How Underwater Tunnels Work

It's a pretty amazing feat to dig a tunnel beneath a body of water that's big enough (and safe enough) to drive a train through. While humans have been digging underwater tunnels for thousands of years, it wasn't until the late 19th century that it became viable on a large scale. In this episode, Chuck and Josh explore the ins and outs of the engineering triumph that is digging below water.

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Episode Transcript

Speaker 1 (00:00):
Brought to you by the all New Toyota Corolla. Welcome
to you stuff you should know from House Stuff Works
dot com. Hey, and welcome to the podcast. I'm Josh Clark.
There's Charles W. Bryant. Noel is with us again. That's right. Really,

(00:21):
it's just been a very short period of time since
he was last with us. Well, who knows, we might
release these weeks apart just to throw people, you know,
it's possible. How you doing fine? How are you? I'm
good man, I'm I'm great, I'm right. A tunnel through
this show and get all up out of him. That's

(00:41):
pretty lame. It was okay, Um, it worked though, because
what we're talking about has to do with tunnels. Yes,
I don't know if you caught that. Yeah, we covered
a little bit of this in the Subways podcast. Yeah,
cutt and cover, cut and cover, But this is this
goes deep undercutting covering. You gotta stop. I don't know. Yeah,

(01:01):
we're talking about underwater tunnel specifically. That's right, which, by
the way, we should probably say for those of you
who are into semantics, um, the word tunnel is applied
only to something that is bored entirely underground. Yes, if

(01:24):
if you say, like we talked about with cut and
cover in subways, if you dig out a trench, put
in your tunnel and then backfill over your tunnel, what
you've created is a conduit. Yeah. And if you if
you correct people when they talk about this kind of thing,

(01:44):
you're so obnoxious or you're an engineer or sea. But
engineers don't even do that because they still want to
be liked, you know, they don't want to be that guy. Um. Yeah,
So we're talking about how and I think a lot
of people wonder how did you managed to get a
tunnel under the water. We're gonna tell you it's really

(02:05):
not that hard and there's a few ways. Yeah, I
don't know if saying it's not that hard is correct. Well,
not that um complicated in a engineering sense. Again, No,
I think none of these Like I was like, what
they bore a tunnel under a river? Right? But just
the this is the the overview. I mean, you can't

(02:28):
read this article ago building underwater railway tunnel? Is that
what you thought I was saying. No, No No, I'm just
saying like there's so much more to like just the details. Yeah,
I mean, but you weren't saying that there's particle physics
and there's digging a big hole under a river. You
know what I'm saying, Man, we're going to hear from
some angry civil engineer. No. I think it's great. I

(02:49):
think it's modern, modern marvel is what it is. It is. Yeah,
so chuck, Yes, it's not necessarily modern, and it's no.
People have been digging under rivers um since the Babylonians. Yeah,
I was quite surprised by this. They managed to build

(03:09):
a three thousand foot bricklined, art supported tunnel twelve by
fifteen feet under well, they diverted the Euphrates River and
it was a pedestrian passageway. That's crazy, right, This is BC.
And I think they diverted it temporarily. Well yeah, sure,
but even still it's still a tunnel. And they still

(03:31):
did this several thousand years ago, and they diverted a
river which is in President's own. I'm impressed with them.
I'm glad to hear you are too. Um. Over the years,
people kind of I imagine, built and failed spectacularly and
trying to build underwater. Um. It wasn't until the nineteenth

(03:54):
century that people really kind of started to advance by
leaps and bounds over say the Babylonian methods to come
up with some techniques that are still in use today. Yeah,
as far as underwater goes, I mean, they were tunneling
all during the eighteenth and nineteen centuries. And in fact,

(04:16):
the word undermine I thought it was fairly interesting. It
came from the fact that there were miners who dug
undercastle walls to collapse them. That's a pretty good idea. Yeah,
it's a very good idea. And I don't think we
covered that in our Castle podcast either. No, I wish
we had. Yeah, that would have been complete. That that
episode is incomplete. But like you said, it was eighteen

(04:37):
hundreds when we finally said, hey, let's try this underwater
thing again because we think we can do it now. Yeah,
and they kind of had it licked. And again, like
I said, some of the techniques that they came up
with at this time are still in use today. Yeah.
I got a question for you, though, If it's dangerous
and it's uh pricey, why do you tunnel at all?

