Magnetic bearing (magnetically levitated) and air bearing centrifugal compressors exist. The sculpture consists of an aluminum sphere magnetically levitated above a walnut disc. The linear-motor magnetically levitated train has a top speed of . It is also used for some classes of magnetically levitated bearings. Antihydrogen, like regular hydrogen, is diamagnetic which allows it to be electromagnetically levitated when refrigerated. For example, the Maglev includes trains that are levitated by a large number of magnets. Laputa purportedly levitated through use of artificial magnetism. The dipole will only be stably levitated at points where the energy has a minimum. A mouse has been levitated against Earth's gravity, creating a condition similar to microgravity. When however this field is moving, a vehicle can be levitated and propelled. Diamagnets may be levitated in stable equilibrium in a magnetic field, with no power consumption. With enough thrust, very large objects can be levitated using this method. This observation would become the basis for a fusion approach known as the Levitated dipole. It was a boosted fission device using plutonium in a "levitated" core design. The composite uranium-plutonium "COBRA" core was levitated in a type-D pit.