John Flinders Petrie

John Flinders Petrie
Died	1972 (65 años)
Nationality	United Kingdom

John Flinders Petrie was born on April 26, 1907, in Hampstead, London. He was the only son of the renowned Egyptologist Sir William Matthew Flinders Petrie.. Already as a student he showed the remarkable potential of his mathematical abilities and his great visual memory, which his father also showed, allowed him to visualize complex geometries. While studying at a boarding school, he met Harold Coxeter in a sanatorium while he was recovering from a minor illness, beginning a friendship that would remain throughout their lives. Looking at a geometry textbook with an appendix on Platonic polyhedra, they wondered why there were only five and tried to increase their number. Petrie commented: How about we put four squares around one corner? In practice, they would lie on a plane, forming a pattern of squares that would cover the plane. Being clever with words, he called this arrangement "tesserohedron"; calling the similar arrangement of triangles a "trigonohedron."

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John Flinders Petrie (April 26, 1907 - 1972) was an English [[mathematician, who demonstrated remarkable geometric aptitude in his youth. As a student, he met the great geometer Harold Scott MacDonald Coxeter, beginning a lifelong friendship. They collaborated in the discovery of infinite warped polyhedra and (finite) warped polyhedra in the fourth dimension, analogous to the previous ones. In addition to being the first to realize the importance of the warped polygon that now bears his name, his skills as a draftsman are still appreciated.

Biography

Petrie was born on April 26, 1907, in Hampstead, London. He was the only son of the renowned Egyptologist Sir William Matthew Flinders Petrie. Already as a student he showed the remarkable potential of his mathematical abilities and his great visual memory, which his father also showed, allowed him to visualize complex geometries. While studying at a boarding school, he met Coxeter in a sanatorium while he was recovering from a minor illness, beginning a friendship that would remain throughout their lives. Looking at a geometry textbook with an appendix on Platonic polyhedra, they wondered why there were only five and tried to increase their number. Petrie commented: How about we put four squares around one corner? In practice, they would lie on a plane, forming a pattern of squares that would cover the plane. Being clever with words, he called this arrangement "tesserohedron"; calling the similar arrangement of triangles a "trigonohedron."

Polyhedral regular tilings

One day in 1926, Petrie told Coxeter that he had discovered two new regular polyhedra; infinite, but free of "false vertices" (points distinct from the vertices, where three or more faces meet, like those that characterize regular star polyhedra): one consisting of squares, six at each vertex and another consisting of hexagons, four at each vertex, which form a dual or reciprocal pair. To the common objection that there is no room for more than four squares around a vertex, he revealed the trick: allow the faces to be arranged up and down marking a zigzag. When Coxeter understood this, he mentioned a third possibility: hexagons, six around a vertex, its own dual.

Coxeter suggested a modified Schläfli symbol, {l, m | n} for these figures, with the symbol {l, m} implying the vertex figure, m l-gons around a vertex and n-gonal holes. Then it occurred to them that, although the new polyhedra are infinite, they could find analogous finite polyhedra by delving into the fourth dimension. Petrie cited one consisting of n2 squares, four at each vertex. They called these figures "regular skew polyhedra". Later, Coxeter would delve deeper into the subject.

University and Work

Because his father belonged to University College London, Petrie enrolled in this institution, where he completed his studies without difficulty. When the Second World War broke out, he enlisted as an officer and was captured as a prisoner by the Germans, organizing a choir during his captivity. After the war ended and he was released, he went to Darlington Hall, a school in southwest England. He had a mundane job, working many years as a school teacher and apparently never culminated his early mathematical ability. He was one of the tutors who attended to the children who were doing poorly in school.

The Petrie polygon

Petrie continued to correspond with Coxeter and was the first to notice that, among the edges of a Regular polyhedron, a skew polygon forming a zigzag can be distinguished, in which the first and second are the edges of one face, the second and third are artists of another face and so on, successively. This zigzag is known as the "Petrie polygon"

and has many applications. The Petrie polygon of a regular polyhedron can be defined as the skew polygon (whose vertices do not all lie in the same plane) such that every two consecutive sides (but not three) belong to one of the faces of the polyhedron.

