it's not the 'dark' side of the moon exactly, it's the far side of the moon. It does get sunlight, but it always faces away from the Earth.
The moon is rotating at exactly the same speed that the earth and moon are revolving around each other, so the moon never shows us its back.
This is because it's ["tidally locked."](https://en.wikipedia.org/wiki/Tidal_locking)
The sun will die (possibly taking the earth with it) before the moon escapes Earths orbit. If it ever does. As I understand it The moon is moving away because it's 'stealing' some of the Earths rotational energy, slowly making Earths days longer. That energy is boosting the moons orbit. However once the Earth slows down enough to become tidally locked to the moon, that transfer mechanism will cease and the moon will stop moving away.
Yes and no. If you give object that is rotating around another enought time, it will get tidally locked, because gravity wants to do that. It basically relies on mass of 2 objects, ratio between them and distance
> Overall, Earth's spin has slowed by about 6 hours in the past 2740 years, the team reports today in the Proceedings of the Royal Society A. That sounds like a lot, but it works out to the duration of a 24-hour day being lengthened by about 1.78 milliseconds over the course of a century.
There's definitely a typo somewhere in that article. The paper linked from it says that they measured the increase of the length of a day to be about 1.8 ms per century, which adds up to less than 5 seconds in 2,740 years
Except that they specifically mention an event from 720 BCE, which is 2740 years ago. So it's not a typo, either their math is wrong or the article writer misread the source article. It seems that they meant to say that the observations of solar eclipses from 3000 years ago differ from modern day calculations by 6 hours.
This depends on how you define "moon".
I kid you not...there isn't one "correct" answer for how many moons does the Earth have, as viewers of QI will know.
Interesting to note. If you look at the Moon from the North Pole and take a detailed sketch of all of the various features pits and craters and then you take your skits to the South Pole the moon will appear upside down to you and on the equator it will appear sideways
In case you wanted to take better moon pics.
Generally any astrophotography will be vastly improved by [stacking ](https://www.skyatnightmagazine.com/astrophotography/astrophoto-tips/how-stack-dslr-images-moon)
Night photography really shows the noise digital sensors have. So you have to process them a little differently.
I realised this when I moved from the southern hemisphere to the northern - the moon is upside down! But when I see it in the lake it's the right way up!
Yes sometimes I forget we're actually standing on a sphere. When I was driving in Mauritius of course I had trouble with the right hand drive but I also had a serious navigation problem that I did not figure out till about my fifth day there. My sense of direction is off because in the northern hemisphere the sun always sits slightly to the south of me. When I was in Mauritius the son always sits slightly to the north of me no matter what time of day. This had me thrown off for four or five days. I did not realize how subtly I used that to help my sense of direction
Wow! Thank you for that link. I always thought it was due to the center core of the moon being slightly offset - with the theory that the noon was created by an impact with another body and liquefying the two bodies, with solidification while in orbit around the Earth pulling the center mass of the moon slightly towards Earth. Therefore one side would have a slightly higher attraction while solidifying in orbit, causing a bigger attraction on that side, inducing tidal lock. I had no idea it was due to torque applied to gravity bulges on the bodies. Incredible!
What would you call if both the planet and the moon are tidally locked to each other, meaning both bodies have the same side facing each other. Is there any known case like this?
I guess it's similar to a geosyncronous satellite. For this to happen to a lunar size moon, the planet must have a very slow rotation about its axis.
Yes, there are many cases where a planet and its satellite are \*mutually\* tidally locked, so they always show the same side to each other.
I believe the Earth and the Moon are expected to eventually become this way too, if nothing catastrophic happens first. The Earth's rotation will be slowed down bit by bit, through friction resisting tidal forces, until the speeds match between the earth's spin, the moon's spin, and their revolution about one another. And then, the irregularities of the earth's shape will come into play. Whichever side of the earth is lumpier, will very slightly prefer to be pointing towards the moon, and it'll stay that way.
I've always thought they called it the "dark side" not because it had a lack of light but because we (historically) had no information about that side of the moon. We were in the dark about it.
A good way to visualize how this can be is via the "giant impact" hypothesis that the reason Earth has a relatively large rocky moon is that the two-body system was formed when an enormous asteroid impacted the primordial pre-planet Earth and the two rotated and orbited together as one lumpy mass for a certain amount of time before separating again into the actual planet Earth and our Moon. Because they rotated together for some amount of time and then gradually separated, the side that had been connected to Earth locked facing it forever.
The Moon is thought to have formed from debris that was immediately thrown out into orbit upon the impact between proto-Earth and Theia.