(05:00):
Why not just build bridges? That's a fantastic question, and
I happen to have some answers. Okay, all right, I
still thinking about this. You build a bridge, it makes sense,
it's beautiful bridge works. We know how to build bridges,
We've been doing it forever. But what if you have
a heavily trafficked shipping lane with ships that are taller
than your bridge. You can build a drawbridge, but it's

(05:21):
gonna be up and down, up and now and up
and down all day. And don't fool yourself. A drawbridge
is pretty expensive too. That's one all right. Uh. If
you are um an enemy of the United States, your
bridge could be a target from air strikes. Yeah, that's
a problem for you if you I mean, if you

(05:41):
want to build it again afterwards, it could be struck
down again and then again. You want your bridges to
remain intact. Yes, I'm gonna argue for tunnels here though,
my friend and say that they will stand tides very
well and currents and storms. It's not out in the
open like a bridge is. Uh. You can go greater
distances with the tunnel, and you can carry like almost

(06:03):
virtually unlimited amounts of weight. So score one for tunnel
and chuck yeah, because with the bridge you have to
worry about it collapsing with the tunnel. It's like, no,
you're probably pretty firm against some sort of bedrock or
seabed or something like that. You're you're you can put
as many trucks as you want on and it's not
gonna break. Yeah, I guess we'd call seismic activity a draw.

(06:25):
You have you ever seen? Why? Not good for either
one the bridges? Yeah, that is nuts. Is that in
Seattle or Washington? I don't know, man, but that's you
look at that and think, how does that move like
that without just completely breaking apart? It does pretty scary. So, um,
we're going to call that a draw though, because earthquakes
are not good for either. Um. Well, cost you said

(06:48):
that the bridges are costly. Well, bridges are get costly
or the bigger they are, whereas tunnels get cheaper the
bigger they are. Yeah, the length. With the tunnel, it
it starts, the cost starts to drop as it gets
longer and longer. Not so with the bridge. So why
then would city planners still use tunneling as a last

(07:09):
uh sort of a last resort? I guess because they
like bridges more. Okay, all right, so that wash and
seen we were play acting. It's not very well either No,
I thought it was pretty good. Oh, I thought was okay. So, uh,
let's talk about some of the tunnels they've got going
on these days that are pretty remarkable. Um, there's one

(07:32):
that actually connects two islands in Japan. Um. It's called
the Well, you're the resident Japanese expert, have you pronounced that?
The Icon Tunnel, the Cicon Tunnel, And that is the
one of those two holds the record for the longest
and deepest underwater rail tunnel. Um. And they did that
in the nineteen fifties after a typhoon sank some ferry

(07:54):
boats and the cigar us straight and killed like over
fo people. They said, you know what, maybe we should
go underwater with this operation, and they did so. And
it connects Hanshoe and Hokkaido, and Hokkaido is known for
its uh sub factories. And you even have a tipit
for me the Simpsons tidbit. Oh was that from the

(08:16):
Mr Sparkle episode man one of the best ever. So
in they completed the Icon Sikan Tunnel. Yeah, I'm gonna
go with Sikan okay um and it stretches thirty three
and a half miles. Yeah, the whole tunnel does. Yeah,
that's impressive. It is, but then, um, only fourteen and

(08:37):
a half miles of it, only fourteen and a half
miles of it are under water. Yeah, but it goes
close to eight hundred feet deep, which is that's sort
of the remarkable part. That's a long way down. Yeah.
You have to pop your ears when you're on that train. Oh,
I'm sure. The Chunnel, which we were laughing about before
we hit record. Just the name, and we should say

