October 1, 2021 • 47 mins
Listener Antriksh asked that I look into subsea cables, the physical connections that link distant lands together for communication and power transmission. We learn about how physics creates unique challenges for subsea transmission and how 19th century engineers and scientists tried to overcome them.
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Episode Transcript
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Speaker 1 (00:04):
Welcome to tech Stuff, a production from I Heart Radio.
Hey there, and welcome to tech Stuff. I'm your host,
Jonathan Strickland. I'm an executive producer with iHeart Radio and
I love all things tech and longtime listener and Tricks
wrote in on Twitter to ask if I had done
(00:24):
an episode on undersea cables, and you know what, I haven't.
So today we're going to start to talk about them, because,
as it turns out, there's a lot to cover with
undersea cables to kind of understand not just how they work,
but the challenges that people faced in order to make
(00:46):
them a reality in the first place. This is also
a timely topic because recently a company called x Links
made headlines for the Morocco UK power plant project. That
project's goal is to create a bowler and wind farm
in Morocco and use a very very long sub sea
power chord, essentially to send electricity to the UK. Now,
(01:09):
while a lot of headlines called this the longest subseed cable,
that's misleading because there are actually many different types of cables,
and technically the ce ME WE three cable that's s
E A dash M E dash W E three, the
number three cable is actually about ten times longer than
(01:30):
what the Morocco UK cable will be. But we're gonna
get to all that probably in the next episode, definitely
not this one. But as and Tricks pointed out in
a tweet to me, undersea cables trace their history back
to the mid nineteenth century. So in order to understand
all of this, we really have to take a moment
and talk about the telegraph and the development of the
(01:52):
first undersea cables. So there were a few things that
had to happen for undersea cables to even become a necessity.
You know. One of those was the development of the
electric telegraph, because without that, there's no need to worry
about subsea cables. Right, If you don't have long distance
electric based communication, then cables aren't really a thing you
(02:13):
gotta worry about, at least as far as connecting, say
an island to a continent. Now, the word telegraph is
Greek and it means essentially distant writing. But this word
actually predates electric telegraphs. For example, there were semaphore systems,
(02:33):
ones that used visual cues with flags. Those were used
throughout France, and we're really developed during the Napoleonic wars,
and that was referred to as telegraph. Before any kind
of electric version came along in the late seventeen hundreds,
you had various smarty pants around the world experimenting with electricity,
you know, like Ben Franklin, and this was just something
(02:56):
that was just beginning to be understood at the time.
Alissandre of Volta had created a sort of proto battery
that we later called a voltaic pile or and then
later on we had the voltaic cells. These inventions could
produce a good electric current, but at a very low voltage.
Now we need a reminder here because we're gonna be
(03:16):
talking about electricity a lot. Voltage in electricity is sort
of similar to water pressure in a plumbing system. You
can think of it as how much oomph a current has,
and current you can think of as the amount of
electricity present in a system of flowing electricity or flowing electrons. So,
(03:40):
if we want a really quick analogy, if you had
a low voltage, high current source of electricity, that's kind
of like a lazy river, right. The river can be
really wide and it might be really deep, so you've
got a lot of water there, but that water isn't
moving very quickly. It's just lazily going down. A high voltage,
(04:00):
low current electric device produces a very tight, high pressured stream.
So think of like a a concentrated stream of water
coming out of a pressure hose. You don't it's not
nearly the same amount of water as the lazy river.
It's much less current in other words, but the pressure
(04:21):
or voltage is way higher. Well before Volta's discovery, scientists
and engineers were mostly reliant on devices that would build
up electrostatic charges. So electro static charges have a high
voltage but a low current, and they have limited applicability
in things where you need sustained electric current. So Volta's
(04:43):
invention would allow for new applications of electricity. Now in
the early eighteen hundreds you had some other smarty pants
like Hans Christian Orstead of Denmark. And by the way,
as always, my apologies for all the mispronunciation, and I'm
going to do of all the different names that is
on me and I apologize. However, he discovered that electricity
(05:07):
and magnetism have a connection. He observed that a magnetic
needle would deflect from magnetic north if it came close
to a wire that was carrying an electric current or
transmitting an electric current, and so we first began to
realize that electro magnetism is a thing, that there is
this relationship between electricity and magnetism. This would lead to
(05:33):
yet more smarty pants people thinking of ways that we
could use electricity through wires to communicate across vast distances.
One way, a way that Sir William Father gil Cook
and Sir Charles Wheatston suggested was to have a multi
wire system that would use up to five needles. They
(05:55):
experiment with different ones, but the one that they would
use heavily would have five needle pointers, and that would
be at the receiving end of this system. So you
could send different electrical signals down these different wires and
thus direct these needles these pointers to point to different
letters on a placard that would have the alphabet there.
(06:19):
Uh The system would remain in use in the UK
up through the early twentieth century, so the UK was
reliant on this system, whereas the rest of the world
would move on to other ones. The neat thing about
the system is that it arranged the alphabet in a
diamond pattern, so it only used twenty letters of the alphabet.
It left out the letters C, J, Q, U, X,
(06:42):
and z, so sometimes you had to do, you know,
approximations of certain words. And the letter A was at
the top point of the diamond, and then you know,
you had B and D at the next level, and
then so on and so forth, and then at the
bottom you had the letter Y. And the five needles
were split right in the middle of this diamond. They
(07:03):
were in the widest part of the diamond, pointing up
and down normally, which meant that they weren't pointing at
any specific letter. So by sending signals down specific wires,
you could make needles point to a specific letter. You
would have both of you know, two needles that were
on a diagonal line with a specific letter, and by
looking at the common letter that both needles were pointing at,
(07:26):
you could spell out words. An interesting approach, not necessarily
the fastest, but it worked. Later on, Wheatstone would create
a different system that had a circular dial uh than
a needle on the inside, and you had the alphabet
laid out along the inside circumference of the circle, so
sort of like an analog clock, except instead of numbers
(07:47):
for the time, you had the alphabet, and you also
could have numbers as well. Then you had keys that
matched the letters and numbers that were along the outside
of the style. So pressing down on a key would indicate, Okay,
I want to send this letter UM, and this is
the sending station, And then you would have a receiving
station on the other end that would have a similar
dial with a needle and the letters and numbers in it,
(08:10):
and pressing down a specific key would end up sending
a signal that would have the needle on the other
side point to the relevant letter or number. This way
was really neat and the way it worked is super cool.
But I'm gonna have to save that for another episode
because I'm supposed to focus on subsei cables, and I
wrote about a page and a half of stuff before
(08:31):
I realized I am getting way off track, so I'll
spare you for now, but that will come up maybe
in a future episode. Now, in America, it was Samuel Morse,
who interestingly was an art professor who came up with
the famous method for transmitting messages electrically using a special code,
one that today, of course, we refer to as the
Samuel Code. Don't wait no, I'm sorry. No. Morse code.
(08:55):
Morse code. Morse code uses dots and dashes to rep
letters and numbers, and by tapping the dots and dashes
on a telegraph key, you could send pulses of electrical
signal down a wire, and a receiver at the other
end could then emboss dots and dashes on a strip
of paper, so you could actually read out the dots
and dashes and translate it that way, or later on
(09:18):
you had engineers who are trained to listen for dots
and dashes, and you had a device that was essentially
tapping like a little anvil, tapping out the messages, and
you would just listen. Later, a guy named Alfred Vale
would partner with Morse to refine this system and make
it a little more practical, essentially looking at the most
(09:40):
frequently used letters and using the the simplest dots and
dash patterns to represent those letters, as well as to
redesign the telegraph key itself. By eighteen thirty seven, Veil
and Morse were demonstrating this technology, and by eighteen forty
three they secured funding to set up an experiment telegraph
(10:00):
line that stretched the thirty five miles around sixty kilometers
between Baltimore, Maryland and Washington, d c Here in America.