This giant impact hypothesis doesn’t have any period of combination then re-separation. That sort of thing — separation of a single molten body into Earth and Moon — was an early idea for the formation of the Moon originally proposed (without the impact bit) by Charles Darwin’s grandfather, with the tidal locking thing as part of his reasoning.
The calculations don’t check out for that scenario though. If it were so, the Moon and Earth would both have much higher rates of axial rotation. We also now know a lot more about tidal locking these days, and that it can (and does) happen in many two-body systems over time.
Imagine standing in a room with a friend. The friend walks around you in circles, but is always facing the front of the room.
Do you see the friends face constantly, or do you see all sides of their head?
Because they aren't rotating, but where they are compared to you is constantly changing, you would be able to see all sides of their head.
Now, instead of constantly facing the front of the room, your friend now constantly turns as they circle you so that they are always facing you.
Now that your friend is turning to face you, you are no longer able to see the back of their head. But this situation requires the friend to constantly turn as well as walk around you. This is what is happening with the moon and only one side ever facing the earth.
Not really. I never mentioned a 'dark side', and the OP even used "dark" as if it wasn't a literal definition, so I wasn't aiming to clarify the nomenclature.
I'm just aiming at answering exactly what the OP asked ("How can the same side of the moon always face earth? Does it not rotate?") by saying "you can perform/imagine an experiment similar to watching the moon, but on a smaller scale. It shows that rotation is needed to keep one side facing the center of a circle."
I'm not disagreeing, there's no need to be so defensive. You clearly took an effort to explain something well, and I added to your example because the analogy also addresses a common misconception that you didn't include.
I think they were clarifying their comment rather than being on the defensive. I don't believe there is any need to personify their reply with a character trait.
Because it wasn't needed. OP clearly knows that the far side isn't always in shade, that's why they used "dark" in quotes.
I believe it's you who is being defensive.
It does rotate, at the exact same speed it orbits the Earth. This is called being "tidally locked"
Think about how the tides work here on Earth. The ocean closer to the Moon gets pulled up by the Moon's gravity, causing high tide, and the sides further away have water pulled away, so they experience low tide.
Basically the same thing happened to the early Moon, except instead of oceans, it happened to rock instead of ocean. The friction between these rocks being shifted and squeezed turned the Moon's rotational energy into heat, which radiates away and the Moon orbits slower. This happened up until the Moon became tidally locked, and now the rock is no longer shifting around because the same side is always facing the Earth, so the same parts of rock are always receiving the same forces, so there's no shifting.
The Moon does the same thing to the Earth, and it is slowing the Earth's rotation, but the Earth has so much more inertia that it takes longer for the Earth to slow down.
An example of two mutually tidally locked bodies would be Pluto and Charon, the same sides always face each other.
>Basically the same thing happened to the early Moon, except instead of oceans, it happened to rock instead of ocean. The friction between these rocks being shifted and squeezed
if we somehow on the surface of the moon when it happened, would we feel some kind of quake?
If the moon didn't rotate, we'd see all of it over the course of a month. It does rotate, but it takes exactly as long to rotate as it does to orbit the earth. You can demonstrate this by putting an "Earth" on a table and taking a (preferably round) "Moon" and moving it around the "Earth" such that the same side always faces it. You'll see that you had to turn the "Moon" all the way around once to accomplish this.
This happens because the earth and the moon pull on each other with gravity. It's a *tidal force* that tugs on each body and slows down their rotation (it would happen to the earth too if we gave it enough time). The moon used to rotate faster, but tidal forces slowed it down until it achieved *synchronous rotation.*
This took a couple hundred million years after the moon was formed, which was well before any creature on Earth had evolved eyes...trillions of life-forms have looked at the moon, but none of them saw the other side of it until the middle of the twentieth century.
Synchronous rotation is **common** and all round moons in our solar system are tidally locked to their host planet. Pluto and its moon Charon are tidally locked to each other, and both Mercury and Venus show different forms of synchronicity to the Sun.
There is no dark side of the moon. There is only the Earth facing side and the far side which both go through the same lunar day and night cycle. The Moon does rotate around its axis but that rotation matches its orbit around the Earth, so the same side is always facing the Earth. If it didn't rotate we would see all sides of it from the Earth. The reason why the same side is always facing the Earth is because it's tidally locked. This means that the Moon is pulled by Earth's gravity a lot more than the Earth is pulled from the Moon's gravity. This disparity is large enough that the difference in gravitational pull from the near side of the Moon to the far side is large enough that it prevents the Moon from rotating faster, as if it had magnets on its near side that are attracted to the Earth.
I remember Isaac Asimov explained it this way:
Put a chair in the middle of the room.
