The Moon and its phases fascinate us all. It is a celestial body that intrigues us, shrouded in mystery but a scientific phenomenon. Amazingly, the Moon is 4.5 billion years old and orbits around the Earth at a distance no closer than 384,467 kilometers. Unlike the Earth, it has no life form and possesses neither atmosphere nor magnetic field. Due to the gravity between the Moon and Earth, it pulls the tides.

Above all, the phases of the Moon bear witness to the passage of time. Since the Moon reflects the light of the Sun, and the Moon's position relative to the Earth changes, the angle at which we view the Moon reflects those light changes. The changes that we see in that reflected light are the phases of the Moon.

The first phase, the New Moon, occurs when the Moon reflects no light to Earth. The Moon then evolves to a crescent as it grows or "waxes" to a First Quarter Moon and then a Half Moon. The Moon then becomes a Full Moon and afterward becomes smaller or "wanes" to another crescent until it becomes another unlit New Moon. The completion of the Moon's phases occurs on approximately a 29.53 day cycle, known as a synodic month. Technically this cycle, a "lunation", occurs every 29 days, 12 hours, 44 minutes and 2.8 seconds.

Because of the regularity of this cycle, the phases of the Moon have been used in astronomy as a form of calendar. In the Western world, the Moon has given definition to the onset of crop cycles and religious holidays such as Easter. In fact, Easter is a function of Moon phases: it is on the first Sunday after the first Full Moon in Spring.

Our fascination with the Moon and its phases goes beyond astronomy and has become an integral part of horology. Watches, instead of only showing hours, minutes or seconds, also began showing moon phases, essentially serving as a calendar function. As early as 1794, Abraham-Louis Breguet designed a watch with a moon phase indication.

A moon phase indication uniquely differs from most other indications on a watch dial. Most other watch indicators are analog: that is, they show something by analogy or conceptually. A hand points to a number, and in our mind that number translates to a given point of the day. But the moon phase indication is graphic and direct: it is intended to depict the actual Moon. Almost uniquely, it shows an actual image on the watch dial. In doing so, moon phase watches are more than a testament to timekeeping, going back to its astronomical origins, but also they are an artistic statement.

Beyond counting every 29.5 days, the depiction of the phase of the Moon on a watch dial can be a beguiling image. Sometimes the representation of the Moon includes a face, and sometimes one that is smiling. Often the Moon is reflective, with a shimmering metallic coat. Sometimes it has been placed on an enamel disk and sometimes we see embedded stars in the celestial sky around the Moon.

Those fanciful and artistic elaborations would not exist if we were not fascinated with the Moon, as we witness its phases that continually evolve and diminish. Our fascination has transferred itself from the Moon itself to moon phase watches. In the past several decades, watches with that complication have become especially sought after.

In the middle part of the 20th century, when wristwatches surged in popularity, not many wristwatches produced by any watch company had moonphase functions. Like the moon itself, interest in this function has waxed and waned. During that epoch IWC prided itself on being a premier manufacturer of basic watches: no-nonsense, highly engineered pieces that kept impeccable time and did so with few frills or complications. But over the past quarter century IWC has been engaged in an ongoing romance with moon phase watches.

In the 1970s, the introduction of inexpensive and highly-accurate watches with quartz movements radically altered the watch market. Suddenly, those finely-crafted, well-engineered mechanical movements had relatively little market appeal. Watch companies went under and the survivors clung to whatever lifelines they could. In IWC's case, the proud mechanical watch company thought for a time that it could survive as a specialty producer of mechanical pocket watches.

Accordingly, as an attempted answer to the quartz revolution in the late 1970s and early 1980s, IWC produced several models of complicated mechanical pocket watches. Many carried special complications, even repeater models and some with a thermometer. Several had a moon phase indication, which is not a technically difficult mechanism to produce, but nonetheless results in a special watch. One of those IWC pocket watch models was the Reference 5250, a basic watch with remarkably clean styling and, yes, a moon phase.

The first important moon phase wristwatch from IWC occurred probably by accident in the early 1980s. In 1982, IWC produced 150 examples of a new model, Reference 3710. That watch had moon phase, calendar and chronograph functions. It apparently was IWC's first wristwatch with a moon phase function and unknowingly became the start of a trend.

