How the compass unlocked the world

Growing up in Missouri,

they would kind of take us
out into the woods,

and 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.

[Small thing.]

[Big idea.]

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 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?

Because 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 multi-tool,

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.