The project used poles that were erected alongside a railroad
line and wires connected to the poles via glass insulators,
and it worked. One thing that really amazed me as
(10:21):
I was doing research into this, just as a quick digression,
is how quickly things moved. Because this was eight three,
and we're gonna be talking about a transatlantic subsea cable
by the end of this episode. That came a little
more than a decade after that. And to think of
it being ten years, a little more than ten years
(10:42):
between stringing sixty kilometers of cable between two cities in
America to laying a subsea cable across the Atlantic Ocean
blows my mind. Well, anyway, the demonstration was a success,
and it didn't take long for railroad companies to start
building out tell alegraph systems, and early on they were
almost exclusively used to help keep track of traffic on
(11:05):
the rail system, to better plan out routes, and to
avoid long delays or accidents. By the end of the
eighteen forties, journalists were starting to make use of the
telegraph system to wire stories across vast distances, and businesses
began to get interested in this as well, the ability
to be able to conduct business between cities without having
to take you know, a train ride or otherwise have
(11:29):
you know, like like people on horseback travel from one
city to another. Because keep in mind this is this
is before the automobile has really become a thing. So yeah,
there were limited ways of getting information from one point
to another. However, until eighteen fifty, these distances were all
over land. The reach of telegraph systems ended at the coastlines,
(11:53):
which meant that while regions could develop a sophisticated internal
communications system you know, inside their border or maybe between
borders of neighboring nations that shared you know, a land border,
once you hit the ocean, you had to rely on
other methods, much slower methods. So a mail ship isn't
(12:13):
a ship that carries mail, not a not a gendered ship,
but a mail ship between London and New York could
take nearly a month to travel across the ocean. A
fast one might be able to make the journey in
three weeks. By the mid nineteenth century, steamships were largely
taking the place of sailing vessels. They could make the
journey in up around ten days, so still more than
(12:36):
a week to get from one point to another. That's
pretty slow for news to travel. It was difficult to
act with alacrity if you were relying upon information from
across the pond. So there was a strong use case
to make for creating an undersea cable infrastructure that could
(12:57):
connect distant parts of the world, you know, parts that
were separated by oceans, and even in Europe, like England
in particular, saw the need to do this because while
the distance was not nearly as great to travel from
say Dover to France, the delay in getting information from
other parts of Europe was still pretty considerable, so there
(13:20):
was definitely a need for that as well. This did, however,
present some engineering challenges because you had to find a
way to make this both practical and affordable. Now this
is going to be obvious, but I need to establish it.
It is way easier to repair and maintain infrastructure that's
above the water than it is to do below the water.
(13:41):
And that's because we live above the water and we
can't live below the water, at least not with the
same amount of freedom. And since the Mr folks seemed
completely uninterested in helping us maintain communication channels. We have
to take that into consideration. To that end, we have
to treat cables subseed cables different from terrestrial cables. We
(14:04):
have to take into consideration what being submersed in ocean
water is going to do to a cable over time.
We have to understand that those effects can be detrimental.
We have to be able to estimate how long a
particular cable is likely to remain viable, assuming no catastrophic
instances occur, like assuming that a ship's anchor doesn't tear
(14:25):
through the cable, for example. So we have to make
sure that we have the budget to not just install
a cable in the first place, but to potentially replace
that cable when we near the end of its estimated lifespan.
It has to make financial sense, or else it's a
loss in the long run. Right. So you can argue, yes,
(14:46):
it's invaluable to have two distant places connected together, but
if you're constantly having to replace the communication channel, then
that invaluable might start to take on of value where
you just say, yeah, it's invaluable, but I don't want
to pay for it. So coming up with a way
to make subsea cables work extends beyond just the technology.
(15:10):
I mean, obviously the tech is a critical component or
else nothing happens. But you can't ignore the financial element,
right or the physical challenges, because if you do that,
you're setting yourself out to fail. So we're gonna take
a quick break. But when we come back, we're gonna
talk about a couple of other things before we get
(15:31):
to the first subseed cable, like some basic things about
electrical transmission. But before we do that, let's take this
quick break. All right, So in the eighteen twenties and
eighteen thirties you had all these various smarty pants is
(15:55):
is all learning about electro magnetism. And we now know
that if you pass an electric current through a conductive material,
that generates a magnetic field. And similarly, should you have
a conductive material like a wire, encounter a magnetic field,
that field will induce an electric current to flow through
the conductive wire. And you've probably played with this in school,
(16:19):
making a simple electro magnet with like an iron nail,
some copper wire, and a battery. You know, you connect
the wire to either terminal of the battery, you've coiled
the wire around the nail to act as a core,
and it becomes magnetic. You can pick up paper clips
and stuff. I remember I did that in school. I
imagined that people still do well. There's a whole lot
(16:41):
more to electro magnets, but we're just going to focus
on a couple of little things first. And the first
important bit is, because of this relationship between electricity and magnetism,
we need to make sure that wires and cables that
we use to transmit electricity have really good insulation around them.
And that's because us Without insulation, that is, without some
(17:02):
sort of barrier that resists the flow of electricity and
the interaction of magnetic fields, you have the potential for interference.
So let's say you've got two copper cables and there's
no shielding on them, you don't have any insulation on them,
and you've got them close to each other. And then
let's say you send electricity through one of those two cables,
(17:24):
not the second one, just cable number one. Well, as
the electricity flows through cable number one, that creates a
magnetic field which overlaps to the second cable, and that
induces a current to flow Now, if we're using direct
current something like a battery, uh, the second cable will
only have electric current running at the very beginning when
(17:46):
that magnetic field first hits it, but then it will stop. However,
if the source is alternating current then which means that
the current is changing direction many times per second, then
what you have is a fluctuating magnet at it field.
Because the magnetic fields direction also changes many times per second,
that will continue to induce electricity to flow in the
(18:08):
second cable. This would be in interference. It creates phantom
signals when no signal is intended, or it interferes as
one signal overpowers or changes another. I remember back in
the day, I had these cheap desktop speakers that I
had connected to my computer, and I would put my
(18:28):
cell phone down on the desk, and every time my
cell phone got a notification, it would make this weird
electric chirping noise in the speakers because that was radio
frequency interference that was inducing a current to flow through
the speakers. So these are things that can happen, and
(18:50):
you don't want them to write. You want to shield
your components so that only the signals you want to
send are going through so you have to protect a
against that. Now, in the nineteenth century, there were people
who discovered a plant that had a kind of sap
essentially that was found to be a really effective insulator,
(19:11):
so it resisted the flow electricity and protects or insulates
against interference. That material is called Gutta percha. It's a
biologically derived latex. And like I said, the plant has
the name Gutta percha, but that's also the name everyone
used for the derived latex from it. Now, this was
(19:31):
fortunate at the time, but I should also add that
the telecommunications industry would spell doom for the Gutta purchase
trees because the rampant harvesting of the trees created an
unsustainable situation. And before too long people realize, oh, we
need an alternative to this, because pretty soon there's not
going to be any of this plant left on the
(19:52):
planet will have harvested at all. Anyway, Gutta percha has
many of the same properties as synthetic rubber, including the
ability to insulate conductive materials. Next, we need to think
about what happens with electricity as it travels over greater
distances of wire um. This is going to get more
complicated later in this episode, because, as it turns out,
(20:15):
there are certain things that we have to take into
consideration with any length of cable, and then there are
other things that come into play when you're talking about
cable that happens to be under the water. But under
most circumstances, even a great electrical conductor has some level
of resistance. Now I say under most circumstances, because as
it turns out, if you're able to super cool a conductor,
(20:40):
like a good conductor, and you're able to get it
down to an incredibly low temperature, like just a few
units of kelvin above absolute zero, then you can have
a superconductor which has no resistance. But under most normal conditions,
you know, conductors have resistance to electricity. You can think
of electrical resistance as kind of being like friction. It's
(21:01):
working against or resisting the flow of electricity. So resistance
depends upon a few different factors, such as the material itself,
like some conductors are better than others, like coppers a
really good conductor, and it also depends upon the thickness
of that material. A thin copper wire has a greater
electrical resistance than a thick copper cable for example. Well,
(21:26):
resistance means that as you transmit electricity across this conductor,
you'll see the electrical energy diminish over distance. And we
know that energy can be neither created nor destroyed, right,
so we're not destroying that energy. However, that energy is
converting from one type to another. In this case, the
(21:46):
resistance causes the conductive material to heat up and we
lose some of that electrical energy in the form of
waste heat. So if you want to push electricity further
down a trans mission line, you really have to use
a lot of voltage. And remember voltage is the pressure
in this system. So with alternating current, we can actually
(22:09):
use devices called transformers, which, while they are not robots,
they are arguably more than meets the eye. If you
were to look at an electrical transformer, like open up
a cover, and by the way, never do that, but
if you did do that, you would see that consists
of two coils of conductive wire wrapped around a core,
usually a ferro magnetic iron core in a simple transformer,
(22:33):
not necessarily a solid core, but a core. So passing
electricity through one coil of this wire induces electricity to
flow through the other. We already talked about inductance, right,
and the number of turns in each coil determines a
change in voltage. So let's say we've got coil number one,
(22:53):
which will call the primary coil. This is the coil
where we're going to send electricity through the wire. Let
say that primary coil has five turns and coil number two,
which is our secondary coil, has ten turns. Well, then
the ratio of turns is one to two, one for primary,
two for secondary, and the voltage of the second coil
(23:16):
will be double that of the first coil. This is
a step up transformer. We're stepping up the voltage. We're
increasing it by a factor of two. Now, if the
primary coil has ten turns and the secondary coil has
five turns, that's a two to one ratio. That means
the voltage of the second coil will be half that
(23:36):
of our first coil. This is a step down transformers.
