In order to let aliens understand the earth's information, they desperately came up with these "garbled codes"

Recently, the U.S. Congress held a public hearing on the UFO phenomenon, the first in 53 years. The U.S. Department of Defense calls this type of phenomenon an unidentified aerial phenomenon (UAP). When the news was released, netizens inevitably linked it to aliens. In fact, most phenomena can be reasonably explained, and the rest give people room for imagination. We always ask questions: Are humans the only intelligent life in the vast universe? After entering the 20th century, humans tried to send messages to the universe to find extraterrestrial civilizations. The most famous of these was the Arecibo message, in which astronomers compiled the basic information of the earth into a "QR code" and broadcast it to the universe. Recently, astronomers have proposed an upgraded version - the Galactic Beacon. However, whether to actively contact aliens is still a controversial issue.

Written by Qu Lijian

The vastness of space always makes us ponder a profound question: Are we on Earth alone? Are there other intelligent civilizations among the stars?

With the development of science, humans have gone beyond fantasy and reveries. Since the early 1900s, they have tried to receive possible signals from alien civilizations. 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, launching a series of planetary exploration spacecraft. The original goal of Pioneer 10 and 11, launched in 1972 and 1973, was to explore the outer solar system. They became the first probes to fly past Jupiter and approach Saturn, respectively, and eventually they would fly out of the solar system. The Americans installed a gold-plated aluminum plate (Pioneer plaque) on Pioneer 10 and 11, which was engraved with some information about the earthlings. If the probe was captured by an alien civilization, the aliens could quickly understand the earthlings through this aluminum plate. See the figure below for the symbols engraved on the aluminum plate.

Figure 1 Pioneer gold-plated aluminum plate

Apart from naked men and women, is it true that everything else is incomprehensible?

In addition to the ambiguity of its meaning, no one is sure whether this aluminum plate can be received by aliens. This gold-plated aluminum plate is like a drifting bottle. Although it left the solar system at a speed of 50,000 kilometers per hour, it is still not worth mentioning compared to the vastness of space.

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

Yes, by sending radio signals, which is also the fastest form of signal propagation.

>>>

Arecibo Information

In 1963, the Arecibo radio telescope in Puerto Rico, USA was completed with a diameter of 305 meters. After its completion, it became the world's largest single-aperture telescope. The record remained until July 2016, when it was broken by China's 500-meter Aperture Spherical Radio Telescope FAST "China Sky Eye".

Figure 2 Comparison of the apertures of the Arecibo radio telescope and China's Sky Eye

There is something special about the Arecibo radio telescope. It is equipped with three radar transmitters, which are used to send radio signals to celestial bodies and analyze the reflected signals.

American astronomer Fank Drake once proposed using the Arecibo telescope's radar to send radio signals into space so that alien astronomers could capture them, decipher the information contained in them, and learn about the existence of humans on Earth.

Figure 3 Frank Drake (May 28, 1930-), an American astronomer, actively promoted the Search for Extraterrestrial Intelligence (SETI). On the blackboard in the picture is the Drake equation named after him, which is used to estimate the number of extraterrestrial intelligent civilizations in the Milky Way that can contact us.

What content to send?

The content should be understandable to both earthlings and aliens.

Is there such content?

Yes, science.

Science applies to the entire universe. If aliens can invent a radio telescope, they must understand science.

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

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

Soon, maybe 50,000 years, because M13 is 25,000 light years away from Earth.

While we quietly wait for the aliens' reply, let's take a look at what message the American astronomers sent.

This signal is converted into audio. Please click and listen.

Arecibo_message Audio: 00:0002:47

Readers who are more sensitive to sound may be able to hear that this audio has two pitches. We can record the pitch series, with the high pitch as 0 and the low pitch as 1, and we will get:

000000101010100000000000010100000101000000010010001000100010010110010…

A total of 1679 0s or 1s equals 1679 bits of information.

Drake hopes that the aliens will arrange this string into a rectangle. Factoring 1679, 1679=23X73, so there are only two ways to arrange 1679 0s or 1s into a rectangle: 23 rows and 73 columns, or 73 rows and 23 columns. However, if the former is used, the resulting pattern is white noise; if the latter is used, a meaningful pixel bitmap will emerge.

