Answer:
What surrounds the world, yet dwells within a thimble?
What has a mouth but can't chew?
In we go, out we go. All around and in a row. Always, always steady flow. When we'll stop, you'll never known. In we go, out we go.
Iβm a word, six letters longΝΎ I sometimes enter with a gong. All in order from A to Z, I start with the letter B. What is the word?
What is lighter than what it is made of?
What is always coming but never arrives?