What do you find fascinating about this universe?

The endless possibility of finding life outside our solar system, whether that life is humanoid or otherwise.

How much we have yet to learn about it. 

Only relatively recently did we come to comprehend that we ride such a tiny speck spinning amidst the unimaginable vastness, there is literally no telling what other discoveries await.

Us in it and are able to see.

How chaotic it is and still how predictable it can be. Amazing how comets and planet alignments can be pin point on time.

How the military is afraid of the unknown

The sheer vastness of it. I met people when I lived in Kansas who would never see the ocean because it was too far to travel. (Which I don't understand.) It was 800 miles away. That is nothing when compared to the moon, or mars, or the next solar system or next galaxy and so on.

Me???? You guys are gonna laugh.... I think it would be so facinating to see the star lights in the sky in a place where city lights and smog don't block their brilliant beauty. I have never seen a star lit sky. I have seen stars out there but never like Yang described to me when he was over the road.

How long have you got?

Nothing can travel faster than the speed of light, but the universe is expanding faster.

What is dark energy? What is dark matter?

Quasars are some of the farthest observable objects in the universe, so they must be VERY old, where did they all go? How come they shine as single points of radiation when to be detectable at such distances they must be HUGE? (Individual quasars are often much brighter than whole galaxies of billions of stars).

We believe we have detected Gravitational "waves". For this to have happened, there must be something creating such waves which is truly monstrous out there, bigger by far than the biggest known black hole, what is it?

I could go on - but I'll be wandering off into particle physics in a minute and that will have you all asleep.