So let’s see what the content of the information is.

In order to facilitate observation, we made it in color.

Figure 4 Arecibo message. Color is used for classification. The message itself does not have any color.

First look at the first part, which is the white square in the picture below. Can you tell what it means?

Figure 5 The first part of the Arecibo message

This is the number 1-10 represented in binary. Here is the explanation.

The white dots in the fourth row are locators, marking the starting point of the binary number. The three rows above the locators are the three digits of the binary number from bottom to top: 20, 21, 22; then jump to the next column, from bottom to top, 23, 24, 25. The following figure shows the correspondence between binary and decimal numbers:

Figure 6 The 10 numbers 1-10 represented by binary numbers in the Arecibo message

The next part is the purple square in the picture below.

Figure 7 The second part of the Arecibo message

Similarly, the bottom row is a placeholder. It is easy to see that these are five binary numbers, namely 1, 6, 7, 8, and 15. These five numbers represent the atomic numbers of the five chemical elements contained in DNA, from left to right: hydrogen (1), carbon (6), nitrogen (7), oxygen (8), and phosphorus (15).

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

Figure 8 The third part of the Arecibo message

What do these numbers mean?

The 12 groups of green squares represent 12 molecules, and the corresponding 5-digit numbers 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 molecular formula, which are the components of DNA: rows 1 and 3 are deoxyribose and four bases; rows 2 and 4 are phosphates. The summary is as follows:

The next part is as follows:

Figure 9 Part 4 of the Arecibo message

The blue color represents the double helix structure of DNA.

The white square in the middle is a binary number, 11111111 11110111 11111011 01011110 (binary) = 4,294,441,822 (decimal). What does this huge number mean?

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

The next part, the pattern is as follows:

Figure 10 The fifth part of the Arecibo message

The red part is the image of the Earthman. The four white dots on the left side represent the binary number 1110 (decimal 14). The horizontal writing here implies that 14 should be multiplied by the wavelength of the signal 126mm, 14 × 126mm = 1,764mm, which represents the average height of American men at that time.

The white pattern on the right is a binary number, starting from the bottom right, 000011 111111 110111 111011 111111 110110 = 4,292,853,750 (decimal), and the white dot in the upper left corner represents the least significant bit. This number represents the total population of the earth in 1974.

Continue down to the yellow square part.

Figure 11 Part 6 of the Arecibo message

This part shows the solar system. The largest pattern on the far left represents the sun, and on the right are the nine planets (in 1974, Pluto was still classified as a planet). The third-placed Earth is raised one level, representing that the information is sent from the Earth. At the same time, it is close to the human form pattern, indicating that humans live on Earth.

Finally, we have reached the last part.

Figure 12 Part 7 of the Arecibo message

The purple arc part represents the Arecibo telescope that sent this information, and the M-shaped part is a schematic diagram of signal reflection. The horizontal white square is a binary number, 100101 111110 = 2,430 (decimal), 2430 × 126mm = 306,180mm, which represents the mouth mirror of the telescope.

The Arecibo message has been interpreted. How do you feel? Do you feel suddenly enlightened or more confused?

If you feel confused, don't be embarrassed. When it was designed and opinions were sought, even several Nobel Prize winners couldn't understand it. How smart would aliens have to be to decipher information about themselves that even the smartest minds on Earth can't figure out?

In 1999 and 2003, astronomers used the Yevpatoria RT-70 radio telescope to send radio messages to several nearby stars in the solar system, which they called Cosmic Calls.

The cosmic call was also encoded in binary, just like the Arecibo message. Its information content is richer than the Arecibo message: it contains knowledge from various fields such as mathematics, physics, astronomy, geography, biochemistry, human morphology, etc., and strives to make the content self-consistent so that it is easy for aliens to interpret. In the end, it also gives the aliens a few questions and waits for the aliens to send answers. There is too much content to interpret one by one here. Interested readers can refer to the link at the end of the article [1].

