Sir Joseph Larmor, an Irish mathematician, proposed in 1919 that it was generated spontaneously by the swirling of molten metal inside the planet.

• 1919年，爱尔兰的数学家约瑟夫?拉莫尔提出它是随着地球内部已溶金属（导电流体）的旋转而自然形成的。