• Fermia Fermi Paradox pixel-art physics T-shirt, white tee, front view

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Fermia

The Fermi Paradox Physics

\[N = R_{*}\cdot f_p \cdot n_e \cdot f_l \cdot f_i \cdot f_c \cdot L\]
$29.99 USD
$29.99 USD
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Size guide S–5XL · inches

Fermia sits on a rocky outcrop with a radio dish, ear cupped to a starfield. It stays silent.

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.

N = R* · f_p · n_e · f_l · f_i · f_c · L

  • N: number of detectable civilisations in the galaxy
  • R*: star formation rate (stars per year)
  • f_p: fraction with planets
  • n_e: habitable planets per system
  • f_l, f_i, f_c: fractions with life, intelligence, detectable signals
  • L: how long they last (years)

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.

Honest caveat: This is an open question. No value of N is known.

On the shirt

Front: Fermia, the pixel-art character, with the title. Back: Fermi's question, the Drake equation with every factor named, the open-question note and the Los Alamos account. Printed on a unisex tee.

Shipping calculated at checkout by destinationMade to order, ships in 2–5 business days

Details

Size & fitS–5XL

Unisex heavy cotton (Gildan 5000), classic fit.

SizeWidthLengthSleeve
S182815.1
M202916.5
L223018
XL243119.5
2XL263221
3XL283322.4
4XL303423.7
5XL323525

पैमाने के लिए: साइज़ M की चौड़ाई 20 in (50.80 cm) है, यानी लगभग 3.143 × 1034 प्लांक लंबाई (lP = 1.616255 × 10−35 m)। इंच-टेप ज़्यादा जल्दी काम करेगा।

Measurements in inches, ±1.5 in tolerance.

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Returns & replacements21 days

Every item is printed to order, so we can’t accept returns or exchanges for change of mind, or if you ordered the wrong size or colour.

Print defect, misprint, damage or the wrong item? We’ll send a free replacement, or a refund if you prefer. Report it within 21 days of delivery with a photo; no need to send it back.

Full refund & replacement policy

The physics

I sit on a rocky outcrop with a radio dish, ear cupped to the stars. It stays silent.

At Los Alamos around 1950, over lunch with Konopinski, Teller and York, Enrico Fermi asked something like "But where is everybody?" (as recalled; the wording varies). 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? In 1961 Frank Drake wrote his equation as the agenda for a meeting at Green Bank, breaking the question into a chain of factors, from the star formation rate to how long a civilisation stays detectable.

Most of those factors are unknown, so the equation organises our ignorance rather than answering it. No value of N is known. The question is still open.

Equations

\[N = R_{*}\cdot f_p \cdot n_e \cdot f_l \cdot f_i \cdot f_c \cdot L\]
SymbolMeaningUnit
\(N\) number of detectable civilisations in the galaxy \(\mathrm{1}\)
\(R_{*}\) rate of star formation \(\mathrm{1/yr}\)
\(f_p\) fraction of stars with planets \(\mathrm{1}\)
\(n_e\) habitable planets per planetary system \(\mathrm{1}\)
\(f_l\) fraction of those that develop life \(\mathrm{1}\)
\(f_i\) fraction of those that develop intelligence \(\mathrm{1}\)
\(f_c\) fraction that produce detectable signals \(\mathrm{1}\)
\(L\) how long they stay detectable \(\mathrm{yr}\)

Sources

  1. Jones (1985) "Where is everybody?" An account of Fermi's question, Los Alamos report LA-10311-MS
  2. SETI Institute, The Drake Equation

Field notes

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