August 29, 2019 • 34 mins
Visit the far side of the moon with Daniel and Jorge
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Speaker 1 (00:08):
Hey, Daniel, did you know we're not the first people
to join physics and cartooning? What I thought we were
definitely on the forefront there. No, you know one of
my favorite comic scripts ever is named after something awesome
in physics. Let me guess, Um, Calvin and Hobbs. No, No,
that's philosophy, Um thinking thinking Garfield? Wait? Do you think
(00:29):
I like Garfield? It's the same joke every time. That's true? Um?
Are you thinking just because of quantum fields? Like? Maybe
Garfield is another quantum field? Maybe peanuts. I don't know.
I have no idea how peanuts could relate to physics.
I am officially disappointed in you. All right, I give up.
(01:02):
Hi am Jorge. I'm a cartoonists and the creator of
PhD comics. Hi. I'm Daniel. I'm a particle physicist, and
I have no idea what cartoons relate to physics, especially ours, right, especially,
and Welcome to our podcast, Daniel and Jorge Explain the Universe,
a production of I Heart Radio in which we talk
about crazy things about the universe, things that are close by,
(01:23):
things that are far away, things on one side, things
on the other side, and we break it down an
attempt to explain something to you that's both mind blowing
and actually understandable. That's right, all the things that are
both maybe right here and kind of far away, that's
at the same time, that's right nearby and yet hidden.
We seek to reveal those truths to you. So to
(01:43):
be on the podcast, we will be talking about something
that is basically in our everyday lives, right every well,
every night live, every nightlife. Yeah, my nightlife is not
that exciting anymore, but back when I used to go
at at night. Yeah, it's something that I was wanking
for Netflix back before kids. But yeah, this is the
kind of thing you know, you can look up in
(02:04):
the sky and easily wonder about. Yeah, it's right there
almost every night, and yet we can't see it. Nobody,
nobody really knows what it looks like. Right until recently,
that's right, nobody had ever seen it, even though it
hangs right there. And so today we're talking about what's
on the far side of the moon. That's right. If
(02:26):
you look up in the night sky often you may
notice the moon, of course, and a sharp observer may
notice that the moon looks similar every time. The portion
of it you can see changes right, becomes a crescent,
becomes larger. But if you pay attention, you notice that
the features you see on the Moon are actually the
same every night. Yeah, it never changes, the right. That's
mind blowing to think, because the Moon is a giant
(02:49):
sphere and we're spear and we're you know, going around
the Sun spinning and the Moon is spinning around us,
and yet we always see the same side of the
Moon all every night. That's right, it doesn't change. One
side of the Moon is the near side, that's the
side the face of the Earth, and the other side
faces away from the Earth towards the rest of the universe.
(03:09):
And until nineteen fifty nine, no human had even seen
a picture of it. We had no idea what could
be on it. It could have been like filled with
crazy lunar civilization, or you know, have a message written
on it, or something like I can't believe you took
you guys this long, or something. Right, it could have
been filled with Israeli tardigrade. I think you're fast forwarding
(03:30):
a few decades. Yeah, but yeah, I mean, there could
have been even nothing, right. It could have been just
a half sphere for all we know. We could have
just been like a like a slice orange and we
only see one side of it, right, Yeah, it could
have been that the moon is actually a big prop
right and always and if we come around the other
side we see like the scaffolding and all that stuff. Um,
that could have been amazing. And you know, we make
(03:51):
a joke even known that the moon was the sphere
and not just like a giant disc floating in space. Um.
I think could be pretty hard to get a giant
disc um in any model of moon formation. But but
you never know, right, And this is why we explore,
because you've got to see stuff to breally understand. You
can speculate, you can say we think we know what
(04:12):
the backside of the moon is like. Turns out when
we saw it there were some surprises and until you
really yeah, there were some surprises. The backside of the
moon is not the same as the front side of
the moon, and you know, you got to go and look.
This is why we do experiments, This is why we
explore the universe because until you see it, you never
really know. And so only a handful of humans have
(04:32):
actually seen the other side of the moon, right, seen it? Yeah,
I mean we've had pictures, and only a handful of
humans have seen it, sort of like with their own eyes. Yes,
that's true. It takes you have to orbit the moon
in order to see that. So yeah, only a few
people have ever seen this, but you know, fewer people
have ever seen my moon, not quite as prestigious. But um, yeah,
(04:53):
let's not get into that on this podcast. Let's say
that for Daniel and Jorge after dark. Okay, all right,
that's folks. That's the sound of Jorge carefully stepping away
backwards from that joke. No, but it's a fascinating topic,
and I was wondering did people understand that because it's
kind of odd. Is it like a giant cosmic coincidence
(05:14):
or is it totally normal for us to only see
one side of it? That's a that's why I'm blowing
to me. Yeah, So, um, I walked around and I
asked people, you know, what do they think about this?
Were they aware of it, did they realized did they
understand it? Could they give a physical explanation? Yeah? So,
as usual, Daniel went out there somewhere in the world.
Where were you at this time? Daniel? Were you in
(05:35):
California or No? I was back in California. So these
are you see Irvine summer students who answered these questions.
As usual, Daniel went out and asked random people on
the screen the question of the episode, and today's question was.
Today's question was did you know that that half of
the moon always faces away? So think about it for
a second, if you had realized this, or if you
(05:57):
knew this. I'm sure a lot of our reader listeners
I knew this, but maybe you hadn't thought about it
for a while. And so think about what you would
answer if a random physicist approach you on the street. Yes,
do you know why that is? Um? Just I know
because I know that the Earth rotates and I know
the Moon doesn't. And there's a reason why you don't.
(06:18):
We only see one face in the moon and never
the other. I did not know that there is a
side of the Moon that did not face the Earth
because the first rotation as well. Yeah, I mean my
understanding is the Moon is rotating around the Earth and
the Earth rotates on its axis because it's spinning. Um.
But yeah, I didn't realize the Moon was spinning too.
I didn't think it was. I guess because both the
(06:38):
Moon and the Earth are rotating, and so we never
see the backside related to rotations of the stellar bodies. Yes,
well do you know why that? Is that a coincidence?
Is there a physical reason? Physics? Physics? All right, So
a lot of people didn't know, and a lot of
(07:00):
people didn't yees. Some people were really shocked, and as
soon as they understood that it was happening, they were like,
that's really weird. How could that be? What? Yeah, it's
almost like it's doing it on purpose, right, Like the
Moon is suspicious of us and doesn't want to turn
its back to us, you know, like it's it's hurling
through space, but it's like I don't want to I
(07:20):
need to be facing Earth at all time. And it's
slowly backing away also, right, don't forget, we're losing it
very gradually. So the moon is sort of like edging
away from us the way you're edging away from my
inappropriate jokes. Yeah, so I guess it's not as well
known as I would have guessed it was. You know,
a lot of people seem surprised, and of the people
who did know that it happened, none of them could
(07:42):
give me an explanation for why, Right, nobody understood the
physics of it. People appreciated the concept, but nobody could
explain why. Well, you know, I think the question I
have is, um, what's the official name for it? I
think we've called it the far side of the moon,
the backside of the moon. Think Floyd called it the
dark side of the moon. It's called the far side
of the moon, right, And I think that's probably the
(08:04):
inspiration for that cartoon, right, the far side, because like,
what's going on over there, like the weird hidden side. Um,
though I'd love to ask Gary Larson about that one day.
It's not the dark side of it because oh, actually
I do know the answer to that, because I just
read a little bit of his biography. What is the answer?
The answer is he had another name for it, but
(08:25):
then when he sold it to a syndicate or a newspaper,
they said, hey, how are we call it the far side?
And He's like, sure, editors actually contribute something, I've never
heard of that before. That's that's the anti climatic story.