So using this we can then push voltage up on
terrestrial power lines that are using alternating current. Again, this
only works with alternating current, not direct current. Then you
can increase the voltage for long distance transmission. You can
(23:57):
overcome the problem of loss due to resistance. Essentially, you've
just you turned the pressure on so much that it's
it's powering through that. Now you have to have the
right kind of cables to make that happen. You have
to have the transformers along the way, and you have
to step down the voltage before you feed that current
into say a business or a house. But it's entirely
(24:21):
possible to send electricity long distances overground using transformers. Anyway,
it's one thing to have a transformer above the waves.
If you've ever been around when a transformer blows out,
you know that this is a spectacular and often terrifying event.
There's a very loud boom, and it's like a thunderclap
(24:43):
or a shotgun going off, and then there's a shower
of sparks, and then all the power goes out and
it happens like in that order instantaneously. It seems now
that is inconvenient here upon the surface world, but below
the waves that would be much worse. So we have
to keep that in mind when we're talking about subsea cables.
(25:04):
Some of the solutions that we have to us here
on the surface would not be available to us underwater.
Now Samuel Morse himself tested the viability of an underwater
telegraph cable. He used a wire coated in tar and
India rubber to insulate the wire from the water because
he didn't want to lose electricity through the water. Essentially,
(25:27):
he submerged the wire in the New York Harbor and
he sent a telegraph signal through it, and the experiment
was a success. This signal came out the other side.
It worked. So as early as eighteen forty two, engineers
understood that an undersea cable was possible. The question was
could be made practical. The first underwater cable using Gutta
(25:47):
Percha as an insulator, was laid between Deut's and Cologne
across the River Rhine in eighteen forty seven, and then
in eighteen forty nine and Electrician with the Southeastern Railway
succeeded in laying two miles of cable off the coast
of England around the Kent region. But the first commercial
(26:08):
subseed cable would follow the year after that. It was
eighteen fifty and two brothers, Jacob Brett and John Watkins
Brett created the English Channel Submarine Telegraph Company. Now the
brothers had proposed laying a cable under the sea through
the English Channel and connecting the port towns of Dover,
England and Calais, France. Both England and France agreed to
(26:32):
this proposal, so the brothers got the funding they needed
to to try and make it happen, and they had
a deadline that they had to meet. So the brothers
purchased cable from a company called the Gutta Purchase Company.
The cable had Gutta Purchase insulation on it, but it
had no armoring to protect it from other hazards. So
it's a copper cable with a rubber like insulating layer
(26:54):
on the outside and that's it. Uh. It was just
a single copper wire too, it was not We're not
multiple cables or wires in this. So in many ways
this would be an experiment and ultimately it would be
only partially successful. Uh. In that really it was a failure,
but it taught them a lot of lessons. So the
cable the brothers used was too light to sink on
(27:16):
its own. It would not sink down to the sea floor.
So every one hundred yards or so, workers on board
the ship that would unspool the coil of cable, had
to attach lead weights to the cable. The weights ranged
between ten to thirty pounds, and the company used a
steam paddle ship called the Goliath to carry the cable
(27:40):
across the channel. They attached one end of the cable
to the dover shore side of the connection that went
up to a telegraph station, and then they began the
journey to France, and the ship would have to stop
every one yards or so in order to sink another
weight down with the cable to keep it in place
on the ocean floor, and had to stop each time.
(28:00):
So it's not like, you know, they were just leading
this out and staying in motion the whole time. They
stopped every hundred yards. It took the whole day for
the ship to lay the cable across to reach France,
and there the team attached the cable on the French
side they attempted to establish an electrical connection. I'm not
entirely sure the outcome of that attempt, Like the accounts
(28:24):
I read don't seem to really indicate whether or not
they were successful in getting an electrical signal all the
way across. At any rate, if they did, it was
a week one and by the next morning, the connection
had been severed and the line was just totally dead.
Not long after that, stories began to circulate that some
French fisherman had accidentally dredged up the cable in some
(28:46):
netting and then subsequently severed the cable. However, that story
was never verified. It didn't stop people from spreading variations
of that story, including variations that made the fisherman look
increasingly dimwitted over time. But the stories that were published
immediately following the failure actually suggested that it was the
(29:08):
action of the waves off the rocky coast of France
that was making the cable rub against rocks and then
and then break that way. What was certain is that
the cable did break, whether it was a human caused
error or because of the action of the waves, and
that's probably because there was no armoring on the cable.
(29:29):
So there you go. The brothers sent a letter to
the Times in England explaining that while their first attempt failed,
they had learned a great deal in the process, and
they explained that the thing that they had attempted had
never been done before, and as such they were going
in ignorant of what would and wouldn't work. But through
this experience they had learned some valuable lessons and were
(29:51):
more convinced than ever that a cable connecting England to
the European continent would work. Whether they wrote that letter
in an effort to, you know, make sure they still
had funding for future attempts, or this was a genuine
expression of their enthusiasm, I don't know. Maybe it was
a mixture of both, or maybe it was something else entirely.
(30:11):
But the important thing is they were right. When we
come back, I'll explain and tell the rest of their story,
all right. So the Brett brothers still had some time
left before their agreements with France and England would expire,
(30:32):
specifically with the French government, and if that happened, they
were going to have to go through the whole process
of securing permission all over again. That was not a guarantee,
especially you know, after having failed their first try. So
they were determined to make another go at it before
time was up, and this time they would add more
protections for the cable. That cable would contain not one,
(30:55):
but four copper wires, each insulated by Gutta percha. In fact,
h wire had a double layer of Gutta purchase installation,
so that you had a wire that was the core,
and then you had a rubber case essentially on the
outside of that, and then a second rubber case on
the outside of that. The engineers then bound those four
(31:17):
wires together with yarn soaked in tar and tallow, so
together the yarn tar tallow mixture. There's some other stuff
in there as well, and the four wires encased in
Gutta percha served as the core of the cable itself,
and that soaked yarn provided some more stability and strength.
(31:40):
The bound cables now formed a kind of rope, and
the next step was to weave ten strands of galvanized
iron wires around the rope to provide armor protection. Galvanization
is a process through which you apply a protective coating
of zinc into onto something like iron or steel. Typically,
the way it works is you make whatever thing you're
(32:03):
making out of iron or steel, and then you immerse
that in molten zinc, which then adheres to the exterior
of the metal. That helps prevent rusting, which has an
important consideration if you've got a cable that's going to
be submerged in salt water. Throughout its lifespan. You know,
saltwater will cause stuff to rust pretty darn quickly. So
(32:25):
the iron wires were protected with this zinc coating and
the they were they measured about five six of an
inch in diameter, and like I said, there were ten
of them that would be woven together to create the
armored sheath for this cable. Now, according to a piece
in the Illustrated London News, the brothers employed an engineer
(32:46):
named George Fenwick, who invented and built a machine in
just ten days to weave these iron wires around the
cable of you know, copper wire and yarn. And it
had to be fast, and it had to be delicate.
It could not damage the copper itself. If the copper
broke inside the rope, then you could have a broken connection.
(33:09):
I would love to describe this machine to you, but
I've only seen a few descriptions without visual aids. I
think I would really do a poor job of explaining it.
But let's talk about what the machine had to do.
It had to draw this rope, this this cable of
yarn and copper wires through a machine and had to
(33:30):
weave around that rope the iron wires in a pattern
that was tight enough to provide armor protection for the
copper inside, and it had to do it without breaking
the copper. The machine was able to draw off eleven
inches of cable in a single revolution of its steam engine,
and it had a revolutions per minute speed of eighteen,
(33:50):
so it would revolve eighteen times and eleven inches of
cable would go through each revolution. That means that if
I'm doing my math correctly, it could weave the iron
armoring for sixteen and a half feet of cable every minute,
which is pretty impressive now, granted they're making miles and
miles of cable. In fact, overall the primary cable was
(34:11):
twenty four miles long, and it took about three weeks
to make the whole thing, And the plan was to
use those twenty four miles of cable to span the
twenty one miles of distance between Dover and Clay, the
thought being that the three extra miles would be plenty
to deal for the fact that you're sinking it under
the water. As it turns out, the cable wasn't quite
(34:33):
long enough to reach, so in the end they actually
had to splice an additional mile of cable onto the
French side of this in order to make a connection work.
But fortunately that would work out. Now, the twenty four
miles of cable, the primary cable weighed around a hundred
eighty tons and when it was coiled up, it made
(34:53):
a coil that measured fifteen feet in diameter on the
inside of the coil thirty feet in diameter on the
outside of the coil. Once constructed, cruise loaded the cable
onto a steamship called the Blazer. Now the ship was
pretty much gutted before the cruise loaded the cable onto it.
