But we do have convincing information obtained from magnetized mineral grains in rocks that tells us that geomagnetic polarity reversals have occurred a great many times in the history of the earth.

• 但是我们确实从岩石破磁化的矿物颗粒中获得了令人信服的信息，这个信息告诉我们在地球史上曾发生了很多次地磁极性倒转。