And if our editors listening to this podcast, we love
everything you suggested, by the way, that's right, and we
meant newspaper that's right. Comic editors. No, So the far
(08:48):
side is the back side of the moon, the side
of the Moon that always faces away into the cosmos,
away from the Earth. The dark side of the Moon
is the name of a pink fluid album, right, And
it's not the same thing because is the side of
the Moon that's lit up is the side of the
Moon that faces the Sun, right, not the side of
them in the faces the Earth. So the dark side
of the moon is the side of the Moon that
(09:09):
faces away from the Sun. Right. So sometimes the far
side of the moon is lit up, like when the
moon is right between the Earth and the Sun, then
the far side is totally bright and the near side
is totally dark. Oh wow, I never thought about that before. Yeah,
because I guess the far side of the moon gets
lit up sometimes it does. And so like sometimes the
(09:30):
sun is just like blasting with energy, but there's nobody
there to look, right. It's like whatever secrets the far
side of the moon holds, you know, are being revealed
by the sun, but nobody's looking at it. So, right,
all those beautiful lunar sunsets and sunrises, nobody there to
appreciate it. Because the moon doesn't have a stable dark side, right,
it's not always the same side that's dark. The temperatures
(09:52):
on the moon very like crazy, right. If you're on
the bright side of the moon, it can get warmer.
If you're on the dark side of the moon, it
gets like super duper cold. And because the no atmosphere
to hold in the temperature, it basically as the boundary
between the bright side and the dark side moves across
the surface of the of the moon, the temperature just
like plummeting super quickly. So the dark side of the
(10:14):
moon changes all the time, but the far side of
the moon never changes. That's the weird part. It's right,
and you heard, and it's never changed, or it's it's
you know what I mean, Like, are we looking at
a different moon than humans ten thousand years ago, or
it's never changed. That's a great question. You know, in
old drawings of the moon it looks the same, but
(10:35):
that only goes back you know, like a thousand years
or so. But the physics that will explain it in in
a few minutes suggests that it hasn't changed in a
long long time. It shouldn't be stable, and that is
so weird. It is weird and you know, let's describe
exactly how weird that is, because in people's responses you
could hear there was some confusion about like exactly what's
doing the spinning and what could be affecting it. So
(10:57):
let's go through that in some detail and explain what's
happened before we explain why. Because the Earth is spinning around,
brispinning around, and the Moon is spinning around us at
a different rate, right, And the only things you really
need to think about. You don't need to think about
the fact of the Earth spins, that doesn't matter, or
the Earth is orbiting the Sun. The only two things
you need to think about are the Moon moving around
(11:18):
the Earth. Right. The Moon is in orbit around the Earth.
It goes around the Earth, and the Moon is spinning.
It's kind of like we are spinning around the Sun
once every year, but we're also spinning in place kind
of that's right, once exactly, and a different part of
the Earth faces the Sun literally every day. Right. It's
the Earth doesn't have a near side and the far
side to the Sun. Right. So, and that's because we orbit,
(11:42):
it takes us a whole year to go around, right,
it only takes us a day to spin right, but
in the case of the Moon, it spins it exactly
the right speed, so that the same side of the
of the moon is always facing the Earth. Those two numbers,
how long it takes to go around the Earth and
how fast it spins around are perfectly sincd up, so
(12:05):
that the same side of the Moon is always facing
the Earth. Oh and not just sinked up, but they
had to be syncd up going the opposite way, right. Yeah,
if the Moon is going around the Earth clockwise, then
the moon has to be going around spinning in place
counterclockwise at exactly the same number of times per per
(12:25):
day or per night. Um, let me just check that
my mental model here, it's hard to figure out. So
if it's moving around clockwise, imagine the nearest you have,
the near side, started twelve o'clock right, and the near
side of the moon is of course facing the Earth.
If the moon didn't rotate, then by the time you've
got to six o'clock, then the what we call the
far side of the moon would be facing their Earth.
(12:46):
So in order for that not to happen, it also
has to rotate actually clockwise right, So it moves around
the Earth clockwise and it rotates clockwise so that it's
the same side as always facing the Earth. Right. Yeah,
it's tricky. Yeah, yes, sorry, I got that totally. It's
hard to hard to keep chaco. Hey, editor, can you please,
(13:07):
can you make Jorge never say anything wrong? Yeah? Can
you make me sound a little bit more intelligent? There?
Thank you? Yeah, there you go. Um, oh, you're right,
you're right. It has to um kind of like spin.
Oh wow. Yes, it has to spend the same direction
at the same rate, exactly, has to spend the same
direction at exactly the same rate. And you know, anytime
you see a coincidence in physics, like these two numbers,
(13:28):
which could be different, happen to be exactly the same thing,
you got to look for a physical reason because either
it's a ginormous coincidence, or it's a signal from the
folks who invented the simulation that is our universe, or
there's a physical reason that it has to be that way, right, right,
because it's it's it's I feel like it's rare, right,
Like the Earth doesn't do that around the Sun, and
(13:50):
none of the other planets do that around the sun, right,
Like they not just spin at different speeds, but they
spin in like different axes and different directions, and so
it's it's like, just because you're going around in a
larger object, doesn't mean that you're going to have this
perfectly sincd orbit. Right. Um, yeah, you're right. None of
the planets in our Solar system have this same feature,
(14:11):
though there are some other moons. Some of the moons
of Jupiter do the same thing to Jupiter, right, So,
and that's a clue, right, because if you have a
one coincidence, that's crazy. If you have the same coincidence
several times, then you know that's a sign that there's
some physics happening. I think you're telling me that it's
all due to this very interesting physical effect, right, Like
(14:31):
there's a physics of why this happens. There's definitely some physics. Yeah, yeah,
so let's get into it. But first let's take a
quick break. All right. We're talking about why the moon
(14:53):
always looks the same every night all the time, Like
it's it's out there spinning around on the Earth, and
it's spinning around it's its own axis, but it always
seems to face the Earth the same way, and so
that's weird. Right. Yeah, it's due to an effect called
tidal locking, which is connected to something we've talked about
(15:14):
several other times called tidal forces. And it's pretty simple, right,
like the like the tides of the ocean, Just like
the tides of the ocean. Right, it's the same effect, um.
And the idea is the gravity will pull more strongly
on stuff that's nearby than stuff that's far away. Right.
That makes perfect sense. We're familiar with that, but we're
used to thinking about objects sort of as points. Like
(15:35):
the Earth goes around the Sun, we just think about
the whole the force on the whole Earth, right, Or
the Moon goes around the Earth, we think about the
force on the whole moon. But the moon is kind
of big, right, which means that the force on the
close side of the Moon is stronger than the force
on the far side of the moon. Right, the Earth
is pulling the parts of the Moon that are closest
(15:55):
to it more than it's pulling the stuff that's in
the behind it, exactly. And those are called tide forces.
And if tidal forces are strong enough, like if you're
near a black hole, then the difference in the force
on one side of the object and the other can
be enough to tear it apart. Right, And you might
be thinking tear it apart. What if you're pulling on
something with two different forces in the back on the
(16:15):
front side, that's the same thing as pulling it apart.
That's the same thing as applying a force from one
side to the other. And so for example, if you
get too close to a black hole, you will literally
get shredded into bits. And you know, we've seen this before,
like Shoemaker Levy was a comet that came too close
to Jupiter and Jupiter pulled it apart into twenty six pieces.
It still went around the Sun and slammed into Jupiter,
(16:37):
so it got its revenge. But tidal forces are a thing.
Anytime you have an object that's large compared to the
force of gravity, then it's gonna have a big difference
in the gravity on one side and the other. And
that's the same way the Moon makes tides on Earth, right,
it pulls the water closer to it to make the tides.
