The project Transmission Hangeul is an interdisciplinary initiative, a collaboration between experts in art, astronomy, and space communication, aimed at transmitting Korea's first interstellar message Transmission Hangeul into space. Transmission Hangeul is the first Interstellar message designed to systematically convey information about human language, specifically Korean and Hangeul, to extraterrestrial intelligence. This is the first Interstellar message created and transmitted by a country in Asia. Transmission Hangeul was transmitted to space on November 16, 2024, exactly 50 years after the transmission of the first human interstellar message, Arecibo Message.

The project has been led by Korean interdisciplinary artist Jongkuk Won also known as Unhappy the Cosmic Traveler. He has been conducting the research and development on his own, with support from organizations such as Hyundai Motor Group's ZER01NE, Asia Culture Center, Seoul Foundation for Arts and Culture, Arts Council Korea, and Gwacheon National Science Museum.

Starting in 2024, the project has been conducted by Unhappy and the National Central Museum of Science. The technical aspects required for transmitting Transmission Hangeul were supported by Korean startups Spacebeam Inc. and METASPACE, specialized in space communication and astronomical observation technologies.

1) SETI and METI

① SETI: Search for Extra-Terrestrial Intelligence

SETI aims to find evidence of extraterrestrial intelligence, primarily through the field of radio astronomy. The main goal of SETI is to capture artificial electromagnetic signals originating from distant space. Since the inception of SETI, signals that could potentially have originated from extraterrestrial civilizations have been occasionally detected. However, most of these signals were either determined to be interference near Earth or the activity of unusual celestial bodies, or they remained unexplained due to the inability to conduct further verification.

[Figure 1] Astronomer Frank Drake initiated the history of SETI in 1960 by conducting the first SETI program, Project Ozma. (Credit: National Radio Astronomy Observatory)
[Figure 2] Drake devised the Drake Equation, a probabilistic formula used to estimate the number of extraterrestrial intelligence within our galaxy that could potentially communicate with humanity. (Credit: SETI Institute)

[Figure 3] In 1974, Drake created the first modern interstellar message, the Arecibo Message, and transmitted it toward the M13. (Credit: Wikipedia)

[Figure 4] The signals sent by the Voyager spacecraft to Earth demonstrate the characteristics of artificial electromagnetic signals arriving from distant space. (Credit: SETI Institute)
[Figure 5] The unusual electromagnetic signal BLC1, observed in 2019 from the direction of Proxima Centauri, was concluded to be caused by interference near Earth after further investigation. (Credit: Nature Astronomy)

② METI: Messaging to Extra-Terrestrial Intelligence

METI, Messaging to Extra-Terrestrial Intelligence, is a field focused on developing interstellar messages, information and data aimed at reaching extraterrestrial intelligence, and transmitting them into space. While SETI focuses on "listening" for signals from space in search of extraterrestrial intelligence, METI is a field dedicated to "alerting" the universe to our existence by sending messages into space. As a result, METI is often referred to as Active SETI. In contrast to SETI, which primarily focuses on radio astronomy, METI is characterized by its interdisciplinary nature, involving perspectives from various fields such as linguistics, anthropology, psychology, archaeology, biology, neuroscience, and the arts. This makes METI unique in its approach.

Before the 2000s, METI was known as Active SETI or CETI (Communication with Extraterrestrial Intelligence). However, Russian astronomer Alexander Zaitzev proposed renaming it METI. The previous two names implied a focus on receiving responses from or communicating with extraterrestrial intelligence, whereas METI emphasizes the larger goal of announcing humanity's existence to the universe itself.

[Figure 6] METI International, led by Dr. Douglas Vakoch, is an interdisciplinary research organization where experts from various fields gather to focus on METI. (Credit: IMDB)
[Figure 7] Astronomer Alexander Zaitzev, who first proposed the name METI, was very proactive in raising awareness about the importance of sending messages into space. (Credit: Seth Shostak)

2) Previous Interstellar Messages

For over the past 50 years, humanity has often sent messages into space. These messages have been transmitted into space in forms such as digital data through radio transmitters, like the Arecibo Message, or made into metal objects, like the Voyager Golden Record, which were carried aboard space probes. These efforts have been not only serious scientific attempts aimed at contacting extraterrestrial intelligence but also a process through which humanity reflects on itself and organizes its existence and culture into a cohesive narrative.