(08:59):
it's called the tunnel because it's actually the Channel Tunnel.
It goes under the English Channel to connect the UK
in France. Yes, and that was finished in the mid
nineties and uh, twenty four of its thirty one miles
or underwater, but it only goes about two six ft down. Yes. Yeah,
it's so funny to use words like only with stuff

(09:21):
like this or just yea yeah. Um. And then the
newest member to the underwater tunnel family is the Marmaray
Tunnel that in Istanbul that connects the Asian portion of
Istanbul and the European portion of Istanbul, which means it's
the only underwater tunnel or the first to connect two continents.

(09:42):
That's right, And The name comes from d c. Of
Marmara and the word ray which is Turkish for rail,
because it is another rail tunnel, meaning train. And uh,
it's pretty cool when they were when they started digging it,
this thing, this project went slow as molasses, not just
because a construction, but because they came upon the port

(10:05):
of Theodosius. Theodosius I think, is that right? Sounds good
to me. So it was um it was a port
in Istanbul. Back then it was constantinople Um for that
was the busiest port in the world for about a
thousand years, and it was lost and they came upon

(10:28):
it while digging this tunnel, and the archaeologists were like, okay, stop, stop, stop, turn. Yeah,
they found forty artifacts from this. They didn't turn, they
went through it, but they documented everything and grabbed it
for the museum. Well, if it hadn't been for the tunnel,
maybe they would have never found that stuff, you know. Uh.
So that was an immersion tunnel and it was the

(10:48):
longest and deepest immersion tunnel ever built. Immersing tunnels are
my favorite. Yeah, that's the one that I didn't think
was super complicated. I saw a couple of videos and
I'm telling you it is. There's a lot to it,
just the pontoons alone or yeah, but it's like the
kind of thing you can replicate in your bathtub, That's
what I mean. But uh so we're gonna get into

(11:13):
what that all means, because, um, there are quite a
few ways to build tunnels and three. Yeah, and there
wells three and use. I bet there's other dudes out
there trying to figure new stuff out. Um, but one
of the oldest that is still in use. It's called
a tunneling shield thanks to a remarkable, remarkable dude, a

(11:38):
Frenchman named Mark Isombard Brunel, who was eventually knighted for
his work as inventing the tunnel shield. Understandably, so yeah,
pretty amazing. He got the idea from watching a shipworm,
which is like a naked clam because these little shells
on one end. It's basically yah, it's like the termite

(12:00):
of the sea is what they call it. Because this
thing bores into docks and boats and basically tunnels into
wood and uh leaves saw dust in his wake. And
this guy saw this things like, hey, that's a pretty
good idea. I think we'll make a tunneling feel exactly. Yeah,
So he came up with the Brunell shield, which is
actually rectangular, but the best way to think of what

(12:22):
a modern tunneling shield looks like. Um, there's a description
given in this article that makes sense if you add
one extra sentence. You take a coffee can. Imagine a
coffee can't without its lid, and the bottom part of
the coffee can is pointed somewhat with some holes in it,
And when you dig it into the ground and then

(12:43):
turn it on its side to bore horizontally, what you
have is something like a tunneling shield. So at the
front end, what part did they miss? They're going straight
down and it just completely confused me, the fact that
it wasn't going to the side. Oh, I couldn't right
at my head around until I finally was like, oh,
I see what they're saying, So that that coffee can't

(13:06):
imagine it jammed horizontally underground. Yeah, let's go in and
explore it. Right in the front, there's holes and you
have different kind of compartments where people stand there called
muckers and they dig out the dirt in front of them, right. Yeah,
And in Brunel's case. Um, they were cast iron shutters,

