The intelligent life search program interstellar Information Organization (METI International) was established in California in 2016 to carry out the activity of "active search for extraterrestrial intelligent life" (hereinafter referred to as "active SETI") The group recently announced that it will send radio messages from the world's first commercial deep space network, the goonhilly earth station in the UK, to an extrasolar planetary system called TRAP-1 later this year.
Many people support sending interstellar information to aliens, but many oppose it, including the late physicist Stephen Hawking
TRAP-1 is a super cold red dwarf with extremely low surface temperature, about 39.13 light-years away from the earth. It was selected as a launch target because the system may have several habitable planets. In February 2017, astronomers found seven earth like planets around the star, which is the second most earth like planet in the known planetary system, second only to the sun and Kepler 90 (both have eight planets). According to previous reports, the three planets of TRAP-1 are located in the so-called "habitable zone", where liquid water may exist. Therefore, the transmission of radio information to the system may be the first contact between mankind and alien civilization - although it is very unlikely. Of course, this will undoubtedly be an amazing feat, but we still have to face an annoying question: is it wise to send such a message?
Many scientists, including the late Stephen Hawking, will answer this question flatly: "no". They believe that we should only keep listening mode to avoid trouble (readers who have read Liu Cixin's science fiction Trilogy "three bodies" can understand this). Although aliens are not necessarily as evil as in the film independence day, misunderstandings can easily lead to potential conflict. Those who support active transmission of information do not agree with this argument. They say that human beings have been sending radio signals for nearly 100 years. If aliens have the technology to invade the earth and have the intention to invade, they should have known how to do it long ago.
Perhaps both views have reasonable elements. However, since the earth is currently our only "lifeboat" in the interstellar ocean, it is wise to be cautious. What is disturbing is that there are no rules on who can deliver information and who can bring us into contact with alien civilization for the first time. Some may think that the United Nations has an opinion on this, but as far as the current situation is concerned, anyone with a large enough transmitter can send any information into space in the form of radio waves.
Information to aliens
METI International's plan raises another major question: if humans agree in principle to send information to space, what should be the content of the information?
In a project called stihia beyond, METI international and its partners are designing a message, "using general chemical principles to explain human environmental crisis", which will be launched into space on October 4 this year together with some selected music. Many people want to see the detailed information and how METI international plans to pass it on to alien civilizations. They also want to know what the residents of the TRAP-1 planetary system (if any) will think of this information. From the existing introduction, this message may be better transmitted to people on earth; If we can't solve the climate crisis by ourselves, we may not be ready to contact alien civilizations.
In addition to the information, will aliens accept METI International's selected music - including "the messenger of God", Eduard artemyev's "the beauty of the earth" and music played at the stihia Music Festival in Muynak, Uzbekistan, which aims to highlight the impact of the shrinking Aral Sea on the environment? How will aliens react? Is it worry, happiness, or trying hard to decode the deeper meaning?
Of course, METI international is not the first team to design interstellar information. In the past attempts, the most famous is the "golden record" carrying the Voyager spacecraft. This is a record launched into space with two Voyager probes in 1977. It contains sounds and images used to express various cultures and life on earth, in order to be discovered by other intelligent life in the universe. After 40000 years ago, Voyager will fly 1.6 light-years away from the star closest to the earth. It is unlikely that it will be captured by aliens, but its ultimate goal is to communicate with aliens, which is of greater symbolic significance for the relationship between mankind and the universe. Previously, in 1972 and 1973, the pioneer program of the United States launched Pioneer 10 and 11 probes respectively, each carrying a gold-plated aluminum plate, indicating the time and location of the launch, so that the space explorers who found them in the future can identify them. "Golden record" is designed on this basis. It is more like a time capsule to introduce the world of human beings to other intelligent life in outer space.
On November 16, 1974, nearly 50 years ago, the Arecibo radio telescope in Puerto Rico sent a message to the globular cluster M13 25000 light-years away from the earth. This is the first time that mankind has tried to send a radio signal that aliens can understand. So far, we haven't received any reply. There are 1679 binary digits (ASC Ⅱ) in the information, and 1679 can only be multiplied by two prime numbers, so the information can only be divided into 73 horizontal columns and 23 straight lines; This assumes that aliens reading the information will first arrange it into a rectangle. If it is arranged in 23 rows, it will become white noise, and if it is arranged in 73 rows, it can discharge a piece of information in the picture. However, the researchers mentioned that even if radio waves travel at the speed of light, the message has only traveled in space for 48 years, less than 0.2% of the target journey.
Recently, the scientific team led by Dr. Jonathan Jiang of NASA's Jet Propulsion Laboratory designed a new message, which they called "the lighthouse in the Milky Way". In essence, this information is an update of Arecibo information, maximizing the information content about human beings, while using as few data bits as possible. Like Arecibo information, this new information is also binary coded, including pixelated images. Starting with basic mathematical and physical concepts, the research team tried to use this information to build a general vocabulary to describe the biochemical composition of life on earth. From this information, aliens will get a way to determine the position of the earth: the time marked position of the solar system in the Milky way relative to a specific easily identifiable globular cluster. The information also includes digital descriptions of the solar system and the earth's surface, as well as digital images of a female and a male human. The end of the message is an invitation to any intelligent life that can receive and respond.
Will aliens understand
Although the METI team will send their information to the star system relatively close to the earth, Dr. Jiang Hongtao and his colleagues suggest that we should aim at a star cluster thousands of light-years away from the center of the Milky way. This seems absurd, because it takes thousands of years for this message to reach alien civilization (if any); When it arrives, the signal will certainly fall into radio noise. It is difficult enough to understand the information of alien civilization. These radio noises may make aliens unable to understand. Even the message sent by METI to TRAP-1 system may have a lot of electrostatic interference when it arrives 39 years later.
However, this may be good news for those who are worried about the dangers of interstellar information. Time, as well as the distance between stars, are major challenges in sending information to aliens. (Ren Tian)