Researchers may have just solved a 300-year-old riddle.

As part of a study to determine the direction in which Earth’s core spins, scientists in the United Kingdom and Switzerland analyzed seismic readings from earthquakes from the past few decades.

But, instead of finding out whether the planet’s center rotates eastward or westward, the team discovered a surprising answer to the question that’s evaded scientists for centuries: It’s both.

“The link is simply explained in terms of equal and opposite action,” lead researcher Dr. Philip Livermore, of the University of Leeds, said in a released statement. “The magnetic field pushes eastwards on the inner core, causing it to spin faster than Earth, but it also pushes in the opposite direction in the liquid outer core, which creates a westward motion.”