The Earth’s surface is drenched in darkness and sunlight every 24 hours as the globe completes a single day. As the Earth revolves on its axis, sunrise and sunset occur regularly. Does the moon, Earth’s satellite, revolve as well?

Yes, the moon spins, although considerably slower than the Earth. According to NASA, a “moon day” is roughly 29.53 Earth days. In other words, whereas the Earth rotates once every 24 hours, the moon rotates once every 709 hours.

The moon’s rotational motion, like that of many celestial bodies, might represent a residue of its formation. According to NASA, an asteroid around the size of Mars slammed into the still-developing Earth some 4.5 billion years ago, according to one idea. The heat from Theia’s impact may have formed lava seas by melting the Earth’s crust and causing the planet to expel spinning vaporized particles into space.

According to the giant-impact concept, these clouds of dust and gas were whirling due to the power of the initial collision. Because mass attracts mass, these spinning particles eventually collided, and the gas started to spin faster as it condensed. Consider a figure skater who spins on the rink while tucking their arms under. Because the skater’s bulk is more compact closer to their center, the skater accelerates. This is due to the conservation of angular momentum, a product of the rotational force required to spin an object, or the moment of inertia and angular velocity. To put it another way, rotating an item away from the center of gravity requires greater force. As a result, if the figure skater’s arms are out, they spin slower, and if they tuck them in, they spin quicker.

Since the first impact billions of years ago, the moon has preserved its angular momentum. “Two spinning things collided, and the principles of physics predict that the huge dust cloud that resulted would continue spinning. The spinning dust cloud eventually condensed to create the spinning moon “Daniel Moriarty, a lunar geologist at NASA Goddard Space Flight Center and the University of Maryland, shared his thoughts.

Because the moon, unlike Earth, lacks an atmosphere, there is no air resistance to slow moving objects; as a result, once items begin spinning, they prefer to keep spinning. There are, of course, different explanations for how Earth acquired its moon. The capture hypothesis proposes that the moon was a wandering body, like an asteroid, grabbed by Earth’s gravitational attraction. According to NASA, the moon was generated somewhere in the solar system and then started to circle Earth as it passed by this; it would have already had its spin when it was drawn into Earth’s gravitational field.

Another explanation is the co-formation theory, which states that the moon and the Earth were formed simultaneously. According to this theory, two gigantic objects five times the size of Mars collided. According to NASA, the Earth and its moon condensed out of the clouds of stuff that arose from the impact.

The speed of the moon’s revolution, on the other hand, is determined by Earth. The moon rotates once every 27 days, roughly identical to the period it takes the moon to circle Earth: 27.32 days. Consequently, humans on Earth only view one side of the moon at any one time. As the moon orbited Earth, we would be able to view all of the moon’s surface if the lunar day was any longer or shorter.

Different phases of the moon, photographed through a telescope. (Image credit: Yaorusheng via Getty Images)

In reality, since the Earth travels in an oval-like elliptical orbit, the orbit and rotation aren’t precisely synchronized. According to, a sister site of LiveScience, when the moon is at the closest point of its orbit to Earth, its rotation is slower than its orbit, enabling us to view an extra 8 degrees of its surface than we would normally.

Tidal locking, or synchronous rotation, occurs when a locked body takes the same amount of time to orbit around its partner and spin once on its axis due to its partner’s gravity. (Other planets’ moons have the same impact.) Furthermore, the moon is not a perfectly round object; it is asymmetrical. Moriarty told Live Science that the moon isn’t symmetric. “The hemispheres [of the moon facing Earth] have different mass and density. Due to gravity, one side of the moon [its longer side] remains stuck toward Earth.”

“As the moon circles the Earth, it turns to face us,” Moriarty said. “A single revolution takes the same amount of time as a single orbit or roughly a month.” To put it another way, Earth and the moon have a gravitational pull on each other, and the gravitational force is highest when the two bodies are directly facing each other, causing both Earth and the moon to stretch somewhat as they are pushed in the same direction. Consequently, the moon has been stretched into an oval shape, with its longest axis constantly facing us. Every day, this is also what causes the Earth’s tides to come in and out.

Although the moon rotates slowly, its rotation is crucial to major phenomena on Earth, such as the tides.

The movement of planets and moons is also affected by tidal locking. Because the Earth and the moon rotated considerably quicker than they do now, days on Earth and the moon were much shorter when these things originally formed. According to a model developed by Harvard academics and the SETI Institute, the early Earth had a day as brief as 2.5 hours at the moment of its impact with Theia. The Earth’s and moon’s days extended throughout time due to gravitational pull dragging on the moon’s longest axis to face the Earth.

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