The Walkie-Talkie Skyscraper
Geometry & Trigonometry
20 Fenchurch Street's curved facade focused sunlight and reportedly damaged a parked car. Model the building's curve as a parabola and find where it concentrates light.
Introduction
In 2013 the curved glass facade of 20 Fenchurch Street, nicknamed the Walkie-Talkie, focused reflected sunlight onto Eastcheap below and melted parts of a parked car. A concave curved surface can focus parallel rays of light to a point, the same property used deliberately in satellite dishes and solar concentrators, but here it was an unintended side effect of the building's shape. This exploration asks how closely the building's curve matches a parabola, and where the reflected sunlight concentrates at different times of day.
Guiding Questions
- The Walkie-Talkie skyscraper melted cars by focusing sunlight. What shape was the facade, and why did it focus light?
- Model the building's curve and find where it concentrates parallel rays at different sun angles.
- How much energy could plausibly concentrate at the hot spot? Estimate with areas.
- How did the fix (sunshades, redesign) change the geometry? Could you design a curve that never focuses?