φ, with the mythology set aside
A perfectly usable constant for dividing space. Not a law of nature, and not more pleasing than 1.5 in any study that has looked.
φ, with the mythology set aside
A perfectly usable constant ratio for dividing space. Not a law of nature, not a property of the Parthenon, and not more pleasing than 1.5 in any study that has looked.
What φ actually is
φ = (1 + √5) / 2 ≈ 1.6180339887. Its defining property is that a + b is to a as a is to b — divide a length at that point and the whole relates to the larger part exactly as the larger relates to the smaller.
It is the limit of the ratio between consecutive Fibonacci numbers, and it genuinely appears in phyllotaxis — the arrangement of leaves and seeds — because it is the number hardest to approximate with a fraction, which is what maximises packing.
None of that transfers to page layout. It is a ratio that produces consistent, slightly dramatic divisions, which is a good enough reason to use it.
The claims that do not hold up
The Parthenon, the Great Pyramid and Leonardo's proportions are all cited routinely and none of them survives measurement — the fits require choosing which edges to measure from, and other ratios fit equally well.
The experimental work on rectangle preference, going back to Fechner in the 1870s, does not find a reliable preference for φ. Nothing here is a reason not to use it; it is a reason not to claim it is objectively right.
Where it earns its place
As one ratio used consistently: a sidebar to a main column, a type scale, a set of nested rectangles. The consistency is doing the work, and 1.5 would do it equally well.