Jaeger-LeCoultre Atmos

At first glance, Jaeger-LeCoultre's Atmos looks like any other table clock. However, the Atmos is incredibly unique: It's not powered by a battery, weights, or key winding, but rather by temperature changes in its immediate environment. Seeing as the clock is sensitive to dust, its ingenious technology is safely contained in a glass case. Jaeger-LeCoultre decided against adding a seconds hand in order to save energy.

In terms of price, most Atmos clocks cost under 10,000 euros. However, some cost more, such as the Atmos Réédition. This clock, first produced in the 1930s, has a historic design with a large, round glass bell jar supported by a steel platform; it is available for 20,000 euros. Even more expensive are the blue crystal Atmos models designed by the Australian designer Marc Newson. Only 28 clocks (reference number Q5165103) were produced, and their price reflects their rarity: They cost around 100,000 euros.

Most Atmos models have conservative designs with metal pieces made of gold-plated brass. You can purchase one of these clocks in good or very good condition for 2,000 euros. The Classique version (reference number 5101202) has a dial featuring Roman numerals and is available for around 5,000 euros. The Jaeger-LeCoultre Atmos Classique is 22.5 cm tall, 20 cm wide, and has a depth of 15.5 cm. In addition to the gold versions, there are also silver-gray versions made of rhodinized brass.

The Marina version (costing around 4,000 euros) is in a solid case and features maritime imagery such as ships, fish, and water plants. You can find a special model of this version, the China Aquarium, under reference number 5806.

Seeing as most complications require massive amounts of energy, Jaeger-LeCoultre forwent extras on the Atmos in favor of a smoothly running clock. One exception is the version with a moon phase display at the six o'clock position; it costs around 6,500 euros.

The round pendulum that functions as a balance wheel swings back and forth once a minute and is sure to catch onlookers' eyes. But where does it get its energy? The secret is temperature change; the Atmos draws its energy from changes in temperature in its immediate environment . The clock features an internal hermetically sealed capsule filled with ethylene chloride. Minimal rises in temperature cause the liquid in the capsule to change into gas, expanding the flexible capsule, which then pushes against a balance spring. It reaches its maximum expansion at 27 degrees Celsius and shrinks again as temperatures drop, thereby relaxing the balance spring.

This growing and shrinking motion is used to wind the caliber's mainspring and put the hands in motion. A temperature change of one degree Celsius is enough to power the clock for two days. Theoretically, the Atmos can function forever, as long as it experiences enough temperature fluctuations in its environment. However, it's recommended to have your Atmos serviced every 15 years to make sure it keeps running smoothly.

The Swiss engineer Jean-Léon Reutter (1899-1971) invented the Atmos in 1928. Jaeger-LeCoultre bought the patent shortly thereafter. The company has more or less kept the design of the atmospheric clock consistent since 1945. From a physics point of view, the Atmos is a heat engine; for Swiss state guests, on the other hand, it's a gift. The Swiss government gives its official visitors an Atmos clock as a lasting memory and symbol of the Swiss people's special watchmaking skills.

The Atmos runs even more precisely than the chronometer norm established for wristwatches . Usually, the clock deviates from the reference time by about one minute each month. When regulated even more precisely, it's possible that the clock will deviate by only 30 seconds per month. This is an astounding value considering the pendulum only undergoes 120 alternations per hour. In comparison, the balance wheel of a modern wristwatch vibrates at 28,800 alternations per hour. The Atmos's pendulum is supported by a suspension wire made of Elinvar, a material that is resistant to temperature changes – an important characteristic for this clock.

Even more impressive is the minimal energy needed to keep the Atmos running. According to Jaeger-LeCoultre, it would take 60 million Atmos clocks to equal the energy use of a 15-watt light bulb. The movement functions with as few components as possible, none of which require lubrication. Friction loss is thus minimized and the caliber runs smoothly; however, this also makes the movement sensitive to dust particles. Thus, the clock's case isn't just decorative, but rather a method of protecting the caliber.