I mean, it makes some sense if there was a big bang X years ago, that everything ends up withing X lightyears of each other.
I find it easy enough to think of there being a beginning, since we know that stars age, and use up energy, so they can't have been running forever.
Since we think the big bang was 13.7 billion years ago, we can put Y at about 2*13.7 billion light years across as a first guess. Though there's something funkey with the spacetime stretching or whatever. So maybe more.
For the Universe having certain age - I don't understand it, b/c whatever is 13 billion years for one, might be 1 sec for another, due to relativistic time dilation. I think of this number as a kind of metaphor :)
Yeah, but in my defense, 46 billion is the same order of magnitude as 13 billion. And a lot easier to understand why it'd be around that magnitude without the stretching of spacetime.
I find it easy enough to think of there being a beginning, since we know that stars age, and use up energy, so they can't have been running forever.
Since we think the big bang was 13.7 billion years ago, we can put Y at about 2*13.7 billion light years across as a first guess. Though there's something funkey with the spacetime stretching or whatever. So maybe more.