua Feng, Yun Meng, and Bai Feng, and they slowly walked towards the empty square below. The atmosphere was quiet, and the air was filled with the aura of everyone cherishing their time and cultivating nervously.

After a series of studies, Hua Feng felt that his current knowledge base had been updated a lot, although it seemed that the level in all aspects was still similar to that of the previous era, but fortunately, it was much better than his previous self.

Before they knew it, another month had passed abruptly, and they had slowly become more and more accustomed to such high-intensity learning, and many times they did not have much time to communicate. But after each class, they also have some small discussions about what they have just learned.

"Little dream, you should be the one who knows the most about the wormhole-like travel time, back then, the Snow Lord didn't know how to send you to the present, so that you could go through thousands of years as if you were born from this land. Hua Feng found a stone bench and sat down, and Yun Meng and Bai Feng also sat on the side.

"Yes, but I was young at the time, and I don't remember much about what happened at that time, but I just knew that it was probably like a dream. All I could remember was my father's instructions to me. Alas, if I could, I really didn't want to spend so much time casually, and although I was happy for a while, I let my father bear too much alone. Yun Meng recalled all the things in the past, and his heart was mixed for a while.

Bai Feng saw that the atmosphere was a little heavy for a while, and hurriedly broke the embarrassment: "Okay, don't get entangled." I'm more interested in extraterrestrial life on our planet and elsewhere. ”

"The evolution of living things is an extremely slow process, and the length of time it has taken is comparable to that of the sun. Fossil studies have found that as early as 3.5 billion years ago, there was a relatively advanced single-celled organism on the earth, called green algae.

According to the theory of stellar evolution and the analysis of ancient rocks and meteorite materials on the earth, it is known that the formation of the sun and the earth is 10~1.5 billion years earlier than the appearance of this creature. It took about 5 billion years after the formation of the solar system to have humans on Earth. Bai Feng continued.

Hua Feng mentioned the problem that he was very concerned about when he was a child, and suddenly became interested: "This, I know a very vivid metaphor, which envisages compressing every 5 billion years into 1 "year" in a simple proportion." On such a scale, one week is equivalent to 100 million years of real life, and one second is equivalent to 160 years. About two years have passed since the Big Bang and the birth of the solar system. The Earth was formed in January of the 3rd year.

In March and April, the ancient single-celled organism of blue-green algae appeared. Since then, life has evolved slowly and without stopping. The first large cells with nuclei appeared on Earth in September, and multicellular organisms may have been present in late October. By the end of November, plants and animals had taken over most of the landmass, and the earth had become active. On December 18th, the dinosaurs appeared, and these incredible behemoths dominated the earth for only a week.

At 11 p.m. on Chinese New Year's Eve, the Pekingese came out, and 10 minutes before midnight, the Neanttes appeared at the Chinese New Year's Eve party. Modern humans are only able to show up 5 minutes before the arrival of the new year, while the written history of mankind begins 30 seconds before midnight. The major events of modern life sped up one after the other in the last seconds of the old year, and the population of the earth tripled in the last second before midnight.

It can be seen that the earth has been nurturing life for most of the time since its birth, but only for a short time life has taken the form of advanced organisms. ”

Yun Meng and Bai Feng looked at Hua Feng with admiration, although they had been exposed to these more or less when they were in school, they were not something they were interested in after all.

Hua Feng continued: "We have seen that the birth of intelligent life requires that stars must be able to emit light and heat stably for at least about 5 billion years. The lifetime of a star is closely related to the size of its mass. The thermonuclear reaction of massive stars can only last for a few million years, which is far from enough for the evolution of life.

Only stars of similar solar mass are suitable candidates, and there are about 100 billion such stars in the Milky Way, and about 40 billion for a single star except for binary stars. Unfortunately, we don't know much about other planetary systems, but observations have gradually led to the presence of planets around some stars.

Considering the objective existence of the solar system, even large planets have their own satellite systems, such as Jupiter in the solar system. It is possible to optimistically assume that all single stars have planets. The existence of planets does not mean that there is life, let alone the existence of higher beings. The key is that the distance from the planet to the parent star must be just right, not far or near. Due to the limited level of understanding, we can only discuss life forms with conditions similar to those of the Earth, and in particular assume that liquid water must exist.

There are eight planets in the solar system, but only the Earth is clearly in the so-called ecosphere that can form living things. Venus and Mars are located on the edge of the biosphere, and no life has been shown on their surface.

It is very rare for a planet to have all the conditions necessary for life to exist. In the solar system, the Earth is unique and lucky. Detailed calculations show that of the 40 billion individual stars mentioned above, only 1 million are surrounded by planets that can allow life to evolve to an advanced stage.

Another constraint is that extraterrestrial life should have a similar chemical composition to life on Earth. Astronomical observations show that, with a few exceptions, the distribution of chemical elements throughout the universe is fairly uniform, and there is every reason to believe that the materials needed to make up all the organic molecules can be found on distant planets.

In fact, many of the more complex organic molecules have been found in many places. Thus it can be assumed that life somewhere, as long as it is theoretically possible, will actually be formed. There will be a million planets in the galaxy that could have life, but life on each planet should be at a different stage of evolution. ”

The three of them sat together and talked for half an hour without realizing it.