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This article comes from the official account of Wechat: back to Park (ID:fanpu2019), author: qu Lijian

Some time ago, the US Congress held a public hearing on the unidentified flying object (UFO) phenomenon for the first time in 53 years. The US Department of Defense called this kind of phenomenon an unknown aerial phenomenon (UAP), and netizens inevitably linked it to aliens when the news was released. In fact, most of the phenomena can be explained reasonably, while the rest gives people room to imagine. We always ask: is human being the only intelligent life in the vast universe? After entering the 20th century, human beings tried to send messages to the universe in search of extraterrestrial civilizations, the most famous of which is Arecibo information. Astronomers broadcast the basic information of the earth into the universe as a "QR code". Recently, astronomers have proposed an upgraded version, the Galactic Beacon. However, whether we should take the initiative to contact aliens is still a controversial issue.

The vast expanse of space always makes people can't help thinking about an esoteric question: are we earthlings alone? Is the place of starlight the place of other intelligent civilizations?

With the development of science, human beings not only fantasize and reverie, but also try to receive possible alien civilization signals from the early 1900s. This still seems passive, why not take the initiative to send messages to alien civilizations?

In 1958, the United States began to implement the Pioneer Program (Pioneer program) to launch a series of planetary exploration spacecraft. Pioneers 10 and 11, launched in 1972 and 1973, initially aimed to explore the outer solar system, becoming the first probes to fly past Jupiter and close to Saturn, respectively, and eventually they will fly out of the solar system. The Americans installed a gold-plated aluminum plate (Pioneer plaque) on Pioneer 10 and 11, engraved with some information about Earth people, through which aliens can quickly learn about Earth people if the probe is captured by an alien civilization. The symbols engraved on the aluminum plate are shown in the picture below.

Fig. 1 is it true that the pioneer gold-plated aluminum plates are confused except for naked men and women?

Apart from the ambiguity of the meaning, no one is sure whether the aluminum plate can be received by aliens. This gold-plated aluminum plate is like message in a bottle, although it left the solar system at a speed of 50, 000 kilometers per hour, but the relative vastness of space is still not worth mentioning.

Is there a more efficient way to send signals to aliens?

Yes, send radio signals, which is also the fastest form of signal transmission.

Arecibo Information in 1963, the Arecibo Radio Telescope in Puerto Rico of the United States was built with an aperture of 305m. Upon completion, it became the largest single-aperture telescope in the world. The record was held until July 2016, when it was broken by China's 500m aperture spherical radio telescope FAST "Chinese Sky Eye".

Fig. 2 there is something special about the Arecibo radio telescope compared with the aperture of the Chinese sky eye. The Arecibo radio telescope is equipped with three radar transmitters to transmit radio signals to celestial bodies and analyze the reflected signals.

American astronomer Frank Drake (Fank Drake) once proposed to use the radar of the Arecibo telescope to send radio signals into space, allowing alien astronomers to capture and decipher the information and learn about the existence of earthlings.

Fig. 3 Frank Drake (May 28, Frank Drake,1930), an American astronomer, actively promotes the search for Extraterrestrial Civilizations (SETI). On the blackboard in the picture is the Drake equation named after him, which is used to speculate the number of extraterrestrial intelligent civilizations in the Milky way that can come into contact with us. What would you like to send?

Should send content that both earthlings and aliens can understand.

Is there any such content?

Yes, science.

Science applies to the whole universe. If aliens can invent radio telescopes, they must understand science.

Drake, with the help of some people, quickly designed the content, and on November 16, 1974, he sent a radio signal to M13, the globular cluster of Perseus, with a duration of 169 seconds, power of 450 kilowatts and a signal wavelength of 126 mm.

If there is an alien intelligent civilization in M13, how long will it take us to get a reply?

Soon, it will be 50, 000 years, because M13 is 25, 000 light-years from Earth.

As we wait for a reply from the aliens, let's take a look at what messages American astronomers have sent.

This audio segment has two pitches. We can record the pitch series, the treble as 0, the bass as 1, and we will get:

000000101010000000001010000010100000001001000100010010110010.

A total of 1679 zeros or ones, that is, 1679 bits of information.

Drake wants the aliens to arrange the string into a rectangle. Do the prime factorization of 1679, 1679=23X73, so that 1679 zeros or ones are arranged in a rectangle, only in two ways, 23 rows and 73 columns, or 73 rows and 23 columns. However, if you arrange the former, the resulting pattern is white noise; if you arrange it in the latter way, a meaningful pixel bitmap will emerge.