But it's not just what big objects in space, it's
it's it's like happening all the time to every one everywhere, right,
(17:01):
that's right, Yeah, Like if I stand up, If I
stand up right here in my studio, my feet are
getting pulled by the Earth more than the top of
my head. That's right, the Earth is literally pulling you apart. Now,
your body is strong enough to withstand that fairly small
difference between the force and your head and the force
and your feet. But yes, the Earth is trying to
(17:21):
pull you apart, unless you're lying down flat, in which
case the Earth is pulling out every part of you
the same way. And if you're really tall, you know,
then um, then the Earth might pull you, pull you
to bits. But it mostly happens to large objects where
the distance between one side and the other side is large,
so that the magnitude of the force of gravity is
(17:41):
large between the between the two and that's when you
difference is larger exactly, So the difference is larger and
the and the Moon is big enough that the Earth's
gravity pulls one part of it harder than the back
side of it, and it actually changes the shape of
the Moon a little bit. So the moon is not
a sphere. It's like and it's like an obloid object,
(18:02):
like a three D ellipse. The moon is not perfectly spherical,
it's not perfectly spherical because it's getting squeezed by the Earth.
And if these tidal forces were stronger, then the Earth
and the Moon get pulled apart. Right, That's what happens
when a moon gets too close to a planet, for example,
it can get pulled into pieces and that's and turned
into rings. Right. And so the Moon is in this
(18:23):
place where it's close enough to the Earth to be
an orbit, close enough to have these strong tidal forces,
but not so close that the Earth pulls it apart. Interesting,
and so Earth kind of squishes the Moon out of
out of us perfectly spherical shape. But but then how
does that relate to why we only see one side
of it? Well, because then it gets stuck. Right, So
now the moon is not a sphere, it's an ellipse.
(18:45):
And the half that's closer to the Earth is even
closer than it was back when it was a sphere. Right,
It's like it's fallen down a little bit, and so
that part gets heavier, right, has a stronger force of gravity.
And on the back side it's an ellipse also, and
part it gets even lighter. So now the near side
of the Moon weighs more than the back side of
the moon, meaning it's a stronger force of gravity. So
(19:08):
now it's sort of stuck. Right, It's like a ball
in a hole. Um, the close side of them can't
can't spin away, right, because if it spins, then the
fat part gets pulled back towards the Earth. You know.
Imagine you have like a bicycle wheel, right, and you're
holding it, and it spins freely, and it's happy to
be in any arrangement, right. It spins because every arrangement
(19:29):
is the same if it's a perfect circle. But now
put something heavy on one spot of the bicycle wheel,
what's gonna happen. It's going to prefer for that part
to be down right, and if you push it away
a little bit, it's gonna spin back so that the
heavy part is down That's what happened to the moon.
The near side of the moon is heavier than the
far side because it's closer to the Earth and sort
(19:49):
of it's sort of stuck in that way, and that's
the reason. That's the reason why we only see the
one side of the moon. That's the reason it's called
tidal locking. Right, Tidal forces change the shape of it
a little bit and then that shape makes it more
conducive to always face the heavier side towards the planet.
And so it happened to the Moon, and it's happened
to several moons of Jupiter, and it's not that uncommon thing.
(20:11):
So it's not a coincidence at all, Right, it's a
it's physics, So blame the tides. The tidal forces of
the Moon caused tides on Earth, but the tidal forces
of the Earth caused the Moon to always have a
near side. But wait, I'm a little bit confused. In
order for the Earth to deform the moon, doesn't the
Moon need to be stationary, do you know what I mean? Like,
(20:33):
if the Moon was spinning, then this tidal force would
even out across all sides, right, kind of like the
Earth is a little bit fat around the middle because
we're spinning and part of it gets more attracted to
the Sun sometimes. Yeah, if that's a good point, I
think if the Moon was spinning fast enough, it might
have been able to avoid this, right, because it could
(20:54):
it could sort of spin out of that little well
that it gets stuck in and have another part of
it stretched, So the stretching would be even doubt um.
But I guess that just means that in the early days,
the Moon was not spinning fast enough to avoid this. Remember,
the Moon formed out of debris, right, The Moon was
just a big cluster of debris. It's not like the
Moon was a perfect sphere that was spinning and then
(21:14):
just sort of placed on Earth. It was formed in place, right,
and the Earth had a role in in that formation.
Oh and when it formed, it formed in this weird,
deformed shape which locked it into always facing the right
the same way. Yea, So it probably was never a sphere, right,
It's not like back in its early days and its youth,
it remembers being having a perfect body and then the
(21:37):
Earth ruined it. And then and then it looked up
with the Earth and exactly, Oh, I see the Moon
formed into the right blob, into that blob. Right. And
but that also means that all of the debris that
formed the Moon didn't have a lot of spin to it, right,
Like maybe it was sort of basically kind of static
(21:59):
when it formed, because it would you know, you know,
I mean like if it formed out of the debris
that's moving, flowing, polling around, it would eventually coalesced into
a spinning ball, right. Yeah, basically everything has some angular momentum, right,
because it didn't have no anglar momentum, would mean for
everything that magically cancel out. So if you just took
all that debris, And for those of you who aren't
(22:19):
familiar with how the Moon is formed, we did a
whole podcast episode about how the Moon probably came from
something the collision of a small planetoid with an early Earth,
and a huge amount of debris was thrown out into
space and and some of that stuff coalesced into rings
and then eventually into the Moon, and so it's you
know there, We don't have a lot of information about
exactly what that collision looked like, but the amount of rotation,
(22:43):
amount of spin in that debris depends a lot on
like how that first planetoid hit the proto Earth, how
much spin there was. There must not have been a
lot of spin, because if there had been a lot
of spin, then it would you know, the Moon would
have started out spinning and maybe this title force would
not have deformed it into the right block. Spinning past
is a good defense against getting stretched out by title forces. Yeah,
(23:06):
it's a good good way to keep your ship keeping shape.
That's right. I recommend spin classes to the moon. There
you go. Cool. So that title forces is the reason
that we always see the same side of the moon.
Physics explains it in the end, one more mystery dismantled
by physics. Once more, the magic is gone, thanks to you,
Moon magic for thousands of years. All right, now let's
(23:28):
get into what is on that far side of the moon?
Are there? Aliens? Are there? Nothing? Are there? Is there
a secret message to you? That's right. But first let's
take a quick break. All right, we're talking about the
(23:54):
Moon and why it always looks the same every night.
It doesn't seem to be spinning the Moon, even though
it's a giant spherical object. And so we figured out
we talked about that it's due to tidal locking. So
it formed in such a way that it's always spinning
at the right rate that we always see it the
same way. That's right. The near side of the Moon
(24:16):
has basically become heavier because it's turned into a little
bit of an ellipse, and that makes it prefer to
keep that side to the Earth. I imagine that that
wasn't always the case. You know, when the first can
you imagine being on the Earth. When the Moon formed, like,
you know, I think that'd be pretty hot and nasty,
given that it formed at a huge collision in the
Earth is basically a ball of lava. Yeah, that'd be
(24:37):
a short trip. Okay, not so romantic, no, no, no, hot, nasty,
but not in a good way. Alright. So, due to
this tidal force, the Moon when it formed, forms such
a way that it basically got locked into always facing
the Earth the same side, that's right, which means that
there's a side of the Moon that we cannot see
(24:57):
from the Earth, and people didn't see until nine when
the Soviets finally sent something up there to take a
picture of it. Really was the Soviets who first saw it. Yeah,
I remember back in the day, the Soviets were leading
us in the space race, right in the fifties and
the early sixties, spot Nick and all that stuff. Um,
they were ahead. And actually it's pretty funny because the
(25:18):
Soviets were there first, right, they have the first ones
to see this stuff, and so the Soviet scientists they
just started naming things in Russian right and bold. This
annoyed the Americans, not only because they didn't get to
see it first, and they didn't get take the first pictures.
But now everything on the back side of the Moon
is like has some crazy Russian name. Wow is that true? Yeah?
