Before sentient life existed in the universe to observe it, what exactly was "the universe" as we come to know it today?

I really cannot subscribe to your premise. Distant galaxies existed long before the 16th century, when humanity still thought Sol was the only star in the universe.

If were far brighter, that would be the size and aspect of the andromeda galaxy in the night sky. And is 2 millon of years away, so that is the way it looked back then, far before mankind existed. We are watching to the past, sometimes galaxies so far away that existed before there was this life in this planet, this planet, and even this solar system. How the emergence of sentience life in this planet changed how it was a galaxy not just too far in space but also in time? You are focusing in the wrong side of the stick, we are the ones that changed, not the universe. The change on giving a meaning to something is on us, not on the observed object.

First, this is just the tree/forest/sound argument cast in a different set of subjects, verbs, and objects.  Of course the universe interacted physically with itself without the observation of the sentient being. Second, please prove to me that sentience wasn't around before the universe.