>>>

Galactic Beacon

So far, humans on Earth 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 - Beacon in the Galaxy (BITG). The details of the Beacon were published in the academic journal Galaxies on March 25 [2].

Figure 13 The leader of the Galaxy Beacon project, Professor Jiang Hongtao of California Institute of Technology, returned to China for academic exchanges

The Galactic Beacon presents information in the same way as the Arecibo message, as a binary bitmap, and its content is also limited to natural sciences.

The Galactic Beacon has thirteen parts, as shown below:

Figure 14: All contents of the Galaxy Beacon

math

The first part is about introducing Earthling mathematics to aliens.

We humans usually use decimal numbers, but we cannot expect aliens to use decimal numbers, but we can boldly assume that aliens understand binary numbers. The Galactic Beacon uses binary notation to represent the decimal notation used by us humans as follows.

Figure 15 The first part of the Galaxy Beacon, digital

The first part of the picture above shows numbers in three ways.

The Arabic numerals 0-9 are represented in the Galactic Beacon as follows:

Figure 17 The decimal numbers 0-9 are represented in the Galactic Beacon

The figure also shows the representation of two decimal numbers. For example, the number 14 is represented as follows:

Figure 18 Number 14, with the binary representation omitted to save space.

Once you are familiar with writing decimal numbers, it will be easier to understand the prime numbers in the lower half of Figure 14. The bottom row is the largest prime number known so far, and it requires the use of the second part of the Galactic Beacon - some basic mathematical operation symbols.

Figure 19 The second part of the Galactic Beacon, mathematical operations

The symbols involved in the figure are as follows:

Figure 20 Basic mathematical operation symbols in the Galactic Beacon

Here are a few examples from the picture to test you:

Figure 21 An example of mathematical operations in the Galaxy Beacon

The above four formulas respectively represent: 4×3=12, 1−2=−1, 3÷2=1.5, 1÷9=0.1111.

Now, do you have a feeling for these symbols? Then, look at the picture below, can you understand it at once?

Figure 22 The third part of the Galaxy Beacon, exponential calculation

Yes, this is exponential operation.

The next step is equations and functions.

Figure 23 The fourth part of the Galactic Beacon: Equations and Functions

Three variables are defined in the figure, let them correspond to a, b, and c respectively:

Figure 24 Three variables in the Galaxy Beacon

physics

After introducing mathematics to the aliens, we will start introducing physics.

First, let's introduce the units of physical quantities. Will aliens use the International System of Units (SI) that we use on Earth?

It's unlikely. Even we on Earth have not yet standardized our system of units.

We must define units using universal constants. The Galactic Beacon chose the spectrum of the hydrogen atom.

Hydrogen is the most abundant element in the universe. Extraterrestrial intelligent civilizations must be able to study hydrogen atoms very clearly. They should not only understand that hydrogen atoms are composed of a proton and an electron orbiting the proton, but also understand the hyperfine spectrum of hydrogen atoms.

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

The probability of the proton and electron spin changing from parallel to antiparallel is extremely low, so the hydrogen atomic hyperfine line cannot be seen in laboratories on Earth, but the natural hydrogen atomic content in the interstellar medium is quite large, which can emit hyperfine radiation and be observed by radio telescopes. Extraterrestrial astronomers should also be familiar with this spectral line.

Figure 25 Schematic diagram of hydrogen atom hyperfine radiation

Through the following information, the Galactic Beacon agreed upon the units of length and time to extraterrestrial civilizations, which are the wavelength and period of the hyperfine spectrum of hydrogen atoms.

Figure 26 The fifth part of the Galactic Beacon, using the hyperfine radiation of hydrogen atoms to define time and length units

In the lower right corner of Figure 23, the pattern shows that the spins of protons and electrons transition from parallel states to antiparallel states and release radiation.

Everyone should have experience in understanding this kind of diagram, right? By comparing it with the English prompts on the right, it should not be difficult to guess the meaning of the symbols behind it.

