In Earth, it is a well know fact that if your dumb enough to go outside a space suit without the proper gear, you will die. However this is Mundus/Oblivion/Atherius./Whatever else if there is anything ele, in which not all of logic in Earth apllies with the ES universe. So anylorebuffs can tell me if someone were to go to space would they die unless they were using something magic?

I dunno. They use suits on the moon, but sound does carry through the void of Oblivion so it really depends on what you feel the rules of sound are. If it still needs air to be heard, then there is air of a sort. Scroll down the lore threads until you find Tiber Septim's Sword-meeting woth Cyrus the restless, which has more space stuff than anything else currently out.

So Tiber and Cyrus were on space? How did they get there? The only people I know of that can potentially do it are the dwemer but they just poofed away.. I';; read that sword meeting when I get a chance.

They floated up there using organic balloons attached to a boat.
The Imperials use Battlespires to travel beyond Nirn.
The Altmer use Sunbirds.
And the Khajiit just climb up, because they have the sugar to do so.

My hypothesis on how they breathe and such rests on the difference between aether and space.
It is entirely possible that physics reasons why things work in this universe, do not do so in the Tamriel one.
Consider the oldest known science fiction story, written by a monk, about flying to the moon in a carriage pulled by swans.
In the frame of mind of this monk, the aether that contains lifegiving air clearly does not end at the confines of Earth and is not there by physics and biochemistry, but rather the grace of god.
Similarly the Mundus. Kyne's influence does not end with the confines of the plane(t) Kyne, but pervades the
entire Mundus.
That you can live on the moons has not so much to do with science as with mythology.
Creation is a place made for mortals to live, therefore mortals can live in creation.

This. It's in the myths. The entirety of the Mundus should be filled with Kyne's breath, not just Nirn. As for Oblivion and Aetherius, I'm pretty sure we've been to both (DF and OB) with no problems.