WEBVTT
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Language: en

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I'm in Basel, in Switzerland.

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The river Rhine runs through here,

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and if you want to get across it,
then there are four ferries.

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I mean, there are bridges as well,
but the ferries keep going

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as a tourist attraction,
as tradition,

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and for some folks, an actual way
to get where you want to go.

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Also occasionally a fondue restaurant,
because Switzerland.

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But these ferries have
no paddles, no oars, no engines,

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nothing on board to power them.

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Put them in the open ocean or a lake
and they'd just drift.

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And yet here, they move.

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So here's how they work:

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there is a wire strung across the river
and the ferry is connected to it.

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There's a little thing called a traveler
that goes back and forth smoothly.

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The ferry does have a rudder for steering,
so when it's time to cross,

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the captain angles the boat against the current,

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and uses the force of the river itself to
push the boat across.

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Without that cable,
it'd drift downstream, fast.

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But since it can't, it just
crosses the river instead.

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No gasoline, no human effort,
just the force of the river.

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Boats like this are called reaction ferries,

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and there are examples all over the world.

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Sometimes the design's a little different,
but the principle is always the same.

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I only learned about them a few weeks ago,

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and in hindsight, they seem incredibly obvious.

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You have an object that needs energy

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sitting on top of a
massive, constant energy source

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just waiting to be harnessed.

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But if you'd asked me how to connect
those two things before I knew the answer,

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then my first thought would probably have
been some overcomplicated, overengineered plan

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like putting a waterwheel
on the side of the river

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and then using that cable to send power to
an electric motor on the boat.

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I mean, there is a hydroelectric dam
not far away.

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I'd like to think that I'd have
worked it out eventually,

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but I'd have probably missed
the easy option to start with.

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To anyone who grew up in a place
with these ferries, it's a really obvious idea.

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But to everyone else, it's an invention
we've never thought of.

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To be fair, this is only a good solution in
a few places.

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You need a strong, fast, steady river,
like the Rhine, at a place where it isn't tidal,

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and where it isn't particularly seasonal either.

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But if I've missed that, then the obvious
follow-up question is, well:

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what else have I missed?

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And is there anything out there that
every single human has missed?

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Maybe there is still some big, obvious-in-hindsight
stuff out there that'll change the world...

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just as soon as someone thinks of it.