Understanding the Universe's Potential for Life

In contemplating the vastness of the universe, it becomes apparent that it is filled with extreme environments. There could be over 100 billion planets in our galaxy alone that fit the criteria for these harsh conditions, and I believe many are likely teeming with life as we speak.

Interestingly, the scientific definition of “life” deviates from our usual understanding. Life is characterized as any self-sustaining entity, isolated by a membrane, capable of metabolism and reproduction. In essence, we are primarily talking about single-celled organisms.

On our planet, these organisms emerged around 3.8 billion years ago. It wasn’t until 1.2 billion years later that the first simple multicellular organisms appeared, with a further 2 billion years passing before the Cambrian explosion unfolded, heralding the rapid diversification of life forms we recognize today. This lengthy timeline suggests that complex life has a significant waitlist, possibly explaining the lack of advanced extraterrestrial civilizations broadcasting their presence across the cosmos.

A Statistical Perspective on Extraterrestrial Life

Even if we conservatively estimate that 1% of all planets harbor life and 1% of those develop into complex multicellular organisms, our galaxy should host millions of such life forms. Perhaps the challenge lies in the evolution of intelligence. Interestingly, it has been suggested that intelligent life is also scarce on Earth, and I find myself in agreement with this notion. Yet, we have still managed to create technology capable of signaling our existence to the universe.

Intelligence, like life, appears to emerge in various forms across our planet. Species like octopuses, corvids, dolphins, and primates exhibit remarkable cognitive abilities. Unfortunately, some of these species have lifespans too short to leverage their intelligence fully, while others lack the physical means to manipulate tools. Apex predators, like orcas, are already well-equipped in their ecological niches.

Despite the apparent abundance of intelligent species, the universe remains eerily quiet.

The Brief Existence of Civilizations

Human civilization has thrived for around 8,000 years, but we only transitioned to a technological civilization capable of being detected from space in the last century. Eight thousand years may seem substantial, but on a cosmic scale, it is merely a fleeting moment. The universe has existed for nearly 14 billion years, providing ample time for technological civilizations to develop.

Even if we consider the last 7 billion years, the potential for millions of technological civilizations to have emerged seems high. Yet, radio silence prevails, leading us to the Fermi paradox: where is everyone?

Numerous theories attempt to explain this phenomenon, including the Great Filter hypothesis, which posits that some natural barrier prevents civilizations from advancing. This idea is indeed unsettling. The universe is filled with cataclysmic events—supernovae, kilonovae, and gamma-ray bursts—that can obliterate life across multiple planets simultaneously. Supernovae occur every 50 to 100 years in our galaxy, dwarfing the asteroid impact that led to the extinction of the dinosaurs.

However, I don’t consider these cosmic catastrophes to be a Great Filter. Given the myriad possibilities of survival, many civilizations should have persisted despite these threats.

Luck and Resources: The Overlooked Factors

One often-overlooked reason for the absence of civilizations broadcasting their signals is less glamorous: luck and access to resources. Our civilization began with muscle power alone, but mastering fire allowed us to develop technologies such as ceramics and bronze. However, to advance to iron, we required a hotter energy source—coal. This pattern continued, as each technological leap demanded increasingly rare materials and energy sources, including oil and gas.

It is essential to recognize that without these energy sources, the rise of technological civilizations would be impossible. While humanity eventually harnessed atomic and solar energy, we first relied on simpler sources with sufficient energy output.

Our fortune on Earth stemmed from a unique combination of circumstances that provided us with combustible materials and oxygen. Initially, life on Earth existed without free oxygen in the atmosphere. It wasn’t until approximately 2.5 billion years ago that certain bacteria evolved photosynthesis, producing oxygen as a byproduct.

This oxygen initially posed no threat; it reacted with dissolved elements like iron in the oceans, sinking to the seabed. However, as oxygen levels rose, it became toxic to anaerobic life forms, nearly wiping them out. It took time for life to adapt to using oxygen for energy. Had oxygen not been produced, life could have evolved along a different metabolic path, potentially without ever leading to a civilization capable of technological advancement.

The Formation of Fossil Fuels

The fossil fuels we rely on today have their origins in the Carboniferous period, roughly 360 to 300 million years ago, when the Earth was blanketed in dense forests. During this time, plants developed lignin, a tough organic polymer that no organisms could decompose. As a result, these trees accumulated, eventually becoming compressed and transformed into coal.

Oil and gas, in turn, originated from marine organisms like algae that sank to the ocean floor under low oxygen levels, preventing decomposition. This organic matter accumulated, underwent compression, and was transformed into petroleum and natural gas over millions of years.

Curiously, had cyanobacteria not introduced free oxygen, the conditions necessary for fossil fuel formation may not have occurred. The complex interplay of random events led to our current situation.

It is plausible that many planets harbor civilizations adept at crafting stone tools or composing beautiful poetry, yet lack the energy resources needed to ascend technologically. Some may indeed have experienced the same fortunate circumstances we did, accessing oxygen and fossil fuels, but luck can be a double-edged sword.

Fossil-powered civilizations often face self-inflicted challenges, as evidenced by our current struggle with climate change. The likelihood of transmitting radio signals into the universe may diminish as our civilization grapples with these issues.

Given that our technological civilization has only been broadcasting signals for about 200 years, it is conceivable that within the last 7 billion years, countless civilizations have arisen and faded without ever overlapping.

Aivaras Grauzinis