How can the Universe grow if it is infinite?

[Daisyroots]

Heuristics won't do the job.

But does anything even look like 'doing the job'? I mean, for example, if we'd have dreamed 30 years ago that we'd have had anywhere near the computing capacity to examine the issues, using modeling etc., that we have today, wouldn't we have actually thought that we'd have got somewhere (other, that is, than effectively deeper in the mire)? What do we actually know reference the thread question? We can apparently observe some sort of expansion, but of what, quite, into what, quite? I can't see that the thread question has been touched yet.

 

[Daisyroots]

Being a new member, you will soon notice that what @weirdoguy said is a common recurring theme here on PF: "one can only go so far in layman terms until you have to start learning the math."

Thanks you Comeback (and weirdoguy). I'll bow out. It seems to me we all want to know how the thing (the world) works, but regardless the language employed (maths, 'the word' or whatever) we incline towards delving deeper and ever deeper into a correspondingly ever more confined space, and in so doing lose sight of the question. We end up vanishing up our own backsides whilst patting ourselves heartily on the back for our cleverness. Philosophy, whilst it makes progress, has come up with no answers. Physics, whilst it makes progress, has come up with no answers. Religion makes no progress but purports to have all the answers whilst patently failing to demonstrate anything. And art, given that it evidences a modicum of creativity, is something of an enigma which seems happy to produce bad copies of the an unfailingly perfect original. Hey ho!

 

[russ_watters]

Depends on what you are trying to accomplish with the analogy: if you want to demonstrate expansion, probably not (unless you know how to inflate the Earth ). If you are simply showing a finite but unbounded object, then yes, it will work.

That's most of what I wanted: a simple yes or no answer to whether it works the way I use it (apparently yes) even if others like to limit it more.

That said, I still don't see an answer (or at least an explanation) as to the balloon and rubber sheet being mutually exclusive, so I will continue treating them as such until someone says I shouldn't. Indeed, given that it seems scientists think the universe is flat and infinite, not curved and finite, that would seem to be the better analogy to focus on.

 

[Comeback City]

Physics, whilst it makes progress, has come up with no answers.

Physics has definitely come up with answers. Sure, not to everything, but more than philosophy and religion. Out of the 3, physics is the only one that come up with evidence and proof for what it explains.

 

[Comeback City]

That said, I still don't see an answer (or at least an explanation) as to the balloon and rubber sheet being mutually exclusive, so I will continue treating them as such until someone says I shouldn't. Indeed, given that it seems scientists think the universe is flat and infinite, not curved and finite, that would seem to be the better analogy to focus on.

If this is the only issue, then it has been addressed several times. The balloon analogy and the rubber sheet analogy can both be used, AS LONG AS you do not begin to think that the there is a center in the rubber sheet (as, once again, there is no center to the universe regardless of its shape)

 

[Daisyroots]

Physics has definitely come up with answers. Sure, not to everything, but more than philosophy and religion. Out of the 3, physics is the only one that come up with evidence and proof for what it explains.

I'm not so sure, Comeback, though I can see why you might suppose it. It has many successes under its belt in the form of partial proofs of theories. For example many fabulous scientific developments are directly attributable to quantum theory and to the extent that each one of them works they of course prove the theory. In common with most things human, for most that is good enough. Those who use quantum theory as a work-a-day experience could not care less what causes the wave function to collapse. But since we do not know what causes it to collapse we have no idea of the nature of what it brings brings about, ie. the 'reality', phenomena, objectivity per se, 'MATTER'. We can ignore the question and pretend we do til the cows come home but the fact is that physics is no nearer an explanation of 'the world' than is even religion.

 

[Comeback City]

I'm not so sure, Comeback, though I can see why you might suppose it. It has many successes under its belt in the form of partial proofs of theories. For example many fabulous scientific developments are directly attributable to quantum theory and to the extent that each one of them works they of course prove the theory. In common with most things human, for most that is good enough. Those who use quantum theory as a work-a-day experience could not care less what causes the wave function to collapse. But since we do not know what causes it to collapse we have no idea of the nature of what it brings brings about, ie. the 'reality', phenomena, objectivity per se, 'MATTER'. We can ignore the question and pretend we do til the cows come home but the fact is that physics is no nearer an explanation of 'the world' than is even religion.

