The Fermi paradox is actually a long-standing proposition. Back in 1950, when the famous Italian-American physicist Enrique Fermi was discussing the issue of UFOs and aliens, he suddenly thought of the following sentence: Where are they? (Where are they?) To understand the cause of this problem, it really takes some tongue-in-cheek. In the field of physics, Fermi has always been known for his astonishing ability to estimate, and Fermi blurted out this sentence, Where are they? It is precisely because of his excellent estimation ability.
The problem he realized was that the milky way was only 100,000 light-years old and 10 billion years old. Even at the speed of one-thousandth of a thousandth of light (in fact, humans already have such navigation technology), intelligent civilizations would only take 100 million years to explore and colonize the entire galaxy. As a physicist, Fermi obviously could not accept such contradictions. He felt that something must have gone wrong.
What's wrong with that? This is the question scientists have been wondering about for decades. Today, we enumerate various possibilities, but none of them are confirmed by observation. In terms of inspiration, this is the "gospel" of science fiction authors, because each of their perfect references can write a science fiction novel with a perfect universe setting. The answer given by Liu Cixin's three-body body is that the cosmic intelligent civilization is in the law of the dark forest. As a die-hard fan of the "Three-Body Problem", I think this is a setting that can write a good novel, but only a novel. From the perspective of modern astronomy, such a story setting is not very scientific.
It's relatively easy to determine whether a star has spawned a higher intelligent civilization from far away. According to the second law of thermodynamics, civilizations must expend a lot of energy to survive, and large-scale means of energy capture, such as Dyson spheres, will inevitably affect the spectral patterns of their stars. Even observatories established by relatively low civilizations such as humans can measure the spectra of thousands of stars at the same time. In addition, the physics of stars is a relatively mature discipline that can explain the spectral types of almost any star we receive.
In addition, NASA has discovered a number of Terrestrial-like planets in the database of the long-retired Kepler Space Telescope. These planets are not only close to Earth in terms of volume and mass, but also orbit in the habitable regions of their parent stars. Considering that the Kepler Space Telescope has only probed a very small part of the Milky Way, in other words, aren't there an astonishing number of Terrestrial planets in the Milky Way? Thus, these two contradictory astronomical discoveries make the Fermi paradox even more bizarre and difficult to explain. It was as if we had accidentally broken into a room. There should have been a lot of people there, but now there isn't a single one. In such a mysterious room, we would blurt out the words: "Where are they?" ”
Maybe our universe is indeed in a state of extreme silence that is consistent with Occam's Razor Law.
Any conclusion that is unfavorable to this inference will force us to make some additional assumptions, which will greatly reduce the mathematical reliability of these conclusions. For example, the Dark Forest Law in the Trisolaran gives the idea of an alien civilization that appears to be in a state of "extreme silence" but is actually crowded. To this end, the additional assumptions given by Liu Cixin are "technology explosion" and "chain of doubt". Regardless of whether these two hypotheses are reliable in an alien civilization, the concept of "technological explosion" itself has a strong color of the history of Western science and technology.
Back to the main topic, let's return to the topic of "great silence". Speaking of "great silence", the word comes from the helpless conclusion that people have come to after years of implementing the "Ozma" program. The "Ozma" project, led by American astronomer Drake (a supporter of Drake), aims to discover biomarker signals near the solar system through radio waves. The project was officially launched in April 1960.
Monitoring has been carried out intermittently for three phases, but no valuable results have been achieved. Although later programs such as "Mita", "Phoenix" and SETI were implemented, they got nothing. This unusual cosmic radio silence seems to show people a certain vastness and desolation hidden behind the cold starry sky. Such a result even changed the understanding of life and wisdom in the universe by many astronomers in the 20th century.
Could it be that we are the only ones in the universe looking for other alien intelligent beings? Does human civilization really represent the strongest civilization in the galaxy? At this point, we must mention the so-called "Great Filter" theory, which gives the possible causes of the "Great Silence". To that end, we try to consider an intelligent civilization as great as Theimov Galactic Empire. It is so huge that its footprints cover countless planetary systems, so finding the birthplace of its civilization has become an archaeological problem.
For such a civilization, it seems unlikely that any natural and man-made catastrophe we can imagine will touch its foundations. In other words, such a civilization is almost immortal. Unfortunately, the Fermi Paradox tells us that this civilization, like the perpetual motion machine of the 18th century, does not actually exist in reality. There is no perpetual motion machine guaranteed by the laws of thermodynamics, but what about the Fermi paradox? The "Great Screening" theory holds that in the Galaxy, early in the development of civilizations, there must be one or more "big sieves", and intelligent civilizations are unlikely to cross these "sieves".