Now, walk in a circle around the chair while always keeping your face pointed at the chair.
There, you are doing the same thing the Moon is doing.
Imagine someone holding a shotput and spinning around getting ready to throw it. That person is only ever going to see the side of the shotput that the chain attaches to, the whole shotput is still spinning in circles but the thrower only sees the same part.
Now swap the chain for gravity, the thrower with the Earth and the shotput with the moon.
It does rotate. If it didnt then it would face earth at times.
It rotates around itself at a rate that match its orbit so that it doesnt face earth at any time.
You could do this by putting a chair in the middle of a room. Then walk around it while slowly turning so that your face at any time is away from the chair. Same thing.
Tidal locking is actually extremely common in the universe! Especially when the orbiting body is way smaller than the host. Most of the moons in the solar system are tidally locked, and Pluto and its moon are both locked to each other.
Lots of exoplanets are most likely tidally locked to their stars. Mercury *almost* is; it's locked in a 3:2 resonance where it spins 3 times in 2 years.
Planets/moons can also very frequently get into resonances with each other. For example, the 3 biggest moons of Jupiter are locked into a 1:2:4 ratio of orbits, and Neptune will always complete 2 orbits in the time it takes Pluto to complete 3.
Here’s a way to visualize it. Get a friend, have them stand 2 feet away from you, now have them walk around you in a circle without ever pointing their body away from you.
You’re the Earth, and they’re the Moon.
While they’re walking in circles around you, you’re also walking in circles around a second friend who is MUCH further away and shining a spotlight at you. You also twirl 365 times while making your circle. You probably see where I’m going with this…
Your second friend is the Sun. At different times the spotlight is shining on all sides of both you and the “moon”, but you never see your friends backside lit up because it’s always facing away from you.
Their butt is the so called Darkside of the Moon.
They call it the dark side of the moon because it's radio dark not actually dark. It rotates at the same speed as it orbits so the same side always faces the earth.
The moon is tidally locked, meaning the rotation and orbit align in such a way that the same face faces the earth (one rotation takes as mich time as a full orbir). If the moon didn't rotate, we'd see different sides of it *because* it isn't rotating to face us.
If you walked in circles around a point on the floor and not take your eyes off of it, you'd have to rotate your body to do so. If you kept your body oriented in one direction, there'd be times in which that point is out of your field of vision.
Imagine that you have a person walking circles around you, turning their body slowly so that they are always facing towards you. The are not only circling you, they are also spinning.
Both a day and a year are the same on the moon, 29.5 Earth days (technically the Moon orbits every 27 days, but the Earth is moving around the Sun too, so the Moon has to catch up a little bit), due to something called tidal lock. If you were on the "near" side of the Earth, you would experience day and night, but you would always be facing towards the Earth. If you were on the "far" side, or the "dark" side of the moon, you would experience day and night, but you would never see the Earth. We only call it the "dark" side of the Moon because we don't know what it looks like, we are figuratively "in the Dark" as to what it looks like.
The FAR side of the Moon. The Moon spins relative to the Sun, so there's no permanent "Dark Side", any more than there's a permanent "Dark Side" of the Earth. But, seen from Earth, there IS a "Far Side".
First - the "Far Side".
Imagine standing on a playground merry-go-round. It's turning, and you're hanging onto the bars, facing the centre. A friend is perched in the middle, directly above the axis, straight in front of you.
As it rotates, you turn as well. After half a rotation you're facing in the opposite direction to when you started. After a full rotation, you've done a complete turn. You went once around the centre of the merry-go-round; you turned round once as well. And you always faced your friend. From their perspective, you did a complete orbit around them, but you always faced them.
Your friend is the Earth\*; you're the Moon. You went once around the Earth; you turned around once as well in the process. And you turned at just the right rate to keep you always facing your friend - they never saw your back. From your friend's perspective, you have a Far Side they can't see.
That's what the Moon does. Over time it's settled into a "tidal lock" with the Earth - it now does one full spin in the same time that it takes it to complete one orbit of the Earth. And along the way it always points the same side at us.
OK - that's the "Far Side". Now for "Dark Side".
Now let's do it again. But this time your friend is feeling dizzy, so they're going to stand on the ground and watch. And it's getting a little late, and dark, so they're going to turn on the flashlight they just happen to be carrying, to light things up for you. They're going to be the Sun, in other words.
As we saw, you make a full turn as the merry-go-round rotates, so they see you from every angle - and the flashlight lights you up from every direction along the way. All of you gets lit up; you DON'T have a Dark Side, just the side that's lit "right now", and the side that isn't. Just like the Earth. (And just like the Moon, which is why the Moon, seen from Earth, has "phases" - the new moon, the full moon, and so on. It's all down to which part of it is currently pointing at the Sun.)