[Figure 8] Messages humanity has sent to space over the past 50 years:
Pioneer Plaque (1972), Arecibo Message (1974), Voyager Golden Record (1977), Cosmic Call (1999), Teen-Age Message (2001)

[Figure 9] Voyager Golden Record contains 116 images depicting humanity, greetings recorded in 55 languages, sounds of nature, and music from around the world. (Credit: NASA)

3) How to Design Interstellar Messages

The greatest challenge in designing a interstellar message is that we know nothing about extraterrestrial intelligence. Therefore, creating a interstellar message requires making minimal assumptions and conditions about extraterrestrial intelligence. METI defines the conditions of the extraterrestrial intelligence the message aims to reach as follows and designs interstellar messages based on these criteria.

Extraterrestrial intelligence
- Beings separated from Earth by astronomical distances in space and time
- A technologically advanced civilization that observes and analyzes the universe using various electromagnetic waves

First, METI assumes that extraterrestrial intelligence is beings located at astronomical distances from Earth. Due to the physical limitation of the speed of light, communication between humanity and these extraterrestrial intelligence would involve a dialogue occurring over astronomical space and time, spanning multiple generations. This means that immediate feedback on each other's messages cannot be exchanged. Therefore, an interstellar message must be designed in a way that allows extraterrestrial intelligence to fully understand.

So, how can we create such an interstellar message? The answer can be found in the second condition regarding extraterrestrial intelligence. Extraterrestrial intelligence that METI aims to reach must possess a level of technological civilization capable of receiving and analyzing the messages we send. In other words, METI assumes the existence of beings with a fundamental understanding of mathematics, science, and the dimensional structure of data. This means that mathematics and science can serve as a "language" that both extraterrestrial intelligence and humanity can share. Cosmic Call is a representative interstellar message designed using the language of mathematics and science.

[그림 10] [Figure 10] Mathematician Hans Freudenthal's book Lincos: Lingua Cosmica (1960) proposed the possibility of communicating with extraterrestrial intelligence by using the grammar of mathematics and logic. (Credit: Open Culture)

[Figure 11] In Carl Sagan's novel and the 1997 film adaptation Contact, mathematics and science are referred to as the only language of the universe. (Credit: WarnerBros.com)

[Figure 12] The interstellar message Cosmic Call, transmitted into space in 1999, intricately expresses various science-based information using the language of mathematics. (Credit: Smithsonian Magazine)

1) How long can we communicate through mathematics?

The Cosmic Call, transmitted into space in 1999, expressed the information in the message using a language based on mathematics and science. This was because mathematics and science were regarded as the only "language of the universe." Indeed, mathematics and science can be seen as knowledge and a language that can permeate the universe. But how long can we communicate solely through the language of mathematics? Humans, unlike the Vulcans in Star Trek, are not beings that think purely through logic. Especially concepts like "happiness," "hope," "freedom," "soul," and "love" are multidimensional concepts that are difficult to define through a logical or quantitative approach. Above all, these concepts are deeply connected to our human culture, psychology, and life. In other words, these are concepts that cannot be omitted when explaining what is humanity. When we need to convey these concepts to extraterrestrial intelligence, can we fully communicate their meaning through the language of mathematics?

2) Why couldn't we create an interstellar message using human languages?

Voyager Golden Record, sent into space in 1977, contains greetings recorded in 55 languages from around the world. Below is one of the greetings recorded in Arabic.

.تحياتنا للأصدقاء في النجوم. يا ليت يجمعنا الزمان

'Greetings to the friends in the stars. We wish time would bring us together.'

Unfortunately, extraterrestrial intelligence can't understand the meaning of this heartfelt greeting. The reason is that the Golden Record did not include the necessary clues to enable extraterrestrial intelligence to decode this message. Carl Sagan and the creators of the Golden Record were aware of this issue. However, instead of selecting one or two human languages and creating a sort of dictionary to explain them, they decided to collect simple greetings recorded in as many languages as possible. While extraterrestrial intelligence may not be able to fully decipher the content of the audio messages on the record, it can be expected that they might at least infer that these messages could be some form of greeting toward them. Additionally, the true goal of the record was not practical contact with extraterrestrial intelligence, but rather to send a message of unity to humanity during the Cold War era, which also influenced this decision.

In fact, human languages are not only numerous but also closely connected to human biological traits, ways of thinking, and culture. Furthermore, new variations are constantly being created, forming a complex and ambiguous system. Moreover, humans acquire language through interaction with others. These characteristics of human language make it unsuitable as a medium for communication with extraterrestrial intelligence. Even languages like foreign or ancient ones can often be difficult for humans to understand.

