B I G

TIL : OK so a light year is how long it takes light to travel in 1 year, As you are aware light is fast like really really fast.
Now our galaxy is huge, like really really big. Just over 100,000 light years across in size. So if something were to have happened on the far side of our galaxy, say a star blows up, way back when humans first popped up in the middle east. Well we would just be seeing it today.
OK so the galaxy is big, really really big. Almost inconceivably big.
Now try and wrap your brain around this.

This picture is of the LQG or the Large Quasar Group
The Large Quasar Group is four billion light years across. The cluster of seventy-four quasars actually breaks the rules of standard astrophysics, since the maximum size of any cosmic structure should be only 1.2 billion light years across. Scientists have absolutely no idea how this huge structure formed, since they had previously only been aware of other clusters of perhaps several hundred million light years across.
Yeah so if something were to happen on one end, like a star blows up, it would take 4 BILLION YEARS for the other side to even know.
Im sure by then they would even care.