Cartier Ronde Louis Silver Dial 18k Rose Gold Brown Leather Automatic Men's Watch W6801004

Was there ever a more primal source of fascination than the celestial dome? Since the beginning of Mankind, the passage from day to night with the Sun giving way to the Moon, plus a full array of stars and constellations, had enabled humans to find some logic in the apparent chaos of the ethereal, including through establishing cycles of time characterized by the changes of the seasons, the tides and the phases of the Moon. The urge to master the space-time environment inspired the first calendars of Antiquity, based on the apparent cyclical movement of the heavenly bodies.

If astronomy is the discipline that studies the working principles of our solar system, horology is the art of measuring time. The evident and historical connection between the two led the Fondation de la Haute Horlogerie - with the contribution of noted historians Dominique Flechon and Gregory Gardinetti - to promote an itinerant exhibition titled "Horology, a Child of Astronomy". After being held at SalonQP in London and Belles Montres in Paris, the exhibition was staged at the Palexpo during the 25th edition of the Salon International de la Haute Horlogerie - and one of the show's major trends (alongside the race to ultra-thinness and the Metiers d'Art craze) was precisely related to astronomical indications, with several prominent models highlighting the Earth, the Moon, the Sun and the cosmos.

Milestones in Celestial Displays
Two historical pieces particularly stand out in the "Horology, a Child of Astronomy" exhibition and the corresponding book. Dated circa 1600 BC and named after the part of Germany near where it was found in 1999, the Nebra Sky Disc is the oldest known depiction of the sky and features 32 heavenly bodies - among them the Sun, a crescent Moon and the Pleiades constellation - in gold on a bronze 32-centimeter disc. It is the father of all moon-phase displays.

The enigmatic Antikythera Mechanism dates from the second half of the second century BC (between 150 and 100 BC) and is the oldest surviving geared machine in the world, used to represent the cosmos and perform both astronomical and calendar-related calculations. It combines a planetarium, a zodiac and several calendars - and inspired the advent of the Hublot Antikythera a couple of years ago.

The Earth
The alternation of daylight and darkness caused by the Earth's rotation on its axis was the basic unit for tracking time in every ancient civilization. The lunisolar calendar was reformed in 1582 under Pope Gregory XIII, leading to the Gregorian calendar now used all over the world. In 1884, the Earth was divided into twenty-four time zones.

Several star timepieces at the SIHH featured perpetual calendars or worldtimers. The Montblanc Meisterstuck Heritage Perpetual Calendar, with its highly attractive price point and classic looks, embodied the brand's new positioning under the leadership of new CEO Jerôme Lambert. The Aquatimer Perpetual Calendar Digital Date-Month was the star of IWC's renewed diver collection, boasting a digital date/month display water-resistant to 100 meters. And the Rotonde de Cartier Astrocalendar watch boasts a flying tourbillon surrounded by a multi-tier circular display for the perpetual calendar powered by a mechanism that is almost entirely free from the typical levers and springs. The most stunning worldtimer seen at the SIHH was the new platinum version of Greubel Forsey's GMT, crowned by a spectacular three-dimensional globe accompanying an inclined 24-second tourbillon.

The Moon
The Earth's satellite has always had a significant cultural and scientific influence; its prominence in the night sky provided early Man with a way of measuring time and developing calendars based on moon phases. The actual duration of the Moon's revolution around the Earth is 29 days, 12 hours, 44 minutes and 2.8 seconds - but is shown as 29 or 29.5 days on conventional dials. The difference adds up to a whole day every three years, requiring manual adjustment of the Moon display mechanism; on more accurate timepieces, correction is only required every 122 years and 46 days, whereas for highly exceptional models the period may be extend to more than 1,000 years.

On the new Grand Lange 1 Moon Phase from A. Lange & Söhne, each lunation is indicated with an accuracy of 99.9978 per cent thanks to a seven-gear transmission and, assuming the watch runs continuously, the display only needs to be corrected by one day every 122.6 years - but it can be adjusted at any time by using the pushpiece embedded in the case flank between 7 and 8 o'clock. The incredibly detailed celestial disc features two textured golden moons and 382 laser-cut gold stars (the smallest one measuring just 0.07mm) enhanced by a patented coating process that gives them a remarkable lifelike appearance.

The highly original Rotonde de Cartier Earth and Moon watch uses its tourbillon (representing the shining Moon) and a moving Lapis Lazuli disc to cover the tourbillon and hence display the moon phase on demand; it also features a second timezone display.

The Sun
Man was first able to measure the flow of time by using the Sun and its positions; the earliest means to measure passing time were gnomons, the ancestors of the sundial. One full orbit of the Earth around the Sun defines the cycle of the seasons. Depending on the season and due to the elliptical orbit of the Earth around the Sun, solar time is some fifteen minutes ahead of or behind mean time shown on clocks and watches - a discrepancy calculated by timepieces featuring the so-called equation of time.

Cartier reinvented its Rotonde de Cartier Day & Night watch, based on a disc highlighted by the Sun and the Moon that rotates over the course of 12 hours, while a retrograde hand denotes the phase of the Moon in the form of a lunar crescent. Greubel Forsey's exceptional Quantieme Perpetuel a Equation calculates solstices and equinoxes alongside a 24-second inclined tourbillon; it features an indicator of the periods when the date should not be adjusted and a new system displaying the moments when solar time and mean time meet up: two superimposed transparent discs reveal the points of intersection as well as showing the equinoxes and solstices, thus providing a clearer indication of the Earth's irregular elliptical orbit around the sun.

The Cosmos
Man has always sought to explain the laws that govern the universe - meaning the totality of galaxies evolving in space and time. Astronomy is the oldest science and inspired many ultra-complicated clocks reproducing a planetary through the depiction of the movement of the planets around the Sun.

A. Lange & Söhne's Richard Lange Perpetual Calendar "Terraluna" has a perpetual calendar on four jumping displays on the regulator-type dial, but on the case back you can see a patent-pending orbital moon-phase display on a disc featuring more than 2,000 micro-stars. The Van Cleef & Arpels Midnight Planetarium Poetic Complication takes the chart of the heavenly bodies even further: it features a three-dimensional cosmic dance on the dial, with each of the planets visible from Earth represented on the watch and their rotation around the Sun occurring in real time (Mercury goes around the dial in 88 days; Saturn takes 29 years). The planet module was designed by Christian van der Klaauw, an authority in movements featuring astronomical indications.