The Hole in the Cupola of the Cathedral

The XV century’s mathematician and cartographer Paolo Toscanelli made a 4-centimeter-wide hole on the cupola of the Cathedral, through which he could observe the sun. The small hole channeled the beams of the sun that entered from the ceiling and formed a sort of sundial on the floor. However, this is not the only reason why this hole is so important. Later on, the hole helped make important astronomic breakthroughs, such as the introduction of the Gregorian calendar in 1582, the definition of the solar year and the discovery of the angle of inclination of the Earth’s axis.

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