How the compass unlocked the world

Growing up in Missouri,
they would kind of

take us out into the woods,

they would give you a map,

and they would give you a compass,

and you had to find your way home,

and without the compass,

you can't even read the map.

That's what I'm here to tell you.

The compass is the key.

(upbeat music)

A compass is most simply a piece of metal

that has been magnetized
so that it will turn

towards the Earth's magnetic pole.

The one that we all think
of is the pocket compass.

It looks like a watch, right?

You can hold it in your hand

and watch the little needle bounce around

until you find north.

Magnetism is still a pretty
mysterious force to physicists,

but what we do know for sure is that

a compass works because the
Earth is this giant magnet,

and when you use a
compass, you are in touch

with the very center of our planet,

where this kind of roiling
ball of molten iron

is spinning around and
creating a magnetic field.

Just like a magnet you can
play with on your tabletop,

it has a north pole and a south
pole, and we use compasses

to find our way north
because of that fact.

The earliest known compass comes
from about 200 BC in China.

They figured out that some of the metal

coming out of the ground
was naturally magnetic

and so they fashioned
this magnetized metal

into this kind of ladle looking thing,

put it on a brass plate, and
then it would point north.

It seems to have been primarily used

to improve feng shui,
so they could figure out

what was the best way for energy to flow

through their living spaces.

Sailors were probably the early adopters

of the more portable versions of it

because no matter where the sun was,

no matter what the
condition of the stars were,

they would always be
able to kinda find north.

Now, much later, the
Europeans are the ones who

innovate and come up
with the compass rose.

It essentially laid out

what north, south, east
and west looked like,

and it also enabled you to
kind of create new directions

like northwest, southeast, what have you,

and for the first time, they
knew where they were going.

That's kind of a big deal,

but also I think it was part of this

general reinvigoration
of European science.

You might know it as the Renaissance.

Lots of new tools were invented,

from the telescope to the microscope.

Maps got better because
of compasses, right?

'Cause then you start to understand

which direction is which,
you get a lot more detail,

and that just kind of changes

the human relationship to the world.

The compass with a map
is like a superpower.

Everything that we think
of as world history

would not have taken
place without the compass,

the age of exploration, Magellan
circumnavigating the globe,

even the fact that we know it is a globe.

The compass ends up getting embedded

in all these other tools because it is

such a functional object,
so you might have it

embedded in your multitool,
you might have it

embedded in your phone.

The compass is everywhere because

it's literally how we find our way

across the face of the Earth.

So you can go off and explore,

and find out what is over that next hill

or that next horizon,
but you can also reliably

find your way home.