To be honest, I don't feel the need to argue over personal beliefs, as it really isn't accepted here on PF. Maybe someone else can chime in on how physics provides evidence to what it explains while philosophy is merely thought experiments and religion is simply "beliefs."

 

[russ_watters]

If this is the only issue, then it has been addressed several times. The balloon analogy and the rubber sheet analogy can both be used...

Fair enough, but since no one actually addressed the concerns I raised about using the balloon analogy for an infinite/flat universe, I'll make a different choice. If it speaks well to other people, great, but I suspect I'm not the only one who has trouble visualizing an infinite/flat sphere.

 

[weirdoguy]

I can't see that the thread question has been touched yet.

Just because you are not satisfied with the answers doesn't mean it hasn't been touched and that we don't know. We know what expands, we know what that means and we know that it does not have to expand into something. And to fully understand it you need to know the maths.

 

[Comeback City]

but I suspect I'm not the only one who has trouble visualizing an infinite/flat sphere.

Here is the issue! The universe is not a sphere (or at least it isn't known to be). Maybe overusing the balloon analogy has gotten you to think that since the balloon is a sphere, then the universe is a sphere. If the universe is infinite, then it will continue in all directions infinitely. The idea of the universe being a sphere implies that it would have boundaries, which is not compatible with an infinite universe.

 

[Daisyroots]

We know what expands,...

Is this to say that we know what matter is?

...to fully understand it you need to know the maths.

But aren't all the mathematical symbols effectively abbreviations? Can't each one of them be literated (or perhaps the expression should be literalised)? If not, then how did you yourself come to comprehend them? I'm not being facetious, weirdoguy, I'm genuinely interested.

 

[russ_watters]

Here is the issue! The universe is not a sphere (or at least it isn't known to be).

I'm aware.

Maybe overusing the balloon analogy has gotten you to think that since the balloon is a sphere, then the universe is a sphere.

No, I'm aware it isn't a sphere.

The idea of the universe being a sphere implies that it would have boundaries, which is not compatible with an infinite universe.

Agreed, but that isn't what the analogy says: the analogy considers only the 2d surface. However:

If the universe is infinite, then it will continue in all directions infinitely.

That, again, is my problem: picking a clearly and exclusively finite object and calling it infinite is.

 

[rootone]

can you have a viable idea of infinity that possesses, yet, a start point?

The set of natural numbers, (positive integers), You can start with 0 or with 1, either way the set has an initial value and extends to infinity.

 

[Daisyroots]

To be honest, I don't feel the need to argue over personal beliefs, as it really isn't accepted here on PF. Maybe someone else can chime in on how physics provides evidence to what it explains while philosophy is merely thought experiments and religion is simply "beliefs."

The set of natural numbers, (positive integers), You can start with 0 or with 1, either way the set has an initial value and extends to infinity.

Hi rootone. Yes I can see how that works. It's just that I wonder about the validity (and/or utility) of a unidirectional infinity, if you see what I mean.

 

[jbriggs444]

Hi rootone. Yes I can see how that works. It's just that I wonder about the validity (and/or utility) of a unidirectional infinity, if you see what I mean.

As for utility, there are a lot of students who have been taken through an approach to Real Analysis which begins with the Peano Axioms which characterize a unidirectional infinity and using this as the basis for a set theoretical construction of the real numbers.

Peano Axioms => unsigned integers with addition
Equivalence classes of ordered pairs of unsigned integers => signed integers with addition, subtraction and multiplication
Equivalence classes of ordered pairs of signed integers => rational numbers with addition, subtraction, multiplication and division
Equivalence classes of Cauchy Sequences [or Dedekind cuts] of rationals => real numbers with addition, subtraction, multiplication and division which satisfy the least upper bound property.