Totally You think I just make this stuff up? Maybe,
(25:43):
uh no, this is totally true. Well, um, so they
they what did they send like a satellite and it
took pictures as it went around the back side of
the moon exactly. Yeah. And back then, you know, we
didn't have digital photographs and all this kind of stuff.
So they they had like the pictures first, and they
started naming the craters and the features exactly. So everything
on the backside is named in Russian. It started out
(26:05):
that way, but then the Americans got the International Astronomical
Union to intervene, and then they decided to do a
sort of international process, which is you know, um, what
do you mean intervened, Like they were in the middle
of naming things and then they're like whoa, whoa stop stop, yeah,
exactly exactly. Anyway, it turns out that the back side
(26:25):
of the Moon is not just like the near side
of the moon, right, it's not exactly this different. How
can it be different? Yeah, it's still sort of a mystery.
We don't actually still understand it. Now, it's not dramatically different.
I mean, in the end, it's still just rocks and dust, right,
it's not like there's a glittering ocean there or some
civilization or like crazy mountains or anything like that. No,
(26:46):
it turns out that there are more craters. And you know,
if you look at the Moon from the Earth, you
see these sort of pop marks and these also see
these open areas that we call seas, even though there's
no water in them. And the backside of the Moon
has more of these craters and fewer of the sea,
so it has a different complexion. Yeah, exactly, it has
more acne. And you might be tended to think, oh,
(27:06):
that's because you know it's facing out and so it's
going to get hit, right, but like a shield. Yeah,
but the Earth is not actually a very large in
the sky of the of the moon, right. The Moon
is kind of far away, and the Earth only protects
the Moon by about like three of its sky or something.
So if there's a rock aiming at the Moon, it's
(27:26):
most likely still just going to hit the Moon. Um,
so that's not enough to account for the difference. And
remember both sides the gravity like the Earth gravity protects
the Moon's like this side of the moon. Maybe no, no, no,
it's not it's not a big enough effect, and so
it's a big mystery. You know. There's a lot of
speculation that maybe, um, there's more like tectonic activity on
(27:47):
the front side of the Moon, which is sort of
smoothing it over. Remember we talked about Eurroba, that weird
moon that has almost no craters on it that are
older than like ten or twenty years old. Because there's
a lot of resurfacing, like stuff coming up and making
a new surface. It could be that that's happening more
quickly on the front side of the moon and in
the backside, but people don't really understand, like why would
that be. So there's some interesting mysteries there. It's like
(28:10):
squishy are on this side. Yeah, sometimes sort of getting refreshed, right,
Like the near side of the moon gets its skin scrubbed,
it gets a spa treatment more often. I think the
moon is just thinking, like, you know what, nobody's going
to look at my back side. Nobody cares. There's nobody
back here. I'm just gonna let it go. Yeah, And folks,
(28:31):
this is your motivation, you know, keep your hygiene spherical,
keep your back end agone free. Yeah, there's hygiene advice
from a scientist and a cartoonist. That's definitely who you
want to be listening to. So why do you think
there's more churn or more like volcanic activity on this side?
Is it related to the fact that it's being it's
(28:53):
closer to the Earth. It could be, right, I mean,
we're talking about how the Moon is formed and the
internals of it and what's going on inside and is
it still hot enough to like flow and move around. Um,
But it's it's something we've only recently really started to
explore and to understand, and so it's still a question.
Lunar scientists don't know the answer to this as far
as I'm aware, So it's it's an open question. And
(29:14):
you know, until recently, we didn't know basic stuff about
the Moon, like does it have a strong magnetic field?
And you know, why are there pockets of magnetism here
and there? And so you know, even though we we
went to the Moon fifty years ago, we haven't been
back very much, and so there's a lot of questions
we just don't have answers to. You know, I think
people who study the moon are officially like to be
called moonies. Well, you're in charge of naming, so if
(29:36):
they're not called that, if they weren't called that before,
they are now. All right. So that's the far side
of the moon. And Daniel was it's somewhere that we
want to go or is it would be interesting to
go to or you know, for vacation or for science.
I wouldn't recommend it for vacation, but it is interesting
just because it's not well explored, which means there's always
an opportunity for surprises, right, which is sort of my
(29:58):
whole philosophy about science. It's like, science is about exploration.
You can think you know what something is gonna do,
you can think you know what something's gonna look like,
you can think you you know whether there are particles there,
But until you go and look, you haven't given yourself
the opportunity to be surprised by the universe. And so
it's definitely worth exploring because it's also not that far away.
And it was in twenty nineteen, right this year, that
(30:21):
humans finally landed something on the far side of the moon. Really,
that's right, Yeah, just now, just a few months ago
China landed something and took a bunch of pictures and
is doing experiments over there, And so it's an interesting place, right,
Like do we understand how the Moon formed? It gives
us insights to how planets formed in the early history
the Earth and stuff. It's also not a terrible place
(30:43):
to do science because it's shielded by the whole Moon
from all this noise of radio broadcast and annoying podcast
hosts and all that stuff that's spewing stuff out into space.
So if you want to build, for example, a radio telescope,
that's a really nice quiet spot. It's the most you
can get away from other people. Exactly, it's an introverts vacation, exactly.
(31:06):
There you go. That's how you how that's how you
market it. But you can only market it to like
one introvert at a time, if you speak Russian and
and one a quiet place too with no signal and
you're on your phone. The far side of the moon
would be ideal. Yeah, the market for that are super
zillionaire Russian introverts, right, which I imagine there might be
(31:29):
a few, right, must brush you have a bunch of
millionaires zillionaire Russian introvers listening to this podcast, we will
sell you a ticket to the far side of the moon.
That's right. We will tell you how to get there, exactly, exactly.
But it's one of my favorite kind of things because
people can really grasp it. You can look up at
the sky and you can think, you know, it's crazy
that my ancestors and my ancestors ancestors, I've all been
(31:49):
looking at the same thing hanging the sky, and the
same side of it too, also not seeing the same thing.
We we don't see, yeah exactly that for thousands of years,
no human who had been looking up at the sky
had seen the backside of this thing until basically our generation,
right for the generation before us, finally cracked this mystery,
finally lifted our eyeballs off the surface so we could
(32:11):
see the other side of this thing, which is right
there in our faces. Cool. Well, it's amazing to think
there are still mysteries even as close as the moon, right,
there are mystery places that are hard to get to,
but just unexplained phenomena in physics. Yeah, yeah, exactly, And
that's you know, that's why physics goes on, right, because
there are always mysteries. Some people ask me, like, you know,
(32:32):
are we ever going to figure things out? And I'm
pretty sure there's always going to be some person with
a question out there, you know, why is this this way?
Why isn't it that way? And why does this look
different from this other thing? Um, there's always questions to
be answered, and they're always interesting insights to be uncovered
when you dig into those questions. Each one is like
a little thread in the fabric of the universe which
if you tug on, it might unravel and reveal something fascinating. Yeah,
(32:55):
humans are annoying like that, you know, never satisfied humans,
or physics sists or three year old kids, basically the same.
It's one category. It's one category, all right. Well, we
hope you enjoyed that and got you to think a
little bit about the moon and how it formed and
what's out there that we still know every time you
go out into the night and look up at the
(33:16):
night's car that's right. And if you have questions about
something you don't understand and you'd like us to explain,
please send them to us at questions at Daniel and
Jorge dot com. And if you are a Russian billionaire
with disposable income. Let us know that's right. Send it
to money at Daniel and Jorge dot com. See you
next time. Thanks for tuning in. If you still have
(33:44):
a question after listening to all these explanations, please drop
us a line. We'd love to hear from you. You
can find us at Facebook, Twitter, and Instagram at Daniel
and Jorge That's one word, or email us at Feedback
at Daniel and Jorge dot com. Thank for listening, and
remember that Daniel and Jorge Explain the Universe is a
production of I Heart Radio. For more podcast from my
(34:06):
Heart Radio, visit the i heart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows. H
Hey, Daniel, did you know we're not the first people
to join physics and cartooning? What I thought we were
definitely on the forefront there. No, you know one of
my favorite comic scripts ever is named after something awesome
in physics. Let me guess, Um, Calvin and Hobbs. No, No,
that's philosophy, Um thinking thinking Garfield? Wait? Do you think
(00:29):
I like Garfield? It's the same joke every time. That's true? Um?