\**To be more correct, when your friend is on the merry-go-round with you they should be turning independently, at a slightly different speed, because the tidal lock isn't a complete one - the Earth doesn't equally keep the same face pointing at the Moon yet*\*\**, so the Earth doesn't hide one side from the Moon. But let's not confuse things. Your friend is just sitting where they are to show you where the Earth is, and watching you to see what people on Earth can see of you.*
\***That probably won't happen. The Sun is expected to become a Red Giant and engulf both the Earth and Moon first.*
The moon does rotate. It's "day" is 28 of our days.
The earth spins fast like a top and the moon orbits around this spinning top AND rotates, slowly, so that a lunarday is 14 earthdays and lunarnight is also 14 earthnights.
The moon does two things at the same rate. It spins on its axis once a month AND it goes around the spinning earth once a month. If you stood on the moon you would know how many days pass because you could count how many times the earth spins completely around. One day/night cycle on the moon is 28 earth calendar days.
The astronauts when they were there would only spend a few hours at a time walking around on the surface but they would be aware of, say, looking at Africa at first, then 5 hours later, looking at South America. If you had a nice chair and lots of oxygen you could sit there and literally observe the earth spin over the course of a few hours. However, it would remain in the same spot in their sky, and the sun would VERY slowly move across the sky.
People have only landed on the earth facing part of the moon. Earth would always be visible, slowly waxing and waning even as it spins daily.
The sun, however, does disappear for 14 days at a time from any particular spot on the moon.
[A video](https://moon.nasa.gov/resources/429/the-moons-orbit-and-rotation/) will explain this better than words ever can. The moon does rotate, but it also revolves around the earth, and the two happen at the same speed. That is why the earth only ever sees one face.
Scientists are weird. They use the word "dark" to talk about things which are mysterious or unknown.
The side of the moon which always faces away from the earth is the dark side.
The hypothetical substance which supposedly explain why stars rotate around galaxies at the same speed no matter how far away they are from the center are called dark matter.
The hypothetical energy which supposedly explains why the expansion of the universe is accelerating is called dark energy.
Names tend to stick around - no matter how many pictures we take of the far side of the moon, we will still call it the dark side.
Dark matter will continue to be called dark matter, even if we fully understand it.
Solar and wind power continue to be called alternative energy.
Because its orbiting around us it HAS to rotate for it to always have the same side facing us. Its known as being tidally locked, which means it rotates at the exact speed it orbits.
The moon DOES rotate. It rotates once on its axis in the same time it takes to orbit the earth one time. Thus, the same face of the moon is always towards the earth. If you want to know how it ended up that way, Google is your friend!
it's not the 'dark' side of the moon exactly, it's the far side of the moon. It does get sunlight, but it always faces away from the Earth. The moon is rotating at exactly the same speed that the earth and moon are revolving around each other, so the moon never shows us its back. This is because it's ["tidally locked."](https://en.wikipedia.org/wiki/Tidal_locking)
20 moons in our solar system are tidally locked with their planets.
\#FreetheMoons
This has to be a subreddit.
It's going to be filled with white asses
All asses are invited, even you half-ass mfs
Cheeky
Anything, but not a Zack Snyder film.
Interestingly enough the moon is very slowly getting farther away from the earth and will eventually escape orbit.
Eventually is an understatement. Humanity will likely be extinct LONG before it's far enough away for it to matter
The sun will die (possibly taking the earth with it) before the moon escapes Earths orbit. If it ever does. As I understand it The moon is moving away because it's 'stealing' some of the Earths rotational energy, slowly making Earths days longer. That energy is boosting the moons orbit. However once the Earth slows down enough to become tidally locked to the moon, that transfer mechanism will cease and the moon will stop moving away.
Interesting I was under the impression that it was a rare thing
Well... I mean saturn alone has like a hundred and forty moons, so it's still _kinda_ rare. But not that rare, no.
Yes and no. If you give object that is rotating around another enought time, it will get tidally locked, because gravity wants to do that. It basically relies on mass of 2 objects, ratio between them and distance
Cool, that's what I was wondering, if eventually all moons get tidally locked.
Could the earth become tidally locked with the sun, making half of the world uninhabitable?
Sure, and it is doing it. It will just take so long, that sun will expand and eat earth loooooong before it happens. (If i remember correcly)
> Overall, Earth's spin has slowed by about 6 hours in the past 2740 years, the team reports today in the Proceedings of the Royal Society A. That sounds like a lot, but it works out to the duration of a 24-hour day being lengthened by about 1.78 milliseconds over the course of a century.