They pretty much stripped it of everything and essentially it
(35:14):
became a barge that would be pulled by tug boats,
a pair of them. Now this was in Wapping, an
area in London on the Thames River, so the tug
boats would tow the Blazer out the Thames, down to
the sea and around the coast of England to Dover. Now,
the laying of the cable would not go smoothly. For
(35:35):
one thing. While the iron weaving machine was a work
of genius, and while it was able to work pretty quickly,
it was not always flawless. Um there were some breaks
in the iron wires along the length of the cable,
so you had little bits where, you know, a strand
of iron would be broken a little bit and it
(35:55):
would start to stick out. This created surfaces upon which
something could snag you weren't careful. This would become important
as the crew laid the cable between Dover and Calais,
and the first problem popped up right away. So the
coil still aboard the blazer, which again was being towed
by some tug steamers, snagged as it was uncoiling and
(36:17):
they were laying the cable into the sea. So the
tug boats had started moving a little too quickly. They
got up to a top speed that was like five knots,
which isn't super fast, but it was too fast to
uncoil the cable safely. And one of those broken iron
wires snagged on a surface as the the cable was
(36:40):
being uncoiled and put into the ocean, and an eighteen
yard length of that cable was stripped of that one
strand of iron wire, not the whole iron casing, but
one of the ten strands of wires stripped away. Now
the armor consisted of ten iron wire, so this was
not you know, a true disaster, but it did send
(37:03):
the message that they needed to go a little more slowly,
which was tough because the weather was also really bad,
so spending more time out in bad weather on the
sea not a high priority. But the captains of the
tug boats were told don't hit the steam quite so hard.
Then the weather started getting rough and the tiny ship
(37:24):
was tossed, so to speak, And as the ships got
closer to France, the seas were very heavy and a
strong wind was blowing, and at one point the tow
rope connecting the Blazer to the tug ships snapped and
the Blazer was set adrift, and it took some time
to reconnect the Blazer to the tug ships, during which
the Blazer had drifted about a mile and a half
(37:46):
off course. The delay meant that it was near nightfall
when they were finally approaching France, and the storms in
the darkness meant conditions were just too dangerous to complete
the connection, so the Blazer anchored for the night. The
next day, the weather was not much better, and the
tug ships pulled the Blazer to within a mile of
the shore of France, but they couldn't really get any
(38:08):
closer because of the weather. So the crew decided to
attach the end of the cable to a buoy, and
this freed up the Blazer and the tug ships towed
it back to England. Now the captain of another ship
called the Fearless took over his ship, took up the
end of the cable that was secured to the buoy,
(38:28):
and then brought a little bit further, like another hundred
yards or so, and then moored the cable. And the
next day representatives from the Gutta Perch Company UH they
joined the Fearless and they brought along with them an
additional mile length of cable. So then the crew spliced
the two cables together and formed a new one. And
(38:51):
then they brought the fresh length of cable onto shore
of France after much delay, and a French crew then
laid the cable up to the French connection uh not
the movie, but the actual connecting terminal point for the
French side of the telegraph system, and the crew also
buried some of the cable to keep it protected. Upon
testing the cable, the teams were pleased to find out
(39:12):
that they had established a working signal line between Dover
and Calais and they actually did a heck of a
demonstration to prove that it was working. It's one of
my favorite stories about testing the technology. Okay, so here's
what they did. At Calais. There are fortifications, it's a
port town on France, and that's across the English Channel
(39:34):
from England. England and France had had sometimes a contentious
relationship in history. So there were ramparts along parts of
Calais and on them was a cannon. So engineers connected
the cannon to this electrical signal line connected back to England,
(39:54):
and a current with sufficient voltage would ignite the cannon
sign system, which would then cause the cannon to fire
and so many miles away across the English Channel, an
engineer sent a pulse of electricity from Dover, England to
go through the subsequent cable, and that provided the juice
necessary to make a cannon in France fire. Obviously, this
(40:19):
was not the first time that the English made the
French fire a cannon, but at least this time there
were no hostilities involved. Now, the telegraph in this case
used the pointing needle mechanism that I referred to earlier,
rather than Samuel Morris's version that makes sense. Morse code
when it was first introduced, only had codes for the
(40:41):
letters that we typically encounter here in America. So in
America it's pretty unusual to run into characters that have
an accent on them, like an accent ague, for example,
or letters that have an oomb out or anything like that.
Over in Europe it's more commons, so they needed to
have a method that would allow for that. Now, despite
(41:05):
all the bumps along the way, the cable seemed to
work exactly as was intended. The insulation around the copper
wires remained secure even after some of that iron armor
had been stripped off. The cable and the Submarine Telegraph
Company that the name had simplified over the years received
some criticism for putting the entire endeavor at risk because
(41:26):
they did this operation during unfavorable weather. Essentially, some people
were saying, you're really lucky that this works, because you're
an idiot for having to lay down subseed cable when
the cs are so rough. However, in defense of the company,
they didn't really have a choice in the matter because
they were rapidly approaching the deadline that France had set,
(41:48):
and if they did not get the cable laid in time,
then the whole project was going to be a failure
and all the money was going to go away. So
really this all happened in the nick of time, and
those risks were necessary once if they wanted to actually,
you know, make this work now. To send signals through
cables of great length, companies need to supply, like I said,
(42:11):
a good deal of voltage to overcome resistance. But there
were other issues that placed fundamental limits on how far
or how fast you could transmit electricity and thus information
across simple copper wire. So we're going to talk a
little bit about that before I wrap up, and then
(42:33):
in the next episode we'll talk more about the Transatlantic
telegraph cables. So I've mentioned resistance and voltage and current,
but things get significantly more complicated when we start talking
about transmitting a signal across very long cables that are
underwater or underground. Now, technically these things happen in shorter
(42:54):
cables too, but if the distance is short enough, you
might not even notice that there's a problem, or it
may not be bad enough for it to be an issue.
But we definitely see them over great distances with cables
that are submerged or buried Michael Faraday, whom I've talked
about frequently on this podcast a true Genius U He
(43:15):
had a hypothesis about undersea cables or buried cables, and
this was based off the observation that another smarty pants
named Sir Francis Ronalds had observed way back in three
He saw that if you had two insulated wires of
equal length and gauge, and you buried one of them,
and you tried to pass electrical signals through each of them,
(43:37):
the above ground one would work just as you would expect,
but the one that was buried would have trouble carrying
the signal. The signals seemed to be moving more slowly,
as if something were putting the brakes along the way.
Faraday concluded that this was because of induction between the
wire and the earth surrounding the wire, or, in the
case of submerged sea cables, the water. So what does
(44:00):
that actually mean. Well, essentially, the cable and the water
behave kind of like a laden jar or liden jar.
If you pass an electric current through the cable, it
induces an electric charge and opposite electric charge in the water,
and opposite charges attract one another. This attraction is kind
(44:20):
of like putting the brakes down on a signal. It
doesn't stop it, but it slows it down. They called
it retardation of a signal. Faraday described the flow of
electricity along and underwater cable as behaving like a wave,
which honestly was really ingenious. He said that the result
is you would first get a weak signal from the
(44:43):
receiving end, and that signal would slowly grow in strength.
Then the strength would start to fade away again, and
this would happen in cycles again, very much like waves
crashing on the beach. Then we've got William Thompson, who
would later be known as Lord Kelvin, and they're super
important scientist. Not only would he propose the system of
(45:03):
absolute temperature, and we would later describe this in units
called kelvin zero, kelvin being absolute zero, he was also
instrumental in telegraphic engineering. Thompson built on Faraday's work, realizing
that the diameter of the conductor was fundamentally important when
determining the speed at which a signal will travel through
a cable, and he also came up with an equation
(45:25):
to describe how signals passed through cable, and it goes
like this. The speed of a signal passing through a
wire decreases as the square of the cable length increases,
So signaling speed has an adversely proportional relationship to cable length,
assuming that you're sticking with the same cable gauge. Gauge
in this case relates to a cable's capacity and resistance.
(45:48):
The larger the diameter of the cable, the lower the
resistance will be. And we're going to stop here, but
that issue that Lord Kelvin found would become um one
of the big challenges to overcome when looking at laying
very long subseed cable. So in our next episode we'll
(46:08):
talk more about the quest to lay a cable along
the Atlantic Ocean so that we could connect Europe to
North America, and about the engineering issues that we needed
to figure out, and then about how Lord Kelvin came
up with even more important ideas about how to deal
with this so that it could become practical. But we'll
(46:31):
cover all that in our next episode. If you have
suggestions for future episodes, be like and tricks send me
a message on Twitter. The handle we use is text
stuff hsw and I'll talk to you again really soon.