[Figure 13] Human language is closely connected to human biological characteristics and way of thinking. Additionally, humans acquire language through interaction with others. (Credit: Yale University Library Online Exhibitions)

3) Teen-Age Message: The First Attempt to Create a Visual Dictionary for Extraterrestrial Intelligence

The Teen-Age Message created by Alexander Zaitsev is a interstellar message composed of various forms of data, including music, images, and text. What is particularly noteworthy among the data included in this message are the text message and the image data that explains the meaning of some words in the message. This heartfelt text message was written by teenagers from Russia and Ukraine who participated in the Teen-Age Message project. Looking back at the situation of the two countries over 20 years after the Teen-Age Message was transmitted to space, this message makes us reflect on the current state of humanity.

[Table 1] The text message contained in the Teen-Age Message (Credit: A Teen-Age Message to the Stars)
[Figure 14] The text message contained in the Teen-Age Message (Credit: The TAM: Teen-Age Message)

However, it would be difficult for an extraterrestrial intelligence to fully understand the content of the entire text using just these 12 words. A dictionary of words must be able to explain the meaning of every word that makes up the message. Furthermore, extraterrestrial intelligence must be able to understand not only the meanings of individual words but also the way these words are combined to form sentences, that is, the grammar. In the end, the Teen-Age Message did not address all the necessary information required for extraterrestrial intelligence to understand the text data contained in the message. However, in terms of presenting the possibility of making extraterrestrial intelligence understand information expressed in human language, the Teen-Age Message became an important foundation for Transmission Hangeul.

4) Language Is the Beginning of Understanding

Despite the recognition that human languages may not be suitable for interstellar messages, our desire to send messages expressed in human language to the universe still seems hard to resist. Since the Voyager Golden Record, there have been several instances where people's written or voice messages were gathered and sent into space, but these messages were not accompanied by the clues needed to decode their contents.

Above all, human language is deeply connected to human ways of thinking, emotions, and culture. This means that understanding human language would allow for a deeper understanding of humanity itself. We are also deepening our understanding of the beings by understanding the languages of different eras, cultures, and species. If, someday, a conversation between extraterrestrial intelligence and humanity begins, the language between the two will become an important issue for mutual understanding, beyond mathematics and science.

[Figure 15] Ted Chiang's novel Story of Your Life (2002) and the film adaptation Arrival (2016) depict the effort of a linguist to understand the language of extraterrestrial intelligence. (Credit: IMDB)

1) What language should we choose?

Transmission Hangeul can be considered a small language dictionary that conveys basic information about human language to extraterrestrial intelligence, focusing on the Korean language and the Hangeul script, among the many languages of Earth. The reason for choosing Korean as the primary language of Transmission Hangeul is simply because it is the language that is most familiar to the creator of the message. In fact, the choice of language may not be that important. Although human languages appear to be different, they statistically share similar characteristics. Linguist Noam Chomsky referred to this as "universal grammar." The development of artificial intelligence translation technology also demonstrates the universal properties inherent in human languages. This means that expanding a interstellar message system built around any arbitrary language to other languages would not be a particularly difficult task.

[그림 16] Most human languages can be classified into groups called "language families." (Credit: Wikipedia)

2) Features of Hangeul

The script Hangeul, primarily used for writing Korean, is a unique script with several distinct features. The shape of the initial Hangeul characters is based on the concept of the shape of the mouth when pronouncing sounds. The structures of the basic consonants, such as 'ㄱ, ㄴ, ㅅ, ㅇ, ㅁ', represent the basic building blocks for the pronunciation and are designed to mimic the shapes of the human vocal organs used in producing the sounds. This represents the characteristics of the Earth's language that communicates through sound.

The form of the Korean vowels is designed in alignment with the concept of "Heaven, Earth, and Humanity." This concept represents the Eastern traditional philosophy of the relationship between the universe and humans. The structure is based on the principle that "Heaven" (sun) is represented by the character '●,' "Earth" (land) by 'ㅡ,' and "Human" by 'ㅣ.' These elements serve as the foundation for vowel sounds such as 'ㅏ,' 'ㅓ,' 'ㅗ,', 'ㅜ,'.

Above all, Hangeul uses a method called "combination," where consonants and vowels are combined to form a single character. This approach allows the characters to be visually recognizable at a glance, making it easier to understand the meaning quickly.

