Aliens: Possibility and Science

 

Although no conclusive evidence of life has yet been found on any planet or moon beyond Earth, many people believe that life exists on other worlds and that such beings are more advanced than humans. In ancient folklore, the arrival on Earth of various creatures from other planets and stars was treated as an entirely natural occurrence. Those imaginative stories have been recast with scientific elements in modern science fiction. Many people, however, regard the aliens of science fiction as real. Although the literal meaning of the word “alien” is “a person from another country,” in common usage it has come to mean a living being from another planet.

In December 2017, the New York Post reported, on the basis of the views of 26,000 people from 24 countries, that half of the world’s population believed aliens existed. Many people in the United States and elsewhere occasionally claim that they have encountered aliens, or that aliens came and abducted them. Some are unwilling to accept that reports of human encounters with aliens may be entirely fabricated. This group includes several prominent individuals. John Mack, a professor of psychiatry at Harvard Medical School, believed that aliens existed and that they sometimes mistreated human beings. He wrote a substantial book on the subject, Abduction: Human Encounters with Aliens [1]. Every incident described in the book concerns contact, conflict, or other interactions between humans and aliens, and Mack regarded them as genuine events.

But do aliens actually exist? We still do not have sufficiently strong evidence to declare that, among the billions upon billions of planets orbiting the countless stars in this enormous universe, none contains any form of life. Humanity does not yet possess the technology to search the entire universe within a short period. For this reason, the possibility that aliens exist somewhere in the universe is now being examined scientifically.

Aliens: From Imagination to a Scientific Question

The idea of the “alien” is ancient, but the scientific question is modern. The fact that no life has yet been found anywhere in the universe beyond Earth can be framed as a scientific question: Is life a common phenomenon in the universe, or is Earth biologically exceptional?

Today, this curiosity is being investigated through astronomy, microbiology, atmospheric spectroscopy, electromagnetic-wave analysis, artificial intelligence, and space exploration. Rather than asking a single direct question about whether aliens exist, scientists now ask a cluster of more specific questions: Are there microorganisms beyond Earth? Is there complex life? Are there intelligent, technology-based civilizations? Have they ever visited Earth? Could alien life be so different from terrestrial life that we would fail to recognise it?

Modern science applies different criteria and parameters to these possibilities. The possibility of microbial life beyond Earth is scientifically accepted as plausible. The emergence of complex life comparable to humans is also possible, but remains uncertain. A technology-based civilization is conceivable, but has not been conclusively demonstrated. Claims that aliens have visited Earth are not supported by reliable scientific evidence.

As of May 2026, more than 6,200 confirmed exoplanets were listed in NASA’s Exoplanet Archive [2]. This has brought about a major change in scientific thinking. Even at the beginning of the twentieth century, we did not know whether planetary systems such as our Solar System were common or rare—that is, whether most stars had planets and moons. We now know that planetary systems are widespread. The question has therefore shifted from “Are there other planets?” to “How many of those planets are habitable, rich in life, or home to technological civilizations?” Conclusive answers to these questions would tell us whether aliens truly exist.

From UFO to UAP

The example most frequently presented as evidence for aliens is the UFO. In discussions of extraterrestrials, the phrase Unidentified Flying Object—UFO—is extremely popular. Many people claim to have seen UFOs. For decades, various groups have tried to establish that flying discs or “flying saucers” are alien spacecraft, although no genuine proof of such objects has been found. Many UFO incidents were recorded by United States investigative agencies. Public release of some of these records has recently generated renewed curiosity.

The modern UFO era is generally considered to have begun in 1947. That year, American pilot Kenneth Arnold claimed to have seen several fast-moving objects near Mount Rainier in Washington State. Newspapers popularised the expression “flying saucers” after the incident, and public curiosity grew rapidly. The alleged Roswell incident in New Mexico occurred in the same year. It involved the recovery of unusual debris near Roswell. The United States military initially announced that it had recovered a “flying disc,” but later described it as a weather balloon. Decades later, Roswell became a centrepiece of UFO conspiracy theories, although the official explanation connected the incident to a secret balloon project rather than an extraterrestrial spacecraft.