(13:26):
and they would just open these shutters one at a
time and just dig a few inches out. And back
then they used screwjacks, but now they use hydraulics and
just inch inch away forward a little by little, little
by little, and the reinforcing them building the sides as
you go right, And that coffee can in the meantime
is holding that tunnel shape right, because it's the exact

(13:50):
shape of the tunnel shield. While the guys in front
are digging, the coffee can is giving them all support.
And then right behind it are mac and steel workers
who are reinforcing the tunnel. And then the the reinforced,
finished concrete tunnel provides the stability for those hydraulic checks
that slowly and little by a little inch the whole

(14:11):
thing forward. Yeah, I mean, it's the It's like every tunnel,
although actually the emergent tones aren't. But when you're digging
a tunnel, it goes back to the Babylonians. You dig,
support advance, dig support advance, just like Charles Bronson in
The Great Escape? Oh yeah, was that his mantra? No,
this was just I'm gonna go tunnel in this tunnel

(14:34):
and build the frame. You're doing a good Bronson. Well
it's sort of Bronson, but it's also sort that the
guy from The Simpsons who was based on Bronson Pankas area.
Is that who does that? Sure? Okay, sure, yeah, I
don't know that for sure, but is it? Okay? Um,
it's Simpsons reference number two. Oh yeah, nice. Uh but

(14:56):
remember in The Great Escape too, they needed uh and
of course we'll see this too. It's very dangerous job
and they needed air. So they had them I think,
uh fire billows, bellows, uh something pumping bellows, just to
pump fresh air in there, because when you're hundred feet
in a tunnel underground, especially the size of one the
Great Escape, just like big enough for your body, you're

(15:16):
gonna run out of air. Yeah, and well that's something
that they ran into. We talked about. I don't remember
what episode it was, but we were talking about building
the Brooklyn Bridge. Um. They had these basically uh an
upright coffee can that they dug the the the posts
out of. Um. This is the same they ran in

(15:37):
the same thing when they were building the the the
tunnel underneath the Thames River. Thanks to Brunel, he built
it with his son. Yeah, very shortet, but it took
about eight or nine years. Um, and it was there
was a shutdown for seven years because it ran out
of money. But um, it was deep enough so that
you had to pump compressed air in to keep the

(15:59):
water out. And since there was compressed are you had
to go through a series of airlocks or else you
get the venture. And UM, I don't know if we've
said this, it seems obvious, but the reason you're doing
all of this is because digging into soft earth is
problematic because you're leading edge is going to continually want
to collapse on top of you unless you have pressurised

(16:20):
there to keep the water at bay, and you have
guys digging out through a support structure e g. A
tunneling shield, sand hogs. That's messive method one, yes, and
it's an old one and it's a good one. It's
still in use today. Um. It has to be softer.
You can't dig through bedrock because you know this thing
moves through hydraulic jacks and there's guys digging. Um. If

(16:45):
you run into like some serious rock, the best thing
to use is called a tunnel boring machine. Yeah, if
you've ever seen die Hard three? You get a good glimpse,
Jeremy ir Yeah, which is a pretty good one. Um
in fact, well actually yeah, one of only two good ones,

(17:05):
Sam Jackson. Yeah, the first one and that one were
pretty good. The second one and I didn't. All the
other ones are just terrible. The second one, it wasn't
so bad. It was all right. I like to see
it was at the airport, Yeah, it was okay. I
love any kind of airport disaster flick. Oh yeah, man,
I'm crazy for those movies. Airport, airport, airport two, whatever, airplane.

(17:30):
I love him. What about that bad Tom Hanks movie
where he played the foreign guy that lived in the airport?
I never saw that, But did you know Terminal? Yeah?
Did you know that it's based on a real guy. Yeah,
I didn't know that. I haven't seen the movie. That
wasn't very good. The I think the fact that it
was like kind of lighthearted and warm, that's not what

(17:51):
the guy was like. Yeah. Well Spielberg plus Tom Hanks
doing accents. Man, have you seen him doing Walt Disney? Yeah?
I thought that It's okay in the preview, now I
can't tell I did. I managed to get through only
about twenty minutes of Cloud Atlas the other night. I
just can't see Tom Hanks is like this Cockney rough ruffian. Well.

