Fermia: Fermi Paradox
Cosmology & the Sky arc, page 143 of 193. Back to The Pixelated Physics Universe
Who they are
Fermia sits on a rocky outcrop with a radio dish, ear cupped to a starfield. It stays silent.
Fermia is a character of the Cosmology & the Sky arc: drawn in pixels, ruled by one piece of real physics, and never allowed to break it.
The physics
If the galaxy is old and full of planets, and travel or signalling between stars is possible, why do we see no sign of anyone else? The Drake equation breaks the question into a chain of factors, from the rate of star formation to how long a civilisation stays detectable. Most of those factors are unknown, so the equation organises our ignorance rather than giving an answer. Enrico Fermi asked "Where is everybody?" at Los Alamos around 1950 (as recalled; wording varies); Frank Drake introduced his equation at Green Bank in 1961.
$$ \begin{gathered} N = R_{*}\cdot f_p \cdot n_e \cdot f_l \cdot f_i \cdot f_c \cdot L \end{gathered} $$
| Symbol | Meaning | SI unit |
|---|---|---|
| $N$ | number of detectable civilisations in the galaxy | 1 |
| $R_{*}$ | rate of star formation | 1/yr |
| $f_p$ | fraction of stars with planets | 1 |
| $n_e$ | habitable planets per planetary system | 1 |
| $f_l$ | fraction of those that develop life | 1 |
| $f_i$ | fraction of those that develop intelligence | 1 |
| $f_c$ | fraction that produce detectable signals | 1 |
| $L$ | how long they stay detectable | yr |
Honest caveat: This is an open question. No value of N is known.
Status: part of this topic is unsolved, unconfirmed or debated. The text above says which part; treat it as an open question, not settled fact.
Sources
- Jones (1985) "Where is everybody?" An account of Fermi's question, Los Alamos report LA-10311-MS
- SETI Institute, The Drake Equation
Crossovers
Fermia meets Nocturna (Olbers' Paradox). Nocturna's paradox about the dark sky has an answer. Fermia's paradox about a silent galaxy does not. One is solved physics; the other is still an open question.
Fermia meets Choralis (Hellings–Downs Curve). Fermia listens to the sky for signals and hears nothing. Choralis listens to pulsars for a gravitational-wave hum and finds evidence, though not yet at 5σ. Patience and statistics decide what counts as a detection.
Wear the lore
Concept keywords: Fermi Paradox, Fermia, Cosmology & the Sky, physics lore, Pixelated Physics