During the Cold War between the former Soviet Union and the United States, UFO reports became associated with American national security. The United States Air Force investigated sightings through Project Sign, Project Grudge, and later Project Blue Book. Project Blue Book operated from 1952 to 1969 and examined thousands of reports. Most incidents were explained as aircraft, balloons, ordinary astronomical or meteorological phenomena, or misidentification. A small number remained unexplained. However, “unexplained” does not mean “alien”; it usually means that the available evidence was insufficient for a definite identification.

From the 1970s, UFOs became deeply embedded in popular culture. Books, films, television programmes, and alleged stories of alien abduction made UFOs appear even more mysterious to the public. Scientists, meanwhile, generally maintained a cautious position because most UFO evidence depended on eyewitness testimony, unclear photographs, incomplete radar information, or personal claims. In the absence of scientific evidence, UFOs remained outside mainstream science.

In recent years, the subject has returned to government discussion under a new name. Scientists and government agencies increasingly use the term UAP, meaning Unidentified Anomalous Phenomena. This change is important. “UFO” implies only an object flying in the sky, whereas “UAP” is broader and carries less cultural bias. Unidentified does not mean extraterrestrial; it means that the event could not be identified on the basis of the available evidence. Many UAP cases can later be explained as aircraft, balloons, satellites, atmospheric effects, military technology, sensor errors, optical illusions, camera artefacts, or deliberate deception. A small number may remain unexplained, but unexplained does not mean alien.

In 2021, the United States Office of the Director of National Intelligence (ODNI) published a preliminary assessment of UAP. It was one of the first major modern government reports to treat UAP not merely as a fringe or imaginative subject, but as an issue of national security and flight safety. The report reviewed many UAP incidents recorded through military observation. The analysis found that the quality of the data was often poor, reporting methods were inconsistent, the information was incomplete, and the analysis itself was frequently inadequate.

The process associated with the National Defense Authorization Act (NDAA) began in 2021. On the basis of this legislation, the All-domain Anomaly Resolution Office (AARO) was established in 2022. Its founding directive stated that AARO would detect, identify, and determine the origins of unknown or anomalous objects near military installations, operational areas, training areas, special-use airspace, and other important locations. At the end of 2023, then United States President Joe Biden signed the NDAA. Under this legislation, the U.S. National Archives created an official UAP Records Collection. NASA views UAP research as a scientific opportunity, while also emphasising the need for better data, standardised reporting, and rigorous analysis.

The current United States President, Donald Trump, directed that files relating to UAP incidents be made publicly available under a system described as the Presidential Unsealing and Reporting System for UAP Encounters, or PURSUE. A large group of UAP files was released under PURSUE on 8 May 2026, followed by another substantial release on 22 May. AARO had previously published detailed information on UAP in a 2024 report. The report stated that none of the UAP files contained evidence of the existence of aliens [3].

NASA has likewise not concluded that UAP are extraterrestrial. Instead, it has stated that better data, standardised reporting, improved sensors, open scientific methods, and artificial intelligence may help classify future events [4].

Aliens have still not been found. We may now consider how likely it is that they could be found.

The Possibility that Aliens Exist

The probability of alien life depends on the kind of life we mean. Most people imagine an alien as some more advanced version of a human being. Scientifically, however, life could take many forms, from simple microorganisms to complex technology-dependent beings. Let us consider the likelihood of each.

(1) Microbial life: Microbial life is the most probable form. Life on Earth may have appeared very early in the planet’s history, perhaps within its first billion years. Microorganisms are metabolically extremely versatile. They can survive in highly inhospitable environments, including hot springs, deep-sea hydrothermal vents, acidic lakes, Antarctic rocks, radioactive settings, and hostile environments deep underground. This indicates that once life begins, it may be capable of adapting even to extreme conditions.

Several places in the Solar System are being considered as possible habitats for microbial life: the soil of Mars; the ocean of Jupiter’s moon Europa; the ocean of Saturn’s ice-covered moon Enceladus; the hydrocarbon-rich environment of Titan, Saturn’s largest moon; and possibly other planets or moons thought to contain reservoirs of subsurface liquid water. Beyond the Solar System, exoplanets in habitable zones may possess liquid water, atmospheres, and chemical energy sources suitable for life. Microbial life may therefore be possible there as well.

