terrellas

/təˈrɛləz/
noun
  1. Plural of terrella; small models or representations of the Earth, especially spherical magnets used to demonstrate magnetic fields.
    • The museum displayed several terrellas used in early experiments on magnetism.
    • The collection of terrellas included models from the 16th century onward.
    • Researchers built terrellas of different sizes to compare magnetic field patterns.