Rhyming Riddle 21

Here is today's riddle:

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Always old, sometimes new;
Never sad, sometimes blue;
Sometimes thin, sometimes full;
The ocean shows how hard I pull.
Who am I?

clue:

I am as old as the earth.

clue:

Sometimes I am so thin you cannot see me at all.

clue:

When I pull, I move the ocean's tides.

reveal/hide answer

The moon.

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There are lots of riddles for this topic, but I liked the scientific detail about the ocean; that's not something you see so often.

NOAA

More Rhyming Riddles with Clues.