Have you ever looked up at the night sky and wondered if humans are the only intelligent life in this vast universe? The twinkling stars, distant galaxies and vast expanse above us evoke a sense of mystery and awe.
It is a question that has intrigued humanity for centuries, driving scientists, philosophers and dreamers to explore the cosmos and seek answers to one of our most profound questions.
What lies beyond Earth in our Milky Way galaxy? Are there other life forms that share the same curiosity and wonder?
What does intelligent life need?
New research brings us closer to understanding why there is no evidence for the existence of advanced alien civilizations.
Dr. Robert Stern, an earth scientist at the University of Texas at Dallas, and Dr. Taras Gerya of the Swiss Federal Institute of Technology in Zurich led the research.
“Life has existed on Earth for about 4 billion years, but complex organisms like animals didn’t appear until about 600 million years ago, which is not long after the modern episode of plate tectonics began,” Stern said. “Plate tectonics really gets the evolutionary machine going, and we think we understand why.”
Understanding the Drake Equation
In the 1960s, Dr. Frank Drake, a pioneer in the search for extraterrestrial intelligence, developed an equation to estimate the number of intelligent civilizations in our galaxy that can communicate with each other.
N = R* X FP X Nand X FI X Fi X FC X I
N: The number of civilizations in the Milky Way whose electromagnetic emissions (radio waves, etc.) are detectable.
R*: The number of stars formed each year.
FP: The part of the stars that contains planetary systems.
Nand: The number of planets per solar system with an environment suitable for life.
FI: The percentage of suitable planets on which life actually exists.
Fi: The part of the planets where life is possible and where intelligent life arises.
FC: The portion of civilizations that develops technology that produces observable signs of their existence.
I: The average length of time (years) for such civilizations to produce such signs.
The above equation is known as the Drake equation. It is now famous in both scholastic and scientific circles and takes into account variables such as the rate of star formation and the percentage of stars with planets that support life.
Despite optimistic predictions, we still have no contact with extraterrestrial civilizations. This mystery is called the Fermi Paradox. Named after nuclear physicist Dr. Enrico Fermi, it asks, “Where is everybody?”
Conditions for intelligent life
Dr. Stern and Dr. Gerya suggest that the Drake equation may have overlooked the crucial role that large oceans and continents play in the emergence of intelligent life.
According to their research, active communicative civilizations (ACCs) require not only a stable environment, but also long-term geological processes that shape and maintain their planet’s surface.
They argue that plate tectonics, the slow but powerful movement of a planet’s outer shell, is crucial to the evolution of complex life forms.
Deconstruction of plate tectonics
Plates aren’t just for dinner. In geoscience, plate tectonics refers to the Earth’s crust and upper mantle, which are fragmented into pieces that move very slowly over geologic timescales.
Imagine continents as colossal rafts that drift and collide, creating mountains and forming oceans.
“It’s much more common for planets to have a solid outer shell that isn’t fragmented, which is known as simple lid tectonics,” Stern said.
“But plate tectonics is much more effective than single-plate tectonics when it comes to the emergence of advanced life forms.”
Without such dynamic processes, life would struggle to evolve beyond simple, microbial forms.
Fixing the Drake Equation
In their study, Stern and Gerya suggest refining a Drake equation factor, fi. This factor represents the fraction of life-bearing planets where intelligent life arises.
They argue that the need for large oceans, continents and plate tectonics on these planets for more than 500 million years must be taken into account.
“In the original formulation, it was thought that this factor was close to 1, or 100 percent — that is, evolution on all planets with life would proceed and, given enough time, turn into an intelligent civilization,” Stern said. “Our perspective is: That’s not true.”
Simply put, not every planet with life will necessarily develop an intelligent civilization. They suggest that the factor must take into account the presence of significant continents, oceans, and long-lived plate tectonics.
This adjustment could dramatically change our estimates of the number of planets where advanced civilizations could emerge.
Intelligent life and galactic conditions
Their revised formula significantly narrows the potential number of exoplanets with optimal conditions for advanced life.
According to Stern, the number of exoplanets with sufficient water and long-term plate tectonics is likely much smaller than previously thought.
How small? Well, they estimate that the values range from as low as 0.0002 to 0.01 for the volume of water and less than 0.17 for the duration of ongoing plate tectonics.
“If we multiply these factors together, we get a refined estimate of fi that’s very small, between 0.003% and 0.2%, instead of 100%,” Stern said.
“This explains the extreme rarity of favorable planetary conditions for the development of intelligent life in our galaxy and resolves the Fermi paradox.”
These numbers imply that the conditions necessary for the emergence of intelligent life are extremely rare.
Our role in the cosmos may be an extraordinary stroke of luck. Stern’s research suggests that the perfect alignment of geographic and geological factors needed to give birth to intelligent life forms like us is more a rare cosmic jackpot than a universal rule.
This knowledge could solve the Fermi paradox by explaining why we have not encountered other advanced civilizations, despite the enormous number of stars and planets in the universe.
In search of intelligent life in the Milky Way
NASA has confirmed the existence of over 5,000 exoplanets in the Milky Way alone, but we are currently unable to detect plate tectonics on these alien worlds.
Despite this limitation, scientists, including Dr. Kaloyan Penev, a planet hunter at the University of Dallas, continue to search tirelessly for habitable planets.
Stern and Gerya’s findings could shed new light on their search and provide new parameters and considerations for identifying planets that may host advanced life.
“Biogeochemistry suggests that the solid Earth, particularly plate tectonics, accelerates the evolution of species,” Stern said.
“Studies like ours are useful because they stimulate broad thinking about larger mysteries and provide an example of how we can apply our knowledge of Earth systems to interesting questions about our universe.”
Expanding our cosmic understanding
This research reminds us how much we still have to learn about the universe. It encourages us to think beyond Earth and consider how our planet’s geological systems can provide insights into cosmic mysteries.
The history of the Earth, with its tectonic movements, volcanic eruptions and changing atmosphere, reflects processes that can occur on distant planets.
By studying our planet, we learn about the possibility of life and how other planets work.
The next time you look up at the stars, remember that each star has its own world, full of stories.
Imagine the possibilities: planets with unique landscapes, climates, and perhaps even life forms unlike our own. The universe is vast and full of wonders.
Our journey to understanding it has only just begun. As we learn more, we find more questions and discover that the cosmos is more complex and beautiful than we ever imagined.
The full study was published in the journal Scientific reports.
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