Let's see what the content of the message is.

For easy observation, we make it in color.

Fig. 4 Arecibo information, the color is used for classification, the information itself does not have any color. First look at the first part, that is, the white square in the following picture. Can you see what it means?

Figure 5 the first part of the Arecibo message is the number 1-10 in binary. Let's explain.

The white dot in the fourth line is the locator, marking the starting point of the binary number. The top three lines of the locator are the three digits of the binary number from the bottom to the top: 20, 21, 22, and then skip to the next column, 23, 24, and 25 from the bottom up. The following figure shows the correspondence between binary and decimal numbers:

Figure 6 the next part of the 10 digits 1-10 represented by binary numbers in the Arecibo message, the purple square part in the following picture.

Figure 7 the second part of the Arecibo message again, the bottom line is a placeholder. It is easy to see that these are five binary numbers, namely 1, 6, 7, 8, 15, which represent the atomic numbers of the five chemical elements contained in DNA. From left to right, they are hydrogen (1), carbon (6), nitrogen (7), oxygen (8) and phosphorus (15), respectively.

The next part is 12 groups of green squares. with the previous experience, we can quickly write down the numbers represented by each set of squares, as shown in the figure below.

Fig. 8 Arecibo Information part 3 what do these numbers mean?

Twelve groups of green squares represent 12 molecules, and the corresponding five digits represent the composition of the molecules, that is, the number of hydrogen, carbon, nitrogen, oxygen and phosphorus atoms in the previous information. Write out the formula, which is part of DNA: lines 1 and 3 are deoxyribose and four bases; lines 2 and 4 are phosphates. The summary is as follows:

Line 1: deoxyribose (C5OH7), adenine (C5H4N5), thymine (C5H5N2O2), deoxyribose (C5OH7)

Line 2: phosphate (PO4), phosphate (PO4)

Line 3: deoxyribose (C5OH7), cytosine (C4H4N3O), guanine (C5H4N5O), deoxyribose (C5OH7)

Line 4: phosphate (PO4), phosphate (PO4).

The next part is shown in the following figure:

Figure 9 the fourth part of the Arecibo message blue represents the DNA double helix structure.

The white square in the middle is a binary number, 11111111 11110111 11111011 01011110 (binary) = 4294441822 (decimal). What does this huge number mean?

It represents the number of bases in the human genome. However, this is the scientific understanding in 1974, and the current scientific result is about 3.055 billion.

In the next part, the pattern is shown below:

Figure 10 the fifth part of the Arecibo message, the red part is the image of the people of the earth. The four white dots in the horizontal direction on the left represent the binary number 1110 (decimal 14). The horizontal writing here implies that 14 is to be multiplied by the wavelength of the signal 126mm, which represents the average height of an American man at that time. 14 × 126mm = 1764mm.

The white pattern on the right is a binary number. From the bottom right, 000011 111111 110111 111011 111111 110110 = 4292853750 (decimal), and the white dot in the upper left corner represents the least significant bit. This figure represents the total population of the earth in 1974.

Continue down, that is, the yellow square part.

Fig. 11 the sixth part of the Arecibo message shows the solar system, with the largest pattern on the left representing the sun and nine planets on the right (Pluto was classified as a planet in 1974); the third Earth has been raised one grid, indicating that the message is sent from the Earth and is close to the human form pattern, indicating that human beings live on Earth.

Finally, the last part.

Fig. 12 Arecibo information part VII purple pattern arc part represents the Arecibo telescope that sent this information, and the M-shaped part is a signal reflection schematic diagram. The horizontal white square is a binary number, 100101 111110 = 2430 (decimal), 2430 × 126mm = 306180mm, representing the mouthpiece of the telescope.

After the interpretation of the Arecibo message, how do you feel, suddenly enlightened or more confused?

If you feel confused, don't be embarrassed. When it was designed for consultation, it could not even be understood by many Nobel laureates. What kind of information do aliens have to be smart to decipher the information about ourselves that even the smartest minds of us on earth can't guess?

In 1999 and 2003, astronomers used the Evpatoria RT-70 radio telescope to send radio messages called cosmic calls (Cosmic Call) to several nearby stars in the solar system.

