# We may never find aliens

Many sci-fi movies and TV dramas have shaped different forms of alien intelligent life, they look cute or weird. After watching so many movies and TV series, have you ever imagined whether there are really aliens in the universe and what will they look like? What kind of sparks will be produced if the earthlings meet the aliens? In this regard, scientists are not so optimistic, they believe that the Earth people will never see aliens.
What is the probability of aliens appearing?

If you want to see aliens, you must first determine how likely they are to exist?
As early as 1961, American astronomer Frank Drake calculated how many space civilizations there are in the universe. He used the product of the following five data to express the probability of the existence of aliens: the number of stars that can emit light and heat, The number of planets surrounding such a star that can give birth to life, the probability of life appearing on a suitable planet, the probability of life evolving intelligence, and the relationship between the time of formation of a civilization and the life of a planet.
Now, we have a better understanding of the size of the universe and the formation of stars, so that we can calculate how many stars there are in the universe. The result is amazing. There are about 1024 stars in the universe. Among them, 80% of the stars are surrounded by planets, and about 20% of the 80% of the stars have at least one planet in the “habitable zone”, and about 20% of them are similar in size and mass to the Earth. . In this way, we have calculated that the number of planets in the universe that may give birth to life is more than 1,022.
Then, the question is, how likely is life on these “suitable planets”? If it is the most ideal situation, the above-mentioned 1022 planets may have life. In the planets and moons of the solar system that our aircraft can reach, we also found that these elements have formed some organic matter, such as carbon rings and amino acids. In other words, on these terrestrial planets, a process similar to the emergence of life on Earth has already begun!
Since the buds of life have appeared on some terrestrial planets, can highly intelligent aliens evolve? Algae plants capable of photosynthesis appeared 1.2 billion years after the earth was formed, complex cells with nuclei and organelles appeared after 2.7 billion years, higher animals appeared after 4 billion years, and intellectual talents appeared 4.5 billion years after the earth was formed. In other words, the emergence of Homo sapiens has experienced at least the following seven extremely low-probability processes-origin of life, photosynthesis, complex cells, gender differentiation, complex animals, bone emergence, and intelligent mutations.
We don’t know the probability of each of these processes, but obviously, the evolution of Homo sapiens has gone through such a long time, which shows that the appearance of each process is extremely accidental. We might as well magnify the probability of each process, assuming it is 10%, then the probability of evolving into an intelligent creature is only one in ten million. But don’t forget that the number of planets in the entire universe where life may appear is more than 1,022. When the two numbers are multiplied, the number of planets capable of intelligent life has reached a trillion.
With this calculation, there are intelligent life almost everywhere in the universe? But the fact is that we have not found an alien so far, so where did the calculation go wrong? Come to think of it, it should be that the probability of intelligent life appearing is far less than one in ten million.
If we look back at the history of evolution, we can see that evolution does sometimes have surprising similarities. For example, the extinct ichthyosaurs and the existing dolphins have evolved flippers that “glide” in the water at different times; the extinct pterosaurs and the existing bats all fly with very similar wings; no matter what Whether it is the extinct thylacine and marsupial anteater, or the existing kangaroo and koala, Australian mammals generally have baby pouches. These similarities show that the probability of these processes is very high, and it is entirely possible that similar processes will occur on other planets.
However, the events that played a key role in the history of evolution have not been repeated, and their probability of occurrence is infinitely close to zero. For example, the photosynthesis of plants, from algae to angiosperms, their photosynthesis has been in use since its appearance, without any changes or new mechanisms. For another example, it took hundreds of millions of years for the first finfish to climb onto land and grow feet. Since then, we have not found a second fish that can evolve into terrestrial animals. So will the process of intelligent mutation occur only once? And the alien planet probably didn’t even have the “lucky” for this intelligent mutation.
If the possibility of intelligent mutation approaches zero, then even if the other six processes are possible, aliens will never exist.
Can we find living aliens?

