/sci/ - Science & Math

I'm retarded. So it's often said that the big bang was 13.7 billion years ago, but does that make sense under relativity? I mean, doesn't the time since the big bang depend on your frame of reference, due to time dilation? Or am I wrong? Like, saying the universe is x years old seems to imply that every part of the universe is currently that old, but I'm told that kind of simultaneity doesn't exist. So are we just describing how old it is from our frame of reference? Or do most "things" in the universe share that reference frame? This is not a creationism post btw.