At about the same time in the early 1980s, two other developments affected the history of moon phase wristwatches at IWC. The first is that pocket watches didn't sell as well as planned, and IWC's designer at the time, Hano Burtscher, discussed that with a watchmaker named Kurt Klaus. They talked one night at a bar about converting that moon phase pocket watch to a wristwatch, simply by adding lugs to the case. With a few quick sketches on a cocktail napkin, the idea for IWC's first "in-house" moon phase wristwatch was born. In 1984, that watch became Ref. 5251 and was later known as the Giant Portofino.

At about the same time, Kurt Klaus was working on another watch movement. He had the very innovative idea for a perpetual calendar movement in which all of the functions would be integrated and set simultaneously via the crown. After all, our calendar, even with its variances in length of months, is mathematically predictable. For any given future date, one can also tell the day and also the accompanying moon phase. Accordingly, Herr Klaus' revolutionary perpetual calendar movement would also show the moon phase.

That new movement was not to have any ordinary moon phase indication. Traditionally, most watch companies used what is called a 59/2 wheel ratio, since that shows a new Moon every 29.5 days and is relatively close to the "true" 29.53 day moon phase cycle. However, a 29.5 moon phase gearing produces an error of the moon phase being "off" one day every three years. That traditional 59/2 gearing also was what IWC used in its Ref. 5250 pocket watch and the Ref. 5251 Portofino Moon phase.

But for his new movement - first used in what is known as the Da Vinci perpetual - Kurt Klaus wanted to achieve even greater accuracy. Because all date functions were integrated, it would be difficult to correct the watch calendar, especially only the moon phase indication, every three years. Consequently, a much more complex gearing was developed and the new movement showed a new Moon once every 29.53125 days, or remarkably an error of one day in every 126 years!

No one then knew how a new mechanical perpetual calendar watch might sell in the mid-1980s, which still was considered the quartz "dark ages". But the Da Vinci perpetual took off. By the late 1980s, a growing group of watch collectors embraced such retro-radical watches. IWC then embraced moon phase indications on many models. All of its perpetual calendar models used them, since IWC had this special movement module ingeniously developed by Kurt Klaus. Also, many of IWC's Porsche Design models, from the 1980s and the early 1990s, had moon phase indications. Some models even had moon phase function added. For example, the IWC Porsche Design compass watch subsequently had a second generation version made with a moon phase indication.

In the late 1980s and early 1990s, wristwatches with moon phase dials almost became synonymous with the renaissance of the mechanical watch. Like the phases of the Moon which wax to a full Moon, the history of the automatic watch in the latter part of the 20th century parallels the rebirth of interest in this complication.

It was within this context that watch collectors rediscovered IWC's Reference 5251. Originally, the watch only sold in limited quantities: a 46 mm pocket watch for the wrist, even with pure design and a fanciful Moon, was too large for the 1980s style. Not many were produced. But watch collectors then began to understand the importance of the pocket watch heritage, especially for IWC. Through IWC's pioneering efforts in the early 1990s, larger watches became especially popular. Moreover, the Giant Portofino's moon phase function had a special allure to collectors. It was a simple complication from a mechanical perspective, but a beautiful one. It was almost uniquely graphic and a representation of the Moon itself - intertwining science and art.

Collectors then began to search worldwide for a Giant Portofino. That watch model, perhaps unwittingly, then rose to become an icon. It might have been its size. It might have been its rarity or its perfect design. It might have been its symbolism as a pocket watch, in the great historical Schaffhausen tradition. But above all else it was undeniable pull of its moon phase. It was that little window on the dial with that moon phase that made the watch.

The good news was that collectors understood and appreciated this special watch with its moon phase. But the more troubling story was that as demand soared, the price of vintage models soared in the marketplace. The model became increasingly difficult to obtain.

In celebration of its 140th anniversary, IWC has solved this problem for all collectors. It has produced a new Portofino moon phase wristwatch. It is a new watch but a clear homage to its predecessor. It both honors and reaffirms a rightful heritage of a company that began making pocket watches and evolved to making complications. Some of those complications are simple and some are complex.

But perhaps no one complication is as attractive as the simple one here that shows the phases of the Moon. The general design of the new Portofino wristwatch possesses grace in its own right, but it is that window, with the disc reflecting the phases of the Moon, that makes this new wristwatch special. The special starry sky was produced by IWC using "Aventurin", a quartz silicia that has a sparkle. Aventurin is often used as a gemstone, and fittingly here results in a strikingly beautiful watch.

This new watch also solves Dr. Einstein's problem. If he could have owned it, the Moon would always have been captured for him to see. For all fortunate collectors who will own one, they will always be able to see the Moon. Every time they glance at their wrist, they will see history, art and science all combined in one simple and very beautiful celestial window.

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