Text Stuff is an I heart Radio production. For more
(46:54):
podcasts from my heart Radio, visit the i heart Radio app,
Apple Podcasts, or wherever you listen to your favorite chips
Welcome to tech Stuff, a production from I Heart Radio.
Hey there, and welcome to tech Stuff. I'm your host,
Jonathan Strickland. I'm an executive producer with iHeart Radio and
I love all things tech and longtime listener and Tricks
wrote in on Twitter to ask if I had done
(00:24):
an episode on undersea cables, and you know what, I haven't.
So today we're going to start to talk about them, because,
as it turns out, there's a lot to cover with
undersea cables to kind of understand not just how they work,
but the challenges that people faced in order to make
(00:46):
them a reality in the first place. This is also
a timely topic because recently a company called x Links
made headlines for the Morocco UK power plant project. That
project's goal is to create a bowler and wind farm
in Morocco and use a very very long sub sea
power chord, essentially to send electricity to the UK. Now,
(01:09):
while a lot of headlines called this the longest subseed cable,
that's misleading because there are actually many different types of cables,
and technically the ce ME WE three cable that's s
E A dash M E dash W E three, the
number three cable is actually about ten times longer than
(01:30):
what the Morocco UK cable will be. But we're gonna
get to all that probably in the next episode, definitely
not this one. But as and Tricks pointed out in
a tweet to me, undersea cables trace their history back
to the mid nineteenth century. So in order to understand
all of this, we really have to take a moment
and talk about the telegraph and the development of the
(01:52):
first undersea cables. So there were a few things that
had to happen for undersea cables to even become a necessity.
You know. One of those was the development of the
electric telegraph, because without that, there's no need to worry
about subsea cables. Right, If you don't have long distance
electric based communication, then cables aren't really a thing you
(02:13):
gotta worry about, at least as far as connecting, say
an island to a continent. Now, the word telegraph is
Greek and it means essentially distant writing. But this word
actually predates electric telegraphs. For example, there were semaphore systems,
(02:33):
ones that used visual cues with flags. Those were used
throughout France, and we're really developed during the Napoleonic wars,
and that was referred to as telegraph. Before any kind
of electric version came along in the late seventeen hundreds,
you had various smarty pants around the world experimenting with electricity,
you know, like Ben Franklin, and this was just something
(02:56):
that was just beginning to be understood at the time.
Alissandre of Volta had created a sort of proto battery
that we later called a voltaic pile or and then
later on we had the voltaic cells. These inventions could
produce a good electric current, but at a very low voltage.
Now we need a reminder here because we're gonna be
(03:16):
talking about electricity a lot. Voltage in electricity is sort
of similar to water pressure in a plumbing system. You
can think of it as how much oomph a current has,
and current you can think of as the amount of
electricity present in a system of flowing electricity or flowing electrons. So,
(03:40):
if we want a really quick analogy, if you had
a low voltage, high current source of electricity, that's kind
of like a lazy river, right. The river can be
really wide and it might be really deep, so you've
got a lot of water there, but that water isn't
moving very quickly. It's just lazily going down. A high voltage,
(04:00):
low current electric device produces a very tight, high pressured stream.
So think of like a a concentrated stream of water
coming out of a pressure hose. You don't it's not
nearly the same amount of water as the lazy river.
It's much less current in other words, but the pressure
(04:21):
or voltage is way higher. Well before Volta's discovery, scientists
and engineers were mostly reliant on devices that would build
up electrostatic charges. So electro static charges have a high
voltage but a low current, and they have limited applicability
in things where you need sustained electric current. So Volta's
(04:43):
invention would allow for new applications of electricity. Now in
the early eighteen hundreds you had some other smarty pants
like Hans Christian Orstead of Denmark. And by the way,
as always, my apologies for all the mispronunciation, and I'm
going to do of all the different names that is
on me and I apologize. However, he discovered that electricity
(05:07):
and magnetism have a connection. He observed that a magnetic
needle would deflect from magnetic north if it came close
to a wire that was carrying an electric current or
transmitting an electric current, and so we first began to
realize that electro magnetism is a thing, that there is
this relationship between electricity and magnetism. This would lead to
(05:33):
yet more smarty pants people thinking of ways that we
could use electricity through wires to communicate across vast distances.
One way, a way that Sir William Father gil Cook
and Sir Charles Wheatston suggested was to have a multi
wire system that would use up to five needles. They
(05:55):
experiment with different ones, but the one that they would
use heavily would have five needle pointers, and that would
be at the receiving end of this system. So you
could send different electrical signals down these different wires and
thus direct these needles these pointers to point to different
letters on a placard that would have the alphabet there.
(06:19):
Uh The system would remain in use in the UK
up through the early twentieth century, so the UK was
reliant on this system, whereas the rest of the world
would move on to other ones. The neat thing about
the system is that it arranged the alphabet in a
diamond pattern, so it only used twenty letters of the alphabet.
It left out the letters C, J, Q, U, X,
(06:42):
and z, so sometimes you had to do, you know,
approximations of certain words. And the letter A was at
the top point of the diamond, and then you know,
you had B and D at the next level, and
then so on and so forth, and then at the
bottom you had the letter Y. And the five needles
were split right in the middle of this diamond. They
(07:03):
were in the widest part of the diamond, pointing up
and down normally, which meant that they weren't pointing at
any specific letter. So by sending signals down specific wires,
you could make needles point to a specific letter. You
would have both of you know, two needles that were
on a diagonal line with a specific letter, and by
looking at the common letter that both needles were pointing at,
(07:26):
you could spell out words. An interesting approach, not necessarily
the fastest, but it worked. Later on, Wheatstone would create
a different system that had a circular dial uh than
a needle on the inside, and you had the alphabet
laid out along the inside circumference of the circle, so
sort of like an analog clock, except instead of numbers
(07:47):
for the time, you had the alphabet, and you also
could have numbers as well. Then you had keys that
matched the letters and numbers that were along the outside
of the style. So pressing down on a key would indicate, Okay,
I want to send this letter UM, and this is
the sending station, And then you would have a receiving
station on the other end that would have a similar
dial with a needle and the letters and numbers in it,
(08:10):
and pressing down a specific key would end up sending
a signal that would have the needle on the other
side point to the relevant letter or number. This way
was really neat and the way it worked is super cool.
But I'm gonna have to save that for another episode
because I'm supposed to focus on subsei cables, and I
wrote about a page and a half of stuff before
(08:31):
I realized I am getting way off track, so I'll
spare you for now, but that will come up maybe
in a future episode. Now, in America, it was Samuel Morse,
who interestingly was an art professor who came up with
the famous method for transmitting messages electrically using a special code,
one that today, of course, we refer to as the
Samuel Code. Don't wait no, I'm sorry. No. Morse code.
(08:55):
Morse code. Morse code uses dots and dashes to rep
letters and numbers, and by tapping the dots and dashes
on a telegraph key, you could send pulses of electrical
signal down a wire, and a receiver at the other
end could then emboss dots and dashes on a strip
of paper, so you could actually read out the dots
and dashes and translate it that way, or later on
(09:18):
you had engineers who are trained to listen for dots
and dashes, and you had a device that was essentially
tapping like a little anvil, tapping out the messages, and
you would just listen. Later, a guy named Alfred Vale
would partner with Morse to refine this system and make
it a little more practical, essentially looking at the most
(09:40):
frequently used letters and using the the simplest dots and
dash patterns to represent those letters, as well as to
redesign the telegraph key itself. By eighteen thirty seven, Veil
and Morse were demonstrating this technology, and by eighteen forty
three they secured funding to set up an experiment telegraph
(10:00):
line that stretched the thirty five miles around sixty kilometers
between Baltimore, Maryland and Washington, d c Here in America.
