[ travisMAKES ]
SIM ?

ARE WE
ALONE?

a galaxy-scale headcount in 6 steps

WE ARE
NOT ALONE

// FRIENDS DETECTED //

click the diamond again to return.

// 01. THE DRAKE EQUATION

N = R* · fp · ne · fl · fi · fc · L
R* : new stars per year
fp : stars with planets
ne : habitable per system
fl : life takes hold
fi : life gets smart
fc : smart goes loud
L : how long it stays loud

Drake's own 1961 calculation gave N = 10. Move any one term and the whole answer flips by orders of magnitude. That's the point.

// 02. THE GREAT SILENCE

If intelligent life is common, the sky should already be packed: probes, beacons, megastructures, Dyson swarms. Instead the sky is quiet. No signals. No artifacts. Nothing.

Enrico Fermi spotted it over lunch in 1950: "Where is everybody?" Michael Hart formalized it in 1975, Frank Tipler sharpened it in 1980, and Stephen Webb's book catalogs 75 attempts to explain it.

DRAKE SAYS THEY EXIST.
THE SKY SAYS THEY DON'T.

// 03. YOUR DRAKE

R* / star formation rate
How many new stars does our galaxy cook up each year?
1.5/yr
barely cookingstarburst
fp / fraction with planets
Of all those stars, how many have planets at all?
100%
naked starseveryone has planets
ne / habitable per system
Per planet system, how many sit in the right zone for liquid water?
0.5
nonemoons too
fl / life takes hold
On a habitable planet, does life ever actually get going?
100%
dead rocklife is everywhere
fi / intelligence emerges
How often does life get smart enough to wonder about other life?
10%
pond scum foreverintelligence is inevitable
fc / they broadcast
Of the smart ones, how many ever build a radio?
10%
silentbroadcasting hard
L / signal lifetime
Once a civilization starts broadcasting, how long does it keep doing it?
1,000 yr
flash in the panforever
CIVILIZATIONS IN THE MILKY WAY
0
RUN THE NUMBERS
N = 1.5 · 1.00 · 0.50 · 1.00 · 0.10 · 0.10 · 1000

// 04. WHY IT'S QUIET

01 / GREAT FILTER Something kills civilizations before they spread. The question is whether that filter is behind us (we already passed it) or ahead (we haven't hit it yet). Microbes on Mars would be terrible news. Hanson, 1998.
02 / RARE EARTH Ward and Brownlee: Earth is a fluke stack. Plate tectonics, a stabilizing big moon, magnetic field, gas-giant bouncer, right star, right neighborhood. Microbes are common. Brains are vanishingly rare. Ward & Brownlee, 2000.
03 / DARK FOREST Every civilization is a hunter. You can't read another's intent, the cost of being wrong is extinction, so the move is silence and pre-emption. The galaxy isn't empty. It's quiet on purpose. Brin, 1983 / Liu, 2008.
04 / ZOO They're here. They see us. They've decided not to interfere. Earth is a wildlife preserve and the aquarium glass is one-way. Untestable until someone breaks the rule. Ball, 1973.
05 / WE'RE EARLY Hard-step models say intelligent life should arrive late, not early. The fact that we're here only 13.8 billion years in suggests fast-expanding "grabby" civilizations are coming, and we're inside the small window before they fill the universe. Hanson et al., 2021.
06 / IT'S RENDERED Maybe the sky is empty because the universe isn't civilizational. It's a render. The stars only fill in when someone looks closely, and nobody has pointed a telescope hard enough. Fermi's question becomes a UI bug.
▶ IS THIS A SIMULATION?

// 05. CAVEATS & SOURCES

  • Drake parameters are guesses, not measurements. Sandberg, Drexler, Ord (2018): when you treat them as full distributions instead of point estimates, the model gives a real probability that we're alone. The paradox dissolves into our own overconfidence.
  • Pessimism still gets you neighbors. Westby & Conselice (2020): strict Earth-analog assumptions yield ~36 communicating civilizations, average distance 17,000 light-years. All undetectable.
  • Evolutionary timing argues for rare. Snyder-Beattie et al. (2021): Bayesian model on the spacing of life's hard steps says expected transition times exceed Earth's window by orders of magnitude.
  • Floor exists either way. Frank & Sullivan (2016): unless the per-planet probability is below 10-24, we are not the first technological species in cosmic history.
  • L is the dominant uncertainty. Sagan called this term the ballgame. Move L from 100 to 1,000,000 and your N changes by four orders of magnitude. Nobody knows how long civilizations stay loud.

// FURTHER READING

Sister page: Is This A Simulation?
Same calculator format. Different question.

1 / 6