Cosmic calls are also binary coded, in line with Arecibo information. Its information content is richer than that of Arecibo: it has knowledge in mathematics, physics, astronomy, geography, biochemistry, human body shape, and other fields, and strives to make the content self-consistent and easy for aliens to interpret; finally, several questions are given to aliens, waiting for answers from aliens. There is too much content, so we will not interpret it one by one here. Interested readers can refer to the link at the end of the article [1].

Galactic Beacon so far, earthlings have sent messages to aliens 12 times.

Recently, scientists from the United States, the United Kingdom, the Netherlands and China (from Beijing normal University and Wuhan University) have launched an upgraded version of the alien information code, Galactic Beacon (Beacon in the Galaxy,BITG). Galaxy Beacon details were published in the academic journal Galaxies on March 25.

Fig. 13 Galaxy beacon project leader, Professor Jiang Hongtao of the California Institute of Technology, returned home for academic exchange. Galaxy beacons present information in the same way as Arecibo information, which is a binary bitmap, and the content is also limited to natural science.

Galaxy Beacon consists of 13 parts, as shown in the following figure:

Fig. 14 full content of Galactic Beacon Mathematics the first part of the content is to introduce the mathematics of Earthman to aliens.

We earthlings usually use decimal numbers, but we cannot expect aliens to also use decimal numbers, but we can boldly assume that aliens understand binary numbers. In the galactic beacon, the binary counting method is used to represent the decimal counting method used by our earthlings as follows.

Fig. 15 the first part of the Galaxy beacon, the first part of the figure above, represents the number in three ways.

Figure 16 shows the number in three ways, = 0111 = 7. The first way is the number of points (for example, the figure above is 7 points), the second way is the four-digit binary number, and the third way is the human number. The three ways are separated by a symbol, which is the equal sign "=".

The Arabic numeral 0-9 is represented in the galactic beacon as follows:

Figure 17 the decimal number 0-9 in the Milky way beacon is also represented by a two-digit decimal number, such as the number 14, as follows:

Figure 18, number 14, omits the binary representation to save space. After being familiar with the writing of decimal numbers, it is easier to understand the prime numbers in the lower half of figure 14. The bottom line is the largest prime number known so far, using the second part of the Galaxy beacon-some basic mathematical symbols.

Fig. 19 the second part of the Galaxy beacon, the symbols involved in the mathematical operation diagram are as follows:

Fig. 20 basic mathematical operation symbols in Galaxy beacons pick out several examples from the diagram to test you:

Fig. 21 examples of mathematical operations in Galaxy beacons the above four expressions are respectively expressed as follows: 4 × 3 × 12 − 2 = − 1, 3 / 2, 5, 5, 1 / 9, 0. 1111.

Now, do you have a feeling for these symbols? So, if you look at the picture below, can you understand it at a glance?

Fig. 22 Galaxy beacon part 3, exponential operation pair, this is exponential operation.

The next step is equations and functions.

Fig. 23 Galaxy beacon part IV, three variables are defined in the equation and function diagram, which correspond to a _ c

Fig. 24 three variables in the galactic beacon finally, the b=a3 image of the function is drawn.

Physics introduces mathematics to aliens, and then begins to introduce physics.

First of all, the units of physical quantities are introduced. Will aliens use our Earthman's international unit system of SI?

It is unlikely that even we people on earth have not been able to unify the unit system.

We have to define units in terms of universal constants. Galactic beacons choose the hydrogen spectrum.

Hydrogen is the most abundant element in the universe. Extraterrestrial intelligent civilizations must be able to study hydrogen atoms very clearly, not only knowing that hydrogen atoms are composed of a proton and an electron that surrounds protons, but also the hyperfine spectral lines of hydrogen atoms.

When the hydrogen atom is in the ground state, the spins of protons and electrons have two states, parallel or antiparallel. The energy of the two states is slightly different, the former is slightly higher than the latter, when the hydrogen atom transitions from the former to the latter, there will be radiation, which is the hyperfine spectral line of the hydrogen atom, the wavelength is about 21cm and the frequency is about 1420MHz.

The spins of protons and electrons change from parallel to anti-parallel, and the probability of this transition is so low that the hyperfine lines of hydrogen atoms cannot be seen in laboratories on Earth, but the content of natural hydrogen atoms in interstellar media is quite high. can emit hyperfine radiation and be observed by radio telescopes. Extraterrestrial astronomers should also be familiar with this spectral line.

Fig. 25 schematic map of hyperfine radiation of hydrogen atoms Galactic beacons agree on the length and time units to alien civilizations through the following information, which are the wavelengths and periods of the hyperfine lines of hydrogen atoms.

