Can rational thought exist without language?

we do it all the time in our dreams. As we find our brains process information symbolically.

Yes, there had to be rational thought to create the language in the first place.
Also, my dogs are capable of rational thought....but incapable of expressing that through language.

Even sign language? Hmmm. Difficult however I think it can be possible simply by gestures

Depends on the nature of rationality.
There are three forms of thinking available to humans :-
Intuition, intellect and instinct.
Intuition doesn't require language but it's not rational either.
Intellect requires both language and rationality.
Instinct doesn't require language but decisions based on it are often products of very simple rational thinking.
Like, I should defend myself because the other person is about to attack me.

I believe so but obviously we couldn't learn from others the way we can with it

We would think in pictures. I think in pictures sometimes.

It's a great question. If only there was a way to test it.

With rational thought a form of communication will develop...maybe a really simple one...too simple to be considered language by us complicated humans...

Yes but how will anyone find it out ..

Yes

yes

Yes. Communication can come through any medium or object if you pay close enough attention to it.