The next question is, has our earth civilization crossed these "sieves"? Thus, Robin Hansen, the founder of the Great Screening Theory, gives nine possible options, in chronological order as follows:
(1) appropriate planetary systems (i.e. the aforementioned terrestrial planets);
(2) Freely reproducible genetic macromolecules (such as RNA and DNA);
(3) Single-celled organisms;
(4) Complex single-celled organisms;
(5) Sexual reproduction;
(6) Multicellular organisms;
(7) Ability to use tools;
(8) our level;
(9) Interstellar colonization.
Article (8) is the level of human civilization. So our previous question is: Are these "big sieves" from Article (7) listed above, or are they entrenched between Articles VIII and IX? Given the principle of human selection, it is impossible for us to realize that we have crossed the ground "sieve." At this point, some discoveries in planetary physics will become particularly dangerous because it allows us to see important information that is obscured by the principle of human selection. For example, the Kepler Space Telescope's discovery essentially ruled out the possibility that the first was the "Big Sieve", as it proved that Earth-like planets are by no means uncommon in the Milky Way.
That's bad news. Worse, similar discoveries could always be on Mars exploration missions. If one day NASA suddenly announced that their rovers had successfully found some kind of primitive fossil multicellular organism on the surface of Mars, even if it was just a vague glimpse under the microscope, we would be in a very bad situation. Because in this case, we can almost certainly win two votes in the solar system alone. If we look at this vast galaxy, there are as many kinds of alien creatures as the sand of the Ganges! Thus, the fabled "Great Screening" is either the seventh one, or it is at the forefront of human civilization and watching us. So in that sense, no news is the best news.
Next, let's take a look at how likely it is that the "Great Screening" is ahead of human civilization. There is no doubt that our civilization is in an era of rapid change, a process that is irreversible. Even a slight slowdown and retrogression would be a human disaster. The wise men of humanity continue to explore uncharted territory of science. This process is like an irrevocable game of touching the ball between man and "God", and every scientific discovery is equivalent to touching a colored ball in God's bag. Different colors represent different scientific and technological essences. There are basically harmless green balls, such as solar technology and computer technology; there are neutral white balls, such as the use of fire; there are red balls that represent danger, such as cloning technology, nuclear technology, etc.; of course, there is a black ball that represents death. At present, humans have not caught black balls, but this does not mean that black balls do not exist. Once the black ball appears, it is the moment when the so-called "big screening" appears. Of course, there is also the possibility that over time, the ball that was originally dangerous, neutral and even harmless suddenly turned into a black ball overnight, catching us off guard. This possibility does exist, such as popular artificial intelligence technologies.
Here, we may have our own answers to the causes of Fermi's paradox. Yes, this is an open topic with a different perspective. From another perspective, however, things may not be that complicated, but the insurmountable distance between intelligent civilizations created today's "Great Silence." Imagine that at this moment, at the other end of the Galaxy, there happens to be an intelligent civilization sending a signal in the direction of the solar system. We have to wait 80,000 years to receive it. Can human civilization last that long? As long as we look at what we bring to Earth's ecosystems, it's not hard to see that this may really be a problem.
Based on the same considerations, in order to achieve a one-way dialogue between two civilizations at a certain moment, at least two conditions must be met: one is a sufficiently high civilization rate; second, a sufficiently long civilization lifespan. The lifespan of civilization defined here is calculated from the moment civilization masters radio technology.
By this standard, human civilization has survived only 110 years. Unfortunately, we still don't know anything about the numerical range of the first condition. Even for the second condition, we can only give a possible lower bound according to our situation. Shockingly, however, such an extremely simplified mathematical programming model, after a little analysis, concludes that no matter how fast a cosmic civilization is formed, civilization must be longer than a certain life to achieve one-way dialogue. The lower limit of life is about 1000 years. We can qualitatively understand the result: two civilizations with too short lifespans exist at the same time, and the possibility of reaching a dialogue is almost non-existent, because one of them disappears before the signal arrives.
However, such a simple result suddenly raises a huge question for us: Does the Fermi Paradox mean that the average lifespan of intelligent civilizations in the universe is much lower than 1,000 years? For human civilization, this result is even more troubling, as it seems to imply that the deadly "great sieve" will take root in the near future.
Of course, the above discussion may trigger some "doomsday panic" among ignorant people, but this is not the original intention of our discussion of the Fermi paradox.
On the contrary, it should become a wake-up call in the hearts of every human wise man, constantly reminding himself to respect nature, think of danger in times of peace, and fear nature.
Ancients Cloud: Gentlemen have something to do, some do not do, this is the reason.
Fatalism and mechanism were thrown into the garbage can of history. Looking to the future, our civilization is unlimited. On the current issues of economic development and environmental protection, at least one thing will become very clear: if human society still postpones changing its energy structure and continues to ignore and blame each other on the issue of carbon emissions, I am afraid that we will all see the "big sieve" of our civilization in our lifetime.