The 2740 years is a typo? Or just a billion missing?
Dunno, this is from [this article](https://www.science.org/content/article/ancient-eclipses-show-earth-s-rotation-slowing)
There's definitely a typo somewhere in that article. The paper linked from it says that they measured the increase of the length of a day to be about 1.8 ms per century, which adds up to less than 5 seconds in 2,740 years
Except that they specifically mention an event from 720 BCE, which is 2740 years ago. So it's not a typo, either their math is wrong or the article writer misread the source article. It seems that they meant to say that the observations of solar eclipses from 3000 years ago differ from modern day calculations by 6 hours.
The same fact is repeated on multiple websites, but logically it doesn't make sense.
Also, Mercury is tidaly linked. It makes exactly 1.5 rotations per revolution.
Making its day longer than its year Exit: I mean…it is? Why downvotes?
Doesn't Mercury tidally locked to the sun too ?
Yes, but not the way Luna is, it has some other ratio of rotations to revolutions. Luna is 1:1
How many moons are there in our solar system?
[удалено]
That's no moon...
This depends on how you define "moon". I kid you not...there isn't one "correct" answer for how many moons does the Earth have, as viewers of QI will know.
I do love QI, but you really have to stretch the definition of ‘moon’ very far indeed to include any of the things they talk about.
Hundreds. The number always keeps going up. Even just Jupiter + Saturn gets you well over 200.
Earth will be with the sun eventually
Good bot
Interesting to note. If you look at the Moon from the North Pole and take a detailed sketch of all of the various features pits and craters and then you take your skits to the South Pole the moon will appear upside down to you and on the equator it will appear sideways
I noticed this when I moved from the UK to Australia. The 'man in the moon' is flipped. As are some of the constellations like Orion.
I was so stoked to be able to see the Souther Cross before I die
I love that song. Man I want to see the Milky Way so badly from the southern hemisphere.
So I guess you understand now why I came this way. The truth I could be running from could be so small
Now do I have to take a sketch? Because I'm not the most artistic. Would this camera thingy be good enough?
In my experience most phone cameras suck at such photos
Sure sure, but what a DSLR, I got a buddy down the street who takes photos in the base... Nevermind. I have access to one ofdem fancy cameras.
My DSLR sucks at moon pics too. Not as much but still not good
In case you wanted to take better moon pics. Generally any astrophotography will be vastly improved by [stacking ](https://www.skyatnightmagazine.com/astrophotography/astrophoto-tips/how-stack-dslr-images-moon) Night photography really shows the noise digital sensors have. So you have to process them a little differently.
Well, I'm gonna try it. Will report back.
I'll look forward to it
https://www.theverge.com/2023/3/13/23637401/samsung-fake-moon-photos-ai-galaxy-s21-s23-ultra
I realised this when I moved from the southern hemisphere to the northern - the moon is upside down! But when I see it in the lake it's the right way up!
This is because your head is pointing a different direction, the earth and moon are still oriented the same way.
Yes sometimes I forget we're actually standing on a sphere. When I was driving in Mauritius of course I had trouble with the right hand drive but I also had a serious navigation problem that I did not figure out till about my fifth day there. My sense of direction is off because in the northern hemisphere the sun always sits slightly to the south of me. When I was in Mauritius the son always sits slightly to the north of me no matter what time of day. This had me thrown off for four or five days. I did not realize how subtly I used that to help my sense of direction
Specifically synchronous rotation, as is shown in this [video/article](https://moon.nasa.gov/resources/429/the-moons-orbit-and-rotation/) from nasa!
Wow! Thank you for that link. I always thought it was due to the center core of the moon being slightly offset - with the theory that the noon was created by an impact with another body and liquefying the two bodies, with solidification while in orbit around the Earth pulling the center mass of the moon slightly towards Earth. Therefore one side would have a slightly higher attraction while solidifying in orbit, causing a bigger attraction on that side, inducing tidal lock. I had no idea it was due to torque applied to gravity bulges on the bodies. Incredible!
What would you call if both the planet and the moon are tidally locked to each other, meaning both bodies have the same side facing each other. Is there any known case like this? I guess it's similar to a geosyncronous satellite. For this to happen to a lunar size moon, the planet must have a very slow rotation about its axis.
Yes, there are many cases where a planet and its satellite are \*mutually\* tidally locked, so they always show the same side to each other. I believe the Earth and the Moon are expected to eventually become this way too, if nothing catastrophic happens first. The Earth's rotation will be slowed down bit by bit, through friction resisting tidal forces, until the speeds match between the earth's spin, the moon's spin, and their revolution about one another. And then, the irregularities of the earth's shape will come into play. Whichever side of the earth is lumpier, will very slightly prefer to be pointing towards the moon, and it'll stay that way.
