The moon phase is a beautiful reminder of an age before time was ruled by gears, crystals and atoms. Yet the moon phase also reminds that though our timekeepers may achieve aesthetic perfection, they will always struggle to keep pace with the imperfect universe we inhabit.
The challenge posed by the moon arises from the fact that it completes a revolution around the earth in 29 days, 12 hours, 44 minutes and 2.9 seconds. Brass wheels and pinions don’t handle these types of periods very well, so watchmakers use approximations, most commonly 29.5 days, which translates to a moon phase disc with 59 teeth. That’s pretty close right? The display is only off by one day in about two years, seven months and two weeks.
Not content with that so-so accuracy, watchmakers developed a disc with 135 teeth, which produced a display accurate to one day in 122 years. That’s the standard most of us know and recognize as a sign of precision. Accuracy that outlives the original owner should be fine, but it’s not, especially when a timepiece is designed to keep time precisely, and to do so as it is handed down through many generations.
This thinking lead the watchmakers at Jaeger-LeCoultre to develop the new Duomètre Sphérotourbillon Moon, which, as you may surmise, endows the already stunning Duomètre Sphérotourbillon with a moon phase display. But not just any moon phase display. This one is accurate to one day in 3,887 years – a breathtakingly long period of time. If you take delivery of one this summer, your heirs 155 generations hence will have to teleport it to Le Sentier to be adjusted in the year 5902.
The astronomical tour de force does not stop there. Lovers of heavenly bodies know that each planet spins around an axis that is never perpendicular to the orbital plane. The angle of the earth’s axis is around 23 degrees. This natural tilt causes our seasons and weather patterns to change. Just as Earth rotates on its tilted axis as it revolves around the sun, the Sphérotourbillon performs a full turn around the axis of its titanium carriage while it spins around a second axis inclined at a 20° angle – a nod to the inclination of the earth that follows an imaginary line stretching to Ursae Minoris, the polestar.
Finally, precise timekeeping aficionados will appreciate Jaeger-LeCoultre’s creative use of its Dual-Wing movement construction in this timepiece. The caliber is designed such that the 2 o’clock push-piece can reset the small seconds at 6 o’clock to zero and restart them instantly, using the flyback principle. Employing the flyback system does not halt the operation of the regulating organ. Unlike so-called hacking seconds which stop the balance wheel when the crown is pulled out, the Duomètre Sphérotourbillon mechanism allows the small seconds hand to return to zero and restart instantly, without the balance wheel missing a beat. No time is wasted between the stopping operation and the resumption of the regulating organ’s steady motion, so the watch remains accurate even when adjusting the time to the nearest second.
Complete technical specifications for the Duomètre Sphérotourbillon Moon appear below.