Measuring in light-years also allows astronomers to determine how far back in time they are viewing , Because light takes time to travel to our eyes. Everything we view during the dark in night has already been happened.
Because the toxins from gas are not good to breath in and eventually we will al die from it
It was caused by a mix of different scenarios. Rome was constantly attacked by Barbarian tribes; they were over-expanded, which made it really hard for them to keep their entire empire under control; they had a lot of economic problems and relied too much on slave labor; and they spent way too much money on their military, just to name a few factors.
I think it's probably position