 

[Daisyroots]

As for utility, there are a lot of students who have been taken through an approach to Real Analysis which begins with the Peano Axioms which characterize a unidirectional infinity and using this as the basis for a set theoretical construction of the real numbers.

Peano Axioms => unsigned integers with addition
Equivalence classes of ordered pairs of unsigned integers => signed integers with addition, subtraction and multiplication
Equivalence classes of ordered pairs of signed integers => rational numbers with addition, subtraction, multiplication and division
Equivalence classes of Cauchy Sequences [or Dedekind cuts] of rationals => real numbers with addition, subtraction, multiplication and division which satisfy the least upper bound property.

I can imagine. Thanks rootone.

 

[Comeback City]

Hi rootone. Yes I can see how that works. It's just that I wonder about the validity (and/or utility) of a unidirectional infinity, if you see what I mean.

Did you want me to respond to that or did you quote me by accident?

 

[weirdoguy]

But aren't all the mathematical symbols effectively abbreviations?

No, it's the other way around. They can be 'literated' but to keep their full meaning it can't be done in laymans terms. That is the whole point of using mathematics to construct physical models. It's not ambiguous, everything has concrete meaning which you can't fully translate to ordinary language. Especially in advanced theories such as cosmology or quantum field theory.

If not, then how did you yourself come to comprehend them?

Well, I studied physics for 6 years at university, learned from textbooks, PhysicsForums and not from pop-sci stuff. Comprehension just 'happend'

Is this to say that we know what matter is?

For me matter=particles=certain states of quantum fields. If that doesn't satisfy you, well... The only thing that matters for physicists is to answer the questions "how it works?" not "what it really is and why it is so?" because at some point trying to answer the latter turns into philosophy.

 

[Daisyroots]

No, it's the other way around. They can be 'literated' but to keep their full meaning it can't be done in laymans terms. That is the whole point of using mathematics to construct physical models. It's not ambiguous, everything has concrete meaning which you can't fully translate to ordinary language. Especially in advanced theories such as cosmology or quantum field theory.
Well, I studied physics for 6 years at university, learned from textbooks, PhysicsForums and not from pop-sci stuff. Comprehension just 'happend'
For me matter=particles=certain states of quantum fields. If that doesn't satisfy you, well... The only thing that matters for physicists is to answer the questions "how it works?" not "what it really is and why it is so?" because at some point trying to answer the latter turns into philosophy.

Thank you very much for your patience and trouble, weirdoguy.

 

[Comeback City]

For me matter=particles=certain states of quantum fields. If that doesn't satisfy you, well... The only thing that matters for physicists

Ahh I see that low key pun you threw out there

 

[Daisyroots]

For me matter=particles=certain states of quantum fields. If that doesn't satisfy you, well...

Yeah, for me the thinking side of things tends to be a little bit more involved than that, though it it doesn't leave it out. For me objective existence (such as, I think, you describe) is only a part of the equation. I can't leave out the sentient beings doing the work of observation/correlation. They are, after all, just as much a part of the 'certain states of quantum fields' as any and everything else. The fact that they (we), as it were turn our eyes back in on themselves and analyse the situation, makes them, for me, warrant more inclusion rather than less.

 

[stoomart]

Fair enough, but since no one actually addressed the concerns I raised about using the balloon analogy for an infinite/flat universe, I'll make a different choice. If it speaks well to other people, great, but I suspect I'm not the only one who has trouble visualizing an infinite/flat sphere.

I'm not familiar with the "balloon analogy", but it seems to me the two analogies are indeed mutually exclusive. My understanding of a "flat universe" means two parallel lines will never intersect, three connected 90^o angles will never create a triangle, and traveling in one direction will never bring you to the same point; all of these would occur in a "curved universe".

 

[Comeback City]

I'm not familiar with the "balloon analogy", but it seems to me the two analogies are indeed mutually exclusive. My understanding of a "flat universe" means two parallel lines will never intersect, three connected 90^o angles will never create a triangle, and traveling in one direction will never bring you to the same point; all of these would occur in a "curved universe".

