You are at the sea. The water comes up around you. Some water comes into your mouth — and oh! You know that taste. Salt.
But wait. The rain is not salty. The rivers are not salty. You drink water every day, and it is not salty. So why is there so much salt in the sea? Where does it come from?
It starts far from the sea. It starts in the rocks.
There is salt in the rocks of the world. Very little — you can't see it, you can't taste it. But it is there, in the rocks and in the ground, everywhere.
Now, the rain falls on the rocks, year after year. The rain is soft, but it works and works. Little by little, the water takes very small things out of the rocks — and one of them is salt. The water runs down, makes little rivers, then big rivers. And all the rivers of the world run to one place: the sea.
So every day, the rivers bring a little salt to the sea. A very little. You can't taste the salt of one river.
But here is the thing: the salt never leaves.
The sun takes water up from the sea, up into the sky — but only the water goes up. The salt can't go up! It stays in the sea. New water comes with new salt... and that salt stays, too. Year after year. A million years. A billion years.
So now you know. The sea is old, very old — and all this time, it is getting its salt, little by little, from all the rocks of the world.
In some places, there is so much salt in the water, you can't go down in it! Look at the Dead Sea. People go in — and they sit on the water. They read books on the water! The salt water is like a bed under them.
So next time the sea water comes into your mouth, think of it: you are tasting old, old rocks — from places far, far away.