[Music]
it's pretty hard to get lost these days
no matter where you are in the world all
you have to do is fire up your favorite
navigation app and you're good even
ships in the middle of the ocean have
GPS so back before all that technology
existed getting lost was a real danger
especially at sea to the untrained eye
the ocean looks a whole lot like wet and
nothing else so people around the world
independently came up with techniques
for squeezing all of the information
they could out of what they could see at
sea lots of them hit on the usefulness
of the stars to tell direction
especially the Sun and Polaris the North
Star and they came up with a nifty
devices to pinpoint their location based
on the stars as well as how to find land
when it was out of sight so here are six
of the earliest ways people from around
the globe mastered the art of navigation
tailored to the different challenges
they had to deal with at sea in Marshall
Islands in Micronesia in the Pacific
Ocean were first settled around 2,000
years ago they belonged to a larger
legacy of navigators who conquered the
Pacific with canoes and brain power
these navigators could find their way
between tiny islands throughout the
Pacific and there's some evidence that
they made contact with South America
long before Europeans did they knew a
ton about stars so even though they
didn't have magnetic compasses they came
up with what was basically an entire
compass made up of knowledge of the
night sky Marshall leaves in particular
also had an unusual device known today
as the stick chart stick charts depict
the ocean around one or a few islands in
the 1,100 kilometre stretch that is the
Marshall Islands but they weren't
exactly mapped instead they showed what
you could feel the ocean doing from a
boat to Marshall Lee is bound together
straight and curved sticks or fibers to
represent swells and currents the
behaviors and patterns of the ocean
small shells marked where islands were
charged were actually mainly used as
teaching tools navigators would memorize
all the information in them before ever
setting out on a voyage over the past
few centuries much of their traditional
knowledge has been lost but there are
people working to revive the art of
getting based on the movements of the
ocean the kemal is a simple looking
device it's basically a rectangular bit
of wood and a knotted string but that's
all the sailors needed to figure out
their latitude compared to European
navigators Arab explorers spent more
time out of sight of land on their
voyages they'd venture farther out
because the water is close to the shore
of East Africa were too dangerous to
have the coast so they needed a good way
to keep track of their location which
was where the kamal came in it was
probably developed sometime after 900
ce-1 sailors got to the right latitude
all they had to do was go east or west
until they bumped into the port that
they were trying to reach to use a Kamal
all you have to do is hold the string in
your teeth and then hold out the wooden
rectangle until the lines match up with
Polaris on top and the horizon on the
bottom the angle between Polaris and the
horizon depends on your latitude it's
directly overhead at the North Pole and
on the horizon at the equator you end up
holding the rectangle closer to your
face the farther north you are and by
measuring the distance from the
rectangle to your face you can figure
out your latitude that's what the string
is for it lets you measure the distance
from the rectangle to your face you can
record the latitude of the port by
making a Kamal while you're there you
just make a string with the right length
and put the rectangle between Polaris
and the horizon then define that
latitude again you sail north or south
until the distance from the rectangle to
your face matches up with the length of
the string oh come on like that only
works for one port so sailors might have
had collections of them for getting
around some more complicated Kamal's
were made to be more general measuring
devices their strings had multiple knots
so you could compare the length of the
string with a list of links that
correspond it to different port or the
marks could be at regular intervals just
like centimeter marks on a ruler with
the distance between the knots
corresponding to a known change in
latitude the Kamal was a simple but
accurate tool so much so that it was
still in use in the 20th century the
cross staff was another latitude
measuring device the earliest European
version is attributed to lady Ben
Gershon a 14th century Jewish
mathematician though it was probably
being used for surveying and astronomy
long before that by 1514 it was being
adapted by European sailors so they
could use it at sea the Cross staff
works just like the kamal and was
probably based on it even
though it looks different it's a long
staff marked with degree measurements
with a perpendicular sliding crosswalk
to use it you hold the staff up to your
cheek and slide the crossbar until the
horizon lines up with the bottom edge
and either Polaris or the Sun at noon
lines up with the top edge then you have
your latitude just like with a kamal as
you can probably imagine looking
directly into the Sun to use a cross
staff turned out to be a bit of an issue
a fancier version was eventually
developed called the BAC staff that let
people use shadows instead of looking
straight at the Sun a cross staff is
most accurate between about 20 and 60
degrees latitude at higher latitudes the
angles got too big for the human eye to
see both sides of the cross bar at the
same time but most of the time it was a
super convenient way for sailors to keep
track of their latitude the astrolabe is
kind of like a fancier version of the
kamal or cross that was probably