There is still no universally accepted definition of life. We can, however, search for biosignatures—possible indicators of life. Atmospheric chemical disequilibrium, for example, may be a sign of life [5]. Oxygen or methane alone would not constitute definite evidence. Yet combinations such as oxygen together with methane, or seasonal atmospheric changes, could provide possible indications of life.

(2) Complex life: Complex life beyond Earth is more uncertain. Microbial life existed on Earth for billions of years before complex organisms gradually developed through evolution. Complex life may require long-term climatic stability, plate tectonics, magnetic protection, suitable oceanic conditions, oxygen, a large moon, a stable orbit, and protection from excessive radiation. We do not yet know which of these are essential and which are merely special features of Earth. We are still searching the universe for an Earth-like habitable planet capable of supporting complex life, and no such planet has yet been found.

(3) Intelligent, technology-based life: The aliens familiar to us from science fiction are far more advanced than humans. In reality, however, technology-based civilizations beyond Earth are even more uncertain. Natural intelligence has evolved in many forms on Earth—in primates, dolphins, corvids, octopuses, and numerous other animals. Yet intelligence itself is not technology. Modern technology—radio astronomy, spacecraft, mathematics, and industrial technology—has emerged only once. A technological civilization is therefore not an automatic result of evolution, but an outcome of the sustained collective exercise of intelligence.

A reasonable scientific position on the existence of aliens is therefore that microbial life may exist beyond Earth. Complex life may be less common, but is not impossible. Technological civilizations may be rare. If such a civilization exists quietly on a distant planet, detecting it would be extremely difficult. To understand mathematically just how difficult, we need to consider the Drake equation.

The Drake Equation

In 1961, the American astronomer Frank Drake introduced a landmark equation for estimating the possibility of finding life elsewhere in the universe. It became known as the Drake equation. Drake proposed that the mere existence of life somewhere in the vast universe would not guarantee that we could detect it. To be detectable, an extraterrestrial society would need to be at least as technologically developed as our own, or more advanced. We therefore need to consider where else in the universe a civilization like ours might arise.

The Drake equation is written as: N = R* × fₚ × nₑ × fₗ × fᵢ × f꜀ × L. In other words, the number of potentially communicative civilizations (N) is calculated from the product of the rate of star formation (R*), the fraction of those stars with planets (fₚ), the number of planets suitable for life (nₑ), the fraction on which life arises (fₗ), the fraction of life-bearing planets on which intelligent life develops (fᵢ), the fraction that develops detectable technology or communication (f꜀), and the length of time such a civilization survives in a detectable form (L).

Some of these factors are now better known than they were in Drake’s time. We have learned much more about the nature and prevalence of planets. Exoplanet surveys have shown that planetary systems are not rare. The biological and sociological factors—fₗ, fᵢ, f꜀, and L—nevertheless remain highly uncertain. Even small changes in these values can produce completely different results.

Simple calculations using the equation have suggested that the universe may contain more than ten thousand planets with civilizations capable of revealing the presence of life. The difficulty is that every component of the equation depends on assumptions. If life begins easily and technological civilizations survive for millions of years, the galaxy may contain many detectable civilizations. But if life is rare, intelligence is extremely rare, or technological societies quickly destroy themselves, we may be effectively alone within our detectable range.

The importance of the Drake equation lies not in precise prediction, but in identifying the unknowns. Better methods are still needed in exoplanet statistics, research on the origin of life, biosignature detection, the search for technosignatures, and the study of long-term planetary habitability before we can successfully detect aliens.

The old question therefore remains new: If aliens exist, where are they? Why is there no evidence of them outside fiction? The Nobel Prize-winning physicist Enrico Fermi asked this question in 1950. His remark about extraterrestrial life—“Where is everybody?”—gradually became a paradox, now known as the Fermi paradox.

Enrico Fermi

The Fermi Paradox: Where Is Everybody?