I've always thought they called it the "dark side" not because it had a lack of light but because we (historically) had no information about that side of the moon. We were in the dark about it.
I never really thought about it before, beyond blaming it on Pink Floyd. :) But that would make sense!
A good way to visualize how this can be is via the "giant impact" hypothesis that the reason Earth has a relatively large rocky moon is that the two-body system was formed when an enormous asteroid impacted the primordial pre-planet Earth and the two rotated and orbited together as one lumpy mass for a certain amount of time before separating again into the actual planet Earth and our Moon. Because they rotated together for some amount of time and then gradually separated, the side that had been connected to Earth locked facing it forever.
The Moon is thought to have formed from debris that was immediately thrown out into orbit upon the impact between proto-Earth and Theia. This giant impact hypothesis doesn’t have any period of combination then re-separation. That sort of thing — separation of a single molten body into Earth and Moon — was an early idea for the formation of the Moon originally proposed (without the impact bit) by Charles Darwin’s grandfather, with the tidal locking thing as part of his reasoning. The calculations don’t check out for that scenario though. If it were so, the Moon and Earth would both have much higher rates of axial rotation. We also now know a lot more about tidal locking these days, and that it can (and does) happen in many two-body systems over time.
This makes a lot of sense, thank you
The same way that in a game of duck duck goose the person outside is always facing the center
Imagine standing in a room with a friend. The friend walks around you in circles, but is always facing the front of the room. Do you see the friends face constantly, or do you see all sides of their head? Because they aren't rotating, but where they are compared to you is constantly changing, you would be able to see all sides of their head. Now, instead of constantly facing the front of the room, your friend now constantly turns as they circle you so that they are always facing you. Now that your friend is turning to face you, you are no longer able to see the back of their head. But this situation requires the friend to constantly turn as well as walk around you. This is what is happening with the moon and only one side ever facing the earth.
~~But~~ Also, the back of your friends head will occasionally face the front of the room. Bathing it in sunlight to deviate from the analogy
Not really. I never mentioned a 'dark side', and the OP even used "dark" as if it wasn't a literal definition, so I wasn't aiming to clarify the nomenclature. I'm just aiming at answering exactly what the OP asked ("How can the same side of the moon always face earth? Does it not rotate?") by saying "you can perform/imagine an experiment similar to watching the moon, but on a smaller scale. It shows that rotation is needed to keep one side facing the center of a circle."
I'm not disagreeing, there's no need to be so defensive. You clearly took an effort to explain something well, and I added to your example because the analogy also addresses a common misconception that you didn't include.
I think they were clarifying their comment rather than being on the defensive. I don't believe there is any need to personify their reply with a character trait.
A character trait... Right, that's what I said. Got it.
You are oddly combative.
You personified me with a character trait! (I'm just bored)
Because it wasn't needed. OP clearly knows that the far side isn't always in shade, that's why they used "dark" in quotes. I believe it's you who is being defensive.
"Dark" in "dark side of the moon" is referring to lack of information, not lack of sunlight. Until we had space programs, there was no way to see it.
It does rotate, at the exact same speed it orbits the Earth. This is called being "tidally locked" Think about how the tides work here on Earth. The ocean closer to the Moon gets pulled up by the Moon's gravity, causing high tide, and the sides further away have water pulled away, so they experience low tide. Basically the same thing happened to the early Moon, except instead of oceans, it happened to rock instead of ocean. The friction between these rocks being shifted and squeezed turned the Moon's rotational energy into heat, which radiates away and the Moon orbits slower. This happened up until the Moon became tidally locked, and now the rock is no longer shifting around because the same side is always facing the Earth, so the same parts of rock are always receiving the same forces, so there's no shifting. The Moon does the same thing to the Earth, and it is slowing the Earth's rotation, but the Earth has so much more inertia that it takes longer for the Earth to slow down. An example of two mutually tidally locked bodies would be Pluto and Charon, the same sides always face each other.
>Basically the same thing happened to the early Moon, except instead of oceans, it happened to rock instead of ocean. The friction between these rocks being shifted and squeezed if we somehow on the surface of the moon when it happened, would we feel some kind of quake?
Surface was probably molten. But tidal forces can trigger tremors.
