New study suggests intelligent life is rare for the Milky Way – and if another civilization exists, it is much older than us
At the EPSC–DPS 2025 joint conference held in Helsinki, findings were presented that shake up the search for intelligent life. According to research by Dr. Manuel Scherf and Prof. Helmut Lammer from the Austrian Academy of Sciences in Graz, the nearest technological civilization in the Milky Way may be located no less than 33 light-years away.
The conclusion is dramatic: if there is another intelligent species in the galaxy, it must survive for at least hundreds of thousands of years – and sometimes millions – for us to live side by side.
Sharf explains that the conditions necessary for an advanced civilization are extremely rare: it is not enough for a planet to be in the habitable zone, but it must have a balanced atmosphere, active plate tectonics, and ultimately the ability to produce fire and metals.
A delicate balance of carbon dioxide
The research focused specifically on the role of carbon dioxide in atmospheres. This gas is essential for preserving heat and preventing the atmosphere from escaping into space, but at too high levels it leads to an irreversible greenhouse effect. Plate tectonics is the mechanism that regulates the amount of carbon dioxide, as part of the carbon-silicate cycle: rocks absorb carbon from the atmosphere, break down, and are replenished through volcanic activity.
“At some point, the carbon gets locked in the rocks and doesn’t return to the atmosphere, causing photosynthesis to stop,” says Scharf. “On Earth, this is expected to happen in 200 million to about a billion years.”
The model the researchers tested suggests that a planet with 10% carbon dioxide could sustain a biosphere for 4.2 billion years – much longer than Earth, where the current concentration of CO2 is only 0.042%. In contrast, an atmosphere with 1% CO2 A biosphere can only last up to 3.1 billion years.
Oxygen and fire – a necessary condition for technology
In addition to carbon dioxide, the concentration of oxygen is important. To enable the existence of complex animals, as well as the use of fire, at least 18% free oxygen is required in the atmosphere. If the level is lower than this, free combustion will not be possible – and neither will the production of metals or the development of technology.
In other words, it is possible that the galaxy has biospheres rich in single-celled or even multi-celled organisms, but only a very small minority can cross the threshold of “technology” – a stage at which the development of an advanced culture is possible.
How long does it take for a civilization to develop?
The researchers examined the length of time it took for humanity to reach a technological level – approximately 4.5 billion years since the formation of the Earth. From there, they concluded that for other civilizations to exist alongside us, they would have to survive for an exceptionally long time.
In a scenario with 10% carbon dioxide, a civilization must exist for at least 280 years for there to be a likelihood of two of its kind in the galaxy. And if you want ten civilizations active simultaneously, each one must last over 10 million years.
Fermi Paradox and Drake Equation
The conclusions fit into a broader debate in science – the Fermi Paradox. On the one hand, the Milky Way is vast and contains hundreds of billions of stars, many of which are sun-like; on the other hand, evidence for the existence of intelligent alien life is nonexistent.
The new model reinforces the pessimistic estimate of the Drake Equation, which is designed to estimate the number of intelligent civilizations in the galaxy. The long chain of conditions – from the emergence of life, through the emergence of photosynthesis and multicellular life, to the ability to develop technology – greatly reduces the chance of the appearance of “neighbors.”
Where they may be found?
According to calculations, the nearest civilization may be located 33 light-years from Earth – a huge distance, which means that our possible neighbors are actually on the other side of the Milky Way.
By comparison, the solar system is 27 light-years from the center of the galaxy. This means that any direct contact with another intelligent species is almost impossible within the framework of human life as we know it.
Implications for S And about humanity
Sharaf and Emer agree that the situation does not negate the importance of the searches.
“Even if the chance is small, the only way to know is to look,” says Scharf. “If we don’t find anything, it will strengthen our model. And if we do, it will be one of the greatest breakthroughs in scientific history.”
This study places the search for extraterrestrial intelligence in a broader context: Even if we look toward nearby stars, most of them will not have the necessary conditions. Future missions by the James Webb Space Telescope, the future Nancy Grace Roman Telescope, and other projects searching for exoplanetary atmospheres will try to find those rare signs of delicate balance.
The philosophical meaning
Beyond the scientific aspect, the findings also touch on existential questions. If intelligent life is indeed rare, humanity may be one of the few civilizations in the universe – a fact that gives enormous weight to our responsibility to preserve our world. On the other hand, if another species is nevertheless found, encountering it would be evidence that we are not alone – a turning point in the history of human thought.
The research presented in Helsinki does not pronounce a death sentence on SETI, but rather poses a challenge: to understand how rare the conditions that led to the development of humanity are. Even if the nearest civilization is tens of thousands of light years away, the very search gives us new insights into Earth, our place in the universe, and the fragility of the conditions that made our existence possible.
Source: "How common are biological ETIs in the Galaxy?” by: Manuel Scherf and Helmut Lammer,
Published on July 8, 2025 EPSC–DPS2025.
More of the topic in Hayadan:
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There are trillions of planets in the universe, so the probability of many intelligent life is certain, but the chance of contacting them using existing technologies is very low. If Western civilization survives, then one day we will have the technology to contact intelligent life in the universe, or they will contact us. And even if not, then human expansion in the universe and natural and unnatural genetic changes will create various intelligent species, including synthetic ones (artificial intelligence).
There will be life even if the amount of carbon dioxide increases, but it will not be humans.
The key question is: Is there a correlation between the percentage of carbon dioxide and oxygen in the biosphere and intelligent life? As far as I know, there is no answer to this question, even on this planet.