The Fermi paradox is the tension between two ideas. First, the galaxy is ancient and enormous, containing hundreds of billions of stars. Yet we have found no conclusive evidence of an extraterrestrial civilization. If advanced civilizations are common and capable of interstellar travel, why have they not spread throughout the galaxy? Even travelling far below the speed of light, a civilization could theoretically explore the galaxy through step-by-step colonisation within a few million to a few hundred million years—a period short compared with the age of the Milky Way. Why, then, have they not found us, or we them?

Many possible answers can be considered. (1) Life beyond Earth may be rare, because the origin of life may be extraordinarily difficult. (2) Microorganisms may exist, but intelligent complex life may be rare; alien organisms and intelligence may also be radically different from ours. (3) Technological civilizations may be short-lived. War, environmental collapse, failure of artificial intelligence, biotechnology, climatic instability, or resource shortages may cause them to destroy themselves. Their civilization may have vanished long before ours arose. (4) Their civilization may be silent. They may intentionally avoid broadcasting and may have designed systems to prevent detection. (5) Humanity may have appeared too early; civilizations like ours may become more common and visible in the future. (6) Interstellar travel may simply be extremely difficult. Physics, energy demands, radiation, biological fragility, and the relativity of time may obstruct real galactic expansion. (7) They may not be interested in us. Advanced civilizations need not behave like human explorers or imperial powers. (8) Another possibility is that they are already here but we cannot recognise them. This idea is popular in science fiction and UFO culture, but there is no verifiable scientific evidence for it.

The Fermi paradox is powerful because it challenges excessively optimistic assumptions. Even a galaxy rich in life may remain silent if intelligent life is rare, the technological phase is brief, or civilizations do not wish to communicate. In those circumstances, aliens might exist while remaining impossible for us to find.

Another theory has become popular from the idea of silent civilizations: the Dark Forest theory.

The Dark Forest Theory

The Chinese writer Liu Cixin’s science-fiction novel The Dark Forest was published in Chinese in 2008. After Joel Martinsen’s English translation appeared in 2015, the Dark Forest theory brought a new dimension to popular thinking about aliens. According to this idea, civilizations remain silent because the universe is dangerous. Every civilization is like a hunter in a dark forest. Revealing one’s position may cause another civilization to take destructive action out of fear of a future threat. Because intentions are difficult to verify across interstellar distances, the safest strategy is either to remain silent or to strike first. Scientifically, the Dark Forest theory is speculative. It assumes that civilizations are expansionist, fearful, capable of long-range attack, and unable to establish mutual trust. These assumptions may not be true. An advanced civilization may have no interest in harming a less developed society. Interstellar attack may be impractical, or detectable civilizations may follow ethical principles.

Nevertheless, the Dark Forest theory is important because it raises a serious question: Should humanity intentionally send messages to extraterrestrial civilizations? Since the Voyager era, we have begun sending messages from Earth towards unknown civilizations in the universe. Some scientists believe deliberate transmission should be a matter for international discussion, because it concerns not merely one observatory or one nation, but all humanity. If aliens exist, they may not appreciate our loudness.

This idea encourages us to think again about what alien life might be like.

Possible Forms of Alien Life

Popular culture portrays aliens as humanoid beings with large heads, large eyes, arms, and legs. A consideration of real biology, however, reveals a far broader range of possibilities. Let us consider several possible forms of alien life.

(1) Carbon-and-water-based life: In the light of current science, the most likely form of life would be carbon-based and dependent on liquid water. Carbon can form complex molecules, and water is an excellent solvent. From Earth’s example, we know that carbon-water chemistry can produce life. This does not mean aliens would look human. Even on Earth, life appears as bacteria, fungi, plants, insects, molluscs, fish, mammals, and innumerable other forms. Alien life might be microbial, oceanic, floating in an atmosphere, living underground, or photosynthetic and adapted to the light of a different star.

(2) Silicon-based life: Silicon is often discussed because it lies directly below carbon in the periodic table. In water, however, silicon chemistry is less flexible and tends to form stable mineral structures rather than the wide variety of organic molecules formed by carbon. Could alien life therefore resemble silicon-based semiconductors? Silicon life is not theoretically impossible, but carbon-based life remains more probable.

