The Moon doesn't orbit the Earth in a simple spiral
In short: We often imagine the Moon following a smooth, spiraling path around our planet. In reality, its trajectory is far more complex. Depending on your perspective, the Moon might actually be orbiting the Sun, tracing a path that looks more like a 12-sided polygon than a simple circle.
The Moon is one of the most anomalous bodies in our solar system. Scientists have long struggled to explain why its orbit is so far from Earth and why it possesses such a large orbital tilt. A 2016 study published in the journal Nature utilized numerical models to suggest that these quirks are relics of a violent, explosive past. The research proposes that a giant impact formed the Moon from a ring of debris, an event that also caused calamitous changes to Earth's rotation and spin axis.
The model indicates that the planet's rotation accelerated significantly and reached a sharper angle following the primary collision compared to current levels. Over billions of years, various tidal forces involving the Sun, Moon, and Earth have moderated most of these shifts, yet certain irregularities persist. Specifically, the Moon's orbit is tilted five degrees away from the ecliptic plane—the plane of Earth's orbit around the Sun. This is unusual because collisional physics suggests the original debris ring should have aligned with Earth's equatorial plane.
From a different geometric perspective, the Moon's path is not a simple spiral. Because the Earth is also moving around the Sun, the Moon's trajectory is more accurately described as a 12-sided polygon with curved corners. Furthermore, while the Moon completes an orbit around the Earth every 27 days, 7 hours, and 43 minutes, it takes 29.5 days to complete its phase cycle. This discrepancy exists because the Moon must travel slightly farther in its path to account for the Earth's movement around the Sun during that time.
These complex interactions mean that the Moon's apparent movement is a combination of three distinct motions: the Earth's rotation (causing daily rising and setting), the Moon's orbit (shifting its position 12–13 degrees east every day), and the Earth's journey around the Sun (governing its phases).
Opens the Intellect+ feed with this card first. Swipe up for the next one.
Sources
- Summary by Intellect · source: The Moon's Orbit is WEIRD
- Also: New Model Explains the Moon’s Weird Orbit | University of Maryland: Department of Astronomy
- Also: New model explains the moon's weird orbit | ScienceDaily
- Also: Phases and orbits of the Moon | Institute of Physics
To cite this card, link to https://intellectplus.co.uk/app/space-the-moon-s-orbit-is-weird.
How we source, check and correct cards: Editorial standards.
General information, not professional advice. Spotted an error? Flag the card or see corrections and complaints.
Intellect Plus is a visual educational discovery platform for exploring fascinating facts and ideas. Brain Food, Not Brain Rot. What is Intellect Plus?
Related
More in Moon · More in Space · Latest · A–Z · All topics
