ARCHITECTURE: Cereal thrillers, sacred geometry and the magic of number seven

Corn circles have been around for nearly 20 years, first appearing on an ancient sacred site below the Westbury White Horse in Wiltshire in 1980. What are they? Skidmarks from space craft? Balls of energy sent from other planets? Plants trying to communicate with mankind? Practical jokers were certainly responsible for some of them. And quite possibly freak winds and hybrid wheat and barley seed for a few.

But does this explain those highly complex patterned crop circles for which there is no obvious maker? They mostly appear in Hampshire and Wiltshire, where ley lines in the earth, supposedly strong enough to force a diviner's rod from his hand when sinking bore holes, encouraged our ancestors to build temples.

These sacred sites seem to attract sacred geometry, in the form of elaborate pattern making. A necklace of corn circles like a triple DNA strand appeared in a wheat field at Allington Down near Devizes, on 26 June. For John Martineau, a graduate from the Prince of Wales Institute of Architecture, this big circle with three arms of nine circles each is a portent for this Wednesday, the seventh day of the seventh month when he expects the planet Mercury to place a sign in a cornfield somewhere in Wiltshire. It will be based on the mathematical configuration of Mercury's orbit.

A circle inside another circle - Mercury's orbit and the earth's orbit - intersected by a five pointed star, Martineau's drawings of these astronomical calculations hang at the Visual Islamic and Traditional Arts school of the Prince of Wales Institute of Architecture. Here a band of tilers and engravers, painters and poets, Moghul miniature makers, and architects learn about sacred geometry from Dr Keith Critchlow.

"Sacredness is as simple as breathing," he says. "The earth, sky, water - all that keeps man alive and centred in the universe is sacred. Geometry unlocks some of the wonder." He believe that corn circles are genuine. "Authentic corn circles have appeared. It would be far too complicated to fake the Mandelbrot fractal pattern with 151 spirals which appeared near Stonehenge a few years back. That is something we cannot explain," he says.

It is harmony that underlies Dr Critchlow's love of Islamic architecture. It perfected the use of Golden Section, the harmonious, though irrational, ratio of dividing space. "Not irrational, transcendental," Dr Critchlow chides me. "Philosophically it translates as `do as you would be done by'."

He uses his hands, ringed and clasped in silver bracelets, to show the distances as zones between us on the golden mean to indicate distance and closeness in communicating as well as the geometric ratios which equate roughly as 5:8. Dr Critchlow, a hybrid of Merlin meeting Liberace, has those ping-pong ball eyes that artists give saints in icons. His favourite example of sacred geometry is the Isphahan mosque in Turkey which he entered at daybreak and left only at evening so that he could follow the passage of light. "Light gently diffused through colours on to the brick, sometimes flaring through screens."

He likes Chartres Cathedral too, and the minimalists' favourite, the Cistercian Abbey of Thoronet. "So acoustically perfect that you can hear your own heartbeat. Form and function delineated in the curvature of the arch and the austerity of the interiors designed to enhance 24-hour chanting."

Under pressure he admits that he gets a buzz from Le Corbusier's chapel at Ronchamp where the light floods in through conical light wells. His respect for some contemporary architects does not extend to modern architects, "if their modernity means the abandonment of traditional values, all things which enhance the meaning of life." Perhaps he did write the crib sheets for the Prince of Wales's thoughts on architecture after all.

So why will 7 July be so important? He answers with a question just as he often speaks in riddles. "How many days are there in creation? The Jew, the Christian, the Moslem all agree." Seven is a sacred number composed of four and three which the Babylonians and Egyptians and all ancient people thought were lucky numbers. There are seven planets - the sun and the moon, Mars, Mercury, Saturn, Jupiter, Venus - seven days in creation, seven days in the week, and seven Graces.

"One, two and three are just as profound - one plus one equals two, just as one times one is two again. The ratio of one to the square root of two is important. In Islam it determines window openings and how light falls. The geometry gets smaller on windows as it goes up.

"As for zero, it was so powerful the ancients kept knowledge of it hidden."

It sounds corny but Dr Critchlow radiates a positive atmosphere; electrifying, even. You could run a wire coat hanger round him to check his aura. The Prince of Wales Institute of Architecture has been through rough times but Critchlow has not lost that sunny optimism which he says was Buckminster Fuller's legacy to him. A former football player, he went to Africa with the great Buckie, the architect's architect, to teach Ghanaians to build geodesic domes from palms and bamboo. "Bamboo, now there's a material for the future. It can grow 70ft in a season. Split its girth and you make roof tiles. Every man can build his own house."

Finally, and most alarmingly, he points out why Wednesday 7 July just might have an impact that Nostradamus never thought of. "The notes in an octave are in powers of seven. The atomic world works in octaves of atoms. The atomic world is the power of all physicality. The word atom comes from the Greek a tom, a word for uncuttable, which means not that matter couldn't be cut but that it shouldn't be. Once cut, it releases forces. Nobody knew when they exploded the atom whether it wouldn't set off a chain reaction going round the world." Let us devoutly hope that the seventh day of the seventh month does not go with a Big Bang.