The whole point of the balloon analogy is to show how galaxies move farther away from each other without they themselves moving at all. It is the expansion of the universe, caused by dark energy, that is moving them. Just because the balloon has a curved surface, DOES NOT imply that the analogy only works for a curved universe. It works equally well for a flat/infinite universe. And I guess I will do the honors... read the article in the link of @phinds signature on the balloon analogy!

 

[stoomart]

The whole point of the balloon analogy is to show how galaxies move farther away from each other without they themselves moving at all. It is the expansion of the universe, caused by dark energy, that is moving them. Just because the balloon has a curved surface, DOES NOT imply that the analogy only works for a curved universe. It works equally well for a flat/infinite universe. And I guess I will do the honors... read the article in the link of @phinds signature on the balloon analogy!

It seems silly to use an analogy with a layman (like myself) that requires so much fine-print so it won't be misunderstood by the target audience. I would just say unbound galaxies are like a bunch of brownies whose space increases between them like they are magically shrinking.

Edit: I was already reading it before your post to see what all the fuss was about. : )

 

[stoomart]

Just because the balloon has a curved surface, DOES NOT imply that the analogy only works for a curved universe. It works equally well for a flat/infinite universe.

I think this thread has gone far too off-topic, so I will conclude with this thought: using curved balloon and flat rubber sheet analogies that can each describe a flat and curved universe is terribly confusing.

My personal belief is God created the infinite universe as a picture of his infinite power and greatness (see my profile for reference), but I do enjoy learning the theories we humans come up with to explain our observations.

 

[PeroK]

My personal belief is God created the infinite universe as a picture of his infinite power and greatness (see my profile for reference), but I do enjoy learning the theories we humans come up with to explain our observations.

When you meet him, you can ask him and that'll resolve the issue. I doubt I'll get the chance!

 

[Comeback City]

using curved balloon and flat rubber sheet analogies that can each describe a flat and curved universe is terribly confusing.

It's because you are overthinking the main purpose of them

 

[phinds]

My personal belief is God created the infinite universe as a picture of his infinite power and greatness ...

Not relevant in a science forum.

 

[infinitebubble]

Excellent topic... new to the conversation... Question just as in a pile of soap bubbles... if the multiverse model is true should the expanding universe model be expanding into other universes and those other universes are expanding into 'our' universe? Would we not see these other universes... so I do not think we have an infinite universe and our expansion of the universe will hit some unseen wall?

 

[jbriggs444]

Excellent topic... new to the conversation... Question just as in a pile of soap bubbles... if the multiverse model is true should the expanding universe model be expanding into other universes and those other universes are expanding into 'our' universe? Would we not see these other universes... so I do not think we have an infinite universe and our expansion of the universe will hit some unseen wall?

There is no need for an expanding universe to be embedded in any containing space within which it is expanding.

 

[infinitebubble]

Why the discussion at all if expansion of the universe is infinite? What is that containing space?

 

[jbriggs444]

Why the discussion at all if expansion of the universe is infinite? What is that containing space?

Expansion has nothing to do with any containing space -- if any.

 

[infinitebubble]

Not visualizing this somehow? Explain... Please.

 

[stoomart]

Not relevant in a science forum.

How good can a discussion about infinity be between science fans and a philosopher without a theologian? : )

A scientist, a philosopher, and a theologian walk into a bar, it hurt.

 

[phinds]

Excellent topic... new to the conversation... Question just as in a pile of soap bubbles... if the multiverse model is true should the expanding universe model be expanding into other universes and those other universes are expanding into 'our' universe? Would we not see these other universes... so I do not think we have an infinite universe and our expansion of the universe will hit some unseen wall?

Absolutely not. (1) As jbriggs said, there is no need for anything to expand "into", and (2) IF there is a multiverse (which I personally do not believe) there is no theory or evidence that different universes could be in casual contact with each other.