I just realized you can't actually tell how big or small the universe is and it's bugging me out.

Think about it, if the entire universe was scaled up 100000x, our units of measure that were invented would also be scaled up and any measurement we took would say the exact same as it does now. And vice versa if we were scaled down. When I say everything scaled that means the totality of the universe, so photons laws of physics etc.

So wtf even is the actual size of a light year spatially speaking? I can only know how big it is or I am relative to something else. Not actually just outright how big I am...