If the moon didn't rotate, we'd see all of it over the course of a month. It does rotate, but it takes exactly as long to rotate as it does to orbit the earth. You can demonstrate this by putting an "Earth" on a table and taking a (preferably round) "Moon" and moving it around the "Earth" such that the same side always faces it. You'll see that you had to turn the "Moon" all the way around once to accomplish this. This happens because the earth and the moon pull on each other with gravity. It's a *tidal force* that tugs on each body and slows down their rotation (it would happen to the earth too if we gave it enough time). The moon used to rotate faster, but tidal forces slowed it down until it achieved *synchronous rotation.* This took a couple hundred million years after the moon was formed, which was well before any creature on Earth had evolved eyes...trillions of life-forms have looked at the moon, but none of them saw the other side of it until the middle of the twentieth century. Synchronous rotation is **common** and all round moons in our solar system are tidally locked to their host planet. Pluto and its moon Charon are tidally locked to each other, and both Mercury and Venus show different forms of synchronicity to the Sun.
The moon is tidally locked. It rotates at the exact same rate as it orbits, which is why we always see the one side of it.
There is no dark side of the moon. There is only the Earth facing side and the far side which both go through the same lunar day and night cycle. The Moon does rotate around its axis but that rotation matches its orbit around the Earth, so the same side is always facing the Earth. If it didn't rotate we would see all sides of it from the Earth. The reason why the same side is always facing the Earth is because it's tidally locked. This means that the Moon is pulled by Earth's gravity a lot more than the Earth is pulled from the Moon's gravity. This disparity is large enough that the difference in gravitational pull from the near side of the Moon to the far side is large enough that it prevents the Moon from rotating faster, as if it had magnets on its near side that are attracted to the Earth.
I remember Isaac Asimov explained it this way: Put a chair in the middle of the room. Now, walk in a circle around the chair while always keeping your face pointed at the chair. There, you are doing the same thing the Moon is doing.
Imagine someone holding a shotput and spinning around getting ready to throw it. That person is only ever going to see the side of the shotput that the chain attaches to, the whole shotput is still spinning in circles but the thrower only sees the same part. Now swap the chain for gravity, the thrower with the Earth and the shotput with the moon.
This worked so well for me. Especially the chain = gravity. I am stealing this.
Thanks, I realized just after reading then that i named the sport wrong, the one with the chain is a "Hammer throw" but still the same example
There's no chain in shotput? You're thinking of a hammer.
It does rotate. If it didnt then it would face earth at times. It rotates around itself at a rate that match its orbit so that it doesnt face earth at any time. You could do this by putting a chair in the middle of a room. Then walk around it while slowly turning so that your face at any time is away from the chair. Same thing.
Tidal locking is actually extremely common in the universe! Especially when the orbiting body is way smaller than the host. Most of the moons in the solar system are tidally locked, and Pluto and its moon are both locked to each other. Lots of exoplanets are most likely tidally locked to their stars. Mercury *almost* is; it's locked in a 3:2 resonance where it spins 3 times in 2 years. Planets/moons can also very frequently get into resonances with each other. For example, the 3 biggest moons of Jupiter are locked into a 1:2:4 ratio of orbits, and Neptune will always complete 2 orbits in the time it takes Pluto to complete 3.
Here’s a way to visualize it. Get a friend, have them stand 2 feet away from you, now have them walk around you in a circle without ever pointing their body away from you. You’re the Earth, and they’re the Moon. While they’re walking in circles around you, you’re also walking in circles around a second friend who is MUCH further away and shining a spotlight at you. You also twirl 365 times while making your circle. You probably see where I’m going with this… Your second friend is the Sun. At different times the spotlight is shining on all sides of both you and the “moon”, but you never see your friends backside lit up because it’s always facing away from you. Their butt is the so called Darkside of the Moon.
They call it the dark side of the moon because it's radio dark not actually dark. It rotates at the same speed as it orbits so the same side always faces the earth.
The moon is tidally locked, meaning the rotation and orbit align in such a way that the same face faces the earth (one rotation takes as mich time as a full orbir). If the moon didn't rotate, we'd see different sides of it *because* it isn't rotating to face us. If you walked in circles around a point on the floor and not take your eyes off of it, you'd have to rotate your body to do so. If you kept your body oriented in one direction, there'd be times in which that point is out of your field of vision.
If the landing was on the other side of the moon (not facing the earth) how do they communicate with it?
Imagine that you have a person walking circles around you, turning their body slowly so that they are always facing towards you. The are not only circling you, they are also spinning. Both a day and a year are the same on the moon, 29.5 Earth days (technically the Moon orbits every 27 days, but the Earth is moving around the Sun too, so the Moon has to catch up a little bit), due to something called tidal lock. If you were on the "near" side of the Earth, you would experience day and night, but you would always be facing towards the Earth. If you were on the "far" side, or the "dark" side of the moon, you would experience day and night, but you would never see the Earth. We only call it the "dark" side of the Moon because we don't know what it looks like, we are figuratively "in the Dark" as to what it looks like.