[그림 17] Structure of Hangeul
The consonants of Hangeul were designed based on the shapes of human speech organs, while the vowels reflect the ideas of Eastern traditional philosophy. This makes Hangeul not only an effective representation of human sounds but also a reflection of Korea's traditional cultural identity. (Credit: Wikipedia)

3) Korean and Hangeul Dictionary for Extraterrestrial Intelligence

Transmission Hangeul consists of two types of data: two-dimensional digital images and one-dimensional audio.
The image data is composed of 180 color images, each with a resolution of 3840 x 2160 pixels, commonly referred to as 4K. These images include 375 Korean vocabulary items: 239 nouns, 56 verbs, 36 adjectives, and 13 adverbs. Additionally, they provide explanations of basic Korean grammar, such as fundamental sentence structures, ways to combine multiple sentences, transformations of parts of speech, verb conjugations, and tenses. The audio data contains pronunciations of all the words and sentences included in the image data.

[그림 18] Complete Image Data of Transmission Hangeul
The image data of Transmission Hangeul consists of 180 color images, each with a resolution of 3840 x 2160 pixels, containing information about Korean vocabulary and grammar.

① First Section: Structure of the Data and Human way of Information Expression

The first section of Transmission Hangeul explains the structure of the data that composes the message and the method of information expression. It is designed to inform extraterrestrial intelligence that they have accurately reconstructed the received data into the intended color images and audio. Additionally, it introduces the way humans convey information through symbols, characters, and images on a two-dimensional plane.

[Figure 19] First Section of Transmission Hangeul
The first part of Transmission Hangeul demonstrates to extraterrestrial intelligence the structure of the data composing the message and the way information is represented.

[Figure 20] Forms of Color Image and Audio Data
The color image data is composed of RGB combinations, represented with 256 levels of brightness ranging from the darkest color (black: 0) to the brightest color (white: 255). The audio data is a one-dimensional digital signal.

[Figure 21] Methods of Representing Numbers and Definitions of Physical Units
This section explains the methods humans use to represent numbers, such as decimal notation, arithmetic operations, exponents, and fractions, as well as definitions of units for basic physical quantities like mass, length, time, and temperature.

[Figure 22] Form and Combination of Hangeul Characters
Among various human languages, Hangeul, primarily used for writing Korean, is a script well-suited for representing human vocalization.

② Second Section: Nouns

The second section of Transmission Hangeul explains the meanings of Korean nouns. These nouns are organized in a sequence, beginning with universal concepts that extraterrestrial intelligence and humans are likely to share, such as "universe", and gradually moving toward uniquely human concepts, such as "love." Words are paired with images to help extraterrestrial intelligence understand their meanings, resembling the way explaining words to children through pictures.

Additionally, Transmission Hangeul presents all vocabulary and sentences in both Hangeul (Korean) and English. While English is currently the most widely used language on Earth, Korean is a minority language primarily spoken in Korea. These two languages differ significantly in form, pronunciation, and grammar. By presenting them together, Transmission Hangeul aims to convey to extraterrestrial intelligence that Earth is home to at least two distinct languages.

[Figure 23] Second Section of Transmission Hangeul
Second section of Transmission Hangeul contains information about Korean noun vocabulary.

[Figure 24] Definition of the Observable Universe and the Position of the Solar System and Earth
This section explains the meaning of the word "universe" through images representing modern cosmology, such as the Big Bang, cosmic expansion, and cosmic microwave background radiation, as well as the current map of the universe observed by humanity. It also informs extraterrestrial intelligence about the position of the solar system and Earth. Will extraterrestrial intelligence ever come to Earth?

[Figure 25] Physical Characteristics and Natural Environment of Earth
Earth is a beautiful planet where the sky, land, and sea harmoniously come together.

[Figure 26] Diverse Lifeforms on Earth and the Cycling Ecosystem
The diverse lifeforms on Earth coexist and live together in ecosystem. However, more and more species are disappearing, and ecosystems are being destroyed.

[Figure 27] Diversity of Humans and Human Communication Using Visual and Auditory Senses
There are various appearances of humans on Earth, and they primarily communicate using visual and auditory senses.

[Figure 28] Diverse Human Cultures and Arts
Songs and poetry are forms of art expressed through human language. These art forms reflect humanity's unique way of thinking and emotions.

[Figure 29] The Bright and Dark Sides of Human Civilization
Human civilization has achieved remarkable progress in a short period, but at the same time, it still holds the potential for self-destruction.

