A Timeless History
A four-century puzzle. Squares and hexagons tile a floor; regular pentagons leave gaps. In 1619 Johannes Kepler drew pentagons, stars and decagons together in Harmonices Mundi and admitted the pattern needed 'monsters' — fused decagons — to go on. In 1966 a first set of tiles that could only tile without repeating was found: it needed more than 20,000 different shapes. In 1974 Penrose got the number down to two.
SourceNobel Prize in Chemistry 2011, Information for the Public · Nature Reviews Physics 6, 408 (2024) · Image: Kepler, Harmonices Mundi, Linz 1619, Book II plate, pattern 'Aa' — Internet Archive, Smithsonian Libraries (PD)
Science In Action
Aperiodic — the tiles cover the plane, but no arrangement of them ever repeats like wallpaper • Matching rules — marks on the edges force the order; ignore them and a dull periodic pattern appears • Fivefold symmetry — stars of five and ten appear everywhere, impossible in a repeating tiling • Golden ratio — in any large patch, fat rhombs outnumber thin ones by 1.618 to 1, never a whole number
SourceWolfram MathWorld, Penrose Tiles · Nobel Prize in Chemistry 2011, Information for the Public · Image: Ho-Mg-Zn quasicrystal, Ames Laboratory, U.S. Department of Energy (PD)
Arts
Artisans got there first. By 1200 the craftsmen of Islamic Persia were building star-and-polygon patterns from a kit of five girih tiles. On the portal of the Darb-i Imam shrine in Isfahan, dated 1453, the large pattern is subdivided into a smaller copy of itself — the same self-similar trick Penrose used, five centuries earlier.
SourceLu & Steinhardt, Science 315, 1106 (2007) · Nobel Prize in Chemistry 2011, press release · Image: portal of the Darb-i Imam shrine, Isfahan — Wikimedia Commons, Somayeh-Ra (CC BY 4.0)
Applications Today
Quasicrystals — in 1982 Dan Shechtman saw atoms packed like a Penrose pattern; Nobel Prize in Chemistry 2011 • Hard steel — quasicrystal grains armour a Swedish steel used for razor blades and eye-surgery needles • The 'hat' — in 2023 a single 13-sided tile was found that tiles only aperiodically; the search took 60 years
SourceNobel Prize in Chemistry 2011, press release and Information for the Public · Smith, Myers, Kaplan & Goodman-Strauss, arXiv:2303.10798 (2023) · Image: wooden hat tiles — Wikimedia Commons, Aschroet (CC0)
One more thingThe first set of tiles that could only tile without repeating, found in 1966, needed more than 20,000 different shapes. Penrose's set of 1974 needs two.
SourceNobel Prize in Chemistry 2011, Information for the Public (Royal Swedish Academy of Sciences)
Roger Penrose won the 2020 Nobel Prize in Physics — not for tiles, but for proving black holes can form.