Is the Universe infinite, a hypersphere, or something else?

[Larry of the Lawn]

41 minutes ago, Ser Scot A Ellison said:

DWF,

But the data we have today pretty clearly indicates the Universe had a beginning.  If there is a beginning that suggests an eventual end.  Because if there is a beginning, by definition, the Universe is not timeless.

IP, Altherion,

On of the hardest things for me to grasp about the Big Bang is that it wasn't an expolsion into space.  It was, and is, an explosion of space.

Not necessarily.  Imagine the universe just repeatedly explodes in a big bang, and then some time later all the matter gravitates back together and then explodes again.  The beginning might not be the real beginning, it's just the observable beginning.

[Ser Scot A Ellison]

10 minutes ago, larrytheimp said:

Not necessarily.  Imagine the universe just repeatedly explodes in a big bang, and then some time later all the matter gravitates back together and then explodes again.  The beginning might not be the real beginning, it's just the observable beginning.

And using empirisim as the guidepost what is the difference between the "beginning" and the "observable beginning"?

[Larry of the Lawn]

51 minutes ago, Ser Scot A Ellison said:

And using empirisim as the guidepost what is the difference between the "beginning" and the "observable beginning"?

Just pointing out that a beginning doesn't necessarily imply an end.  I mean the horizon looks like the end of the world from where you're standing.  But it's not the beginning or end of anything but your line of sight.

[maarsen]

1 hour ago, larrytheimp said:

Just pointing out that a beginning doesn't necessarily imply an end.  I mean the horizon looks like the end of the world from where you're standing.  But it's not the beginning or end of anything but your line of sight.

Cool. A very perceptive answer.

[The guy from the Vale]

On 5/5/2017 at 10:27 PM, Ser Scot A Ellison said:

PotN,

Tell your son that if the Universe is flat and infinite that means out in that infinite space... we are repeated infinitely.

That's a... debatable understanding of infinity, Scot. Infinite expansion is not the same thing as infinite incidence. They are connected to different concepts of infinity that do not necessarily have a connection. For example, even an infinite universe might contain only a finite amount of matter (or energy, to be more precise), so infinite parallel existence of living beings would be impossible in an infinite universe.

[Iskaral Pust]

I was always bothered by the common notion of an infinite universe alongside the Big Bang and expansion model.  I can accept the pre-Bang universe was "infinitely" hot and dense relative to what we can measure or conceive, but it seems possible/probable that the far-flung matter of our universe today is merely immeasurable rather than infinite, and space-time appears to be linked to the expansion of that matter rather than inherently infinite.  Our universe may be a local, finite bubble and we have no idea of whether there are other bubbles -- possibly some very shortlived because they lack the balance in our cosmological constant -- or whether our bubble goes through cycles of expansions and contractions.  Those are what would make the universe infinite in space/matter/energy and/or in time. 

[DireWolfSpirit]

Very well put Larry. I believe there's most likely a difference  between  "beginning" and "observable beginning", Sagan is also talking about our limitations at observing  other dimensions  like he's portraying in the Flatland example in the video I posted  earlier.

I'm  still  most comfortable  imagining the universe as one without beginning  nor end. There's much we haven't  observed, much that we still do not know. 

[Stubby]

The Wheel of Time turns. Ages pass and ages begin. In an unobservable place somewhere, in an age yet to come, or an age long gone, a universe rose.  It was neither the beginning or the ending, but it was a beginning.

[Altherion]

Actually, from what we can tell, the universe does have an end. Time is not a wheel; it has an "arrow" we call entropy. The stars will eventually burn out, then even black holes will evaporate and finally there will be nothing but a uniform distribution of subatomic particles and radiation. It might be possible to work around this if the universe re-collapsed, but it appears that it will expand forever so no luck there.

That said, if you'd really like to think of time as a wheel, there is an amazing theorem called the Poincaré Recurrence Theorem which might be of use to you. It's kind of tricky because it's not clear whether it applies to our universe or not, but given a finite phase space (not the same thing as space-time), a system will eventually come arbitrarily close to its initial state (or really, almost any state). It's truly bizarre.

[IheartIheartTesla]

On 5/5/2017 at 4:05 PM, Ser Scot A Ellison said:

So, you aren't a Popperian, I take it?