[Figure 30] The Strengths of Humanity
The pursuit of knowledge, the continuous effort to overcome limitations, and the ability to help and cooperate with one another are strengths inherent to humanity. Based on these qualities, humanity engages in scientific research and explores the universe.

[Figure 31] Human Emotion: Loneliness
Carl Sagan, through the phrase "Pale Blue Dot," extended the human emotion of loneliness to encompass not just humanity as a whole, but all life in the universe.

[Figure 32] Human Emotion: Love
Physical affection between close relationships and altruistic actions for others are universal expressions of love shared by humanity.

Love is one of most deepest human emotion. It also plays a vital role in strengthening social bonds and forming relationships. The most basic forms of love arise from very intimate relationships, such as between lovers and family members. Transmission Hangeul express the meaning of love, universally shared by humanity, through depictions of physical closeness in intimate relationships, such as between lovers of different genders, or between parents and children.

However, love is not only an emotion that appears between lovers and family members. Altruistic actions, such as caring for others and dedicating oneself to the community, can also stem from love. Transmission Hangeul demonstrates to extraterrestrial intelligence that love is not merely an emotion that arises between close individuals, but an essential element that forms the foundation of human culture through altruistic behaviors.

[Figure 33] Human Life
The pictures show human life cycle: an elderly human facing death, a young person aging into old age, and the birth and growth of a new individual. these pictures of human life can form a cosmic empathy between extraterrestrial intelligence and humanity, as we share the experience of being solitary and finite beings living in the universe.

The only thing in common between extraterrestrial intelligence and human beings is that we are infinitely small and weak beings compared to the vast universe, living time like a moment while isolated on each other’s planet. So this project aims to create cosmic sympathy among all lonely beings living in this universe by messaging on life.

③ Third Section: Verbs and Grammar

The third section of Transmission Hangeul explains the meanings of Korean verbs, as well as the method of combining words to form a sentence, Korean grammar, to extraterrestrial intelligence. It also includes ways to combine simple sentences into more complex ones, as well as explanations of tenses and transformations of parts of speech.

[Figure 34] Third Section of Transmission Hangeul
Third section of Transmission Hangeul explains the meanings and verbs and Korean grammar to extraterrestrial intelligence.

[Figure 35] 'Subject-Verb-Object' Structure Sentence
This section explains to extraterrestrial intelligence how to form a simple 'subject-verb-object' structure sentence by combining words like 'person', 'night', 'sky', 'star', and 'look' to create the sentence 'People look at the stars in the night sky.'

[Figure 36] Method of Combining Simple Sentences to Form More Complex Sentences
The ability to combine sentences and infinitely expand them is one of the most important characteristics of human language, allowing humans to express complex thoughts and emotions and communicate in a variety of situations.

4) Towards the Interstellar Rosetta Stone

Transmission Hangeul can ultimately be seen as a kind of 'Rosetta Stone' and 'Hunminjeongeum' for extraterrestrial intelligence. While it does not cover everything about human language, it can at least provide extraterrestrial linguists with a sufficient understanding of the structure and characteristics of human language, particularly Korean.

Above all, Transmission Hangeul envisions a future where, instead of being led by a few countries or peoples, every nation and individual across the world creates and sends interstellar messages that reflects their own language, culture, and life. It also imagines a future where, across astronomical spacetime, extraterrestrial intelligence and humanity exchange languages, cultures, and life experiences.

[Figure 37] The Rosetta Stone that provided a crucial key to decoding ancient egyptian hieroglyphs (Credit: British Museum)
[Figure 38] 'Hunminjeongeum Eonhae' Explaining the Principles of Hangeul Creation (Wikipedia)

5) From Earth, beyond the distance between the stars

The ultimate message that Transmission Hangeul aims to convey to the universe through our human language is as follows. All the information contained in Transmission Hangeul is structured to enable extraterrestrial intelligence to understand this message.

[Table 2] The full text of the message Transmission Hangeul intends to convey to the universe.
Transmission Hangeul aims to connect all beings in the universe through love.

The message that Transmission Hangeul seeks to convey to extraterrestrial intelligence is that all of humanity's efforts to create a better future, explore the universe, and send messages to extraterrestrial intelligence are rooted in love. The meaning of love that Transmission Hangeul aims to send into the universe is courage and effort to understand one another, overcome difficulties together, and move toward a positive future.