The last piece of information in Figure 23 is worth mentioning. This is the timestamp, that is, the time when the information was sent. How can the time be explained when the earthlings and aliens have different eras? Fortunately, the earthlings and aliens can find a common starting point in time - the Big Bang. The last piece of information in the figure says that the earth sent this information 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 figure below is the spectrum of hydrogen atoms and the atomic numbers of several chemical elements.

Figure 27 Galactic Beacon Part VI, Hydrogen Atom Spectrum and Chemical Elements

With the above knowledge of mathematics, physics and chemistry, we can present the four bases of DNA, the basic unit of genetic material of life on Earth. According to the chemical element symbols in the above figure, 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.

Figure 28 Galactic Beacon Part 7, Four DNA Bases

Figure 29 The structural formulas of the four bases in DNA

The double helix structure of DNA is crucial to its genetic function. The figure below shows the body shape of men and women on Earth and the double helix structure of DNA.

Figure 30 Galactic Beacon Part 8: Human Body

Earth Features

The Galactic Beacon then visually presents a map of the solar system and Earth.

Figure 31 Galactic Beacon Part IX, Solar System

Figure 32 Galactic Beacon Part 10, Earth Map

Figure 33 Galactic Beacon Part 11: Earth Features

The eleventh part of the Galactic Beacon shows the characteristics of the Earth. As shown in Figure 30, the Earth has land, oceans, and atmosphere. People live on land. There are mountains on land, the highest of which is 8,848 meters above sea level, and the deepest in the ocean is 11,000 meters. The figure also marks some of the material components of the land, ocean, and atmosphere.

Finally, the aliens were invited to contact the earthlings at a frequency of 2380MHz, and the coordinates of the earth's location were also given.

Figure 34 Galactic Beacon Part 12, Inviting Aliens to Reply

Figure 35 Galactic Beacon Part 13 (not fully shown), Earth's position coordinates (the technical details are too complicated to be introduced in this article.)

>>>

To send or not to send?

The Galactic Beacon has only been designed, not yet sent.

Where to send from?

The Arecibo telescope, the first telescope to send radio messages to extraterrestrial space, was completely destroyed on December 1, 2020, on the eve of its decommissioning.

Figure 36 The tragic scene after the destruction of the Arecibo telescope

Fortunately, there are two devices on Earth that can take on the task of contacting aliens. One is the "China Sky Eye"; the other is the Allen Telescope Array (ATA) in the United States, which covers an area of ​​1 hectare and was also called the Hectare Telescope.

Figure 37 China's Sky Eye

Figure 38 Artistic image 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 them. It is not difficult to modify the telescopes and equip them with radars that transmit information. After the modification, both astronomical devices can send signals to the areas in the Milky Way where intelligent life is most likely to exist.

Another key question is, should it be issued or not?

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

Actively sending information to possible aliens may be a sheer waste of manpower, material resources, and financial resources. This is not a big deal. What is more serious is that it may lead to danger.

Figure 39 Cover of The Three-Body Problem II: The Dark Forest

This danger is reflected in the "Dark Forest Law" proposed by Liu Cixin, a famous Chinese science fiction writer, in his novel:

The universe is like a dark forest. Every civilization is a hunter with a gun. He sneaks through the forest like a ghost, gently pushing aside branches to explore the outside world, and tries his best not to make any footsteps to hide his whereabouts, because there are hunters sneaking like him everywhere in the forest. If he finds other life, whether it is a hunter or not, whether it is an angel or a devil, there is only one thing he can do: shoot and kill it. In this forest, others are hell, the eternal source of threat, and any life that exposes its existence will be quickly eliminated.

Fictional stories are not to be trusted. But some reputable scientists have said that it is dangerous to actively contact aliens.

Stephen Hawking once said in a TV show that we should not contact aliens. If aliens find the Earth, it would be like Columbus discovering the New World. We humans on Earth will repeat the tragedy of the Indians.

In 2006, American scientist and science fiction writer David Brin published an article[3] stating that actively sending radio waves to aliens could put humans on Earth in danger, and that those who actively search for aliens should stop and fully listen to and discuss the opinions of experts in various fields, including not only astronomy, but also history, astrobiology, ethics, and animal behavior.

Figure 40 David Brin (October 6, 1950-), American astronomer, futurist, NASA consultant, and science fiction writer.

