What does の mean in the sentence after いる verb form


Below is from a children's book that I am reading and I am confused as to the
way の was used in the sentence.

あれは 亀が吹いて いるのに違いない

I would appreciate any inputs/infos regarding this.

Thank you in advance

Dan




This の is a nominalizer. It turns the clause, 亀が吹いている, into a noun. It's the
same の as in 彼が来る **の** を知っている ("I know **that** he will come").

[(noun/na-adj) +
に違いない](http://jisho.org/word/%E3%81%AB%E9%81%95%E3%81%84%E3%81%AA%E3%81%84) is
"It must be ～" or "I am sure ～". This is a fixed pattern to memorize. For
example, 嘘に違いない means "It must be a lie."

So 亀が吹いているのに違いない means "It must be that a turtle is blowing it." or "I'm sure
a turtle is blowing it."

**EDIT:** More specifically, this の is explanatory-の described
[here](https://japanese.stackexchange.com/q/5398/5010) (technically I believe
it's still a nominalizer). Actually you can also directly connect a verb and
～に違いない, e.g., 彼は来るに違いない ("I am sure he will come.").