Through the Voyager Golden Record, Carl Sagan sought to send a message of peace, harmony, imagination about the universe, and hope for the future to the world, despite the context of the Cold War era. Over 50 years since the Voyager Golden Record was sent into space, conflicts, war, and environmental destruction continue to divide our society and threaten our very existence on Earth. In this global situation, the message of Transmission Hangeul ultimately turns inward, towards ourselves. Above all, announcing our existence in this universe and attempting communication is the manifestation of love on a cosmic scale, something only a mature civilization can do. Imagine the fate of a being that isolates itself, not communicating with anyone due to vague fear. Ultimately, Transmission Hangeul is a message of love extended from humanity, a lonely and finite existence living on the 'pale blue dot', to other beings somewhere in the universe, who, like us, might be looking up at the night sky, wondering, "Are we the only ones in this universe?"

[Figure 39] All the information contained in Transmission Hangeul is structured to make this message comprehensible to extraterrestrial intelligence.

1) Transmission Date and Place

Transmission Hangeul was sent into space on November 16, 2024, from the Metaspace Observatory in Osong, South Korea. This date marks the 50th anniversary of the Arecibo Message, humanity's first interstellar message, transmitted on November 16, 1974.

[Figure 40] On November 16, 1974, the Arecibo Message, the first modern interstellar message from humanity, was transmitted into space from the Arecibo Observatory in Puerto Rico. (Credit: University of Central Florida)

2) Data Encoding and Transmission Method

Unlike previous interstellar messages, Transmission Hangeul was transmitted into space using a laser in the infrared spectrum with a wavelength of 1550 nm. The primary advantage of lasers over radio waves is their ability to transmit significantly more data in the same amount of time. Additionally, unlike radio waves that spread out as they travel further, lasers maintain a concentrated beam, making them far more energy-efficient. These advantages have made laser communication technology a promising candidate for next-generation space communication. Now, over 50 years since the Arecibo Message was sent via radio waves, Transmission Hangeul has used cutting-edge modern communication technology to reach out there.

[Figure 41] Telescope with laser transmitter used to transmit Transmission Hangeul
One of the features of TMDS is encoding 8-bit data into 10-bit data for transmission. This allows TMDS to transmit data quickly and reliably.

The data of Transmission Hangeul, composed of high-capacity digital images and audio, was encoded using a method called TMDS (Transition Minimized Differential Signaling). TMDS is widely recognized as the encoding technology used in HDMI, which connects monitors or projectors to computers. This encoding method offers several advantages: it enables the transmission of high-capacity data, such as high-resolution video, at very high speeds without compression, and it is highly resilient to errors that can occur during data transmission.

[Figure 42] Data Transmission Method of TMDS
One notable feature of TMDS is that it encodes 8-bit data into 10-bit data for transmission. (Credit: Wikipedia)

Technical Limitations of the First Transmission
While laser communication technology and TMDS are undoubtedly advanced methods of data transmission, there are still issues that need to be addressed for sending interstellar messages to outer space. First, the short wavelength of lasers makes them highly susceptible to interference from space dust, clouds, and planetary atmospheres. Since interstellar messages must travel beyond our solar system, sometimes spanning dozens or hundreds of light-years, the limitations of lasers become significant. Additionally, the high directivity of lasers, a major advantage, also presents a challenge as it requires precise targeting of a specific celestial object.

Furthermore, the greatest challenge lies in the fact that the infrared spectrum, where the transmitter operate, is one of the primary energy emission wavelengths of the Sun. To enable extraterrestrial intelligence to detect our signal, the signal would need to be emitted at a higher intensity than the Sun's infrared radiation.

The TMDS encoding method also has disadvantages that make it unsuitable for transmitting interstellar messages. It is highly complex and operates based on pre-agreed rules between its users. Therefore, it is unlikely that any entity without prior knowledge of TMDS encoding would be able to decode the data.

Unfortunately, the first transmission of Transmission Hangeul did not overcome all of these technical limitations. While laser communication and TMDS are cutting-edge technologies capable of transmitting large amounts of data quickly and reliably, additional considerations for contact with extraterrestrial civilizations are also needed.

[Figure 43] The medium used for data transmission is a 1550 nm infrared laser, which is not visible in the picture. The green laser visible in the picture is a guide laser pointing toward the target celestial object.
[Figure 44] The laser transmitter and telescope aimed at the star 'Vega,' approximately 25 Light-Years from Earth.

3) Target Celestial Objects

The Transmission Hangeul was transmitted towards six celestial objects that are observable from the transmission observatory, including exoplanets similar to the Earth and stars similar to the Sun. The list of selected celestial objects is as follows.