Are you thinking just because of quantum fields? Like? Maybe
Garfield is another quantum field? Maybe peanuts. I don't know.
I have no idea how peanuts could relate to physics.
I am officially disappointed in you. All right, I give up.
(01:02):
Hi am Jorge. I'm a cartoonists and the creator of
PhD comics. Hi. I'm Daniel. I'm a particle physicist, and
I have no idea what cartoons relate to physics, especially ours, right, especially,
and Welcome to our podcast, Daniel and Jorge Explain the Universe,
a production of I Heart Radio in which we talk
about crazy things about the universe, things that are close by,
(01:23):
things that are far away, things on one side, things
on the other side, and we break it down an
attempt to explain something to you that's both mind blowing
and actually understandable. That's right, all the things that are
both maybe right here and kind of far away, that's
at the same time, that's right nearby and yet hidden.
We seek to reveal those truths to you. So to
(01:43):
be on the podcast, we will be talking about something
that is basically in our everyday lives, right every well,
every night live, every nightlife. Yeah, my nightlife is not
that exciting anymore, but back when I used to go
at at night. Yeah, it's something that I was wanking
for Netflix back before kids. But yeah, this is the
kind of thing you know, you can look up in
(02:04):
the sky and easily wonder about. Yeah, it's right there
almost every night, and yet we can't see it. Nobody,
nobody really knows what it looks like. Right until recently,
that's right, nobody had ever seen it, even though it
hangs right there. And so today we're talking about what's
on the far side of the moon. That's right. If
(02:26):
you look up in the night sky often you may
notice the moon, of course, and a sharp observer may
notice that the moon looks similar every time. The portion
of it you can see changes right, becomes a crescent,
becomes larger. But if you pay attention, you notice that
the features you see on the Moon are actually the
same every night. Yeah, it never changes, the right. That's
mind blowing to think, because the Moon is a giant
(02:49):
sphere and we're spear and we're you know, going around
the Sun spinning and the Moon is spinning around us,
and yet we always see the same side of the
Moon all every night. That's right, it doesn't change. One
side of the Moon is the near side, that's the
side the face of the Earth, and the other side
faces away from the Earth towards the rest of the universe.
(03:09):
And until nineteen fifty nine, no human had even seen
a picture of it. We had no idea what could
be on it. It could have been like filled with
crazy lunar civilization, or you know, have a message written
on it, or something like I can't believe you took
you guys this long, or something. Right, it could have
been filled with Israeli tardigrade. I think you're fast forwarding
(03:30):
a few decades. Yeah, but yeah, I mean, there could
have been even nothing, right. It could have been just
a half sphere for all we know. We could have
just been like a like a slice orange and we
only see one side of it, right, Yeah, it could
have been that the moon is actually a big prop
right and always and if we come around the other
side we see like the scaffolding and all that stuff. Um,
that could have been amazing. And you know, we make
(03:51):
a joke even known that the moon was the sphere
and not just like a giant disc floating in space. Um.
I think could be pretty hard to get a giant
disc um in any model of moon formation. But but
you never know, right, And this is why we explore,
because you've got to see stuff to breally understand. You
can speculate, you can say we think we know what
(04:12):
the backside of the moon is like. Turns out when
we saw it there were some surprises and until you
really yeah, there were some surprises. The backside of the
moon is not the same as the front side of
the moon, and you know, you got to go and look.
This is why we do experiments, This is why we
explore the universe because until you see it, you never
really know. And so only a handful of humans have
(04:32):
actually seen the other side of the moon, right, seen it? Yeah,
I mean we've had pictures, and only a handful of
humans have seen it, sort of like with their own eyes. Yes,
that's true. It takes you have to orbit the moon
in order to see that. So yeah, only a few
people have ever seen this, but you know, fewer people
have ever seen my moon, not quite as prestigious. But um, yeah,
(04:53):
let's not get into that on this podcast. Let's say
that for Daniel and Jorge after dark. Okay, all right,
that's folks. That's the sound of Jorge carefully stepping away
backwards from that joke. No, but it's a fascinating topic,
and I was wondering did people understand that because it's
kind of odd. Is it like a giant cosmic coincidence
(05:14):
or is it totally normal for us to only see
one side of it? That's a that's why I'm blowing
to me. Yeah, So, um, I walked around and I
asked people, you know, what do they think about this?
Were they aware of it, did they realized did they
understand it? Could they give a physical explanation? Yeah? So,
as usual, Daniel went out there somewhere in the world.
Where were you at this time? Daniel? Were you in
(05:35):
California or No? I was back in California. So these
are you see Irvine summer students who answered these questions.
As usual, Daniel went out and asked random people on
the screen the question of the episode, and today's question was.
Today's question was did you know that that half of
the moon always faces away? So think about it for
a second, if you had realized this, or if you
(05:57):
knew this. I'm sure a lot of our reader listeners
I knew this, but maybe you hadn't thought about it
for a while. And so think about what you would
answer if a random physicist approach you on the street. Yes,
do you know why that is? Um? Just I know
because I know that the Earth rotates and I know
the Moon doesn't. And there's a reason why you don't.
(06:18):
We only see one face in the moon and never
the other. I did not know that there is a
side of the Moon that did not face the Earth
because the first rotation as well. Yeah, I mean my
understanding is the Moon is rotating around the Earth and
the Earth rotates on its axis because it's spinning. Um.
But yeah, I didn't realize the Moon was spinning too.
I didn't think it was. I guess because both the
(06:38):
Moon and the Earth are rotating, and so we never
see the backside related to rotations of the stellar bodies. Yes,
well do you know why that? Is that a coincidence?
Is there a physical reason? Physics? Physics? All right, So
a lot of people didn't know, and a lot of
(07:00):
people didn't yees. Some people were really shocked, and as
soon as they understood that it was happening, they were like,
that's really weird. How could that be? What? Yeah, it's
almost like it's doing it on purpose, right, Like the
Moon is suspicious of us and doesn't want to turn
its back to us, you know, like it's it's hurling
through space, but it's like I don't want to I
(07:20):
need to be facing Earth at all time. And it's
slowly backing away also, right, don't forget, we're losing it
very gradually. So the moon is sort of like edging
away from us the way you're edging away from my
inappropriate jokes. Yeah, so I guess it's not as well
known as I would have guessed it was. You know,
a lot of people seem surprised, and of the people
who did know that it happened, none of them could
(07:42):
give me an explanation for why, Right, nobody understood the
physics of it. People appreciated the concept, but nobody could
explain why. Well, you know, I think the question I
have is, um, what's the official name for it? I
think we've called it the far side of the moon,
the backside of the moon. Think Floyd called it the
dark side of the moon. It's called the far side
of the moon, right, And I think that's probably the
(08:04):
inspiration for that cartoon, right, the far side, because like,
what's going on over there, like the weird hidden side. Um,
though I'd love to ask Gary Larson about that one day.
It's not the dark side of it because oh, actually
I do know the answer to that, because I just
read a little bit of his biography. What is the answer?
The answer is he had another name for it, but
(08:25):
then when he sold it to a syndicate or a newspaper,
they said, hey, how are we call it the far side?
And He's like, sure, editors actually contribute something, I've never
heard of that before. That's that's the anti climatic story.