If we are more optimistic, human beings are not alone in the universe. Aliens do live in places we haven’t discovered yet, can we find them again?
The most likely scenario is that the people on Earth and the aliens were extinct before they were “connected”. We know that the maximum speed in space is the speed of light, which can travel 300,000 kilometers per second. But for an infinite universe, this speed is too slow. Take the Milky Way as an example. The diameter of the Milky Way is about 100,000 light-years. If humans send out video signals, it will take tens of thousands of years to complete. To send a signal to the planet where the alien is located, it may have to cross one or several galaxies, and perhaps 100,000 years will not be able to transmit the information. The same is true for messages sent by aliens.
Of course, there is also the possibility that there are some extraterrestrial civilizations that have evolved far beyond the humans on the earth. They have discovered the earth tens of thousands of years ago and predicted the emergence of humans on the earth, so they sent us in advance. Greeting signal. However, even if we receive it, it will still take tens of millions of years for the information we reply to be delivered to them. Is this kind of contact for tens of thousands of years only once, is it useful? Are we and them alive then?
First consider the external conditions. The universe is not a stable environment. The planet is constantly in motion, and “car crashes” occur from time to time. For example, we already know that about 65 million years ago, the collision of an asteroid with the earth ended the life of a dinosaur that had ruled the earth for 100 million years. If mankind encounters this impact, can we survive? Where’s the alien? We don’t know how often this kind of collision that will lead to mass extinction will occur, but if we refer to the previous period of mass extinction, the frequency can be estimated to be once every 100 million years. If every 100 million years or so, there will be a devastating natural disaster between the Earth and the aliens’ home planet, can the Earth and the aliens survive until they meet?
If the technology of aliens has been developed to interstellar communication, it should not be difficult to escape the extinction caused by the collision of the planets. But to escape the interference of external factors, powerful technology may also bring another hidden worry to aliens-improper use of high and new technology is likely to cause their self-destruction.

British astronomer Martin Reese discussed more than a dozen “accidents” that may cause the destruction of the earth in the book “The Ultimate Moment”. In addition to natural disasters, he prefers to discuss the risks brought by the development of human technology, such as nuclear weapons, “Transformed” deadly germs, nano robots, etc. In fact, these are not alarmist. Now more and more countries have mastered the method of manufacturing nuclear weapons, and the power of the nuclear weapons they manufactured is also increasing. If World War III breaks out again, will it be the day when mankind is extinct?
The way nanobots destroy humans may be relatively “gentle”. It is a kind of micro-robot. In order to achieve the purpose of diagnosing and curing diseases, scientists from various countries are working on studying how to make it move freely and uninterrupted inside the human body. Martin described the “human extinction” caused by nanorobots: In the future, these small robots will be mass-produced, injected into the human body, and move autonomously in the human body until they occupy the human body, control human behavior, and finally replace humans to rule the earth. . Who dares to say that this will never come true?

The universe is too vast, and the time it takes to find aliens is far beyond our imagination, so long we don’t know whether we can meet each other “alive”.
Do we know that we have found an alien?

If we are “lucky” enough to search for extraterrestrial signals during our lifetime, and to an undestructed alien planet, can we find aliens? The possibility is still very low, because we are not only “language barrier”, there may even be “jet lag”.
As two “races” that have never met and developed independently of each other for thousands of years, how do we achieve “inter-language”? Lawrence Dole, a scientist at the United States Search for Extraterrestrial Civilizations (SETI), has been searching for signals from aliens for many years. He believes that he has found a way to distinguish alien signals by analyzing whale language. Ziff’s Law is the law of language summarized by the American linguist George Kingsley Ziff, that is, in human languages, the most commonly used letters such as E and A in English, the frequency of use is the least frequently used letters 2n times. Doll found that whale calls also have such a law, so it can be considered that whales do have language. The alien signal is also likely to follow this rule. If we find a qualified alien signal, we may be able to decipher the alien language.
But this is actually just a conjecture. Zipf’s law is a law of human language. Does alien language necessarily follow this law? Maybe their way of communication is lower than whale language, so that they don’t follow the language laws we know; maybe their way of communication is far more advanced than ours, mixing many kinds of complicated laws that we can’t understand; maybe their technology It has progressed to the point that there is no longer a need for language, text, or even lightwave communication, but brain waves or other signals that we cannot capture.
We and the aliens may also have a “jet lag” that is difficult to overcome. Humans appeared 4.5 billion years after the formation of the earth, so when did aliens appear when their planet was formed? When we visited their homes, what period were they in, what did they look like, and how far did they evolve? Maybe they are only the size of a microbe. When we go to an extraterrestrial, they are densely gathered around us, but we can’t see them; maybe they are the same size as a mouse, hiding underground, shivering under the rule of “dinosaurs”; maybe they Having got rid of the limitations of the physical body and realized the immortality of consciousness, every wave of air fluctuates because they are communicating or moving.
Imagination is beautiful, reality is cruel, and perhaps in our lifetime, we can only meet aliens in our imagination.