(NewsNation) — Newly corroborated research suggests the rotation of Earth’s innermost core has slowed down so much it’s now moving backward, part of a larger pattern of changing speeds and trajectories.

The rotation, direction and pace of Earth’s solid metallic inner core have divided scientists for decades, as it’s impossible to observe or sample it directly. In that back-and-forth, countless models have projected what might be going on inside our planet.

New research published June 12 confirmed the core’s slowdown and seems to support a model, first published in 2023 in Nature, that posits the earth’s inner core has begun moving backward as part of a cyclical shift.

Using seismic waves produced by decades worth of earthquakes, researchers analyzed the arrival time of the waves to the core — which changes depending on its rotation at that moment.

The study used these timing measurements to conclude the core’s rotational speed shifts follow a 70-year cycle.

Researchers found that, in the 1970s, the core was spinning slightly faster than Earth itself before slowing again in 2008. Between 2008 and 2023, the core began spinning opposite the planet.

If their prediction is accurate, the team estimates a hastening core rotation within the next five to 10 years.

The inner core was only discovered in 1936 by Danish seismologist Inge Lehmann, and the first seismological evidence of alternating inner core rotation was first published in the ’90s. However, researchers are confident in their findings.

“We’ve been arguing about this for 20 years, and I think this nails it,” study co-author Dr. John Vidale told CNN. “I think we’ve ended the debate on whether the inner core moves and what’s been its pattern for the last couple of decades.”