The moon isn’t just a pretty rock that reflects light from the sun to illuminate our night skies. I mean, even that is an impressive demonstration of natural cosmic skill. But there is more to the moon than just being Earth’s very own night light. The moon has an integral part to play in the daily and nightly running of our planet. It controls the Earth’s tides, axis angle, and the length of our days here. Much of the moon’s interaction with Earth is influenced by the gravitational relationship between the two. Does this relationship go as far as the two objects being tidally locked? If so, how did this come to be? How long did it take? So many complex questions to get through, so let’s get started.
So, is the moon tidally locked? The moon is tidally locked to the Earth, meaning that it rotates in exactly the same amount of time it takes for it to orbit the Earth once. The moon would have become tidally locked with Earth when it was created billions of years ago during the early years of the planet’s existence.
It’s been a process.
In fact, it has taken about 100 million years for the moon to become tidally locked with Earth the way it is today (since the formation of the moon).
Fascinating stuff, for sure.
So let’s continue to explore the moon and Earth’s relationship and everything to do with tidal locking.
How Did The Moon Get Tidally Locked?
The moon got totally locked to Earth during its creation when a large object crashed into the Earth billions of years ago. A large segment of Earth that detached from the surface would have endured immense gravitational pressures until the moon tidally locked.
So, tidal locking. A magical phenomenon, isn’t it?
If you’re not sure what exactly tidal locking is, let’s have a quick look at the scientific theory behind it.
Tidal locking is a process that causes one object to have the same rotational period as its orbital period around another object.
The moon is tidally locked to Earth. This is because it rotates in exactly the same amount of time it takes for it to orbit the Earth once. Hence why we can only see one side of the moon at one time.
The moon’s rotation and orbital period take just under four weeks.
Now, how did this perfect process come to fruition? It would be lazy to just say that the universe works in mysterious ways or that these things just happen because, well, they happen.
Instead, we do have a proper, scientific explanation for how the moon came to be tidally locked with Earth.
Remember, tidal locking is not unique to just Earth and the moon. This phenomenon occurs throughout the universe between extraterrestrial objects.
In the case of the moon, we know that tidal locking started at its origin. Scientists believe the moon was created when a ginormous object collided with Earth billions of years ago, early in the planet’s history.
This collision caused some of Earth to break apart from the main body and float off into space.
By this time, it would have been a large, hot, molten object spun by a tremendous amount of force. But at the same time, Earth’s gravitational pull would have been drawing it back towards its surface.
These two opposing forces, that of Earth’s gravity and the energy behind driving the rock out towards space, would have worked in unison to change the shape of the rock, whipping it up into a spherical shape.
But then, these forces would have also been engaged in a tug of war over the object, producing vast amounts of energy in the form of heat.
Once this energy dissipated, the moon’s rotation would have slowed until one spin took the same amount of time as it did for the moon to orbit the Earth.
Today, the moon continues to orbit Earth because of the gravitational relationship between the two objects.
How Long Did It Take For The Moon To Tidal Lock To Earth?
It took the moon about 100 million years from its creation for it to become tidally locked the way it is today with Earth.
Scientists believe that the moon was tidally locked to Earth about 3.8 billion years ago during what was known as the Heavy Bombardment period.
Earth right now is a little over 4.5 billion years old, so in relative terms, the moon became tidally locked quite early in the planet’s existence.
Now, we know that the moon was tidally locked with Earth during the moment it was created upon the impact of a collision. Before this moment, the Earth had been without a moon.
So it took 700 million years after Earth’s creation for the planet to get a moon in the first place.
But once its moon was formed, how long did this process of tidal locking take?
Well, you might think that it was quite a quick process, but you’d be wrong.
Amazingly, for the moon to become tidally locked the way it is today, it would have occurred within 100 million years of its creation.
Now that is one long game of tug of war.
But after this 100 million years, the rotational and orbital periods would have remained the same. And they still are the same today!
Many things have changed about the moon throughout its existence. It’s withstood a lot, from asteroid collisions to stray human rockets crashing into its surface.
Such incidents have altered the appearance of the moon, often leaving craters on its lunar surface.
And yet, no such event has altered the tidal locking the moon has with Earth. Scientists believe that if such a collision were to disrupt the tidal locking, it would need to be substantial enough to destroy the moon altogether.
What Would Happen If The Moon Was Not Tidally Locked?
If the moon was not tidally locked, we’d be able to see more of it and also see it spinning.
Now the whole process that occurred to tidally lock the moon with the Earth seemed to be very dramatic.
After all, it was a giant tug-of-war that lasted 100 million years.
But would there be dramatic consequences for us on Earth if the moon wasn’t tidally locked with Earth? Well, sorry to disappoint you, but there probably wouldn’t be.
The moon would still be there, so it would still perform its regular duties, like illuminating the night sky, controlling the tides, and prolonging our daylight hours.
The only significant changes would be that we would see other faces of the moon at the same time, such as the dark side, and we’d be able to see it spinning in motion.
This would mean that the moon would actually look bigger in the sky because more of it would be visible.
Some people might prefer the idea of seeing the moon spin in the sky, while others might prefer a stationary moon.
The reality is that we’ll be stuck with tidal locking for the foreseeable future.
There have been claims that if the moon wasn’t tidally locked with Earth, then our days would become shorter.
The logic behind this argument is that the moon’s gravitational relationship with Earth has extended our days to 18 to 24 hours. Without the moon tidally locked, our days would shorten to about 6 hours.
Now, if the moon was destroyed, yes, it is true; our days would be much shorter.
But guess what? This impact would not occur if the moon wasn’t tidally locked with Earth.
The fact that the Earth’s rotation is ahead of the moon’s orbit causes the Earth to slow down. Sure, the moon’s tidal effect plays a part, but the fact that it is tidally locked does not.
At the end of the day, no real harm would be done if the moon wasn’t tidally locked with Earth. After all, it survived without a moon for 700 million years.
And it’s worth noting that moons aren’t always tidally locked to their planets anyway. As we discussed earlier, it took 100 million years for our moon to be tidally locked with Earth.
So planets can survive for a long whilst they wait for their moons to tidally lock.
At the moment, scientists are unaware of any moons that are not tidally locked with their planets.
But the universe is quite big, so you can be assured that somewhere out there, a moon is yet to tidally lock with its planet.
Tidal locking is a complicated process.
It’s no wonder it is, as it does take 100 million years to complete.
Because of tidal locking, we see one face of the moon at the same time.
Without tidal locking, we’d see the moon spin in the sky.
Other than that, life would go on…
My other moon guides you may want to check out:
- Why Does The Moon Orbit The Earth? [And Not The Sun!]
- Why Does The Moon Have Phases? [The Scientific Explanation]
- Why Can’t You See the Moon Every Night?
- Does The Moon Produce Its Own Light?
- What Would Happen If The Moon Was Destroyed?
Hey, my name is Jeremy. I’m a passionate and seasoned astronomer who loves nothing more than observing the night sky. I also love researching, learning, and writing all things Space and the Universe. I created Astronomy Scope to share my knowledge, experience, suggestions, and recommendations of what I have learned along the way while helping anyone to get into and maximize their enjoyment of the hobby.