Chapter 77: The Great Filter

“Let’s operate under the temporary assumption that basic life is common in the universe.”

Since no one could present a solid counterargument, the gathered scientists agreed to accept this premise for the time being.

“However, we cannot jump to the conclusion that intelligence is equally common. We simply lack the data,” Professor Hazel stated, steering the conversation. “But we can make educated guesses based on the data we do have. The key to this puzzle lies in the Great Filter theory.”

As Hazel spoke, the underlying logic of the symposium began to take shape.

According to the scale proposed by the Old World astrophysicist Nikolai Kardashev, civilizations can be categorized into three tiers: Type I, Type II, and Type III. Each ascending tier represents a billionfold increase in harnessable energy.

“Our Federation, even at the peak of the Old World, has never reached Type I status. According to the scale, our technological level sits roughly at 0.7. We are barely scratching the surface of a Type I civilization.”

“I believe that only a Type I civilization, or perhaps one transitioning between Type I and Type II, possesses the capability for true interstellar travel. Does anyone disagree with this baseline?”

By “interstellar travel,” Hazel didn’t just mean launching satellites or landing on a local moon. She meant physically traversing the void between neighboring stars.

The distances between solar systems are incomprehensibly vast, measured in light-years. The closest star system to their original sun, Alpha Centauri, was 4.37 light-years away.

How far is a single light-year? Roughly 9.46 trillion kilometers.

That distance was an absolute nightmare. At the maximum velocity of current human spacecraft, a one-way trip would take a hundred thousand years! A hundred millennia was far too long; it was practically impossible for a biological species to survive the journey.

Therefore, a civilization would need to be well on its way to Type II status to develop sub-light propulsion capable of compressing that travel time into decades or a single century. Only then could a species truly call itself an interstellar civilization.

The auditorium hummed with quiet discussion as the scientists nodded in agreement.

By this metric, humanity was at the absolute bottom of the cosmic ladder. It was a bitter pill to swallow, but it was the undeniable truth. Even relying on the physics-defying mass-dampening fields of the Noah, they couldn’t reach sub-light speeds. Their energy grid simply couldn’t output the required power.

“Such interstellar civilizations must be exceedingly rare. At the very least, humanity has never observed one during our centuries of modern astronomy. Nor has any advanced civilization ever attempted to contact us,” Hazel continued. “Are there any objections to this point?”

Jason thought about it for a moment. It’s true. A few centuries is nothing on a cosmic scale, but the absolute silence of the stars strongly implies that interstellar empires are incredibly rare. Hazel’s logic was structurally sound.

“So, the ultimate question is this,” Hazel said, leaning forward. “If basic life is common, but interstellar civilizations are rare… why?”

Jason couldn’t help but frown. He had no clear answer. If the universe was teeming with microbes and primitive plants, why weren’t the stars swarming with ships?

According to Hazel’s hypothesis, there had to be a catastrophic, universal obstacle blocking the evolutionary progress of almost all lifeforms.

“We call this cosmic barrier the Great Filter!”

Hazel’s voice was solemn. “This Great Filter wipes out unqualified lifeforms, leaving behind only a microscopic fraction of lucky survivors. Only those rare species that survive the Filter can eventually ascend to become an interstellar civilization.”

“This barrier is absolute. I believe that life on almost every planet will eventually face it! It acts as an iron wall, halting the progress of evolution. Breaking through it is monumentally difficult, perhaps even statistically impossible for most.”

“Only an exceptionally lucky, incredibly resilient species can cross the Great Filter and continue its journey to the stars. The survival probability might be one in ten million… or perhaps one in a hundred million.”

Hazel gripped the edges of the podium. “I believe this is the most mathematically sound explanation. And if the Great Filter theory holds true, it must occur before a species achieves interstellar flight!”

A heavy silence descended upon the auditorium.

Jason forced himself to keep listening, his heart pounding against his ribs. The theory made terrifying sense. If life was common, but space was empty, something was exterminating life before it could leave its home system.

Scientists were truly remarkable creatures. Despite knowing almost nothing about the wider universe and possessing pitifully little data, they could deduce so much through pure logic and probability. It was a testament to humanity’s greatest weapon: its intellect.

But what exactly was the Great Filter?

Had humanity already survived it, or was it still waiting for them in the dark?

Those were the two ultimate extremes. If humanity had unknowingly bypassed the Great Filter in its evolutionary past, their path forward was clear. But if the Great Filter still lay ahead… they would have to beat one-in-a-hundred-million odds just to survive.

Even the most hardened veteran would pale at those odds. Was humanity really lucky enough to survive a one-in-a-hundred-million slaughter? As the leader of the Federation, Jason desperately needed to know if this “Great Filter” was a tangible threat, or just an academic ghost story.

“Professor Hazel, I have a few thoughts.” Arthur Lambert suddenly raised his hand from the front row.

“I’ve read up on the Great Filter theory. Let’s break down some of the most likely candidates for this barrier, so we can analyze them logically.”

Arthur stood up, turning to face the room. “First candidate: the genesis of life itself. We used to believe that abiogenesis, the formation of life from non-living matter was a miraculous, near-impossible accident. Because we could never artificially create life in a lab, we assumed this was the Great Filter. But, thanks to the Martian pathogen, we now suspect that abiogenesis is actually quite common. Therefore, we can cross this candidate off the list.”

“Second candidate: the evolutionary leap from prokaryotic life to eukaryotic life.”

“Back on the Old World, it took over a billion years for single-celled organisms to make that leap,” Arthur explained. “It requires an incredibly specific sequence of biological coincidences. An event with a probability that low is a prime candidate for the Great Filter.”

“I agree, Arthur,” Hazel nodded from the podium. “After life originated on Earth, it stagnated for over a billion years before eukaryotic cells formed. We have no way of knowing if that evolution was biologically inevitable or a freak mathematical accident. If the chances of a cell developing a nucleus are one in a hundred million, then that leap could absolutely be the Great Filter.”

“Furthermore, the Martian pathogen never made that leap. It is strictly a prokaryotic organism,” another biologist chimed in from the back. “The fact that the Martian microbes never evolved into eukaryotes is actually fantastic news for us.”

A wave of excited chatter broke out among the scientists.

The Martian lifeforms were primitive, carbon-based prokaryotes. They had never formed complex cellular structures.

If true, this meant the evolutionary leap from simple to complex cells was astonishingly rare. And if that was the Great Filter… humanity had successfully passed it over a billion years ago!

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