Count the spirals in a sunflower head and you usually get two neighbouring Fibonacci numbers, like 34 and 55. Each new seed grows at about 137.5 degrees from the last, the "golden angle", which packs in the most seeds.
Truth label: Established. Strong evidence and broad agreement among experts.
Go deeper
The sequence
Each number is the sum of the two before: 1, 1, 2, 3, 5, 8, 13, 21, 34, 55. The ratio between them closes in on the golden ratio, about 1.618.
Where it holds up
Pinecones, pineapples and many plants show the same spiral counts.
Where it does not
Claims that the Parthenon or the Mona Lisa were built on the golden ratio rest on choosing convenient measurements.
Learn
- Why plants do it. Growing each new seed at the golden angle means none line up, so no space is wasted.
- Spotting it. Look for two sets of spirals turning in opposite directions. Count each set.
Test yourself
Which pair is consecutive Fibonacci numbers?
34 and 55. 21 + 34 = 55.
Was the Parthenon proven to be built on the golden ratio?
No. The evidence for that claim is weak.
Sources
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