(3) Ammonia-, methane-, or other solvent-based life: In extremely cold worlds, liquid ammonia, methane, or ethane might act as a solvent. Titan, a moon of Saturn, has lakes of methane and ethane. If life exists there, it could be chemically very different from terrestrial life. At low temperatures, its metabolism might be slow, and it might use biochemistry that does not depend on water.

(4) Mechanical life: If aliens are much more technologically advanced than humans, their technological civilizations may no longer remain biological. They might create artificial intelligence, upload the information contained in their brains, send robotic probes, or transform themselves into machine-based life. In that case, alien “life” might not need oxygen, food, sleep, or an Earth-like planet. It might prefer the cold outer regions of solar systems, asteroid belts, or locations rich in energy.

(5) Plasma or magnetic-field life: More speculative ideas include plasma-based life, life in stellar atmospheres, life in interstellar clouds, or self-organising electromagnetic systems. These ideas lie beyond established biology, but they remind us that terrestrial life may not represent the full range of possible complexity.

Whatever form alien life takes, could it come to Earth?

Would Aliens Need Spacecraft to Reach Earth?

If by “aliens” we mean biological beings physically travelling from another star, then some form of spacecraft or protected transport would probably be required for them to reach Earth. Interstellar space is extremely hostile: vacuum, radiation, micrometeoroids, extreme cold, and immense distances. Alpha Centauri, the nearest star system to the Solar System, is about 4.37 light-years away. At the speed of present human spacecraft, reaching it would take more than ten thousand years. Aliens would therefore require vehicles with far greater speed and energy than ours. Yet “coming to Earth” need not mean that a crewed spacecraft lands in a field.

What alternative methods might aliens use to reach Earth? Several possibilities can be considered.

(1) Robotic probes: They might send mechanical robots that are more durable than biological bodies. (2) Von Neumann probes: The Hungarian-American mathematical physicist John von Neumann developed the mathematical theory of systems that could reproduce themselves using energy and locally available material. On this basis, self-replicating probes might arrive in the form of machines or energy systems and use local resources to make copies of themselves. The idea is entirely theoretical and potentially very risky. (3) Microbial transfer: Microorganisms might travel inside rocks ejected by cosmic impacts. This would not be the travel of a civilization, but a natural biological transfer. Aliens might therefore arrive on Earth accidentally rather than by intention. (4) Signals rather than bodies: Instead of a civilization coming physically, its signals might arrive—as radio transmissions, laser pulses, mathematical messages, or encoded artificial intelligence. (5) Artificial objects: Alien technology might come not as living visitors but as probes, satellites, or deliberately engineered asteroids. (6) Remote detection rather than travel: We might detect aliens through atmospheric biosignatures or technosignatures without any physical contact. In other words, aliens could establish their presence through technology without coming here. With sufficient technological capability, quantum teleportation might also be possible for them.

Aliens therefore would not necessarily need Hollywood-style spacecraft. Nevertheless, if complex biological beings truly travelled to Earth from another star, they would require technology far beyond present human capabilities, including systems for extremely long-duration travel.

Even if we assume that aliens have come to Earth, or simply live somewhere else in the universe, how would we detect them?

How Could We Detect Alien Life?

The method of detecting aliens would depend on the form of life involved. Several principal methods can be considered.

(1) Biosignatures within the Solar System: Direct exploration is possible within our Solar System. Missions to Mars search for evidence of past habitability, organic molecules, and possible ancient biosignatures. Samples returned by future missions may be extremely important. Europa and Enceladus are particularly attractive because both may contain subsurface oceans. Enceladus regularly ejects material into space. A spacecraft could collect this material and indirectly sample the contents of its ocean, then examine it for possible signs of microorganisms.

