Extraterrestrial intelligence

Extraterrestrial intelligence, often called ETI, refers to hypothetical life forms possessing the capacity for intelligence. This concept explores whether beings exist beyond Earth that can think, learn, and use technology. While the idea is a central theme in science fiction and popular culture, no extraterrestrial life of any kind has been detected. Scientists sometimes use the term "Extraterrestrial Technological Instantiations" to describe these beings. This specific name helps avoid ambiguous words like "civilization" or "species." Using more precise language allows researchers to discuss intelligence without making assumptions about how that life might look or behave in its own local context.

To understand how we might find such life, we must look for technosignatures. A technosignature is a detectable effect created by a technological civilization. These might be radio signals, large structures, or other physical traces of advanced technology. One way to search is through Active SETI, which is the attempt to send messages to intelligent life. This is often done via radio signals or physical objects, like the Pioneer plaque. Another branch is Communication with Extraterrestrial Intelligence, or CETI. CETI focuses on the science of semiotics, which is the study of signs and symbols. The goal is to compose and decipher messages that any technological civilization could theoretically understand.

There are different ways to describe the level of mind an extraterrestrial might have. Intelligence is often used to describe cognitive abilities similar to those of humans. Some researchers use the term sapience to describe even more complex reasoning. Another term, sophoncy, refers to being wise or wiser. It was first coined by Karen Anderson and published in 1966. It is important to distinguish these from sentience. Sentience refers to the capacity to feel or perceive, but it does not necessarily require high-level intelligence or sapience. Therefore, a creature could be sentient without being intelligent in the way humans are.

History shows that our understanding of our place in the universe has shifted over time. People have debated the existence of inhabited worlds since ancient history. The modern version of this debate emerged during the Copernican Revolution. This era demonstrated that Earth is a planet revolving around the Sun. This meant that other planets were not just points of light, but were other worlds. This shift made the question of inhabited planets a natural consequence of science. Since then, scientists have used various frameworks to estimate the probability of life. The Drake equation is a probabilistic tool used to estimate the number of active, communicative civilizations in the Milky Way galaxy.

Probability plays a massive role in these scientific discussions. The Copernican principle suggests that humans are not privileged observers of the universe. This means we are likely not in a unique or special position. Many prominent scientists, including Stephen Hawking, argued that the sheer scale of the universe makes it improbable that intelligent life would not emerge elsewhere. However, this leads to the Fermi paradox. This paradox highlights the contradiction between high mathematical estimates for life and the total lack of evidence or contact. We see a massive universe that should be full of life, yet we observe nothing.

Scientists use several methods to categorize and measure potential civilizations. The Kardashev scale is a speculative method for measuring a civilization's technological advancement. It bases its measurements on the amount of energy a civilization can utilize. We also look at specific estimates for our own galaxy. A 2020 study estimated there could be approximately 36 alien civilizations in the Milky Way today. If there were 36 communicating civilizations, the average distance between them would be about 17,000 light-years. Some scientists even suggest that contact might not be with biological beings, but with extraterrestrial artificial intelligence.

The potential impact of making contact could be massive and vary in many ways. The results would depend on the civilization's technology, their benevolence or malevolence, and how well we understand each other. Some theories suggest advanced civilizations might even move past biology to live inside computers. The method of contact, such as electromagnetic radiation or physical artifacts, would also change the experience. Some scholars compare the potential meeting of cultures to the Columbian Exchange on Earth. Historically, such meetings have often led to the destruction of the civilization receiving contact. Because we have had no contact yet, these ideas remain largely speculative.

Despite the challenges, the search continues through various signals and observations. The "Wow!" signal remains the best candidate for an extraterrestrial radio signal ever detected. However, because no similar signal was ever seen again, its cause remains difficult to prove. In June 2022, astronomers using China's FAST telescope reported possible artificial signals. However, experts like Dan Werthimer noted these might actually be radio pollution from Earthlings. Even with these uncertainties, the topic remains a major part of human culture. New Mexico even declared February 14th as Extraterrestrial Culture Day in 2003.