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The "Fermi Paradox" about aliens suggests that if life appeared here on Earth, and the universe tends not to do things just once, then life must have appeared elsewhere too.
According to this theory, the current universe should be full of civilizations with technology advanced enough to conduct space travel. However, it's clear that humans haven't found them yet. And no one has found us either.
NASA's pair of Voyager spacecraft, carrying two golden records with messages from Earth's people, have traveled far beyond our solar system after nearly half a century of journeying, but no visitors have encountered them yet.
Writing in The Conversation, Professor Chris Impey, a renowned astronomer from the University of Arizona (USA), suggests that one of the main reasons humanity hasn't found extraterrestrial life is that we don't know their true appearance or form.
"But what if life could develop in different ways? How can you search for alien life when you don't know what alien life looks like?" Professor Impey points out.
These questions have troubled astrobiologists for many years. They have tried to establish general rules that govern the emergence of complex physical and biological systems both on Earth and beyond.
Since the first discovery of an exoplanet in 1995, more than 5,000 exoplanets, which are planets orbiting other stars, have been found. Many of these are small and rocky, similar to Earth, and lie within their stars' habitable zones.
Other studies predict there must be around 300 million potentially habitable locations in our Milky Way galaxy, including exoplanets, their moons, dwarf planets, and more.
The uncertainty for researchers begins with the definition of life itself. This fundamental question has sparked ongoing debates among scientists trying to understand what exactly constitutes life and how it might manifest differently in other parts of the universe. The challenge of defining life makes the search for extraterrestrial beings even more complex, as we might be looking for something that doesn't match our Earth-based understanding of living things.
NASA defines life as "a self-sustaining chemical reaction capable of Darwinian evolution." This means that living organisms have complex chemical systems that evolve by adapting to their environment.
Darwin's theory of evolution also states that an organism's survival depends on how well it can adapt to its surroundings.
Therefore, life forms born on another world would be very different from us. If they had evolved into humanoid forms, they would likely be quite different from us and much stranger than the aliens we see in movies. As a result, we should probably focus on analyzing and predicting how different environments from Earth might make life - if it exists - vary from what we know. Additionally, there is another famous argument that goes against Fermi's paradox: The "Great Filter" argument, which economist Robin Hanson detailed in 1996.
He suggests that very few civilizations in the universe reach a stage of space travel advanced enough to meet civilizations from other star systems. This could explain why we haven't encountered any alien civilizations yet, despite the vast number of potentially habitable planets in our galaxy. The great filter might be a challenge or obstacle that most civilizations fail to overcome, preventing them from becoming spacefaring societies capable of interstellar travel.
We humans are one such example. While NASA's spacecraft have managed to escape our solar system, they are still wandering at the edges of our "home," far from reaching even the nearest star system. If there is an advanced civilization out there - advanced enough to come across NASA's Voyager Golden Records, for instance - they would need to possess technology far superior to ours, possibly centuries ahead.
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Source: cafef.vn / 01-02-2025 / https://cafef.vn/vi-sao-chung-ta-chua-gap-duoc-nguoi-ngoai-hanh-tinh-188250201092416435.chn
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