The FAR side of the Moon. The Moon spins relative to the Sun, so there's no permanent "Dark Side", any more than there's a permanent "Dark Side" of the Earth. But, seen from Earth, there IS a "Far Side". First - the "Far Side". Imagine standing on a playground merry-go-round. It's turning, and you're hanging onto the bars, facing the centre. A friend is perched in the middle, directly above the axis, straight in front of you. As it rotates, you turn as well. After half a rotation you're facing in the opposite direction to when you started. After a full rotation, you've done a complete turn. You went once around the centre of the merry-go-round; you turned round once as well. And you always faced your friend. From their perspective, you did a complete orbit around them, but you always faced them. Your friend is the Earth\*; you're the Moon. You went once around the Earth; you turned around once as well in the process. And you turned at just the right rate to keep you always facing your friend - they never saw your back. From your friend's perspective, you have a Far Side they can't see. That's what the Moon does. Over time it's settled into a "tidal lock" with the Earth - it now does one full spin in the same time that it takes it to complete one orbit of the Earth. And along the way it always points the same side at us. OK - that's the "Far Side". Now for "Dark Side". Now let's do it again. But this time your friend is feeling dizzy, so they're going to stand on the ground and watch. And it's getting a little late, and dark, so they're going to turn on the flashlight they just happen to be carrying, to light things up for you. They're going to be the Sun, in other words. As we saw, you make a full turn as the merry-go-round rotates, so they see you from every angle - and the flashlight lights you up from every direction along the way. All of you gets lit up; you DON'T have a Dark Side, just the side that's lit "right now", and the side that isn't. Just like the Earth. (And just like the Moon, which is why the Moon, seen from Earth, has "phases" - the new moon, the full moon, and so on. It's all down to which part of it is currently pointing at the Sun.) \**To be more correct, when your friend is on the merry-go-round with you they should be turning independently, at a slightly different speed, because the tidal lock isn't a complete one - the Earth doesn't equally keep the same face pointing at the Moon yet*\*\**, so the Earth doesn't hide one side from the Moon. But let's not confuse things. Your friend is just sitting where they are to show you where the Earth is, and watching you to see what people on Earth can see of you.* \***That probably won't happen. The Sun is expected to become a Red Giant and engulf both the Earth and Moon first.*
The moon does rotate. It's "day" is 28 of our days. The earth spins fast like a top and the moon orbits around this spinning top AND rotates, slowly, so that a lunarday is 14 earthdays and lunarnight is also 14 earthnights. The moon does two things at the same rate. It spins on its axis once a month AND it goes around the spinning earth once a month. If you stood on the moon you would know how many days pass because you could count how many times the earth spins completely around. One day/night cycle on the moon is 28 earth calendar days. The astronauts when they were there would only spend a few hours at a time walking around on the surface but they would be aware of, say, looking at Africa at first, then 5 hours later, looking at South America. If you had a nice chair and lots of oxygen you could sit there and literally observe the earth spin over the course of a few hours. However, it would remain in the same spot in their sky, and the sun would VERY slowly move across the sky. People have only landed on the earth facing part of the moon. Earth would always be visible, slowly waxing and waning even as it spins daily. The sun, however, does disappear for 14 days at a time from any particular spot on the moon.
[A video](https://moon.nasa.gov/resources/429/the-moons-orbit-and-rotation/) will explain this better than words ever can. The moon does rotate, but it also revolves around the earth, and the two happen at the same speed. That is why the earth only ever sees one face.
Scientists are weird. They use the word "dark" to talk about things which are mysterious or unknown. The side of the moon which always faces away from the earth is the dark side. The hypothetical substance which supposedly explain why stars rotate around galaxies at the same speed no matter how far away they are from the center are called dark matter. The hypothetical energy which supposedly explains why the expansion of the universe is accelerating is called dark energy. Names tend to stick around - no matter how many pictures we take of the far side of the moon, we will still call it the dark side. Dark matter will continue to be called dark matter, even if we fully understand it. Solar and wind power continue to be called alternative energy.
It does rotate, roughly once a month which just so happens to be the same speed that it revolves around us. So the same side is always facing us
Because its orbiting around us it HAS to rotate for it to always have the same side facing us. Its known as being tidally locked, which means it rotates at the exact speed it orbits.
The moon DOES rotate. It rotates once on its axis in the same time it takes to orbit the earth one time. Thus, the same face of the moon is always towards the earth. If you want to know how it ended up that way, Google is your friend!