And if our editors listening to this podcast, we love
everything you suggested, by the way, that's right, and we
meant newspaper that's right. Comic editors. No, So the far
(08:48):
side is the back side of the moon, the side
of the Moon that always faces away into the cosmos,
away from the Earth. The dark side of the Moon
is the name of a pink fluid album, right, And
it's not the same thing because is the side of
the Moon that's lit up is the side of the
Moon that faces the Sun, right, not the side of
them in the faces the Earth. So the dark side
of the moon is the side of the Moon that
(09:09):
faces away from the Sun. Right. So sometimes the far
side of the moon is lit up, like when the
moon is right between the Earth and the Sun, then
the far side is totally bright and the near side
is totally dark. Oh wow, I never thought about that before. Yeah,
because I guess the far side of the moon gets
lit up sometimes it does. And so like sometimes the
(09:30):
sun is just like blasting with energy, but there's nobody
there to look, right. It's like whatever secrets the far
side of the moon holds, you know, are being revealed
by the sun, but nobody's looking at it. So, right,
all those beautiful lunar sunsets and sunrises, nobody there to
appreciate it. Because the moon doesn't have a stable dark side, right,
it's not always the same side that's dark. The temperatures
(09:52):
on the moon very like crazy, right. If you're on
the bright side of the moon, it can get warmer.
If you're on the dark side of the moon, it
gets like super duper cold. And because the no atmosphere
to hold in the temperature, it basically as the boundary
between the bright side and the dark side moves across
the surface of the of the moon, the temperature just
like plummeting super quickly. So the dark side of the
(10:14):
moon changes all the time, but the far side of
the moon never changes. That's the weird part. It's right,
and you heard, and it's never changed, or it's it's
you know what I mean, Like, are we looking at
a different moon than humans ten thousand years ago, or
it's never changed. That's a great question. You know, in
old drawings of the moon it looks the same, but
(10:35):
that only goes back you know, like a thousand years
or so. But the physics that will explain it in in
a few minutes suggests that it hasn't changed in a
long long time. It shouldn't be stable, and that is
so weird. It is weird and you know, let's describe
exactly how weird that is, because in people's responses you
could hear there was some confusion about like exactly what's
doing the spinning and what could be affecting it. So
(10:57):
let's go through that in some detail and explain what's
happened before we explain why. Because the Earth is spinning around,
brispinning around, and the Moon is spinning around us at
a different rate, right, And the only things you really
need to think about. You don't need to think about
the fact of the Earth spins, that doesn't matter, or
the Earth is orbiting the Sun. The only two things
you need to think about are the Moon moving around
(11:18):
the Earth. Right. The Moon is in orbit around the Earth.
It goes around the Earth, and the Moon is spinning.
It's kind of like we are spinning around the Sun
once every year, but we're also spinning in place kind
of that's right, once exactly, and a different part of
the Earth faces the Sun literally every day. Right. It's
the Earth doesn't have a near side and the far
side to the Sun. Right. So, and that's because we orbit,
(11:42):
it takes us a whole year to go around, right,
it only takes us a day to spin right, but
in the case of the Moon, it spins it exactly
the right speed, so that the same side of the
of the moon is always facing the Earth. Those two numbers,
how long it takes to go around the Earth and
how fast it spins around are perfectly sincd up, so
(12:05):
that the same side of the Moon is always facing
the Earth. Oh and not just sinked up, but they
had to be syncd up going the opposite way, right. Yeah,
if the Moon is going around the Earth clockwise, then
the moon has to be going around spinning in place
counterclockwise at exactly the same number of times per per
(12:25):
day or per night. Um, let me just check that
my mental model here, it's hard to figure out. So
if it's moving around clockwise, imagine the nearest you have,
the near side, started twelve o'clock right, and the near
side of the moon is of course facing the Earth.
If the moon didn't rotate, then by the time you've
got to six o'clock, then the what we call the
far side of the moon would be facing their Earth.
(12:46):
So in order for that not to happen, it also
has to rotate actually clockwise right, So it moves around
the Earth clockwise and it rotates clockwise so that it's
the same side as always facing the Earth. Right. Yeah,
it's tricky. Yeah, yes, sorry, I got that totally. It's
hard to hard to keep chaco. Hey, editor, can you please,
(13:07):
can you make Jorge never say anything wrong? Yeah? Can
you make me sound a little bit more intelligent? There?
Thank you? Yeah, there you go. Um, oh, you're right,
you're right. It has to um kind of like spin.
Oh wow. Yes, it has to spend the same direction
at the same rate, exactly, has to spend the same
direction at exactly the same rate. And you know, anytime
you see a coincidence in physics, like these two numbers,
(13:28):
which could be different, happen to be exactly the same thing,
you got to look for a physical reason because either
it's a ginormous coincidence, or it's a signal from the
folks who invented the simulation that is our universe, or
there's a physical reason that it has to be that way, right, right,
because it's it's it's I feel like it's rare, right,
Like the Earth doesn't do that around the Sun, and
(13:50):
none of the other planets do that around the sun, right,
Like they not just spin at different speeds, but they
spin in like different axes and different directions, and so
it's it's like, just because you're going around in a
larger object, doesn't mean that you're going to have this
perfectly sincd orbit. Right. Um, yeah, you're right. None of
the planets in our Solar system have this same feature,
(14:11):
though there are some other moons. Some of the moons
of Jupiter do the same thing to Jupiter, right, So,
and that's a clue, right, because if you have a
one coincidence, that's crazy. If you have the same coincidence
several times, then you know that's a sign that there's
some physics happening. I think you're telling me that it's
all due to this very interesting physical effect, right, Like
(14:31):
there's a physics of why this happens. There's definitely some physics. Yeah, yeah,
so let's get into it. But first let's take a
quick break. All right. We're talking about why the moon
(14:53):
always looks the same every night all the time, Like
it's it's out there spinning around on the Earth, and
it's spinning around it's its own axis, but it always
seems to face the Earth the same way, and so
that's weird. Right. Yeah, it's due to an effect called
tidal locking, which is connected to something we've talked about
(15:14):
several other times called tidal forces. And it's pretty simple, right,
like the like the tides of the ocean, Just like
the tides of the ocean. Right, it's the same effect, um.
And the idea is the gravity will pull more strongly
on stuff that's nearby than stuff that's far away. Right.
That makes perfect sense. We're familiar with that, but we're
used to thinking about objects sort of as points. Like
(15:35):
the Earth goes around the Sun, we just think about
the whole the force on the whole Earth, right, Or
the Moon goes around the Earth, we think about the
force on the whole moon. But the moon is kind
of big, right, which means that the force on the
close side of the Moon is stronger than the force
on the far side of the moon. Right, the Earth
is pulling the parts of the Moon that are closest
(15:55):
to it more than it's pulling the stuff that's in
the behind it, exactly. And those are called tide forces.
And if tidal forces are strong enough, like if you're
near a black hole, then the difference in the force
on one side of the object and the other can
be enough to tear it apart. Right, And you might
be thinking tear it apart. What if you're pulling on
something with two different forces in the back on the
(16:15):
front side, that's the same thing as pulling it apart.
That's the same thing as applying a force from one
side to the other. And so for example, if you
get too close to a black hole, you will literally
get shredded into bits. And you know, we've seen this before,
like Shoemaker Levy was a comet that came too close
to Jupiter and Jupiter pulled it apart into twenty six pieces.
It still went around the Sun and slammed into Jupiter,
(16:37):
so it got its revenge. But tidal forces are a thing.
Anytime you have an object that's large compared to the
force of gravity, then it's gonna have a big difference
in the gravity on one side and the other. And
that's the same way the Moon makes tides on Earth, right,
it pulls the water closer to it to make the tides.
