The Earth's inner core has suddenly slowed down and started its rotation along the reverse direction, researchers have found. This raises a few questions on the Earth's rapidly changing dynamics and how this reverse movement of the Earth's core can affect the world.
The Earth’s magnetic field has alternated between periods of normal polarity, in which the predominant direction of the field was the same as the present direction, and reverse polarity, in which it was the opposite. These periods are called chrons.
Reversal occurrences are statistically random. There have been at least 183 reversals over the last 83 million years (on average once every ~450,000 years).
It’s happened before.
https://en.wikipedia.org/wiki/Geomagnetic_reversal