The project used poles that were erected alongside a railroad
line and wires connected to the poles via glass insulators,
and it worked. One thing that really amazed me as
(10:21):
I was doing research into this, just as a quick digression,
is how quickly things moved. Because this was eight three,
and we're gonna be talking about a transatlantic subsea cable
by the end of this episode. That came a little
more than a decade after that. And to think of
it being ten years, a little more than ten years
(10:42):
between stringing sixty kilometers of cable between two cities in
America to laying a subsea cable across the Atlantic Ocean
blows my mind. Well, anyway, the demonstration was a success,
and it didn't take long for railroad companies to start
building out tell alegraph systems, and early on they were
almost exclusively used to help keep track of traffic on
(11:05):
the rail system, to better plan out routes, and to
avoid long delays or accidents. By the end of the
eighteen forties, journalists were starting to make use of the
telegraph system to wire stories across vast distances, and businesses
began to get interested in this as well, the ability
to be able to conduct business between cities without having
to take you know, a train ride or otherwise have
(11:29):
you know, like like people on horseback travel from one
city to another. Because keep in mind this is this
is before the automobile has really become a thing. So yeah,
there were limited ways of getting information from one point
to another. However, until eighteen fifty, these distances were all
over land. The reach of telegraph systems ended at the coastlines,
(11:53):
which meant that while regions could develop a sophisticated internal
communications system you know, inside their border or maybe between
borders of neighboring nations that shared you know, a land border,
once you hit the ocean, you had to rely on
other methods, much slower methods. So a mail ship isn't
(12:13):
a ship that carries mail, not a not a gendered ship,
but a mail ship between London and New York could
take nearly a month to travel across the ocean. A
fast one might be able to make the journey in
three weeks. By the mid nineteenth century, steamships were largely
taking the place of sailing vessels. They could make the
journey in up around ten days, so still more than
(12:36):
a week to get from one point to another. That's
pretty slow for news to travel. It was difficult to
act with alacrity if you were relying upon information from
across the pond. So there was a strong use case
to make for creating an undersea cable infrastructure that could
(12:57):
connect distant parts of the world, you know, parts that
were separated by oceans, and even in Europe, like England
in particular, saw the need to do this because while
the distance was not nearly as great to travel from
say Dover to France, the delay in getting information from
other parts of Europe was still pretty considerable, so there
(13:20):
was definitely a need for that as well. This did, however,
present some engineering challenges because you had to find a
way to make this both practical and affordable. Now this
is going to be obvious, but I need to establish it.
It is way easier to repair and maintain infrastructure that's
above the water than it is to do below the water.
(13:41):
And that's because we live above the water and we
can't live below the water, at least not with the
same amount of freedom. And since the Mr folks seemed
completely uninterested in helping us maintain communication channels. We have
to take that into consideration. To that end, we have
to treat cables subseed cables different from terrestrial cables. We
(14:04):
have to take into consideration what being submersed in ocean
water is going to do to a cable over time.
We have to understand that those effects can be detrimental.
We have to be able to estimate how long a
particular cable is likely to remain viable, assuming no catastrophic
instances occur, like assuming that a ship's anchor doesn't tear
(14:25):
through the cable, for example. So we have to make
sure that we have the budget to not just install
a cable in the first place, but to potentially replace
that cable when we near the end of its estimated lifespan.
It has to make financial sense, or else it's a
loss in the long run. Right. So you can argue, yes,
(14:46):
it's invaluable to have two distant places connected together, but
if you're constantly having to replace the communication channel, then
that invaluable might start to take on of value where
you just say, yeah, it's invaluable, but I don't want
to pay for it. So coming up with a way
to make subsea cables work extends beyond just the technology.
(15:10):
I mean, obviously the tech is a critical component or
else nothing happens. But you can't ignore the financial element,
right or the physical challenges, because if you do that,
you're setting yourself out to fail. So we're gonna take
a quick break. But when we come back, we're gonna
talk about a couple of other things before we get
(15:31):
to the first subseed cable, like some basic things about
electrical transmission. But before we do that, let's take this
quick break. All right, So in the eighteen twenties and
eighteen thirties you had all these various smarty pants is
(15:55):
is all learning about electro magnetism. And we now know
that if you pass an electric current through a conductive material,
that generates a magnetic field. And similarly, should you have
a conductive material like a wire, encounter a magnetic field,
that field will induce an electric current to flow through
the conductive wire. And you've probably played with this in school,
(16:19):
making a simple electro magnet with like an iron nail,
some copper wire, and a battery. You know, you connect
the wire to either terminal of the battery, you've coiled
the wire around the nail to act as a core,
and it becomes magnetic. You can pick up paper clips
and stuff. I remember I did that in school. I
imagined that people still do well. There's a whole lot
(16:41):
more to electro magnets, but we're just going to focus
on a couple of little things first. And the first
important bit is, because of this relationship between electricity and magnetism,
we need to make sure that wires and cables that
we use to transmit electricity have really good insulation around them.
And that's because us Without insulation, that is, without some
(17:02):
sort of barrier that resists the flow of electricity and
the interaction of magnetic fields, you have the potential for interference.
So let's say you've got two copper cables and there's
no shielding on them, you don't have any insulation on them,
and you've got them close to each other. And then
let's say you send electricity through one of those two cables,
(17:24):
not the second one, just cable number one. Well, as
the electricity flows through cable number one, that creates a
magnetic field which overlaps to the second cable, and that
induces a current to flow Now, if we're using direct
current something like a battery, uh, the second cable will
only have electric current running at the very beginning when
(17:46):
that magnetic field first hits it, but then it will stop. However,
if the source is alternating current then which means that
the current is changing direction many times per second, then
what you have is a fluctuating magnet at it field.
Because the magnetic fields direction also changes many times per second,
that will continue to induce electricity to flow in the
(18:08):
second cable. This would be in interference. It creates phantom
signals when no signal is intended, or it interferes as
one signal overpowers or changes another. I remember back in
the day, I had these cheap desktop speakers that I
had connected to my computer, and I would put my
(18:28):
cell phone down on the desk, and every time my
cell phone got a notification, it would make this weird
electric chirping noise in the speakers because that was radio
frequency interference that was inducing a current to flow through
the speakers. So these are things that can happen, and
(18:50):
you don't want them to write. You want to shield
your components so that only the signals you want to
send are going through so you have to protect a
against that. Now, in the nineteenth century, there were people
who discovered a plant that had a kind of sap
essentially that was found to be a really effective insulator,
(19:11):
so it resisted the flow electricity and protects or insulates
against interference. That material is called Gutta percha. It's a
biologically derived latex. And like I said, the plant has
the name Gutta percha, but that's also the name everyone
used for the derived latex from it. Now, this was
(19:31):
fortunate at the time, but I should also add that
the telecommunications industry would spell doom for the Gutta purchase
trees because the rampant harvesting of the trees created an
unsustainable situation. And before too long people realize, oh, we
need an alternative to this, because pretty soon there's not
going to be any of this plant left on the
(19:52):
planet will have harvested at all. Anyway, Gutta percha has
many of the same properties as synthetic rubber, including the
ability to insulate conductive materials. Next, we need to think
about what happens with electricity as it travels over greater
distances of wire um. This is going to get more
complicated later in this episode, because, as it turns out,
(20:15):
there are certain things that we have to take into
consideration with any length of cable, and then there are
other things that come into play when you're talking about
cable that happens to be under the water. But under
most circumstances, even a great electrical conductor has some level
of resistance. Now I say under most circumstances, because as
it turns out, if you're able to super cool a conductor,
(20:40):
like a good conductor, and you're able to get it
down to an incredibly low temperature, like just a few
units of kelvin above absolute zero, then you can have
a superconductor which has no resistance. But under most normal conditions,
you know, conductors have resistance to electricity. You can think
of electrical resistance as kind of being like friction. It's
(21:01):
working against or resisting the flow of electricity. So resistance
depends upon a few different factors, such as the material itself,
like some conductors are better than others, like coppers a
really good conductor, and it also depends upon the thickness
of that material. A thin copper wire has a greater
electrical resistance than a thick copper cable for example. Well,
(21:26):
resistance means that as you transmit electricity across this conductor,
you'll see the electrical energy diminish over distance. And we
know that energy can be neither created nor destroyed, right,
so we're not destroying that energy. However, that energy is
converting from one type to another. In this case, the
(21:46):
resistance causes the conductive material to heat up and we
lose some of that electrical energy in the form of
waste heat. So if you want to push electricity further
down a trans mission line, you really have to use
a lot of voltage. And remember voltage is the pressure
in this system. So with alternating current, we can actually
(22:09):
use devices called transformers, which, while they are not robots,
they are arguably more than meets the eye. If you
were to look at an electrical transformer, like open up
a cover, and by the way, never do that, but
if you did do that, you would see that consists
of two coils of conductive wire wrapped around a core,
usually a ferro magnetic iron core in a simple transformer,
(22:33):
not necessarily a solid core, but a core. So passing
electricity through one coil of this wire induces electricity to
flow through the other. We already talked about inductance, right,
and the number of turns in each coil determines a
change in voltage. So let's say we've got coil number one,
(22:53):
which will call the primary coil. This is the coil
where we're going to send electricity through the wire. Let
say that primary coil has five turns and coil number two,
which is our secondary coil, has ten turns. Well, then
the ratio of turns is one to two, one for primary,
two for secondary, and the voltage of the second coil
(23:16):
will be double that of the first coil. This is
a step up transformer. We're stepping up the voltage. We're
increasing it by a factor of two. Now, if the
primary coil has ten turns and the secondary coil has
five turns, that's a two to one ratio. That means
the voltage of the second coil will be half that
(23:36):
of our first coil. This is a step down transformers.
