Over the last few years, Omega has increasingly become one of the watchmaking industry’s leaders in making watches that can withstand extremely powerful magnetic fields and emerge unscathed. With the opening of a new exhibition at the Omega Museum in Bienne, Omega replica watches are underscoring just how far it has come – and part of the exhibition is a watch that’s survived what is, by far, the strongest magnetic field to which any watch has ever been exposed (as far as we know).
Magnetism is of course a huge issue in watchmaking. Ultra-powerful magnetic fields like those created in labs studying magnetism are less an issue than the magnetic fields found in everyday life, such as those produced by permanent powerful magnets used in consumer products. Though Nivarox-type balance springs are not nearly as vulnerable to magnetism as plain steel, they can nonetheless be affected; even brief exposure to a strong field can badly impair accuracy. Less noticeable is the effect of magnetic fields over the long term – you might not notice it immediately, but over time, exposure to magnetism can negatively affect the ability of a Nivarox-type balance spring to compensate properly for temperature variations.
Traditionally, the way to deal with magnetic fields was to place the movement in an inner case made of so-called “soft iron.” In this case, “soft” means soft magnetically – that is, a material that will conduct a magnetic field, but not become magnetized itself; such materials are generally nickel-iron alloys, and are also called “mu-metals,” the Greek letter mu (μ) being the symbol for magnetic permeability.
In January 2013, Omega announced the Omega Aqua Terra series fake watches >15,000 Gauss, which is capable of withstanding a 15,000 gauss magnetic field (that’s MRI machine-level stuff; your average refrigerator magnet is about 50 gauss). Also, 15,000 gauss is equivalent to 1.5 tesla, a more convenient unit for expressing very strong magnetic fields.
Incredibly, the Seamaster Aqua Terra at the heart of the exhibition withstood a field 16 tesla, or 160,000 gauss. The experiment took place at the Laboratoire National des Champs Magnetiques Intenses (LNCMI) in Grenoble, France, a lab which specializes in research into extremely powerful magnetic fields. Equipment at LNCMI can generate sustained fields of up to 35 tesla, and at the lab’s Toulouse facility, millisecond-duration fields of up to 250 tesla have been generated (although this destroys the field generator coil). For reference, the magnets used to confine the particle beams of the Large Hadron Collider operate at about 8.3 tesla – more than 100,000 times as powerful as the Earth’s magnetic field.