Each finite regular polyhedron can be orthogonally projected onto a plane in such a way that the Petrie polygon becomes a regular polygon, with the rest of the projection inside it. These polygons and their projected graphs are useful in visualizing the symmetrical structure of regular polytopes of higher dimensions, which are very difficult to conceive or imagine without this aid.

His skills as a draftsman can be appreciated in an exquisite set of drawings of the stellated icosahedron, which provides much of the fascination of the much-discussed book he illustrates. On another occasion, to explain the symmetry of the icosahedron, Coxeter showed an orthogonal projection, representing 10 of the 15 great circles as ellipses

. The difficult task of drawing was performed by Petrie around 1932. It now prominently features on the cover of a popular recreational mathematics book, garnished with a touch of color. It is reported that, in periods of intense concentration, he could answer questions about complex figures of the fourth dimension by "visualizing" them.

Final years

Petrie got married and had a daughter. In late 1972, his wife suffered a sudden heart attack and passed away. He missed her so much and was so distracted, that one day he walked onto a highway near his home and, while trying to cross it running, was hit by a car. He died in Surrey, at the age of 64, just two weeks after his wife.

See also

• Petrie polygon
• Skew polygon

References

{{Reflist}

• Ball, W. W. Rouse; Coxeter, H. S. M. (1987). Mathematical recreations and essays (in inglés) (13.ª ed.). Nueva York: Dover Publications. ISBN 0-486-25357-0.{{cite book}}: CS1 maint: unrecognized language (link)
• Coxeter, H. S. M. (1973). Regular polytopes (in inglés) (3.ª ed.). Nueva York: Dover Publications. ISBN 0-486-61480-8.{{cite book}}: CS1 maint: unrecognized language (link)
• Coxeter, H. S. M. (1989). Introduction to geometry. Wiley Classic Library (in inglés). Vol. 19 (2.ª ed.). Nueva York: Wiley. ISBN 9780471504580.{{cite book}}: CS1 maint: unrecognized language (link)
• Coxeter, H. S. M. (1995). Kaleidoscopes: selected writings of H. S. M. Coxeter (in inglés). Introducción y compilación de F. A. Sherk; P. Mullen; A. C. Thompson; Ivić Weiss. Nueva York: Wiley–Interscience Publication. ISBN 9780471010036.{{cite book}}: CS1 maint: unrecognized language (link)
• Coxeter, H. S. M.; Du Val, P.; Flather, H. T.; Petrie, J. F. (1999a). The fifty–nine icosahedra (in inglés) (3.ª ed.). Tarquin. ISBN 9781899618323.{{cite book}}: CS1 maint: unrecognized language (link)
• Coxeter, H. S. M. (1999b). The beauty of geometry: twelve essays (in inglés). Nueva York: Dover Publications. ISBN 0-486-40919-8.{{cite book}}: CS1 maint: unrecognized language (link)
• Hargittai, Balazs; Hargittai, István (2005). Candid science v: conversations with famous scientists (in inglés). Londres: Imperial College Press. ISBN 9781860945069.{{cite book}}: CS1 maint: unrecognized language (link)
• Kepler, Johannes (1997). Harmonices mundi (in latín). Tr. al inglés con introducción y anotaciones por E. J. Aiton; A. M. Duncan; J. V. Field. The American Philosophical Society. ISBN 0-87169-209-0.{{cite book}}: CS1 maint: unrecognized language (link)
• McMullen, Peter; Schulte, Egon (2002). Abstract regular polytopes (in inglés). Cambridge: Cambridge University Press. ISBN 0-521-81496-0.{{cite book}}: CS1 maint: unrecognized language (link)

• Jenkins, Nicholas. "John Flinders Petrie". W. H. Auden – ‘Family Ghosts’ (in inglés). Retrieved 2012-10-11.{{cite web}}: CS1 maint: unrecognized language (link)
• Jenkins, Nicholas. "John Flinders Petrie". Kindred Britain (in inglés). Retrieved 2017-07-18.{{cite web}}: CS1 maint: unrecognized language (link)
• Weisstein, Eric W. "Petrie polygon". MathWorld.
• Weisstein, Eric W. "Skew polygon". MathWorld.
• Weisstein, Eric W. "Regular skew polyhedron". MathWorld.