But it's not just what big objects in space, it's
it's it's like happening all the time to every one everywhere, right,
(17:01):
that's right, Yeah, Like if I stand up, If I
stand up right here in my studio, my feet are
getting pulled by the Earth more than the top of
my head. That's right, the Earth is literally pulling you apart. Now,
your body is strong enough to withstand that fairly small
difference between the force and your head and the force
and your feet. But yes, the Earth is trying to
(17:21):
pull you apart, unless you're lying down flat, in which
case the Earth is pulling out every part of you
the same way. And if you're really tall, you know,
then um, then the Earth might pull you, pull you
to bits. But it mostly happens to large objects where
the distance between one side and the other side is large,
so that the magnitude of the force of gravity is
(17:41):
large between the between the two and that's when you
difference is larger exactly, So the difference is larger and
the and the Moon is big enough that the Earth's
gravity pulls one part of it harder than the back
side of it, and it actually changes the shape of
the Moon a little bit. So the moon is not
a sphere. It's like and it's like an obloid object,
(18:02):
like a three D ellipse. The moon is not perfectly spherical,
it's not perfectly spherical because it's getting squeezed by the Earth.
And if these tidal forces were stronger, then the Earth
and the Moon get pulled apart. Right, That's what happens
when a moon gets too close to a planet, for example,
it can get pulled into pieces and that's and turned
into rings. Right. And so the Moon is in this
(18:23):
place where it's close enough to the Earth to be
an orbit, close enough to have these strong tidal forces,
but not so close that the Earth pulls it apart. Interesting,
and so Earth kind of squishes the Moon out of
out of us perfectly spherical shape. But but then how
does that relate to why we only see one side
of it? Well, because then it gets stuck. Right, So
now the moon is not a sphere, it's an ellipse.
(18:45):
And the half that's closer to the Earth is even
closer than it was back when it was a sphere. Right,
It's like it's fallen down a little bit, and so
that part gets heavier, right, has a stronger force of gravity.
And on the back side it's an ellipse also, and
part it gets even lighter. So now the near side
of the Moon weighs more than the back side of
the moon, meaning it's a stronger force of gravity. So
(19:08):
now it's sort of stuck. Right, It's like a ball
in a hole. Um, the close side of them can't
can't spin away, right, because if it spins, then the
fat part gets pulled back towards the Earth. You know.
Imagine you have like a bicycle wheel, right, and you're
holding it, and it spins freely, and it's happy to
be in any arrangement, right. It spins because every arrangement
(19:29):
is the same if it's a perfect circle. But now
put something heavy on one spot of the bicycle wheel,
what's gonna happen. It's going to prefer for that part
to be down right, and if you push it away
a little bit, it's gonna spin back so that the
heavy part is down That's what happened to the moon.
The near side of the moon is heavier than the
far side because it's closer to the Earth and sort
(19:49):
of it's sort of stuck in that way, and that's
the reason. That's the reason why we only see the
one side of the moon. That's the reason it's called
tidal locking. Right, Tidal forces change the shape of it
a little bit and then that shape makes it more
conducive to always face the heavier side towards the planet.
And so it happened to the Moon, and it's happened
to several moons of Jupiter, and it's not that uncommon thing.
(20:11):
So it's not a coincidence at all, Right, it's a
it's physics, So blame the tides. The tidal forces of
the Moon caused tides on Earth, but the tidal forces
of the Earth caused the Moon to always have a
near side. But wait, I'm a little bit confused. In
order for the Earth to deform the moon, doesn't the
Moon need to be stationary, do you know what I mean? Like,
(20:33):
if the Moon was spinning, then this tidal force would
even out across all sides, right, kind of like the
Earth is a little bit fat around the middle because
we're spinning and part of it gets more attracted to
the Sun sometimes. Yeah, if that's a good point, I
think if the Moon was spinning fast enough, it might
have been able to avoid this, right, because it could
(20:54):
it could sort of spin out of that little well
that it gets stuck in and have another part of
it stretched, So the stretching would be even doubt um.
But I guess that just means that in the early days,
the Moon was not spinning fast enough to avoid this. Remember,
the Moon formed out of debris, right, The Moon was
just a big cluster of debris. It's not like the
Moon was a perfect sphere that was spinning and then
(21:14):
just sort of placed on Earth. It was formed in place, right,
and the Earth had a role in in that formation.
Oh and when it formed, it formed in this weird,
deformed shape which locked it into always facing the right
the same way. Yea, So it probably was never a sphere, right,
It's not like back in its early days and its youth,
it remembers being having a perfect body and then the
(21:37):
Earth ruined it. And then and then it looked up
with the Earth and exactly, Oh, I see the Moon
formed into the right blob, into that blob. Right. And
but that also means that all of the debris that
formed the Moon didn't have a lot of spin to it, right,
Like maybe it was sort of basically kind of static
(21:59):
when it formed, because it would you know, you know,
I mean like if it formed out of the debris
that's moving, flowing, polling around, it would eventually coalesced into
a spinning ball, right. Yeah, basically everything has some angular momentum, right,
because it didn't have no anglar momentum, would mean for
everything that magically cancel out. So if you just took
all that debris, And for those of you who aren't
(22:19):
familiar with how the Moon is formed, we did a
whole podcast episode about how the Moon probably came from
something the collision of a small planetoid with an early Earth,
and a huge amount of debris was thrown out into
space and and some of that stuff coalesced into rings
and then eventually into the Moon, and so it's you
know there, We don't have a lot of information about
exactly what that collision looked like, but the amount of rotation,
(22:43):
amount of spin in that debris depends a lot on
like how that first planetoid hit the proto Earth, how
much spin there was. There must not have been a
lot of spin, because if there had been a lot
of spin, then it would you know, the Moon would
have started out spinning and maybe this title force would
not have deformed it into the right block. Spinning past
is a good defense against getting stretched out by title forces. Yeah,
(23:06):
it's a good good way to keep your ship keeping shape.
That's right. I recommend spin classes to the moon. There
you go. Cool. So that title forces is the reason
that we always see the same side of the moon.
Physics explains it in the end, one more mystery dismantled
by physics. Once more, the magic is gone, thanks to you,
Moon magic for thousands of years. All right, now let's
(23:28):
get into what is on that far side of the moon?
Are there? Aliens? Are there? Nothing? Are there? Is there
a secret message to you? That's right. But first let's
take a quick break. All right, we're talking about the
(23:54):
Moon and why it always looks the same every night.
It doesn't seem to be spinning the Moon, even though
it's a giant spherical object. And so we figured out
we talked about that it's due to tidal locking. So
it formed in such a way that it's always spinning
at the right rate that we always see it the
same way. That's right. The near side of the Moon
(24:16):
has basically become heavier because it's turned into a little
bit of an ellipse, and that makes it prefer to
keep that side to the Earth. I imagine that that
wasn't always the case. You know, when the first can
you imagine being on the Earth. When the Moon formed, like,
you know, I think that'd be pretty hot and nasty,
given that it formed at a huge collision in the
Earth is basically a ball of lava. Yeah, that'd be
(24:37):
a short trip. Okay, not so romantic, no, no, no, hot, nasty,
but not in a good way. Alright. So, due to
this tidal force, the Moon when it formed, forms such
a way that it basically got locked into always facing
the Earth the same side, that's right, which means that
there's a side of the Moon that we cannot see
(24:57):
from the Earth, and people didn't see until nine when
the Soviets finally sent something up there to take a
picture of it. Really was the Soviets who first saw it. Yeah,
I remember back in the day, the Soviets were leading
us in the space race, right in the fifties and
the early sixties, spot Nick and all that stuff. Um,
they were ahead. And actually it's pretty funny because the
(25:18):
Soviets were there first, right, they have the first ones
to see this stuff, and so the Soviet scientists they
just started naming things in Russian right and bold. This
annoyed the Americans, not only because they didn't get to
see it first, and they didn't get take the first pictures.
But now everything on the back side of the Moon
is like has some crazy Russian name. Wow is that true? Yeah?
Totally You think I just make this stuff up? Maybe,
(25:43):
uh no, this is totally true. Well, um, so they
they what did they send like a satellite and it
took pictures as it went around the back side of
the moon exactly. Yeah. And back then, you know, we
didn't have digital photographs and all this kind of stuff.