(18:13):
I love the guy. He's an amazing actor. But it's
just it didn't work. No, why did they do that?
To know? Hodgman's got some good stories about Tom Hanks,
by the way, I don't know if you should be
telling people that. No, I'm not gonna tell the stories.
I don't even know if you yes, all right man,

(18:34):
that was a nice hank Sean sidebar. Tunnel boring machines
Die Hard two three. Yeah, so these things are like
a couple of stories tall. Yeah, they're amazing. They're they're
tunnel boring machines is the right word for him. They're
all inclusive machines. They cut, they support, and they build

(18:58):
as they go along. They're magnificent as far as as
mechanical engineering goes. Yeah, they have a spinning cutting head
and he's basically huge giant steel wheels that twist and
turn in different directions and then that whole thing turns
and it's just a destructo mobile that goes straight ahead

(19:21):
and uh lifts that pummels that rock and shoots it
out on a conveyor behind. Yeah, just like a five
valve a ship worm. And then uh, this is the
part I didn't get that they're actually building it with
an erector as it goes. Man, that's crazy. Yeah, it's
all this one big machine that's you just basically pressed
start and it goes forward. And they actually used tunnel

(19:45):
boring machines, a pair of them for the chunnel construction,
one from one side and one from the other side.
And thanks to GPS, Yeah, good GPS um, they were
able to keep them on a course for one another.
First I thought missing, Yeah, the first thing I thought
was I would end up like ten ft above. Oh man,

(20:06):
I wouldn't even end up that close. Yeah, and you'd
be screwed. You'd have to start all over. I would
end up in Scotland. Well, it'd be great. We'd be
like just tunnel up and get drunk distilleries. Uh. But
luckily they had a lot smarter people than us working
on the channel. Right. Um. They drive forward, Uh at

(20:29):
a rate of about two and fifty per day. That's
significant because we're talking like bedrock, you know, like if
you if you were able to take away all of
the Dirk and all of the water on Earth. What
you would have is rock. That's the mantel, and that's
what you're digging through. Is this rock it's made to

(20:49):
support the earth exactly. Heck, it is the earth. Yeah,
and um, this is what these machines dig through at
a rate two fifty ft a day. That's impressive. Yeah,
in they work, Apparently they're uh something this violent is
prone to breaking down. So I guess when you have
them up and running, that's a good thing. When they're down, then, um,
you're obviously gonna be losing time. Did you see how

(21:11):
the author of this article put it? I did. I
didn't even want to comment. You want to go ahead? Well,
he just says that they breakdown more often than he
used jaguar, except he probably said jag earra jar. I
didn't know that, or jaguars. Are they famous for not working? Yeah?
Oh yeah, I really didn't know that. The older ones

(21:34):
are well, that's like any old car, right, I think
they they? And like if you w rabbits had like
real bad track records. Remember the rabbit mhm or the cabriolet? Yeah,
every story girl's favorite car, right? What else? Remember Looker? Yeah?

(21:55):
It even said look car on the side. Yeah, it's
French for the car, is it? Alright? So UM, did
you know Josh that they are have been banning about
the idea of a transit plant tunnel for decades. It's
pretty awesome. I don't think it will ever happen though. No.
They would be very costly because it would be the

(22:16):
um It would be an immersion tube. But they wouldn't
be able to go to the sea floor obviously, because
that's just crazy. It would be tethered, floating essentially at
about a hundred and fifty ft below the water, right
dangling from a pontoon on the surface, and uh fifty
four thousand football field side size sections. And that's how

