It is generally known that a compass needle will point north. It does not point to the geographical North Pole, but to the magnetic north pole. The Chinese tell stories of their seagoing ancestors whose compasses pointed south. For a long time, no one believed these stories. Then scientists discovered that periodically the magnetic poles of Earth reverse themselves.
What assumption made scientists unwilling to believe the stories about the ancient Chinese sailors?
Until researchers discovered that Earth's magnetic poles could reverse themselves, there was no reasonable explanation for compasses pointing south.