Fig. 26 Galactic beacon part V, using hydrogen atomic hyperfine radiation to define the lower right corner of time and length units in figure 23, this pattern shows that the spins of protons and electrons transition from parallel to antiparallel and release radiation.

You should have the experience to understand this kind of picture, right? Compared with the English hint on the right, it should not be difficult to guess the meaning of the following symbols.

The last piece of information in figure 23 is worth mentioning, which is the timestamp, that is, the time the message was sent. The era of earthlings and aliens is different, how to explain the time? Fortunately, earthlings and aliens can find a common starting point of time-the Big Bang. The last message in the picture is that the Earth sent this message 4.355X1017 seconds after the Big Bang.

Chemistry and life sciences the next part of the Galactic Beacon begins to talk about chemical elements. The information in the following figure is the hydrogen atomic spectrum and the atomic number of several chemical elements.

Fig. 27 Galactic beacon part VI, with the above mathematical, physical and chemical knowledge of hydrogen atomic spectrum and chemical elements, it is possible to present four bases of DNA, the basic unit of genetic material for life on Earth. According to the chemical element symbols in the above picture, combined with the normal DNA structure of earthlings in figure 26, it is not difficult to understand the representation of the four bases in the galactic beacon.

Fig. 28 Galaxy beacon part VII, four bases of DNA

Fig. 29 the double helix structure of the structural DNA of the four bases in DNA is crucial to its genetic function. The following picture shows the figure and DNA double helix structure of men and women on earth.

Fig. 30 Milky way beacon part 8, human earth characteristic galactic beacon then visually presents a map of the solar system and the earth.

Fig. 31 Galactic beacon part IX, solar system

Fig. 32 Galactic beacon part X, Earth Map

Fig. 33 Galactic beacon part 11, Earth characteristics Galactic beacon part 11 shows the characteristics of the earth, as shown in figure 30, the earth has land, sea and atmosphere, and people live on land and mountains on land, with a maximum of 8848 meters above sea level and 11000 meters at the deepest depth of the ocean. The picture also shows the composition of some substances in the land, ocean and atmosphere.

Finally, aliens are invited to contact the earthlings at the frequency of 2380MHz. Finally, the position coordinates of the earth are given.

Fig. 34 Galactic beacon part 12, inviting aliens to reply

Fig. 35 Galaxy beacon part 13 (not fully shown), Earth's location coordinates (technical details are too tedious to be introduced in this article. (send it or not? Galactic beacons have only been designed and haven't been sent yet.

Where is it sent from?

The first Arecibo telescope to send radio messages to extraterrestrials was completely destroyed on the eve of retirement on December 1, 2020.

Fig. 36 the tragedy of the destruction of the Arecibo telescope is that there are still two devices on Earth that can undertake the task of contacting aliens, one is the Chinese Heavenly Eye, and the other is the Allen Telescope Array (Allen Telescope Array,ATA) in the United States, which covers an area of 1 hectare, also known as the hectare telescope.

Fig. 37 Chinese Sky Eye

Fig. 38 Art Picture of the Allen Telescope Array (ATA) in the United States however, both the Chinese Sky Eye and the Allen Telescope Array can only receive signals, not send signals. It is not difficult to retrofit the telescope and equip it with radar that transmits information. After the transformation, both astronomical devices can send signals to the sky in the Milky way, where intelligent life is most likely to exist.

Another key question is, whether to send it or not?

Although astronomers have sent messages to possible alien civilizations many times, there have been voices against such activities.

It may be a waste of manpower, material and financial resources to take the initiative to send messages to possible aliens. This is nothing, and what is more serious, it may lead to danger.

Fig. 39 the danger on the cover of "three-body II: dark Forest" is reflected in the "Dark Forest Law" put forward by Liu Cixin, a famous Chinese science fiction writer:

The universe is like a dark forest, and every civilization is a hunter with a gun, sneaking through the forest like a ghost, gently plucking away the branches to explore the outside world, while trying not to make a footstep to hide its tracks, because there are hunters like him everywhere. If he finds another life, whether hunter or not, angel or devil, there is only one thing he can do: shoot to destroy it, in this forest, others are hell, the source of eternal threat, any life that exposes its existence will soon be wiped out.

The words of the novelist can not be relied on. But some reputable scientists say it is dangerous to contact aliens on their own initiative.

