The tidal influences of such a close Moon led to a progressive slowing down of Earth’s spin, which allowed our satellite to break free. Moving away from our planet, the Moon helped reduce Earth’s tilt, but it wasn’t a smooth transition. The change was abrupt, with our satellite's orbital tilt changing wildly.
“As the Moon moved outward, the Earth’s steep tilt made for a more chaotic transition as the Sun became a bigger influence,” lead author Matija Ćuk said in the statement. “Subsequently, and over billions of years, the Moon’s tilt slowly decayed down to the five degrees we see today. So today’s five-degree tilt is a relic and a signature of a much steeper tilt in the past.”
These results, discussed in a paper published in Nature, solve several unknowns about the Moon, but there’s still more left to discover. Nevertheless, this research underlines the crucial role that the Moon has had on Earth.
“This work shows that there are multiple ways a planet could get a small axial tilt, making moderate seasons possible,” Ćuk said in another statement. “We thought Earth was this way because of the direction of the giant impact 4.5 billion years ago, but it looks like Earth achieved this state later through a complex interaction with the Moon and the Sun.”