Helios Orrery

The Orrery, developed by Helios for the Swiss watchmaker Audemars Piguet in Le Brassus, is an Earth-Sun model. The Earth moves through an elliptical path around the Sun, not in its traditional circular orbit. This enables us to graphically illustrate the special functions of the Audemars Piguet "equation du temps" wristwatch, which displays true noon and the equation of time.

For this reason, in the Earth-Sun model we consciously deviate from reality. The eccentricity of the Earth's path is overemphasized and the tropical year only has 12 days, in order to show the elliptical path's impact on the path's speed and to clearly illustrate the day's real length from noon to noon. This enables us to display the dynamic part of the equation of time, based on Kepler's 2nd law.

By tilting the Earth's path (originally horizontal) by 23,5°, we can display the effect of the geometric part of the equation of time and the shortening or lengthening of the day's real length, by projecting the movement of the Earth's path onto the equator level. The model copies nature with absolute precision, the gimbal mounted globe can even maintain its direction upwards to the celestial pole while moving along the elliptical path, so that the direction from which the Sun's rays hit the Earth is constantly changing and the seasons emerge.