(22:38):
we're going to get into that in a minute. But
that's how they work with these immersion tunnels. They do
it one section at a time. It's just too much
money and too much stuff. There's well, there's actually an
immersion tube tunnel UM that's proposed in Norway across the
Sogna Fiord. That sounds much more manageable than the Atlantic Ocean. Really,

(22:58):
I mean, just the idea of this this ontoon getting
pummeled by UM by cyclones and and just bad weather
in general. Plus why do it these people who just
want to drive to England from New York. I don't know.
I don't know that the logic behind any advantage behind
something like that. It just seems like it would just

(23:20):
every every foot of it is a potential for it
to just break and the whole thing's trashed. But the
one in Norway is that an I T T an
emerged tube tunnel. It is dangling from a pontoona bu
that one's dangling, right, So that technology exists. Uh well,
it's it's in proposal stage. And like the thing I saw,

(23:40):
it was still probably kind of an overview, but they
seemed pretty confident about it. They had like you know,
titled charts and all that kind of stuff. But it's
it's it's only something that's um like twenty kilometers or
thirty kilometer or something like that. It's not all the
way across the Atlantic Ocean, you know. All right, So
I guess we should fully explain in the I T
T then, which is our final way that you can

(24:03):
tunnel underground and again my favorite, But before we get
to it, let's do a message break and chuck now
we finally get to talk about my favorite type of tunneling,
the immersion tube tunnel. That's right. So these rubber seals
have gina gaskets actually is what they're called. And you

(24:26):
winch the two together and you pump the water out
and these gaskets and seals the change and water pressure
creates compresses them and creates an airtight seal. But it's underwater,
so you would go in, say we want an underground
tunnel going from this part of land that part of

(24:47):
land under here, So we're just gonna go in. We're
gonna dredge and dig and create a trench where we're
gonna eventually put the tunnel. But we're gonna make the
tunnel an individual piece of is here on dry land,
usually at some sort of shipyard, and they're going to
use the amount the equivalent of stealing concrete to make

(25:08):
an average size ten story building. So just tip it
on its side, and that's what your section looks like.
That's one section um and then once the concrete cures
after a month, we'll take it out to see in
a pontoon crane, which is exactly what it sounds like
that they're gigantic um. We seal it up first so

(25:29):
that it floats and right. And then once we do
get it over the site roughly where we want it,
we will kind of start to sink it a little bit.
Or I've also seen they'll weight it down, uh, and
then they'll sink the thing and eventually they'll link it
up to another segment, so they use winches to to
pull one segment to another UM. And then these rubber

(25:51):
gaskets hold the seal. And in this this bulkheads, these
temporary bulkheads that are keeping the two um the two
segments separate like inside the tunnel, you couldn't go through them.
Yet you pump the water out, that changing air pressure
compresses the rubber gaskets, forming a watertight seal. Then you

(26:13):
remove the steel bulkheads. Bam, there's two connected segments of
the tunnel. And you just keep adding and adding and
adding and adding until you've created your prefab underwater tunnel.
It's beautiful. Then you cover that up backfillet or something
with rock. And we have a guy named W. J.
Wilgas to thank for this because he invented it way

(26:35):
back in the early nineteen hundreds. There's in early nineteen
hundreds name w J. Wilgas look at my immerse tube
tunnel where the world's fast, and everyone said, this is
a pretty good idea. Yeah, and it um. He pioneered
the technique when he built the Detroit River Railroad tunnel
connecting uh Michigan to Canada. So technically the first immersed

(26:59):
to tunnel is a sewer line in Boston in and
when he built that railway line, that was like, Okay,
this thing works because we've been shuttling poop in exactly
and this is like, now we can do it with trains,
and you are now the man of the hour, w J.
Because what is a train except a lot of poop?
You know, there's a similarity in but that has been

