It seems the horizon is right there…

but it’s actually closer than you imagine.

Due to the Earth’s curvature,

from a height like this, the visible horizon is a few kilometres away.

Approximately 4 to 5 kilometres if you’re at sea level.

That means everything you see beyond…

appears little by little.

First the highest part of a boat…

then the rest.

It’s a real effect, not an illusion.

And it’s been key for centuries in navigation.

In fact, sailors knew that seeing a boat’s mast first

meant something was approaching from far away.

It’s another way of understanding what you’re seeing.

Because the sea isn’t just observed…

it’s also interpreted.

Had you realised that the horizon isn’t as far away as it seems?