So using this we can then push voltage up on
terrestrial power lines that are using alternating current. Again, this
only works with alternating current, not direct current. Then you
can increase the voltage for long distance transmission. You can
(23:57):
overcome the problem of loss due to resistance. Essentially, you've
just you turned the pressure on so much that it's
it's powering through that. Now you have to have the
right kind of cables to make that happen. You have
to have the transformers along the way, and you have
to step down the voltage before you feed that current
into say a business or a house. But it's entirely
(24:21):
possible to send electricity long distances overground using transformers. Anyway,
it's one thing to have a transformer above the waves.
If you've ever been around when a transformer blows out,
you know that this is a spectacular and often terrifying event.
There's a very loud boom, and it's like a thunderclap
(24:43):
or a shotgun going off, and then there's a shower
of sparks, and then all the power goes out and
it happens like in that order instantaneously. It seems now
that is inconvenient here upon the surface world, but below
the waves that would be much worse. So we have
to keep that in mind when we're talking about subsea cables.
(25:04):
Some of the solutions that we have to us here
on the surface would not be available to us underwater.
Now Samuel Morse himself tested the viability of an underwater
telegraph cable. He used a wire coated in tar and
India rubber to insulate the wire from the water because
he didn't want to lose electricity through the water. Essentially,
(25:27):
he submerged the wire in the New York Harbor and
he sent a telegraph signal through it, and the experiment
was a success. This signal came out the other side.
It worked. So as early as eighteen forty two, engineers
understood that an undersea cable was possible. The question was
could be made practical. The first underwater cable using Gutta
(25:47):
Percha as an insulator, was laid between Deut's and Cologne
across the River Rhine in eighteen forty seven, and then
in eighteen forty nine and Electrician with the Southeastern Railway
succeeded in laying two miles of cable off the coast
of England around the Kent region. But the first commercial
(26:08):
subseed cable would follow the year after that. It was
eighteen fifty and two brothers, Jacob Brett and John Watkins
Brett created the English Channel Submarine Telegraph Company. Now the
brothers had proposed laying a cable under the sea through
the English Channel and connecting the port towns of Dover,
England and Calais, France. Both England and France agreed to
(26:32):
this proposal, so the brothers got the funding they needed
to to try and make it happen, and they had
a deadline that they had to meet. So the brothers
purchased cable from a company called the Gutta Purchase Company.
The cable had Gutta Purchase insulation on it, but it
had no armoring to protect it from other hazards. So
it's a copper cable with a rubber like insulating layer
(26:54):
on the outside and that's it. Uh. It was just
a single copper wire too, it was not We're not
multiple cables or wires in this. So in many ways
this would be an experiment and ultimately it would be
only partially successful. Uh. In that really it was a failure,
but it taught them a lot of lessons. So the
cable the brothers used was too light to sink on
(27:16):
its own. It would not sink down to the sea floor.
So every one hundred yards or so, workers on board
the ship that would unspool the coil of cable, had
to attach lead weights to the cable. The weights ranged
between ten to thirty pounds, and the company used a
steam paddle ship called the Goliath to carry the cable
(27:40):
across the channel. They attached one end of the cable
to the dover shore side of the connection that went
up to a telegraph station, and then they began the
journey to France, and the ship would have to stop
every one yards or so in order to sink another
weight down with the cable to keep it in place
on the ocean floor, and had to stop each time.
(28:00):
So it's not like, you know, they were just leading
this out and staying in motion the whole time. They
stopped every hundred yards. It took the whole day for
the ship to lay the cable across to reach France,
and there the team attached the cable on the French
side they attempted to establish an electrical connection. I'm not
entirely sure the outcome of that attempt, Like the accounts
(28:24):
I read don't seem to really indicate whether or not
they were successful in getting an electrical signal all the
way across. At any rate, if they did, it was
a week one and by the next morning, the connection
had been severed and the line was just totally dead.
Not long after that, stories began to circulate that some
French fisherman had accidentally dredged up the cable in some
(28:46):
netting and then subsequently severed the cable. However, that story
was never verified. It didn't stop people from spreading variations
of that story, including variations that made the fisherman look
increasingly dimwitted over time. But the stories that were published
immediately following the failure actually suggested that it was the
(29:08):
action of the waves off the rocky coast of France
that was making the cable rub against rocks and then
and then break that way. What was certain is that
the cable did break, whether it was a human caused
error or because of the action of the waves, and
that's probably because there was no armoring on the cable.
(29:29):
So there you go. The brothers sent a letter to
the Times in England explaining that while their first attempt failed,
they had learned a great deal in the process, and
they explained that the thing that they had attempted had
never been done before, and as such they were going
in ignorant of what would and wouldn't work. But through
this experience they had learned some valuable lessons and were
(29:51):
more convinced than ever that a cable connecting England to
the European continent would work. Whether they wrote that letter
in an effort to, you know, make sure they still
had funding for future attempts, or this was a genuine
expression of their enthusiasm, I don't know. Maybe it was
a mixture of both, or maybe it was something else entirely.
(30:11):
But the important thing is they were right. When we
come back, I'll explain and tell the rest of their story,
all right. So the Brett brothers still had some time
left before their agreements with France and England would expire,
(30:32):
specifically with the French government, and if that happened, they
were going to have to go through the whole process
of securing permission all over again. That was not a guarantee,
especially you know, after having failed their first try. So
they were determined to make another go at it before
time was up, and this time they would add more
protections for the cable. That cable would contain not one,
(30:55):
but four copper wires, each insulated by Gutta percha. In fact,
h wire had a double layer of Gutta purchase installation,
so that you had a wire that was the core,
and then you had a rubber case essentially on the
outside of that, and then a second rubber case on
the outside of that. The engineers then bound those four
(31:17):
wires together with yarn soaked in tar and tallow, so
together the yarn tar tallow mixture. There's some other stuff
in there as well, and the four wires encased in
Gutta percha served as the core of the cable itself,
and that soaked yarn provided some more stability and strength.
(31:40):
The bound cables now formed a kind of rope, and
the next step was to weave ten strands of galvanized
iron wires around the rope to provide armor protection. Galvanization
is a process through which you apply a protective coating
of zinc into onto something like iron or steel. Typically,
the way it works is you make whatever thing you're
(32:03):
making out of iron or steel, and then you immerse
that in molten zinc, which then adheres to the exterior
of the metal. That helps prevent rusting, which has an
important consideration if you've got a cable that's going to
be submerged in salt water. Throughout its lifespan. You know,
saltwater will cause stuff to rust pretty darn quickly. So
(32:25):
the iron wires were protected with this zinc coating and
the they were they measured about five six of an
inch in diameter, and like I said, there were ten
of them that would be woven together to create the
armored sheath for this cable. Now, according to a piece
in the Illustrated London News, the brothers employed an engineer
(32:46):
named George Fenwick, who invented and built a machine in
just ten days to weave these iron wires around the
cable of you know, copper wire and yarn. And it
had to be fast, and it had to be delicate.
It could not damage the copper itself. If the copper
broke inside the rope, then you could have a broken connection.
(33:09):
I would love to describe this machine to you, but
I've only seen a few descriptions without visual aids. I
think I would really do a poor job of explaining it.
But let's talk about what the machine had to do.
It had to draw this rope, this this cable of
yarn and copper wires through a machine and had to
(33:30):
weave around that rope the iron wires in a pattern
that was tight enough to provide armor protection for the
copper inside, and it had to do it without breaking
the copper. The machine was able to draw off eleven
inches of cable in a single revolution of its steam engine,
and it had a revolutions per minute speed of eighteen,
(33:50):
so it would revolve eighteen times and eleven inches of
cable would go through each revolution. That means that if
I'm doing my math correctly, it could weave the iron
armoring for sixteen and a half feet of cable every minute,
which is pretty impressive now, granted they're making miles and
miles of cable. In fact, overall the primary cable was
(34:11):
twenty four miles long, and it took about three weeks
to make the whole thing, And the plan was to
use those twenty four miles of cable to span the
twenty one miles of distance between Dover and Clay, the
thought being that the three extra miles would be plenty
to deal for the fact that you're sinking it under
the water. As it turns out, the cable wasn't quite
(34:33):
long enough to reach, so in the end they actually
had to splice an additional mile of cable onto the
French side of this in order to make a connection work.
But fortunately that would work out. Now, the twenty four
miles of cable, the primary cable weighed around a hundred
eighty tons and when it was coiled up, it made
(34:53):
a coil that measured fifteen feet in diameter on the
inside of the coil thirty feet in diameter on the
outside of the coil. Once constructed, cruise loaded the cable
onto a steamship called the Blazer. Now the ship was
pretty much gutted before the cruise loaded the cable onto it.
