DA VINCI CODE 20-7
"You do?"
"Yup. PHI."
The girl gaped. "NO WAY!"
"Way!" Langdon fired back, smiling as he projected a slide of a spiral seashell. "Recognize this?"
"It's a nautilus," the bio major said. "A cephalopod mollusk that pumps gas into its chambered shell to adjust its buoyancy."
"Correct. And can you guess what the ratio is of each spiral's diameter to the next?"
The girl looked uncertain as she eyed the concentric arcs of the nautilus spiral.
Langdon nodded. "PHI. The Divine Proportion. One-point-six-one-eight to one."
The girl looked amazed.
Langdon advanced to the next slide—a close-up of a sunflower's seed head. "Sunflower seeds grow in opposing spirals. Can you guess the ratio of each rotation's diameter to the next?"
"PHI?" everyone said.
