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Growing up in Missouri,

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they would kind of take us
out into the woods,

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and they would give you a map,
and they would give you a compass,

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and you had to find your way home.

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And without the compass,

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you can't even read the map.

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

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The compass is the key.

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[Small thing.]

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[Big idea.]

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A compass is most simply a piece of metal
that has been magnetized,

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so that it will turn towards
the Earth's magnetic pole.

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

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It looks like a watch, right?

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You can hold it in your hand

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and watch the little needle bounce around

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until you find north.

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Magnetism is still a pretty
mysterious force to physicists,

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but what we do know for sure
is that a compass works

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because the Earth is this giant magnet.

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And when you use a compass,

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you are in touch with
the very center of our planet,

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where this kind of roiling
ball of molten iron

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is spinning around
and creating a magnetic field.

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

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it has a north pole and a south pole,

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and we use compasses to find our way
north because of that fact.

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

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They figured out that some of the metal
coming out of the ground

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was naturally magnetic,

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and so they fashioned
this magnetized metal

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into this kind of ladle-looking thing,

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put it on a brass plate

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and then it would point north.

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It seems to have been primarily
used to improve feng shui,

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so they could figure out
what was the best way for energy to flow

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through their living spaces.

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Sailors were probably the early adopters

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of the more portable versions of it,

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because no matter where the sun was,

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no matter what the condition
of the stars were,

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they would always
be able to find north.

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Now, much later, the Europeans
are the ones who innovate

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and come up with the compass rose.

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It essentially laid out

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what north, south, east
and west looked like,

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and it also enabled you
to kind of create new directions,

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like northwest, southeast, what have you.

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

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That's kind of a big deal.

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But also, I think it was part
of this general reinvigoration

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of European science.

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You might know it as the Renaissance.

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Lots of new tools were invented,

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from the telescope to the microscope.

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Maps got better because
of compasses, right?

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Because then you start to understand
which direction is which,

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you get a lot more detail,

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and that just kind of changes

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the human relationship to the world.

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The compass with a map
is like a superpower.

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Everything that we think
of as world history

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would not have taken place
without the compass:

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the age of exploration, Magellan
circumnavigating the globe,

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even the fact that we know it is a globe.

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The compass ends up getting embedded
in all these other tools,

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because it is such a functional object.

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So you might have it
embedded in your multi-tool,

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you might have it
embedded in your phone.

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The compass is everywhere,

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because it's literally how we find our way
across the face of the Earth.

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So you can go off and explore,

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and find out what is over that next hill
or that next horizon,

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but you can also reliably
find your way home.