They pretty much stripped it of everything and essentially it
(35:14):
became a barge that would be pulled by tug boats,
a pair of them. Now this was in Wapping, an
area in London on the Thames River, so the tug
boats would tow the Blazer out the Thames, down to
the sea and around the coast of England to Dover. Now,
the laying of the cable would not go smoothly. For
(35:35):
one thing. While the iron weaving machine was a work
of genius, and while it was able to work pretty quickly,
it was not always flawless. Um there were some breaks
in the iron wires along the length of the cable,
so you had little bits where, you know, a strand
of iron would be broken a little bit and it
(35:55):
would start to stick out. This created surfaces upon which
something could snag you weren't careful. This would become important
as the crew laid the cable between Dover and Calais,
and the first problem popped up right away. So the
coil still aboard the blazer, which again was being towed
by some tug steamers, snagged as it was uncoiling and
(36:17):
they were laying the cable into the sea. So the
tug boats had started moving a little too quickly. They
got up to a top speed that was like five knots,
which isn't super fast, but it was too fast to
uncoil the cable safely. And one of those broken iron
wires snagged on a surface as the the cable was
(36:40):
being uncoiled and put into the ocean, and an eighteen
yard length of that cable was stripped of that one
strand of iron wire, not the whole iron casing, but
one of the ten strands of wires stripped away. Now
the armor consisted of ten iron wire, so this was
not you know, a true disaster, but it did send
(37:03):
the message that they needed to go a little more slowly,
which was tough because the weather was also really bad,
so spending more time out in bad weather on the
sea not a high priority. But the captains of the
tug boats were told don't hit the steam quite so hard.
Then the weather started getting rough and the tiny ship
(37:24):
was tossed, so to speak, And as the ships got
closer to France, the seas were very heavy and a
strong wind was blowing, and at one point the tow
rope connecting the Blazer to the tug ships snapped and
the Blazer was set adrift, and it took some time
to reconnect the Blazer to the tug ships, during which
the Blazer had drifted about a mile and a half
(37:46):
off course. The delay meant that it was near nightfall
when they were finally approaching France, and the storms in
the darkness meant conditions were just too dangerous to complete
the connection, so the Blazer anchored for the night. The
next day, the weather was not much better, and the
tug ships pulled the Blazer to within a mile of
the shore of France, but they couldn't really get any
(38:08):
closer because of the weather. So the crew decided to
attach the end of the cable to a buoy, and
this freed up the Blazer and the tug ships towed
it back to England. Now the captain of another ship
called the Fearless took over his ship, took up the
end of the cable that was secured to the buoy,
(38:28):
and then brought a little bit further, like another hundred
yards or so, and then moored the cable. And the
next day representatives from the Gutta Perch Company UH they
joined the Fearless and they brought along with them an
additional mile length of cable. So then the crew spliced
the two cables together and formed a new one. And
(38:51):
then they brought the fresh length of cable onto shore
of France after much delay, and a French crew then
laid the cable up to the French connection uh not
the movie, but the actual connecting terminal point for the
French side of the telegraph system, and the crew also
buried some of the cable to keep it protected. Upon
testing the cable, the teams were pleased to find out
(39:12):
that they had established a working signal line between Dover
and Calais and they actually did a heck of a
demonstration to prove that it was working. It's one of
my favorite stories about testing the technology. Okay, so here's
what they did. At Calais. There are fortifications, it's a
port town on France, and that's across the English Channel
(39:34):
from England. England and France had had sometimes a contentious
relationship in history. So there were ramparts along parts of
Calais and on them was a cannon. So engineers connected
the cannon to this electrical signal line connected back to England,
(39:54):
and a current with sufficient voltage would ignite the cannon
sign system, which would then cause the cannon to fire
and so many miles away across the English Channel, an
engineer sent a pulse of electricity from Dover, England to
go through the subsequent cable, and that provided the juice
necessary to make a cannon in France fire. Obviously, this
(40:19):
was not the first time that the English made the
French fire a cannon, but at least this time there
were no hostilities involved. Now, the telegraph in this case
used the pointing needle mechanism that I referred to earlier,
rather than Samuel Morris's version that makes sense. Morse code
when it was first introduced, only had codes for the
(40:41):
letters that we typically encounter here in America. So in
America it's pretty unusual to run into characters that have
an accent on them, like an accent ague, for example,
or letters that have an oomb out or anything like that.
Over in Europe it's more commons, so they needed to
have a method that would allow for that. Now, despite
(41:05):
all the bumps along the way, the cable seemed to
work exactly as was intended. The insulation around the copper
wires remained secure even after some of that iron armor
had been stripped off. The cable and the Submarine Telegraph
Company that the name had simplified over the years received
some criticism for putting the entire endeavor at risk because
(41:26):
they did this operation during unfavorable weather. Essentially, some people
were saying, you're really lucky that this works, because you're
an idiot for having to lay down subseed cable when
the cs are so rough. However, in defense of the company,
they didn't really have a choice in the matter because
they were rapidly approaching the deadline that France had set,
(41:48):
and if they did not get the cable laid in time,
then the whole project was going to be a failure
and all the money was going to go away. So
really this all happened in the nick of time, and
those risks were necessary once if they wanted to actually,
you know, make this work now. To send signals through
cables of great length, companies need to supply, like I said,
(42:11):
a good deal of voltage to overcome resistance. But there
were other issues that placed fundamental limits on how far
or how fast you could transmit electricity and thus information
across simple copper wire. So we're going to talk a
little bit about that before I wrap up, and then
(42:33):
in the next episode we'll talk more about the Transatlantic
telegraph cables. So I've mentioned resistance and voltage and current,
but things get significantly more complicated when we start talking
about transmitting a signal across very long cables that are
underwater or underground. Now, technically these things happen in shorter
(42:54):
cables too, but if the distance is short enough, you
might not even notice that there's a problem, or it
may not be bad enough for it to be an issue.
But we definitely see them over great distances with cables
that are submerged or buried Michael Faraday, whom I've talked
about frequently on this podcast a true Genius U He
(43:15):
had a hypothesis about undersea cables or buried cables, and
this was based off the observation that another smarty pants
named Sir Francis Ronalds had observed way back in three
He saw that if you had two insulated wires of
equal length and gauge, and you buried one of them,
and you tried to pass electrical signals through each of them,
(43:37):
the above ground one would work just as you would expect,
but the one that was buried would have trouble carrying
the signal. The signals seemed to be moving more slowly,
as if something were putting the brakes along the way.
Faraday concluded that this was because of induction between the
wire and the earth surrounding the wire, or, in the
case of submerged sea cables, the water. So what does
(44:00):
that actually mean. Well, essentially, the cable and the water
behave kind of like a laden jar or liden jar.
If you pass an electric current through the cable, it
induces an electric charge and opposite electric charge in the water,
and opposite charges attract one another. This attraction is kind
(44:20):
of like putting the brakes down on a signal. It
doesn't stop it, but it slows it down. They called
it retardation of a signal. Faraday described the flow of
electricity along and underwater cable as behaving like a wave,
which honestly was really ingenious. He said that the result
is you would first get a weak signal from the
(44:43):
receiving end, and that signal would slowly grow in strength.
Then the strength would start to fade away again, and
this would happen in cycles again, very much like waves
crashing on the beach. Then we've got William Thompson, who
would later be known as Lord Kelvin, and they're super
important scientist. Not only would he propose the system of
(45:03):
absolute temperature, and we would later describe this in units
called kelvin zero, kelvin being absolute zero, he was also
instrumental in telegraphic engineering. Thompson built on Faraday's work, realizing
that the diameter of the conductor was fundamentally important when
determining the speed at which a signal will travel through
a cable, and he also came up with an equation
(45:25):
to describe how signals passed through cable, and it goes
like this. The speed of a signal passing through a
wire decreases as the square of the cable length increases,
So signaling speed has an adversely proportional relationship to cable length,
assuming that you're sticking with the same cable gauge. Gauge
in this case relates to a cable's capacity and resistance.
(45:48):
The larger the diameter of the cable, the lower the
resistance will be. And we're going to stop here, but
that issue that Lord Kelvin found would become um one
of the big challenges to overcome when looking at laying
very long subseed cable. So in our next episode we'll
(46:08):
talk more about the quest to lay a cable along
the Atlantic Ocean so that we could connect Europe to
North America, and about the engineering issues that we needed
to figure out, and then about how Lord Kelvin came
up with even more important ideas about how to deal
with this so that it could become practical. But we'll
(46:31):
cover all that in our next episode. If you have
suggestions for future episodes, be like and tricks send me
a message on Twitter. The handle we use is text
stuff hsw and I'll talk to you again really soon.
Text Stuff is an I heart Radio production. For more
(46:54):
podcasts from my heart Radio, visit the i heart Radio app,
Apple Podcasts, or wherever you listen to your favorite chips
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