On October 11, 2006, Nature published an editorial[4] stating that extraterrestrial civilizations may not be friendly. Even if we do contact a friendly extraterrestrial civilization, it may cause serious chaos among us humans on Earth. The search for extraterrestrial civilizations should transparently explain the discussions of people in this field to the outside world, and not declare themselves ambassadors of the Earth just because they have a big telescope.

Some scientists have echoed these concerns.

In 2008, Russian radar astronomer and expert on the search for extraterrestrial civilizations Zaitsev published an article[5] stating that as long as humans on Earth conduct radar astronomy, there is no need to worry about sending messages to extraterrestrial civilizations. The signals sent by humans’ radar astronomy research have long illuminated the entire sky, and the messages sent to extraterrestrial civilizations are only a drop in the ocean and are not worth mentioning. If we want to eradicate the trouble, we must ban radar astronomy research as well. However, if that happens, we will not be able to monitor and prevent asteroids from hitting the Earth, and will eventually be doomed.

Figure 41 Alexander Zaitsev (May 19, 1945 - November 29, 2021), a Russian and Soviet astronomer and radio engineer, mainly studied radar astronomy equipment, near-Earth asteroids, and searches for extraterrestrial civilizations.

In 2016, Nature Physics published an article stating[6] that the radio signals leaked by humans are very weak and can only reach the 7,000 stars closest to us; even if there are alien civilizations near these 7,000 stars, it is unlikely to detect the radio signals leaked by humans without a radio telescope with a diameter of more than 300 meters. The radar signals tracking asteroids are randomly distributed in space and cannot be compared with radar beams that are directly directed to specific star systems.

Some people believe that alien civilizations with more advanced technology are also more morally advanced and will treat humans peacefully. In this regard, the author says that such people are too simple and sometimes naive.

The article in Nature Physics said that patience should be a quality that an advanced civilization should possess. We should exercise patience and wait until the conditions are ripe before contacting aliens. Before that, we should not let impatient earthlings cause trouble.

This article quickly attracted a rebuttal article [7]. The article first said that the electromagnetic waves leaked by humans on Earth are enough to let alien civilizations know of the existence of humans on Earth, and it is too late to worry about alien invasion now. On the other hand, loss aversion makes people pay more attention to the risks of contacting aliens and less attention to the benefits of contacting aliens.

The article also discusses a question: who has the final say on whether to contact aliens? Should the people on Earth reach a consensus and act according to the consensus? This is unrealistic and impossible to reach a consensus. A more feasible way is for scientists to have the final say, act according to scientific practice, and conduct peer review.

Let’s not talk about these controversies for now, and let’s talk about the Galactic Beacon.

Earthlings have confirmed more than 5,000 exoplanets. Perhaps in the near future we will discover habitable planets or even alien intelligent civilizations. We should make some preparations now.

The Galactic Beacon's information is concise in form and rich in content. It can be sent to the areas of the sky most likely to contain aliens, thus greatly increasing the probability of receiving a reply from aliens in the distant future.

If aliens received and cracked the galactic beacon, what would they reply?

We hope to at least reply to the content already in the Galactic Beacon, such as their number system, reply time, location coordinates in space, genetic material (aliens may not be carbon-based life), appearance, etc., and it may also be possible to provide other information, such as alien culture, interstellar communication language, etc.

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

Contacting aliens, should we do it or not? This is a question worth pondering for everyone.

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, 12, 720, https://www.nature.com/articles/nphys3852

[7] Nature Physics, 2016, 12, 890, https://www.nature.com/articles/nphys3897

Special Tips

1. Go to the "Featured Column" at the bottom of the menu of the "Fanpu" WeChat public account to read a series of popular science articles on different topics.

2. Fanpu provides a function to search articles by month. Follow the official account and reply with the four-digit year + month, such as "1903", to get the article index for March 2019, and so on.

Copyright statement: Personal forwarding is welcome. Any form of media or organization is not allowed to reprint or excerpt without authorization. For reprint authorization, please contact the backstage of the "Fanpu" WeChat public account.