A scientific breakthrough with profound implications

For millennia, humans have searched the skies—sometimes with wonder, often with fear—for signs of life beyond Earth. Today, science may be closer than ever to an answer. Astronomers recently reported evidence of dimethyl sulfide (DMS) in the atmosphere of K2-18b, a distant planet more than 120 light years away. On Earth, DMS is produced only by marine microbial life.

If confirmed, the detection of DMS would be the most promising sign of alien life to date. Professor Nikku Madhusudhan of Cambridge University, who leads the research, described it as “as big as it gets.” The findings were made using NASA’s James Webb Space Telescope (JWST), which is equipped to detect chemical fingerprints—called biosignatures—in planetary atmospheres.

Fermi’s Paradox and the “great silence”

But this discovery reopens an old mystery: if life is so likely, why haven’t we encountered it already?

This contradiction is known as Fermi’s Paradox, named after physicist Enrico Fermi, who in 1950 famously asked, “Where is everybody?” Given the age and vastness of the Milky Way—estimated to be 10 billion years old with over 100 billion stars—there should be countless planets capable of supporting life.

Jason Wright, director of the extraterrestrial intelligence centre at Penn State University, noted, “It’s a numbers game.” He added that given enough time, alien civilisations should emerge and expand—some even developing technologies like interstellar travel.

That we have not heard from them is part of “the mystery of the great silence.”

So why the silence?

Scientists have proposed more than 75 speculative solutions to Fermi’s Paradox. Here are a few:

  • We are alone: Life may be exceedingly rare or unique to Earth—though many experts consider this unlikely.
  • Aliens are here already: Civilisations may have visited or observed us without our knowledge—or their presence may be actively concealed.
  • Space is just too vast: Even with advanced technology, interstellar travel may be prohibitively slow or costly.
  • The “great filter”: There could be a barrier preventing life—or intelligent life—from evolving or surviving long enough to explore space.
  • Civilisational self-destruction: Technological species might destroy themselves with nuclear weapons, climate collapse, or resource depletion before reaching other stars.

Many of these reflect fears about humanity itself, which remains our only known example of intelligent life.

Alternative theories: hiding, observing, transcending

Some hypotheses delve deeper into the philosophical or science-fiction realm:

  • The “zoo” hypothesis: Advanced aliens may choose not to interfere with humanity, observing us from a distance like animals in a preserve.
  • The “planetarium” theory: Reality itself may be manipulated to appear empty—a concept drawn from Chinese author Liu Cixin’s The Three-Body Problem.
  • The “dark forest” theory: Civilisations may remain silent out of fear—lest they be destroyed by more advanced rivals.
  • Transcendence: Alien civilisations may choose to leave the physical universe entirely, existing in simulated or non-material realms.

But these all share a flaw, Wright says: they assume universal behaviour across all civilisations, a logic trap known as the “monocultural fallacy.”

The role of human technology and perception

Wright also challenges the assumption that if aliens exist, we should already have detected them. Civilisations may use communication technologies vastly different from anything humanity can currently detect.

“Those of us looking for life in the universe generally don’t think of the Fermi Paradox or the great silence as such a big problem,” he said.

Indeed, efforts like the SETI (Search for Extraterrestrial Intelligence) initiative continue scanning the skies for radio signals or laser pulses from advanced civilisations. So far, the silence persists.

What would alien life mean for us?

If even microbial life is confirmed on another world, it would transform our understanding of life as a universal phenomenon—not a one-off miracle unique to Earth.

Dr Robert Massey of the Royal Astronomical Society believes such a finding would “diminish humanity’s specialness,” just as Copernicus displaced Earth from the centre of the Universe.

But others see it differently. “Knowing that we’re part of a larger fabric will make us bigger,” said Prof Michele Dougherty of Imperial College London. It could unite humanity across cultures and ideologies.

Nikku Madhusudhan echoed this: “The societal ramifications are immense. We would see a living sky. Barriers will dissolve.”

The road ahead

Despite the excitement, caution remains. A biosignature is not definitive proof of life—alternative non-biological explanations may exist. Scientific consensus could take years or decades.

Meanwhile, missions to our own solar system—like NASA’s Dragonfly (2034) to Saturn’s moon Titan, and ESA’s ExoMars (2028)—may offer more immediate answers.

In the long view, the discovery of life elsewhere may not answer just whether we’re alone. It may clarify who we are.

As cosmologist Prof Catherine Heymans put it:
“Confirmation of alien life would be the most enormous scientific, cultural and social transformation in human history.”
A transformation so gradual, we may not notice the moment when everything changes.