① The Stars Within 50 light-years That Have Earth-like Exoplanets

One of the key methods for searching for extraterrestrial life is finding Earth-like exoplanets. As far as we know, Earth is the only place in the universe where life exists, So environments similar to Earth are the first criteria for the possibility of life. However, it's not necessarily true that life can only exist in environments exactly like Earth's. Therefore, the term "habitable zone" is often referred to as the "conservative habitable zone" to account for the possibility of life existing in Earth-like environments. Transmission Hangeul has selected two stars that have exoplanets within these habitable zones as follows.

TRAPPIST-1
TRAPPIST-1 is a much smaller and dimmer red dwarf star located about 40 light-years away from Earth. Seven Earth-like planets orbit TRAPPIST-1, and at least three of them are situated within the habitable zone, where conditions may be suitable for life. Research on the potential presence of water, atmosphere, and life on these planets is expected to continue actively in the future.

[Figure 45] Comparison of the Solar System and the TRAPPIST-1 system
Among the seven planets orbiting TRAPPIST-1, TRAPPIST-1 e, f, and g are located within the habitable zone. (Credit: Wikipedia)

Wolf 1069
Wolf 1069 is a star located about 31 light-years away from Earth. It is similar in size to the Sun but is classified as a red dwarf. Additionally, the planet orbiting Wolf 1069, "Wolf 1069 b," is known to be similar in size to Earth and is located in the habitable zone.

[Figure 46] Comparison of the Wolf 1069, Proxima Centauri, and TRAPPIST-1 systems
Wolf 1069 b, an Earth-sized planet, is located within the habitable zone. (Credit: Max Planck Institute)

② 50th Anniversary of Arecibo Message

If it weren’t for previous space messages like the Arecibo Message and the Voyager Golden Record, as well as astronomers like Carl Sagan and Alexander Zaitsev, Transmission Hangeul would not have existed. Therefore, Transmission Hangeul, on the 50th anniversary of the Arecibo Message, has selected the following three celestial objects to honor the pioneers of METI.

Messier 13 (M13, Hercules Globular Cluster)
Messier 13 is a globular cluster located about 22,000 light-years from Earth, consisting of approximately 300,000 stars packed closely together. It was also the target location for the transmission of the Arecibo Message in 1974. In reality, both Arecibo Message and Transmission Hangeul are unlikely to reach M13 within a meaningful timeframe for humanity, as it is 22,000 light-years away. Can humanity live long until that time?

[Figure 47] Messier 13, consisting of approximately 300,000 stars
In 1974, Arecibo Message was transmitted towards Messier 13. Both Arecibo Message and Transmission Hangeul will reach M13 in 22,000 years. (Credit: Wikipedia)

Vega (α Lyrae)
Vega is a hot and bright blue-white main-sequence star located about 25 light-years from Earth in the Lyra constellation. It is one of the brightest stars in Earth's night sky and has appeared an important role in many cultures, both ancient and modern. Additionally, there is a dust disk around Vega, which is being studied as a potential condition for planet formation.

[Figure 48] Vega, a blue-white main-sequence star located about 25 light-years from Earth
Vega is the star of extraterrestrial intelligence featured in Carl Sagan's novel and its film adaptation, Contact. (Credit: Wikipedia)

Above all, Vega is familiar to us as the extraterrestrial star featured in Carl Sagan's novel and its film adaptation, Contact. In Contact, Sagan says, ‘For small creatures such as we, the vastness is bearable only through love.’ (In the film, this was adapted into the line: ‘The only thing we've found that makes the emptiness bearable is each other.’) Sagan also mentioned about humanity's cosmic loneliness through the expression ‘Pale Blue Dot.’ In this way, Sagan expanded the concepts of loneliness and love, not as feelings felt by individuals, but as emotions that connect all of humanity, and even all existence in the universe. The reason Transmission Hangeul speaks of love toward the universe is influenced by Sagan’s philosophy.

[Figure 49] The extraterrestrial intelligence in the movie Contact tells, ‘The only thing that makes the emptiness bearable is each other.' (Credit: IMDB)

16 Cygni
16 Cygnus is a triple star system located about 70 light-years from Earth, consisting of two sun-like stars (16 Cygni A, B) and one red dwarf (16 Cygni C). In 1999, the interstellar message Cosmic Call was transmitted in the direction of star A, and a Jupiter-sized gas giant orbiting star B was also discovered.

