Hello y'all,
after taking a very long break from my active interest in astronomy (15-20yrs) I've recently come back and I'm trying to get up to speed with all the new shiny discoveries.
One thing I've stumbled across is that apparently now the "observable" universe is a about 90Gly in diameter
Wikipedia
Paul Halpern
This confuses me.
I get the basic idea. The light source was 13.x Gly away some 13.x billion years ago and according to our prediction that light source should now be 46.x Gly away because of the expansion of space.
But it's trivially obvious that we've never observed anything further than 13.x Gly away, the rest is prediction/theory. Even if the theory behind it is 100% correct than we can only say - the last time we observed an object that is now 46.x Gly away was when it was only 13.x Gly away.
So why speak of an "observable" universe 90Gly across?
Or am I missing something easy (or tricky) here?
Thank you very much