prolly — a probabilistic graphical spreadsheet
Every cell is a random variable: a number, a range like 5 to 20, a distribution like beta(2, 5), a
shape drawn by hand, or a formula over other cells like A * B or given(C, C > mean(C)). The
sheet re-derives live. The same letter is the same variable (A − A is exactly 0), constants stay constants, and
a document reads the same on every reload. Any cell answers what drives it, what happens when everything goes against
it, what it would take to reach a number, and how it changes across an input. The whole thing runs in your browser;
share publishes a snapshot link.
A fresh document opens on the Drake equation under honest uncertainty (Sandberg, Drexler & Ord 2018, "Dissolving the Fermi Paradox"):
R: new stars per year = 1 to 100 // in the Milky Way — the one Drake factor astronomy has nearly pinned down
fp: stars with planets = [0.9, 1] // Kepler settled this: nearly all of them
ne: habitable worlds per system = [0.1, 1]
fl: a habitable world gets life = 10 ** uniform(−30, 0) // abiogenesis — honestly unknown across ~30 orders of magnitude
fi: life becomes intelligent = 10 ** uniform(−3, 0)
fc: intelligence becomes detectable = 10 ** uniform(−2, 0)
L: years a civilization stays detectable = 10 ** uniform(2, 10) // a century to ten billion years
N: civilizations in the Milky Way = R * fp * ne * fl * fi * fc * L // Drake 1961, every term a belief instead of a number
alone: chance we are alone in the galaxy = pr(N < 1) // the mean of N says millions; this says the silence was never surprising
company: if not alone, how many? = given(N, N > 1) // the same beliefs, conditioned on company
The mean of N says millions of civilizations; pr(N < 1) reads 0.86 — an empty galaxy was never surprising — and given(N, N > 1) says company comes in hundreds.
This page needs JavaScript to run the sheet. prolly is made by Scry.