invented by the greek scholar
Hipparchus in the second century BC when
it was used for astronomy it's used as a
navigational tool wasn't recorded until
much later in 1481 seee by portuguese
sailors travelling down the coast of
africa it was probably being used for
navigation before then version used for
navigation was called the Mariners
astrolabe and it was another tool for
measuring latitude based on the Sun and
stars but its advantage over the kamal
and cross staff was that you didn't have
to be able to see the horizon to use it
that meant that it worked in fog or when
it was too dark to see the horizon a
Mariners Asscher lab is a heavy brass
disc with a rotating arm in the middle
to use it a sailor would dangle the disc
from a ring at the top so that it would
hang perpendicular to the ocean then
they would turn the arm until it lined
up with the Sun or with Polaris the disc
was marked with angle measurements
around the edge so whatever angled the
arm pointed to was the altitude of the
star and their navigators could use math
to figure out their latitude it might
sound easy and accurate but on a rocking
ship's deck it was actually the opposite
of those things angling instrument would
swing back and forth too much to get a
good reading massive errors were common
and if you really wanted an accurate
measurement you had to go ashore which
if you're lost buddy it would have also
been hard to use a kamal or cross tap on
a rocking ship but it was probably at
least a little easier to get a
measurement add to that the fact that
the other two were easier to make and
can see why some sailors preferred them
China was a great naval power in the
15th century and its greatest Navigator
was a 2 metre tall burly Muslim by the
name of Zhang ha on the orders of ming
dynasty emperor zhu da he sailed to
places like the red sea the persian gulf
and the eastern coast of africa in seven
voyages with dozens of huge treasure
filled ships in tow and he didn't using
one of China's greatest inventions the
magnetic compass the compass had been
invented long before Zhang has time but
his expeditions were among the earliest
well known voyages to use the compass
for navigation originally compasses were
used for divination during the Qin
Dynasty of more than 200 years BCE
someone noticed that a naturally
occurring magnet called a lodestone
would align itself in a particular
direction when you laid it down on a
fortune-telling board eventually people
realize that a lodestone was not
pointing to your future or your fate it
was aligning with north and south and we
now know that in general magnetic
materials will line themselves up with
Earth's magnetic field early lodestone
compasses were shaped like spoon then
people figured out that you could
magnetize a needle using a lodestone
they started making compasses with iron
needles which are more accurate because
their point they also realized that if
you attach the needle to a piece of wood
or cork and let it float in water it
would spin without friction resisting as
much by his first voyage in 1405 the
compass had been perfected enough to
lead young Hass fleet across the ocean
the Sunstone was another material with a
special property that helped with
navigation about a thousand years ago
ancient Viking texts recorded the use of
a magical crystal that could sense the
direction of the Sun even when it was
hidden by clouds or below the horizon
for a long time historians wrote this
off as a myth sure the Vikings had magic
rocks they also had trolls and thunder
gods that looked like Chris Hemsworth
the drift experiments have shown that
you can use a rock that would have been
available to the Vikings to work out the
direction of the Sun accurately enough
to navigate
it's called Icelandic spa it's made of a
mineral called calcite and some
historians think it was the real
Sunstone calcite has a property called
birefringence the mineral has two
different indices of refraction which
means that light passing through it gets
split into both beams of refracted light
form an image so anything you look at
through a biro
Christel becomes double do this with
sunlight and one of the images will be
brighter than the other that's because
of the way sunlight is polarized that is
the way that the waves line up in
different directions when it passes
through the atmosphere if you rotate the
crystal so it's pointing at the Sun the
light coming from the Sun will line up
so that the two images are equally
bright well if you know how Sun stones
work it's pretty easy to use one to
pinpoint the location of the Sun based
on the way that light waves line up even
when you can't actually see the Sun that
said we don't know for sure that Vikings
used calcite for their Sun stone calcite
crystals have never been recovered from
Viking sites except for a few small
fragment like an extended to burn their
dead and calcite is fragile so even if
the Vikings use calcite Sun stones we
may never find one but researchers did
discover a piece of Icelandic spar from
an English shipwreck dating back to the
late 1500s which could have been a
holdover from the Vikings so the
mythical Sunstone might be real after
all and just another one of the creative
ways people came up with it to help them
navigate the oceans thanks for watching
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and i want to say thank you to whoever
ended up doing the animations for this
show because I'm sure that with a lot of
work right at this moment in the episode
put your name right here and take credit
good job those have all sorts of bizarre
adaptations to get stuff done whether
that's finding enough speed gluing a
mate or raising the rock but some pieces
have figured out shortcuts to make
things a little easier