I'm not sure Popper himself was a Popperian. According to this confusing paragraph from wikipedia:

Quote

Many philosophers^{[weasel words]} believe that mathematics is not experimentally falsifiable, and thus not a science according to the definition of Karl Popper.^[27] However, in the 1930s Gödel's incompleteness theorems proved that there does not exist a set of axioms for mathematics which is both complete and consistent. Karl Popper concluded that "most mathematical theories are, like those of physics and biology, hypothetico-deductive: pure mathematics therefore turns out to be much closer to the natural sciences whose hypotheses are conjectures, than it seemed even recently."^[28] Other thinkers, notably Imre Lakatos, have applied a version of falsificationism to mathematics itself.

 

[IheartIheartTesla]

6 hours ago, Altherion said:

That said, if you'd really like to think of time as a wheel, there is an amazing theorem called the Poincaré Recurrence Theorem which might be of use to you. It's kind of tricky because it's not clear whether it applies to our universe or not, but given a finite phase space (not the same thing as space-time), a system will eventually come arbitrarily close to its initial state (or really, almost any state). It's truly bizarre.

I couldnt tell from the link whether the theorem explicitly assumes an ergodic hypothesis....there are certain systems that remain in a metastable state for long periods, sometimes as long as the lifetime of the universe, such as a glass. Is an atomic/molecular glass supposed to satisfy the recurrence theorem?

[Altherion]

4 hours ago, IheartIheartTesla said:

I couldnt tell from the link whether the theorem explicitly assumes an ergodic hypothesis....there are certain systems that remain in a metastable state for long periods, sometimes as long as the lifetime of the universe, such as a glass. Is an atomic/molecular glass supposed to satisfy the recurrence theorem?

Yes, I think so. From what I can tell, all it assumes is a finite phase space and transformations that don't create or destroy new states. The reason it doesn't conflict with long-lived structures (or, for that matter, the Second Law of Thermodynamics) is that the timescale of the recurrence is incredibly long. It's not the lifetime of the universe; it's that exponentiated to the 10 a few times.

[Relic]

On 5/5/2017 at 8:23 PM, Ser Scot A Ellison said:

"Something else" is a really safe bet.  I have to wonder whether we aren't all simulations in God's version of "Sim Universe 6.5".  

My question, with all due respect, is ho wyou can watch the video you linked and still believe in an all knowing all loving higher power. 

[Ser Scot A Ellison]

43 minutes ago, Relic said:

My question, with all due respect, is ho wyou can watch the video you linked and still believe in an all knowing all loving higher power. 

Relic,

Because I do.  I do not expect you to agree or to understand.  It is a matter of faith to me.

[Jo498]

On 9.5.2017 at 0:00 PM, Relic said:

My question, with all due respect, is ho wyou can watch the video you linked and still believe in an all knowing all loving higher power. 

I really don't see any clear positive or negative connection between that cosmology video and most kinds of religious belief. Sure, there would be a conflict with young earth creationism, but certainly no tension with Scott's christian theism, even less an obvious, blatant conflict that could only be resolved by "blind faith in spite of science". Where do you see the supposedly obvious tension?

[Ded As Ned]

Likewise, the more I learn about the universe, the more it reaffirms my belief in a higher power.  ymmv

[Ser Scot A Ellison]

15 minutes ago, Ded As Ned said:

Likewise, the more I learn about the universe, the more it reaffirms my belief in a higher power.  ymmv

Pretty much.

[DireWolfSpirit]

I'm sure ive previously posted NDT sermonizing that "Its not that were in the universe, its that the universe is in us." I just never get tired of this point. Tyson (who is agnostic) does note its interesting that the same area of the brain likely lights up for for him when he's exposed to cosmology, that same feeling is replicated with the religious when they go to mecca or listen to their religious sermons, its likely the same area of your brain reacting. 

 

[Iskaral Pust]

You could argue that entropy is the long term reversion of individuals back to a universal collective, as posited by some religions.

Similar to the axe of my grandfather, for which both the handle and head have been replaced several times but it remains in my mind the axe of my grandfather, all of us have seen full turnover of our atomic constituents several times in our lives but we retain a notion of persistent individual identity for the atoms we currently bind together up until our expiration releases those atoms back to entropy.

[Relic]

22 hours ago, Ded As Ned said:

Likewise, the more I learn about the universe, the more it reaffirms my belief in a higher power.  ymmv

That's interesting, and I'm curious to know why that is. If you'd like can you share your view on that?

Personally, the more I learn the more I'm convinced that we are living on a quark within a cell within the stomach lining of a galactic space goat, or something equally ridiculous. The larger our universe gets, the less "greater" meaning our lives have, imho.