(27:22):
the go to since then. Then there's been more than
a hundred of these built in the twentieth century alone.
Uh and that didn't even count the twenty first century.
So I don't even know what's been going on the
past thirteen years. I saw like an engineering thing that's
that referred to him as rare. But I don't have
the impression that they're rare at all, you know, I
think they're kind of like the go to technique for
any well as many as possible. Yeah. Well, the one

(27:47):
advantage is, um, is that they you can make them
any shape. You know. It's not like when you have
a tunnel boring machine. Um, it's gonna have the shape
of the tunnel borer or the same with the tunnel shields. Well, yeah,
I guess it's the same. It's the size of the
giant coffee can. But you can make a tunnel in
the shape of a diamond if you wanted to. Well,

(28:07):
maybe not diamond. Well you could be kind of crazy,
be a big waste of money. But yeah, you can
take any shape, and um, you will also have to
use some of those other methods eventually, because this is
just for the what's along the bottom. To get down
to that section and then out the entrances and exits,
you're gonna have to use some other methods, right, you
might have to tunnel through through some sort of rock

(28:30):
or whatever. But yeah, when you put these tunnel segments
in and you pump the water out of the the
the chamber that connects the two, you take the bulkheads off,
Like there's your finished tunnel right there. I mean, you've
got the floors, the walls, the ceiling roadway. You go
in and put the wiring in and the lighting and
all that stuff afterward. But your tunnels set. Yeah, I

(28:51):
just think it's neat. I think it's very neat. Um
what else you got? I got nothing else. There's one
proposed right now that will be the long gus immersed
tube tunnel in the world when it's finished in two
thousand sixteen. There's a fifty kilometer bridge that connects or
will connect Hong Kong to Macau, and part of it
is a six point seven kilometer long immersed tube tunnel

(29:13):
which will probably be real nice, awesome. Yeah, I guess
that's it. All right, Go forth and build tunnels, Go
forth and build underwater tunnels. Let's see. If you want
to learn more about underwater tunnels, you can type that
word into the search bar at how stuff works dot com. Uh.
And since I said search part, that means it's time

(29:35):
for listener mail. All right, I'm gonna call this another
chess email, and this is gonna be it on the
chess emails. But thank you to everyone who wrote in
about your chess strategies and stuff. It's pretty great. Hey, guys,
thanks for doing the podcast on chess. It's a great game.
Here are a few things that you sort of missed jumping.

(29:55):
Josh implied or maybe even outright said that a night
only appears to jump over other pieces, it really just
goes around them. Nights actually can jump over other pieces.
For example, if you were so inclined on your very
first move, you could jump your Night over your ponds
and place it in front of the rest of your pieces.
There aren't any empty spaces to take your Night around

(30:16):
your islands in the stream, So that's jumping baby. A
little more on castling a couple of things. As you said,
you cannot castle if it either if either piece involved
has moved during the game. You also can't do it
if the king is in check or has to move
through check to castle. So the opposition queen is attacking

(30:36):
a square that the king has to go through the
castle it it cannot be done. Yeah, yeah, you got that.
You should probably all go back rewind that and listen
to it again. That's right, and um that's from Matt
in Pittsburgh. I'm sorry in l A via Pittsburgh, but
I did want to point out someone else in in
um another correction. I think we we got them pawn

(31:01):
promotion right, like if you make get your pawn all
the way to the other end of the table. But um,
I don't think we pointed out that you can only
promote it to a piece that you've already lost. Oh no,
we definitely did not. In other words, you can't have
two queens. But if you specifically said you have two queens,
oh did Yeah, Okay, I genuinely didn't know that. I

(31:22):
thought that. I didn't catch that. I knew that, but
I didn't catch it. So that was from someone else.
But thank you Matt in l A via Pittsburgh. Yeah,
he also described on poissant, but I think we've already
taken that up in another listener mail. So yeah, thanks
for all the corrections on Chester. Yeah, everybody, thank you
very much. If you want to get in touch with us,
tweet to us. Our Twitter handle is s y s

(31:44):
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