Originally posted by @vivify
If the universe has a mass, does that mean it has it's own gravitational pull?
*If* so, is there a way to calculate how strong the gravity of the universe is?
Well qualitatingly it roughly, it is clearly not enough to attract itself back to itself at least not yet since the entire universe has been and is stil expanding faster than the speed of light and it seems perhaps the speed of expansion sped up 5 billion years ago which lately there are theories that cast that into doubt.
What is not in doubt is the universe is still expanding faster that c so that says at least qualitatingly gravity is not strong enough to start the universe clumping back to a big crunch at least not in our epic of time.
Maybe a trillion years from now it might be different. One thing for sure, as the universe expands there is less and less we will see locally, in a billion years or so Andromeda and the Milky way will crunch into each other causing a burst of new star growth and such and they will settle down a billion years or so after that into a nice elliptical galaxy and then billions of years later all the other stuff will be flying away and we will see less and less and after a trillion years or so our galaxy will be the only thing seen in the entire visible universe leaving us in our epic knowing more about the universe in general than a civilization arising on some star a trillion years from now who may develop as technologically advanced as us (not that that is so huge in itself, but our present level)
At that time this far far future up and coming civilization will have telescopes at least as good as Hubble or James Webb and such maybe even better, say a 100 meter scope on an airless moon.
Even with that, there will be nothing for them to see no matter how hard they look because there will be nothing visible as the universe will have expanded to such a degree that the only thing in the observable horizon would be the home galaxy.
That's it for them so they will have a very truncated understanding of the universe compared to us who can at least see nearly 14 billion light years and have the advantage of seeing galaxies in all states of development.
Their red shift which will be very minor in their case since there will be nothing outside their home galaxy to reference any kind of doppler shift of light since there will be no light from distance sources to doppler at all. So we in fact ARE in a fairly special time in the universe to understand how it all got here, those folks from a trillion years from now will have no clue, only unprovable theories.
But back to the calculation of the mass of the observable universe, the fact the equation of the Shwartzchild radius and my method of just algebraicaly solving for M and coming so close to the Phd's estimate from a different direction says to me the idea that the observable universe IS the Schwarzchild radius of the universe which is like saying maybe a universe grows inside most black holes, a black hole in our universe becoming a white hole generating a daughter universe.
Maybe it takes a certain mass of a black hole to make a real universe if indeed that theory has any street cred at all, say a star of Sol's mass making a black hole a few km across would not be able to make a real universe just some kind of non-developing pile of gamma rays or something at the 'white hole' end of it.
Just me waving my hands to try to make sense of it all