What is permanent magnetism?

Permanent magnetism refers to the stable magnetic condition of an object that results from the materials it is constructed from. In the context of a ship, certain materials used in the construction can retain magnetic properties over time, becoming magnetized. This can influence the magnetic compass onboard, affecting navigation.

When a ship is built, ferromagnetic materials can absorb some magnetic field lines based on their composition and structure, leading to a consistent magnetic influence even after the original external magnetic fields are removed. This permanent magnetism can introduce a deviation in the compass readings, as the compass responds not only to the Earth’s magnetic field but also to the ship's inherent magnetic field.

Understanding permanent magnetism is crucial for navigators to correct any deviations that may occur due to the ship's materials, ensuring accurate compass readings and effective navigation.