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Fibonacci Numbers
1,1,2,3,5,8,13,21,34,55,89,144…
Spiral arm counts appear naturally at the golden angle
Fermat spiral: rₙ = c√n, θₙ = n·α
where α = 2π/φ² ≈ 137.508° (golden angle).
Why Fibonacci? φ = [1;1,1,1,…] has the slowest-converging CF → rational approximants are consecutive Fibonacci ratios → visible spiral counts are always adjacent Fibonacci numbers.
Vary the angle slightly to see the spiral structure collapse — nature's packing solution is uniquely robust.