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

[Ser Scot A Ellison]

Great video talking about the potential implications of either an infinite or closed universe.   If it is infinite there is a possiblity that an infinite number of me are at this time typing this same post.

[Ded As Ned]

From the subject line, my money's on "something else".  Probably all adds up to the equivalent of a quark or proton in some other physics frame of reference.

[Ser Scot A Ellison]

7 minutes ago, Ded As Ned said:

From the subject line, my money's on "something else".  Probably all adds up to the equivalent of a quark or proton in some other physics frame of reference.

"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".  

[Corvinus85]

2 minutes ago, 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".  

What happens when God rolls out 7.0?

[Altherion]

1 minute ago, Ser Scot A Ellison said:

I have to wonder whether we aren't all simulations in God's version of "Sim Universe 6.5".

SpaceTime has a video about that too. Regarding your question in the thread title, it looks infinite, but, as the video points out, it's impossible to be sure. In general, most questions of this nature are unfalsifiable.

3 minutes ago, Corvinus said:

What happens when God rolls out 7.0?

From our perspective, probably not all that much -- unless it is deliberately done in a way that alerts us (e.g. by changing a fundamental constant, but not adjusting our memories, written work and creations accordingly), we would assume that we've always been living in 7.0.

[Ser Scot A Ellison]

Altherion,

Given that the nature of such a question is "unfalsifiable" isn't it necessarily metaphysical?  If it is metaphysical wouldn't Popper claim that it is outside the purview of "science" even though it is written in the idiom of science?

[IheartIheartTesla]

Just because something is 'unfalsifiable' doesnt make it metaphysics, it could easily be mathematics which I consider to be in the purview of science.

[Ser Scot A Ellison]

4 minutes ago, IheartIheartTesla said:

Just because something is 'unfalsifiable' doesnt make it metaphysics, it could easily be mathematics which I consider to be in the purview of science.

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

[Altherion]

15 minutes ago, Ser Scot A Ellison said:

Altherion,

Given that the nature of such a question is "unfalsifiable" isn't it necessarily metaphysical?  If it is metaphysical wouldn't Popper claim that it is outside the purview of "science" even though it is written in the idiom of science?

There are different degrees of unfalsifiable. For example, the simulation hypothesis is well and truly unfalsifiable because if it is true, you're playing against an intelligent entity that, by its very definition, can easily prevent you from discovering the truth.

The question about the curvature of the universe is not like that. You can measure the value of the parameter and you can set limits on the deviation from 1. That much is fully scientific. The problematic part is when you try to convert it into a description because the limit on the size of the deviation can never be exactly 0.

[Ser Scot A Ellison]

2 minutes ago, Altherion said:

There are different degrees of unfalsifiable. For example, the simulation hypothesis is well and truly unfalsifiable because if it is true, you're playing against an intelligent entity that, by its very definition, can easily prevent you from discovering the truth.

The question about the curvature of the universe is not like that. You can measure the value of the parameter and you can set limits on the deviation from 1. That much is fully scientific. The problematic part is when you try to convert it into a description because the limit on the size of the deviation can never be exactly 0.

How can we measure the curvature of the Universe in a way that gives us an answer to the question before the heat death of the Universe, or the "Big Rip"?

[Prince of the North]

Heh...I don't know.  All I know is my 8 year old son asked me just this morning "Hey, Dad!  What if you could push a button and duplicate the universe?!"  I said "That'd be awesome!  It'd probably be nice to have a spare but...where would you put it?" 

[Ser Scot A Ellison]

2 minutes ago, Prince of the North said:

Heh...I don't know.  All I know is my 8 year old son asked me just this morning "Hey, Dad!  What if you could push a button and duplicate the universe?!"  I said "That'd be awesome!  It'd probably be nice to have a spare but...where would you put it?" 

PotN,

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

[Prince of the North]

8 minutes ago, 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.

Actually, that's kinda what he answered to my smartass question.  Basically, he said "We could put it right next to the other one, silly!" 

[Altherion]

22 minutes ago, Ser Scot A Ellison said:

How can we measure the curvature of the Universe in a way that gives us an answer to the question before the heat death of the Universe, or the "Big Rip"?

As far as we can currently tell, it is not possible to do this. You can visualize an identical problem in one fewer dimensions. We live on a planet that, based on a cursory observation, appears to be flat, but is small enough for us to see that it is in fact roughly spherical with a more clever analysis. However, suppose that we lived on something that looked like it was flat and, as far as anyone could tell, extended forever. Could you ever prove that it was flat rather than, say an unbelievably huge sphere with a curvature that your experiments were simply too small to measure?

[A True Kaniggit]

And I always thought we were just an elementary school science experiment grown in a giant Petri dish. 

[Ser Scot A Ellison]

56 minutes ago, A True Kaniggit said:

And I always thought we were just an elementary school science experiment grown in a giant Petri dish. 

It would explain a lot.

[Iskaral Pust]

I've never studied astrophysics but my understanding from nerd interest is the observable universe is constrained by proximity in space-time.  We can observe only what was sufficiently close to us in space-time that it's light or other data has reached us during human observation and records.

We have no idea if many other Big Bang expansions occurred outside of our observable range in space and/or time. 

What we call the universe so far appears to be the expanding detritus of just one local Big Bang expansion.  And know very little about the space it expanded into -- extent, age, provenance, static or expanding, etc

[Altherion]

13 minutes ago, Iskaral Pust said:

I've never studied astrophysics but my understanding from nerd interest is the observable universe is constrained by proximity in space-time.  We can observe only what was sufficiently close to us in space-time that it's light or other data has reached us during human observation and records.

We have no idea if many other Big Bang expansions occurred outside of our observable range in space and/or time.

Correct.

14 minutes ago, Iskaral Pust said:

What we call the universe so far appears to be the expanding detritus of just one local Big Bang expansion.  And know very little about the space it expanded into -- extent, age, provenance, static or expanding, etc

Not quite. As far as we can tell, the observable universe did not expand into extraneous space. Instead, the original space expanded together with (and in fact significantly faster than) the matter moving through space. We can surmise quite a bit about this expansion. For instance, there pretty much had to be something like a very rapid burst of expansion ("inflation") that gave way to the much more leisurely expansion we see today.

[DireWolfSpirit]

I'm most comfortable imagining a universe without beginning nor end.

i really like this Sagan video towards the latter part when he's discussing a loop that is folding into itself. 

 

[Ser Scot A Ellison]

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.