Stephen Hawking once said in a television program, do not contact aliens, aliens find the earth, just like Columbus found the new world, we earthlings will repeat the tragedy of the Indians.

David Brin, an American scientist and science fiction writer, published an article in 2006 saying that actively sending radio waves to aliens may put earthlings at risk, and that fanatics actively searching for aliens should stop and fully listen to and discuss all fields-- not only astronomy. It also includes but is not limited to the opinions of experts in history, cosmobiology, ethics and animal behavior.

Fig. 40 David Brin (October 6, David Brin,1950), American astronomer, futurist, NASA consultant and science fiction writer. On October 11, 2006, Nature published an editorial [4], saying that alien civilizations may not be kind, and that even if they are really linked to friendly alien civilizations, they may bring serious chaos within us, and the search for alien civilizations should openly and transparently explain to the outside world the discussions of people in this field, and call themselves Earth ambassadors without a big telescope.

Some scientists have responded to these concerns.

In 2008, Zaytsev, a Russian radar astronomer and expert in searching for extraterrestrial civilizations, published an article [5] saying that as long as earthlings engage in radar astronomy, they should not worry about sending messages to alien civilizations. The signal from Earthman's radar astronomy research has long lit up the whole sky, and the message to alien civilization is only a tiny drop in the ocean. To eradicate the aftermath, unless we even ban radar astronomy research, but, in that case, we will not be able to monitor and prevent asteroids from hitting Earth, and eventually go to destruction.

Figure 41 Alexander Zaytsev (May 19, Alexander Zaitsev,1945-November 29, 2021), Russian and Soviet astronomer and radio engineer, focusing on radar astronomical equipment, near-Earth asteroids, search for alien civilizations, etc. In 2016, Nature Physics published an article saying that the radio signals leaked by humans are so weak that they can only reach the nearest 7000 stars; even alien civilizations near these 7000 stars are unlikely to detect leaked radio signals without radio telescopes with a caliber of more than 300m. Radar signals tracking asteroids are scattered indiscriminately in space and cannot be compared with radar beams that lead directly to specific star systems.

Some people believe that alien civilizations, which are more technologically advanced, are also more morally advanced and will treat earthlings peacefully.

Nature Physics's article said that patience should be a quality that an advanced civilization should possess. We should exercise patience and contact aliens when the conditions are ripe. Before that, do not let impatient earthlings cause trouble.

This article soon led to a rebuttal [7]. First of all, the article says that the electromagnetic waves leaked by the earthlings are enough to let the alien civilization know the existence of the earthlings, and now it is too late to worry about the alien invasion. On the other hand, loss aversion makes people pay more attention to the risks of contacting aliens and less about the benefits of contacting aliens.

The article also discusses the question of whether or not to contact aliens, who has the final say? Do the people of the earth reach a consensus and do it according to the consensus? This is not realistic and it is impossible to reach a consensus. A more feasible way is for scientists to have the final say, do it in accordance with the practice of the scientific community, and peer review.

Leaving aside these controversies, let's talk about galactic beacons.

Earthlings have identified more than 5000 exoplanets and may discover habitable planets or even extraterrestrial intelligent civilizations in the near future. We should make some preparations now.

Galactic beacons, which are simple in form and rich in content, can be sent to the skies where aliens are most likely, so they can also greatly improve the probability of receiving alien responses in the distant future.

What will aliens reply if they receive and decipher the galactic beacon?

We hope to at least reply to what is already in the galactic beacon, such as their digital system, reply time, location coordinates in space, genetic material (aliens may not be carbon-based life), shape, etc., and may provide other information, such as alien culture, interstellar communication language, and so on.

Communicating with aliens is a fascinating area of cosmic scientific exploration, and it is now technically feasible. We humans have exciting stories to share with aliens, and we are eager to know about them. Now, we have the means to do it.

Contact the aliens, yes or no? This is a question worthy of everyone's consideration.

references

[1] https://blog.plover.com/aliens/dd/intro.html

[2] https://www.mdpi.com/2075-4434/10/2/55

[3] http://www.davidbrin.com/nonfiction/shouldsetitransmit.html

[4] Nature, 2006, 443,606, https://www.nature.com/articles/443606a

[5] http://jre.cplire.ru/jre/may08/2/text_e.html

[6] Nature Physics, 2016, 12720, https://www.nature.com/articles/nphys3852

[7] Nature Physics, 2016, 12890, https://www.nature.com/articles/nphys3897

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