The Great Filter
🔬Where is everybody? Explore the Fermi Paradox and discover why we might be alone in the universe.
The universe is vast and old. Our galaxy alone contains 100-400 billion stars. Many of these stars have planets, and some planets are in the habitable zone.
With billions of potentially habitable planets, and billions of years for life to evolve, shouldn't the galaxy be teeming with civilizations?
"So where is everybody?" - Enrico Fermi, 1950
The Great Filter theory suggests there's at least one incredibly difficult step in the evolution from dead matter to a space-faring civilization. This filter is so hard to pass that it prevents most life from becoming detectable.
The key question: Is the Great Filter behind us, or ahead of us?
Grains of Sand
There are more stars in the universe than grains of sand on all Earth's beaches. Even if life is rare, the numbers are staggering.
Time Scale
The universe is 13.8 billion years old. If advanced civilizations exist, some could be millions of years ahead of us.
Distance Problem
Our galaxy is 100,000 light-years across. Even at light speed, crossing it takes 100,000 years. Space is really, really big.
Brief Signals
We've only been broadcasting radio for ~100 years. That's a tiny bubble just 100 light-years across in a vast galaxy.
Proposed by Frank Drake in 1961, this equation breaks down the problem into manageable variables. Each variable represents a step in the evolution from stars to detectable civilizations.
Hover over the
Visual Equation
Watch how each variable multiplies to estimate civilizations
Our Galaxy (Top View)
Visualization of communicative civilizations
Dozens of civilizations - but space is VAST 🚀
Average rate of star formation per year in our galaxy
Fraction of stars that have planetary systems
Number of planets per star system that could support life
Fraction of habitable planets where life actually emerges
Fraction of life-bearing planets that develop intelligent life
Fraction of intelligent civilizations that develop detectable technology
Years a civilization remains detectable
Result Interpretation:
A handful of civilizations might exist, but they could be very far apart or short-lived.
Scale: 0.000001 to 10,000,000 (logarithmic)
The huge variation shows how uncertain we really are!
If the values are high, thousands of civilizations should exist. Yet we see no evidence. This is the Fermi Paradox.
With middle-ground values, a few hundred civilizations might exist, but they could be far away or short-lived.
If any variable is extremely small, we might be alone or nearly alone. This suggests a Great Filter somewhere.
Finding microbial life on Mars or Europa would be terrible newsfor humanity.
Why? Because it would suggest that abiogenesis is common, meaning the Great Filter is likely still ahead of us. The more common life is, the more worried we should be about our survival.
Explore the variables. Consider the implications. Where do you think the Great Filter lies?