Considering that our solar system is quite young compared to the rest of the universe, which is 14 billion years old, and that interstellar travel would be quite easy to achieve if other civilizations existed over such a large period of time, it is thought that Earth should have already been visited by aliens. After all, if there were other living things like human beings in the 14 billion years of universe history, we should have found traces of them by now, but so far we have not found any traces of living things other than us in the universe.
What is the Fermi Paradox?
The Fermi Paradox is named after Nobel Prize-winning physicist Enrico Fermi, who supposedly made the above points during a casual lunch conversation in 1950. The Fermi Paradox focuses on the question of why, despite the enormous number and age of stars and planets in the universe, we have not yet made any contact with extraterrestrial intelligent life forms.
The universe is incredibly vast and old. Data collected by various telescopes indicate that the observable universe is approximately 92 billion light-years across (and growing faster and faster). Separate measurements indicate it is approximately 13.82 billion years old. In other words, we can say that alien civilizations had plenty of time to emerge and spread. When Fermi made that famous statement, the only planet scientists knew of was in our solar system. But in 1992, astronomers detected worlds orbiting an extremely dense stellar corpse known as a pulsar. And a few years later, it was confirmed as the first exoplanet around a sun-like star. There are currently more than 5,000 confirmed exoplanets known, and new exoplanets are discovered every year. The sheer number of alien worlds suggests that life may be abundant throughout the universe. In fact, recent measurements show that there may be water on some of these exoplanets. For example, one of the last found exoplanets, Gliese 12b, is capable of hosting humanoid life, and another is LHS 1140b, which is thought to contain water.
Understanding the size of the universe is one of the keys to understanding the Fermi Paradox. It is estimated that there are approximately 100-400 billion stars in the Milky Way galaxy, and each star may have a variety of planets orbiting it. Moreover, the number of galaxies in the universe is more than 100 billion. These huge numbers combined add up to billions of planets that could potentially harbor life.
The Drake Equation Tells Us How Many Civilizations There Are in Our Galaxy
Formulated by Frank Drake in 1961, the Drake Equation attempts to estimate the number of communicating civilizations in our galaxy. The equation takes into account various factors, such as the number of stars forming per year, the fraction of those stars that have planets around them, the fraction of those planets that could harbor life, the likelihood of advanced life forms emerging, and the time it takes for these civilizations to have the ability to communicate. The Drake Equation is not a definitive result because it depends on so many variables, but it suggests that there may be hundreds or even thousands of advanced civilizations even in our galaxy. According to the Drake equation, there are an estimated 20,000 intelligent civilizations in our galaxy.
So Why Didn’t We Encounter Aliens?
The following theories have the potential to explain why we do not encounter other civilizations, according to the Fermi Paradox.
Grand Filter Theory
One possible explanation for the Fermi Paradox is the Grand Filter Theory. According to this theory, there are difficult stages in the process from the emergence of life to advanced technological civilizations, and one or more of these stages are so difficult that most civilizations cannot pass these stages. The Great Filter could be any of several stages, including the formation of life, the development of multicellular organisms, the emergence of intelligent life, and technological development. If the Great Filter is somewhere in the future, it means that human civilization may not pass this stage either.
Time and Distance Factors
The age of the universe is approximately 14 billion years, and it is possible for advanced civilizations to emerge and disappear during this time period. These cycles, which last billions of years in the universe, make it difficult for civilizations existing in different time periods to communicate with each other. Additionally, interstellar distances are incredibly large. Even the nearest star system, Alpha Centauri, is about 4.37 light-years away. These distances pose a serious obstacle to civilizations that are not capable of traveling close to the speed of light.
Silent Civilizations Hypothesis
Some theories suggest that advanced civilizations deliberately kept silent and concealed themselves. According to this hypothesis, advanced civilizations hide their existence to protect themselves from other potential threats. Additionally, these civilizations hiding themselves may be a strategy to avoid possible conflicts with other advanced civilizations.
Technological Challenges and Resource Constraints
Space travel and communications present major technological challenges and resource requirements. Even an advanced civilization may struggle to develop the technology and resources necessary for interstellar travel or communication. These difficulties may be one of the reasons why extraterrestrial civilizations cannot reach us.
Rare Earth Hypothesis
The Rare Earth Hypothesis holds that conditions that support the emergence and evolution of life are extremely rare. This hypothesis suggests that many special conditions must come together for life to emerge on Earth, and that these conditions may be very rare on other planets. Therefore, the existence of extraterrestrial life may be a very rare occurrence.
Universal Catastrophic Events
Universal catastrophic events can cause the destruction of civilizations. Events such as supernova explosions, gamma-ray bursts, or large meteor impacts can prevent the emergence of advanced civilizations or destroy existing ones. Such events can seriously affect the number and lifespan of civilizations in the universe.
Artificial Intelligence Obstacle
Another explanation has been popularized by scientists recently. This means that extremely developed artificial intelligence will behave in ways that will bring about the end of every civilization, and thus different civilizations cannot reach the outside.
Thus, the Fermi Paradox attempts to explain why, despite the assumption that we are not alone in the universe, we have not yet made contact with extraterrestrial intelligent life. This paradox can be explained by various factors, such as the enormous number of stars and planets in the universe, technological difficulties, the Great Filter Theory, time and distance factors, the silent civilizations hypothesis, the rare earth hypothesis, and universal catastrophic events. However, a definitive answer has not yet been found, and this is an important issue that continues to be researched and debated in the scientific world. However, many scientists continue to work on this subject, and every information obtained offers us many clues about understanding our universe. Thus, the aerospace sector will continue to examine this question for decades.
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