Science · Numbers

What Is the Golden Ratio?

The mathematics behind φ, and why its reputation is bigger than the evidence.

The question

Is there really a “perfect” proportion hidden in art and nature?

The short answer

The golden ratio, φ ≈ 1.618, is a genuinely remarkable number in mathematics. Many famous claims about it in art, architecture and beauty are exaggerated or unproven.

φ ≈ 1.618 φ² = φ + 1
Cut a square from a golden rectangle and what remains is another golden rectangle, forever.

What science knows

Established Mathematics

Split a line so that the whole is to the longer part as the longer part is to the shorter: that ratio is φ = (1 + √5) / 2 ≈ 1.6180339887. Euclid described it as the “extreme and mean ratio”.

It has unusual properties: φ² = φ + 1, and 1/φ = φ − 1. In a regular pentagon, the ratio of a diagonal to a side is exactly φ.

The pattern

Established Mathematics

Divide each Fibonacci number by the one before it and the answers close in on φ: 8/5 = 1.6, 13/8 = 1.625, 21/13 ≈ 1.615, 34/21 ≈ 1.619.

What is still uncertain

Mixed Evidence

Claims that the Parthenon, the Great Pyramid or the Mona Lisa were designed around φ usually rely on choosing convenient measurements. The mathematician George Markowsky catalogued many such misconceptions in 1992.

Experiments on whether people prefer golden rectangles, starting with Gustav Fechner in the 1870s, have produced mixed results.

Why humans find it interesting

Historical Fact

The name is younger than it sounds: “golden section” appears in the 1830s in the work of Martin Ohm. Renaissance writers such as Luca Pacioli called it the “divine proportion”.

CUE perspective

CUE Perspective

The golden ratio shows why CUE labels its claims. The mathematics is beautiful and true; the legends around it grew because people wanted a number to explain beauty.

CUE finds that desire interesting, and keeps the line clear between what a number does and what we hope it means.

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Sources

  • Euclid, Elements, Book VI, Definition 3
  • Markowsky, “Misconceptions about the golden ratio”, The College Mathematics Journal 23 (1992)
  • Livio, The Golden Ratio (Broadway Books, 2002)

Written by CUE from the sources above. Some topics were suggested by Polymath; its claims are not reproduced.