The right answer is: 2. We would begin to fly. All matter, subjected to a sufficiently powerful magnetic field, generates its own, opposing magnetic field in response. It thus transforms into a sort of magnet with a repulsive force pushing it away from the external magnetic field. This phenomenon, called diamagnetism, results in levitation when the source is coming from below. There’s no magic to it – it’s all quantum mechanics. The game is played out on the atomic level, where the externally applied magnetic force engenders a modification in the orbitals of the electrons spinning around the nucleus. A quick voyage into the world of materials will reveal how some materials acquire magnetic properties, and thus magnetism. Let’s look at things like a quantum physicist, starting with the idea of atomic orbitals. “The magnetic properties of a material depend on two basic principles,” explains Henrik Rønnow, head of EPFL’ Laboratory of quantum magnetism. “The first is that any electron orbiting the nucleus of an atom creates a magnetic field. The second is a law of quantum physics that says that there is always room for two electrons in any orbital, but they can never spin in the same direction. There is thus always one spinning in one direction and one in the other.” When there are two electrons in the same orbital, they generate opposing magnetic fields that cancel one another out. But when there’s just one electron, its magnetic field is present. To be magnetic, an atom must therefore have a single electron, as is the case in many metals. This is why magnetic properties are found principally in the family of metallic elements. Aligned, dispersed or bunched So why aren’t all the metals magnetic? To be a magnet, not only must the atoms be magnetized in the manner described above, but their respective magnetic fields must also be aligned in the same direction. If the atoms are arranged in a non-coordinated manner in the material and don’t interact, their magnetic fields will point in all directions and cancel one another out. These materials are described as paramagnets. Sometimes, the atoms interact and the fields align, but only in small packets called domains. Since they are oriented in different directions, the magnetic forces of the domains will also cancel each other out. Iron and cobalt are among the elements with this characteristic, and are described as ferromagnets. Paramagnets and ferromagnets aren’t magnetic as such. But this property can be conferred on them if they are put in contact with a powerful magnet that aligns their atomic magnetic fields in the same direction. Ferromagnets, with their atoms grouped into magnetic domains, are interesting materials because the energy needed to magnetize them is smaller than for paramagnets, which are about 1000 times weaker. Ferromagnets are divided into two categories. Those that remain magnetized once their domains are aligned are known as permanent magnets – these are used in ordinary magnets and compasses, electric motors, and windmills. The second category includes metals that don’t maintain their orientation in the absence of an external electric field; they’re known as “soft magnets”. They’re found in electric transformers and are used to augment the fields of electromagnets. Temporarily single As mentioned earlier, even atoms of elements that aren’t intrinsically magnetic – whose orbitals are all occupied by two electrons spinning in opposite directions – can be magnetized by a phenomenon known as diamagnetism. If it’s sufficiently powerful, an external magnetic force acts so strongly on these atoms that it modifies the orbital, separating the electrons slightly. The electrons thus find themselves in a temporarily isolated state. Their magnetic fields no longer cancel each other out. In contrast to ferromagnets or paramagnets, whose magnetic fields are aligned in the same direction as the applied external magnetic source, diamagnetic materials create a field that opposes the source, and can thus end up levitating. Thanks to Henrik Rønnow, Laboratory for Quantum Magnetism EPFL.