(2) Exoplanet biosignatures: We cannot collect samples from distant planets, so instead we analyse the light arriving from them. When a planet passes in front of its star, some starlight travels through the planet’s atmosphere. Spectral analysis can reveal the composition and environmental conditions of that atmosphere. Oxygen, ozone, methane, carbon dioxide, water vapour, and nitrous oxide may all be important. The James Webb Space Telescope and future observatories may help determine atmospheric composition. Biosignatures must be interpreted cautiously. Oxygen can be produced by non-biological processes, and methane may arise from geological sources. A genuine detection would require the exclusion of abiotic processes and consideration of the full planetary context.

(3) Technosignatures: The detectable indicator of an advanced civilization is its technological signature. By identifying signs of highly advanced technology, we might infer that such a civilization exists. NASA now treats technosignatures as an important part of the broader framework for searching for life [6]. Possible technosignatures include radio signals, laser pulses, industrial atmospheric gases, artificial illumination, waste heat, enormous orbital structures, artificial satellites, and unusual patterns in starlight. The Search for Extraterrestrial Intelligence, or SETI, has traditionally emphasised narrowband radio signals because natural astronomical sources generally do not produce extremely narrow, artificial-looking radio transmissions. Modern SETI, however, is broader and includes optical, infrared, atmospheric, and data-mining approaches.

(4) Searching for anomalies: Another possibility is to look for signs of aliens within our own Solar System. If the normal operation of the Solar System displayed unexplained anomalous behaviour, one might be tempted to attribute it to aliens. This field is scientifically difficult because the search space is immense and the risk of falsely identifying aliens is high.

The natural question then arises: Why have we not detected aliens? Where are the limitations of present science?

Stephen Hawking

Limitations of Current Science in Assessing Claims of Aliens on Earth

Stephen Hawking once joked that aliens might already be on Earth but that we fail to recognise them. Such remarks are possible in popular discussion, but scientific claims that aliens are present on Earth are weak because extraordinary claims require extraordinary evidence. Current science faces several limitations in detecting aliens. (1) Lack of physical evidence: No publicly verifiable alien biological specimen, device, component, fragment of a spacecraft, or genetic material has been found. The objects that have been recovered have not been shown to be extraterrestrial. (2) Poor-quality observations: Many UFO/UAP images are blurred, distant, uncontrolled, and unsupported by adequate data. (3) Sensor confusion: Infrared cameras, radar, optical systems, and human vision can all produce misleading interpretations. (4) Lack of reproducibility: Scientific evidence becomes stronger when an event observed by one person can be observed again by independent investigators who can collect comparable data. UAP events are generally fleeting. (5) Human error and illusion: When people rely only on their senses to collect information, mistakes are common. Humans may misjudge distance, speed, size, and altitude, particularly at night, in low light, or under psychological stress. (6) Secret military technology: Some incidents may involve military aircraft, drones, or sensor systems that cannot be publicly explained. Many such events have been recorded as UAP. (7) Absence of biological traces: If aliens were biological and present on Earth, one would expect some ecological, biochemical, or genetic evidence. (8) Limitations of interstellar travel: In the light of known physics, the demands of energy, time, radiation protection, and technological sophistication make frequent biological travel unlikely.

These limitations do not prove that alien visitation is impossible. They show only that the present evidence does not meet scientific standards. Scientists have therefore been conducting several projects for many years to search for life beyond Earth. A few of these are considered briefly below.

Projects Searching for Life in the Universe

(1) SETI: The Search for Extraterrestrial Intelligence, or SETI, is not a single telescope, but a broad scientific effort to detect evidence of technology-based life. The SETI Institute was established in California in 1984. It describes SETI as the search for evidence of intelligent life in other star systems [7]. SETI investigations generally analyse radio frequencies, optical flashes, or other unusual signals that might indicate technology.

(2) Breakthrough Listen: This is one of the largest modern SETI programmes. It aims to observe one million nearby stars, the Galactic Centre, the Galactic Plane, and nearby galaxies [8]. It has made large datasets available for analysis by scientists and members of the public.

(3) Berkeley SETI and machine learning: Researchers at the Berkeley SETI programme have used machine learning to analyse large radio datasets. A deep-learning search for technosignatures among 820 nearby stars found several interesting signals, although these were later interpreted as probably resulting from human-made interference. The work nevertheless showed that artificial intelligence can identify unusual signals that conventional methods may overlook [9].

