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Scientists Discover Way to Send Information into Black Holes Without Using Energy

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How Long Do Civilizations Last? The Fermi Paradox and the 5,000-Year Warning

In the 1950s, during a casual lunch conversation, the brilliant physicist Enrico Fermi asked a simple yet powerful question: “Where is everybody?”

He was talking about aliens.

The universe is about 13 billion years old. Our galaxy alone has hundreds of billions of stars. Many of those stars have planets. And many of those planets sit at just the right distance to allow liquid water — the key ingredient for life as we know it.

With such enormous numbers, intelligent life should not be rare. It should be everywhere.

And yet — we see nothing.

No signals.
No alien spacecraft.
No signs of advanced engineering.

This mystery is known as the Fermi paradox, and scientists have been trying to solve it for more than 75 years.

Now, two physicists from Sharif University of Technology — Sohrab Rahvar and Shahin Rouhani — have taken a bold new approach. Instead of asking why we have not found aliens, they asked a different question:

What does the silence itself tell us?

Their study, published on arXiv, suggests a surprising answer:
Technological civilizations may not survive for very long.

The Universe Should Be Full of Life

Let’s break down the logic.

Scientists know that:

  • The Milky Way galaxy is extremely old.

  • Many stars are billions of years older than our Sun.

  • Planets are common.

  • Some planets exist in the “habitable zone,” where water can remain liquid.

This means life could have started billions of years before Earth even formed.

If intelligent life develops easily, there should have been countless civilizations long before humanity appeared.

And if even one of those civilizations survived for millions of years, we should have seen evidence by now.

But we haven’t.

That’s the paradox.

The Drake Equation and the Sound of Silence

To explore this puzzle, the researchers built on the famous Drake equation.

The Drake equation is a formula used to estimate how many communicating civilizations might exist in our galaxy. It considers factors such as:

  • The rate of star formation

  • The fraction of stars with planets

  • The number of planets that could support life

  • The probability that life becomes intelligent

  • The length of time civilizations release detectable signals

That last factor — lifespan — is critical.

Because even if intelligent life appears often, it won’t matter if civilizations destroy themselves quickly.

Our Radio “Light Cone”

Here’s where the math becomes powerful.

For about 100 years, humans have been sending radio signals into space. At the same time, we’ve been listening with increasingly advanced radio telescopes.

These telescopes can detect strong signals from across the galaxy. Over time, the region of space from which signals could have reached us — known as our light cone — has expanded.

According to the researchers, our listening window now effectively covers the galaxy’s history for roughly the last 100,000 years.

This means:

Any civilization in our galaxy that existed during that time and was broadcasting detectable radio signals should have been heard by now.

But we’ve heard nothing.

The silence is not because our technology is too primitive. It appears to be real.

The 5,000-Year Ceiling

After running the numbers, the researchers reached a striking conclusion:

If intelligent life is common in the galaxy, then technological civilizations must survive, on average, no more than about 5,000 years.

Not millions of years.
Not even tens of thousands.

Just five thousand.

To understand how serious that is, consider this:

  • Recorded human history goes back about 5,000 years.

  • We have only been a truly technological civilization for around 200 years.

That means we are still at the very beginning of the most dangerous period of our existence.

Statistically speaking, we may be entering the “danger zone.”

Why Would Civilizations Collapse?

The researchers openly discuss possible threats that could end a technological civilization:

  • Asteroid impacts

  • Supervolcano eruptions

  • Climate change

  • Global pandemics

  • Nuclear war

  • Artificial intelligence gone wrong

  • Rogue biotechnology

History shows that civilizations collapse. The Roman Empire fell. The Maya civilization declined. Easter Island society collapsed after environmental strain.

In the past, collapses were regional. Today, humanity is globally connected. A major catastrophe could affect the entire planet at once.

For the first time in history, extinction-level risks are truly global.

Is 5,000 Years Our Fate?

The authors are careful to clarify something important:

Their result is not a prediction.

It is an upper limit based on the Fermi paradox.

In simple terms, the math suggests civilizations cannot usually last much longer than 5,000 years if the galaxy is to remain as silent as we observe.

But other explanations are still possible:

  • Maybe advanced civilizations choose not to communicate.

  • Maybe they use technologies we cannot detect.

  • Maybe we are one of the first intelligent species to arise.

  • Maybe interstellar distances are simply too vast.

The study does not rule out these possibilities.

However, it does highlight an uncomfortable truth:

If intelligent life is common, then most civilizations may not survive long enough to explore the stars.

A Galaxy of Silent Ruins?

The deeper implication is both fascinating and unsettling.

The galaxy may once have been filled with civilizations that:

  • Rose from primitive beginnings

  • Built cities and machines

  • Mastered science and technology

  • Looked up at their skies with curiosity

And then fell silent.

Perhaps through war.
Perhaps through environmental collapse.
Perhaps through misuse of their own inventions.

The universe may impose a strict limit on how long intelligence persists.

We simply do not yet know whether humanity will overcome that limit — or become another silent statistic.

What This Means for Us

We are only about 200 years into our technological age. In cosmic terms, that is nothing.

If the 5,000-year ceiling is even roughly correct, then our most vulnerable centuries may still lie ahead.

But this is not a message of doom.

It is a reminder.

Unlike other civilizations that may have existed, we are aware of the risks. We understand climate systems. We track asteroids. We study pandemics. We debate AI safety. We have the ability to plan.

If civilizations typically fail, then survival may require something rare:

Long-term thinking.

The Fermi paradox may not just be a scientific puzzle. It may be a warning.

The Big Question

So how long do civilizations last?

We don’t know for certain.

But if the galaxy’s silence means what this research suggests, the answer might be:

Not very long — unless they learn how to survive their own power.

The future of humanity may depend not on discovering alien life, but on ensuring we do not become another lost voice in a quiet universe.

And perhaps one day, if we endure, someone else will look up at the stars — and finally hear us.

Reference: Sohrab Rahvar et al, Constraining the Lifespan of Intelligent Technological Civilization in the Galaxy, arXiv (2026). DOI: 10.48550/arxiv.2602.22252

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