So they they had like the pictures first, and they
started naming the craters and the features exactly. So everything
on the backside is named in Russian. It started out
(26:05):
that way, but then the Americans got the International Astronomical
Union to intervene, and then they decided to do a
sort of international process, which is you know, um, what
do you mean intervened, Like they were in the middle
of naming things and then they're like whoa, whoa stop stop, yeah,
exactly exactly. Anyway, it turns out that the back side
(26:25):
of the Moon is not just like the near side
of the moon, right, it's not exactly this different. How
can it be different? Yeah, it's still sort of a mystery.
We don't actually still understand it. Now, it's not dramatically different.
I mean, in the end, it's still just rocks and dust, right,
it's not like there's a glittering ocean there or some
civilization or like crazy mountains or anything like that. No,
(26:46):
it turns out that there are more craters. And you know,
if you look at the Moon from the Earth, you
see these sort of pop marks and these also see
these open areas that we call seas, even though there's
no water in them. And the backside of the Moon
has more of these craters and fewer of the sea,
so it has a different complexion. Yeah, exactly, it has
more acne. And you might be tended to think, oh,
(27:06):
that's because you know it's facing out and so it's
going to get hit, right, but like a shield. Yeah,
but the Earth is not actually a very large in
the sky of the of the moon, right. The Moon
is kind of far away, and the Earth only protects
the Moon by about like three of its sky or something.
So if there's a rock aiming at the Moon, it's
(27:26):
most likely still just going to hit the Moon. Um,
so that's not enough to account for the difference. And
remember both sides the gravity like the Earth gravity protects
the Moon's like this side of the moon. Maybe no, no, no,
it's not it's not a big enough effect, and so
it's a big mystery. You know. There's a lot of
speculation that maybe, um, there's more like tectonic activity on
(27:47):
the front side of the Moon, which is sort of
smoothing it over. Remember we talked about Eurroba, that weird
moon that has almost no craters on it that are
older than like ten or twenty years old. Because there's
a lot of resurfacing, like stuff coming up and making
a new surface. It could be that that's happening more
quickly on the front side of the moon and in
the backside, but people don't really understand, like why would
that be. So there's some interesting mysteries there. It's like
(28:10):
squishy are on this side. Yeah, sometimes sort of getting refreshed, right,
Like the near side of the moon gets its skin scrubbed,
it gets a spa treatment more often. I think the
moon is just thinking, like, you know what, nobody's going
to look at my back side. Nobody cares. There's nobody
back here. I'm just gonna let it go. Yeah, And folks,
(28:31):
this is your motivation, you know, keep your hygiene spherical,
keep your back end agone free. Yeah, there's hygiene advice
from a scientist and a cartoonist. That's definitely who you
want to be listening to. So why do you think
there's more churn or more like volcanic activity on this side?
Is it related to the fact that it's being it's
(28:53):
closer to the Earth. It could be, right, I mean,
we're talking about how the Moon is formed and the
internals of it and what's going on inside and is
it still hot enough to like flow and move around. Um,
But it's it's something we've only recently really started to
explore and to understand, and so it's still a question.
Lunar scientists don't know the answer to this as far
as I'm aware, So it's it's an open question. And
(29:14):
you know, until recently, we didn't know basic stuff about
the Moon, like does it have a strong magnetic field?
And you know, why are there pockets of magnetism here
and there? And so you know, even though we we
went to the Moon fifty years ago, we haven't been
back very much, and so there's a lot of questions
we just don't have answers to. You know, I think
people who study the moon are officially like to be
called moonies. Well, you're in charge of naming, so if
(29:36):
they're not called that, if they weren't called that before,
they are now. All right. So that's the far side
of the moon. And Daniel was it's somewhere that we
want to go or is it would be interesting to
go to or you know, for vacation or for science.
I wouldn't recommend it for vacation, but it is interesting
just because it's not well explored, which means there's always
an opportunity for surprises, right, which is sort of my
(29:58):
whole philosophy about science. It's like, science is about exploration.
You can think you know what something is gonna do,
you can think you know what something's gonna look like,
you can think you you know whether there are particles there,
But until you go and look, you haven't given yourself
the opportunity to be surprised by the universe. And so
it's definitely worth exploring because it's also not that far away.
And it was in twenty nineteen, right this year, that
(30:21):
humans finally landed something on the far side of the moon. Really,
that's right, Yeah, just now, just a few months ago
China landed something and took a bunch of pictures and
is doing experiments over there, And so it's an interesting place, right,
Like do we understand how the Moon formed? It gives
us insights to how planets formed in the early history
the Earth and stuff. It's also not a terrible place
(30:43):
to do science because it's shielded by the whole Moon
from all this noise of radio broadcast and annoying podcast
hosts and all that stuff that's spewing stuff out into space.
So if you want to build, for example, a radio telescope,
that's a really nice quiet spot. It's the most you
can get away from other people. Exactly, it's an introverts vacation, exactly.
(31:06):
There you go. That's how you how that's how you
market it. But you can only market it to like
one introvert at a time, if you speak Russian and
and one a quiet place too with no signal and
you're on your phone. The far side of the moon
would be ideal. Yeah, the market for that are super
zillionaire Russian introverts, right, which I imagine there might be
(31:29):
a few, right, must brush you have a bunch of
millionaires zillionaire Russian introvers listening to this podcast, we will
sell you a ticket to the far side of the moon.
That's right. We will tell you how to get there, exactly, exactly.
But it's one of my favorite kind of things because
people can really grasp it. You can look up at
the sky and you can think, you know, it's crazy
that my ancestors and my ancestors ancestors, I've all been
(31:49):
looking at the same thing hanging the sky, and the
same side of it too, also not seeing the same thing.
We we don't see, yeah exactly that for thousands of years,
no human who had been looking up at the sky
had seen the backside of this thing until basically our generation,
right for the generation before us, finally cracked this mystery,
finally lifted our eyeballs off the surface so we could
(32:11):
see the other side of this thing, which is right
there in our faces. Cool. Well, it's amazing to think
there are still mysteries even as close as the moon, right,
there are mystery places that are hard to get to,
but just unexplained phenomena in physics. Yeah, yeah, exactly, And
that's you know, that's why physics goes on, right, because
there are always mysteries. Some people ask me, like, you know,
(32:32):
are we ever going to figure things out? And I'm
pretty sure there's always going to be some person with
a question out there, you know, why is this this way?
Why isn't it that way? And why does this look
different from this other thing? Um, there's always questions to
be answered, and they're always interesting insights to be uncovered
when you dig into those questions. Each one is like
a little thread in the fabric of the universe which
if you tug on, it might unravel and reveal something fascinating. Yeah,
(32:55):
humans are annoying like that, you know, never satisfied humans,
or physics sists or three year old kids, basically the same.
It's one category. It's one category, all right. Well, we
hope you enjoyed that and got you to think a
little bit about the moon and how it formed and
what's out there that we still know every time you
go out into the night and look up at the
(33:16):
night's car that's right. And if you have questions about
something you don't understand and you'd like us to explain,
please send them to us at questions at Daniel and
Jorge dot com. And if you are a Russian billionaire
with disposable income. Let us know that's right. Send it
to money at Daniel and Jorge dot com. See you
next time. Thanks for tuning in. If you still have
(33:44):
a question after listening to all these explanations, please drop
us a line. We'd love to hear from you. You
can find us at Facebook, Twitter, and Instagram at Daniel
and Jorge That's one word, or email us at Feedback
at Daniel and Jorge dot com. Thank for listening, and
remember that Daniel and Jorge Explain the Universe is a
production of I Heart Radio. For more podcast from my
(34:06):
Heart Radio, visit the i heart Radio app, Apple Podcasts,
or wherever you listen to your favorite shows. H
Hosts And Creators
Daniel Whiteson
Kelly Weinersmith
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