(4) Astrobiology and exoplanet projects: NASA’s astrobiology programme investigates the origin and evolution of life beyond Earth and its distribution throughout the universe. Exoplanet programmes assist in discovering and characterising planets outside the Solar System. With more than 6,200 confirmed exoplanets currently catalogued, the search for life is becoming increasingly data-rich [2].

(5) Missions to Mars, Europa, and Enceladus: Scientists are working on a range of projects to investigate habitability and biosignatures on planets and moons in the Solar System. Mars rovers are searching for evidence of life on Mars. Europa Clipper is investigating Jupiter’s ice-covered moon Europa. Astrobiological investigation of Saturn’s moon Enceladus has also begun.

As artificial intelligence continues to develop, new possibilities are emerging in the study of aliens.

Artificial Intelligence in the Search for Aliens

Artificial intelligence may transform research on alien life, but without data, AI cannot find aliens. Its principal roles in alien research may include: (1) Signal classification—distinguishing human-generated radio waves from possible alien technosignatures. (2) Anomaly detection—machine learning can identify unusual patterns among billions of signals received by space telescopes, including patterns that humans might miss using conventional methods. (3) Exoplanet discovery—AI can play a specialised role in detecting planets outside the Solar System. (4) Atmospheric modelling—AI can construct models of planetary atmospheres and help compare exoplanet spectra with chemical models. (5) Autonomous future missions—AI may play a major role in operating robotic missions to other worlds. Exploring spacecraft may use AI to select sampling sites and identify unusual chemistry. (6) UAP/UFO data analysis—AI can help classify unusual activity by analysing reports and sensor data. (7) Multidisciplinary integration—AI can combine methods from astronomy, chemistry, geology, atmospheric science, and biology to assess whether a signal is biological, technological, or natural.

Scientific investigation of aliens requires both imagination and discipline. Imagination is necessary because alien life may not resemble life on Earth, human intelligence, or the beings of science fiction. Discipline is necessary because the history of UFO claims shows how easily uncertainty can turn into belief. UAP are real as observations, but without reliable, reproducible, and independently verifiable information, they are not evidence of aliens. Given the abundance of planets and the adaptability of life on Earth, the possibility of microbial life beyond Earth is scientifically reasonable. The likelihood of intelligent technological civilizations, however, remains unknown. The Drake equation organises our ignorance. The Fermi paradox challenges our optimism. The Dark Forest theory warns that cosmic sociology may be much more complex than a simple story of communication. Aliens might be microorganisms, ocean-dwelling organisms, machine intelligence, atmospheric beings, or forms of chemical life unknown on Earth. They may never come to our planet. We may detect them through light, chemistry, radio signals, or subtle statistical anomalies. The future of alien science will depend on better telescopes, better spacecraft, better biology, better artificial intelligence, and better scientific scepticism.

Do aliens exist? The most scientific answer today is that the universe is so vast and rich that life beyond Earth is a serious scientific possibility, but we still do not possess enough evidence to reach a final conclusion.

References

1. Mack, J. Abduction: Human Encounters with Aliens. New York: Scribner, 1994.

2. NASA Exoplanet Archive. Exoplanet Counts. Caltech/IPAC, May 2026.

3. All-domain Anomaly Resolution Office. Report on the Historical Record of U.S. Government Involvement with Unidentified Anomalous Phenomena, Volume 1. U.S. Department of Defense, 2024.

4. NASA Independent Study Team. Unidentified Anomalous Phenomena Independent Study Team Report. NASA, 2023.

5. NASA Exoplanet Exploration Program. “Can We Find Life?” NASA Science.

6. NASA Astrobiology. “Technosignatures and the Search for Extraterrestrial Intelligence.” NASA, 2018.

7. SETI Institute. “A Primer on SETI at the SETI Institute.”

8. Breakthrough Initiatives. “Breakthrough Listen.”

9. Ma, P. X., et al. “A Deep-learning Search for Technosignatures of 820 Nearby Stars.” Nature Astronomy, 2023.