[Figure 50] 16 Cygni, a triple star system, consists of two Sun-like stars and a red dwarf
Cosmic Call was transmitted toward the triple star system 16 Cygni in 1999. (Credit: Wikipedia)

Alexander Zaitsev also participated in the transmission of Cosmic Call. He was more passionate than anyone else about sending messages into space, believing that humanity should be the first to reach out and make contact with extraterrestrial beings. If no one announces their existence, we will never know of each other's presence in this vast universe. This philosophy of Zaitsev became a foundation for Transmission Hangeul.

③ Stars and Exoplanets Titled with Hangeul Names

Baekdu (8 Ursae Minoris) and Halla (8 Ursae Minoris b)
"Baekdu" and "Halla" are stars and gas giant exoplanets, respectively, named with Hangeul, located about 530 light-years away from Earth. As Transmission Hangeul is a interstellar message centered around the Hangeul, these stars and planets have also been selected as target objects.

[Figure 51] Baekdu and Halla are a star and an exoplanet, respectively, named in Hangeul. (Credit: IAU NameExoWorlds)

Transmission Hangeul started from a human desire to create a message that could connect all beings in the universe. And finally, the first transmission to space has been achieved. However, this is just the first step. In order to truly become the Interstellar Rosetta Stone, Transmission Hangeul still has many areas to improve. There is still much to be done in refining the content and structure of the message, especially the way to explain human language to extraterrestrial intelligence, as well as addressing the technical aspects of transmitting the message, deciding which celestial body to target, and how to consider the potential recipients of the message. This project is not merely a personal passion but a task that requires the collaboration of various fields and people. It will take a long time for our message to reach extraterrestrial intelligence, and the journey will require patience and constant exploration.

Sending a message to space is not just about dreaming of contact with extraterrestrial civilizations, but it also prompts reflection on the essence and meaning of human existence. Sending our language, culture, and traces of life to space is, in a sense, engraving answers to who we are and what we cherish in the universe. One day, we hope that we connect with all the lonely beings across the stars. That will likely be humanity's first conversation with the universe and the beginning of a vast connection. Until that day comes, Transmission Hangeul will continue to take one step at a time on that long journey.

We hope that all of our lives will shine like starlight, and that, until we meet again, everyone is living well somewhere in the universe.

[Figure 52] A picture taken of Unhappy during the message transmission test
Unhappy hopes to connect the meaning of human life and existence with the universe. Someday, He dreams of a future where all beings in the universe are aware of one another and interconnected.

Jongkuk Won (언해피의 우주여행, @unhappy.cosmictraveler)
Jongkuk Won is a Korean artist known by the name Unhappy the Cosmic Traveler. As the representative of this project, he designed and developed the interstellar message Transmission Hangeul and was responsible for selecting the list of celestial objects to which the message would be sent.

Changhyun Baek (National Science Museum)
Dr. Changhyun Baek is an astronomer and a curator at the National Science Museum. Along with Jongkuk Won, he co-planned the project Transmission Hangeul and was responsible for the formation of the team and handling all administrative tasks required for the project.

Soonchang Park(METASPACE)
CEO Soonchang Park operates a company METASPACE, which specializes in astronomical observation equipment. He was responsible for the construction and operation of the observatories where the telescope and transmitter used in this project were installed.

Wonseok Kang (Spacebeam inc.)
Dr. Wonseok Kang is an astronomer and the COO of Spacebeam Inc., a company focused on research and development of space communication technologies using lasers. He was responsible for designing the technical aspects required for message transmission and also contributed to the selection of the celestial objects to target.

Taewoo Kim (Spacebeam inc.)
Researcher Taewoo Kim is an astronomer and technician at Spacebeam. He was responsible for calculating the positions of the target celestial objects and overseeing the operation of the telescope and transmitter used for sending the message.

Kanghwan Lee
Dr. Kanghwan Lee is an astronomer who contributed to selecting the target celestial objects for the transmission of Transmission Hangeul.

Sungju Kang (Unrealscience)
Dr. Sungju Kang is an astronomer and science communicator under the name 'Star.' He was in charge of the public talk session held on the day the message was transmitted.

Myunghyun Rhee
Dr. Myunghyun Rhee is an astronomer and science communicator. As a SETI expert in Korea, he lectured on SETI during the public talk session held on the same day as the message transmission.

Haeim Jeong (Korea Astronomy and Space Science Institute)
Team Leader Haeim Jeong manages the Public Relations Team at the Korea Astronomy and Space Science Institute. The image materials from the KASI, provided by her, are also included in Transmission Hangeul.

Youtube: Unhappy the Cosmic Traveler