Is the Universe infinite?

[Dubbelosix]

There's some really cool things though, with large implementation on the cosmic scale.

 

For instance, can we really use gravitational corrections as a negative energy density to prevent singularities? In my own model, they are prevented by a non-trivial sign change between the Gibbs Helmholtz phase change - negative sign on pressure prevents a Friedmann equation from collapsing. The LQG generalizes the correction to

 

[math]\rho ( 1 - \frac{\rho}{\rho_C})[/math]

 

And then you introduce the corrections which act like a negative gravity. This is how you create quark stars! So assume we find  quark star in nature, then we have evidence on the cosmological scale these corrections exist in nature. I am skeptical though. 

2 minutes ago, MigL said:

Penrose and Hawking introduced their singularity theory in the late 60s/early 70s. Penrose was more interested in Black Hole singularities while Hawking, on Big Bang singularities.
By the middle 80s both had changed their minds about the existence of singularities describing either event.
So you're on your own on this.

I would go a step further than Strange or BeeCee, and say that what came before inflation  ( at 10^-35 sec ) is currently undefined. Since we don't know the cause for inflation, how can causality be extended backwards ? For all we know the universe existed in the pre-inflation, hot dense state forever until a quantum fluctuation sent it on its merry way.

If on the other hand, your argument is that our universe began when geometry was first evident, then that is the beginning of time. But quantum foam has no geometry ( that is its definition ) so it was there before time ( as we know it ) began .

Yup both of them are working on different things... Penrose appears to be working on cyclic universes while Hawking constantly changes his mind. First of all he likes fluctuation theory, then he changes his mind into string theory development, especially the M-theory. 

As Penrose says though... ''we are allowed to change our minds.''

 

Edited September 28, 2017 by Dubbelosix

[Dan B.]

On 28.9.2017 at 1:38 PM, Dubbelosix said:

Also, it seems like semantic nonsense to say the big bang doesn't imply an origin - unless something is cyclic in nature, then the big bang will always be the origin of everything we see today; questions like what happened before a big bang, is just again proposing a semantic argument, because again, everything still has to come from the big bang phase, regardless of what came before it.

If the Universe is infinite, then by definition it must have an infinite mass.

How this infinite mass (everything) could come from the Big bang phase? 

Is there no finite mass capacity for a bang (even if it is an Ultra Big Bang)?

 

[Dubbelosix]

It's an old philosophical question... it's even hard enough to imagine trying to squeeze [math]3 \times 10^{80} [/math] particles into a point, let alone infinity.

 

Let's be clear for a moment, for the universe to be infinite, it needs to have expanded for an infinite amount of time. Assuming the universe needs to expand for an infinite amount of time, the universe is never infinite in any moment of time.

 

(this is of course assuming absence of cyclic or pre big bang phases.)

Edited September 30, 2017 by Dubbelosix

[Strange]

2 minutes ago, Dan B. said:

How this infinite mass (everything) could come from the Big bang phase? 

If the mass is infinite then it has always been infinite.

There is no "Big Bang phase" where either a finite or infinite mass comes from. There is just the Big Bang model that describes how the universe cooled from an early hot dense state. 

If the universe is infinite now then it was infinite in that hot dense state. 

However, as you keep ignoring this I give up. 

[Dan B.]

2 minutes ago, Dubbelosix said:

Let's be clear for a moment, for the universe to be infinite, it needs to have expanded for an infinite amount of time. Assuming the universe needs to expand for an infinite amount of time, the universe is never infinite in any moment of time.

 

If "it needs to have expanded for an infinite amount of time" does it mean that the Big bang must take place infinite amount of time ago?

I still don't understand how the current BBT (which its age is limited to only 13.8 BY) gives an explanation for an infinite Universe.

 

 

[Dubbelosix]

No because the universe evidently has a finite past.  The idea is if this is true, then it would need to expand for eternity, to be truly infinite. But I have also argued, that in any moment of time, the universe will always be finite...

 

why?

 

Because infinities purport to unphysical situations. It's unfeasible to assume something can  ''get to infinity.''

 

For instance, imagine you created a machine capable of counting to infinity, a ''countable infinity.'' But to do that, you need to sit next to the machine for an infinite amount of time!

 

Why? It's because the machine spits out numbers and infinity is not a number, its a concept and poorly understood and abused one. 

sorry typos fixed (edit)

Edited September 30, 2017 by Dubbelosix

[Strange]

15 minutes ago, Dubbelosix said:

No because the universe evidently has a finite past. 

Only from a naive extrapolation using GR which is almost certainly wrong as it doesn't take quantum effects into account.

Quote

 The idea is if this is true, then it would need to expand for eternity, to be truly infinite. 

As there is good reason to think it is not true, then the conclusion is moot.

(Also, there are functions that atom from zero to infinity in finite time. But I don't really think that is relevant.)

[Dan B.]

3 minutes ago, Strange said:

There is no "Big Bang phase" where either a finite or infinite mass comes from. There is just the Big Bang model that describes how the universe cooled from an early hot dense state. 

If the universe is infinite now then it was infinite in that hot dense state. 

Do you mean that about 13.5 BY the whole infinite Universe was an infinite hot dense?

Based on the BBT, this hot dense has a specific limited size.

If it is infinite hot dense (bigger than this limited size) then by definition we need to update the BBT.

Why not?

 

7 minutes ago, Dubbelosix said:

No because the universe evidently has a finite past.  The idea is if this is true, then it would need to expand for eternity, to be truly infinite. But I have also argued, that in any moment of time, the universe will always be finite...

why?

Because infinities purport to unphysical situations. It's unfeasible to assume something can do something can ''get to infinity.''

I disagree.

Infinite Universe means Infinite Universe.

If it was Finite Universe, then it must be called Finite Universe.

It is a mistake to call it Infinite Universe while it is finite Universe.

[Dubbelosix]

6 minutes ago, Strange said:

Only from a naive extrapolation using GR which is almost certainly wrong as it doesn't take quantum effects into account.

As there is good reason to think it is not true, then the conclusion is moot.

(Also, there are functions that atom from zero to infinity in finite time. But I don't really think that is relevant.)

 

 

Strange, I find all these discussions moot. I am not dragging these factors into the discussion though, you are. The questions he is positing are exact and I am giving him exact answers in a very limited theory. 

6 minutes ago, Dan B. said:

 

I disagree.

Infinite Universe means Infinite Universe.

If it was Finite Universe, then it must be called Finite Universe.

It is a mistake to call it Infinite Universe while it is finite Universe.

 

I'm giving you a situation, where a finite universe, to be infinite by definition, has to expand for infinity, if you want to go into semantics and say it was infinite all along, then fine... but let's be clear, that we need to make sense of why the universe is expanding. I am not sure the expansion dynamics works in an infinite universe - certainly the static universe theories suffered this problem? Hoyle's infinite steady state universe suffered this problem.  

Edited September 30, 2017 by Dubbelosix

[Strange]

4 minutes ago, Dan B. said:

Do you mean that about 13.5 BY the whole infinite Universe was an infinite hot dense?

I do not mean it was infinitely hot and dense. At the earliest time our current models go to, the temperature and density are finite.

Quote

Based on the BBT, this hot dense has a specific limited size.

Why? Where does it say that?

5 minutes ago, Dubbelosix said:

The questions he is positing are exact and I am giving him exact answers in a very limited theory. 

And I am simply pointing out where the limitations are and why they make your answers irrelevant. (I have reported him as a likely sock puppet, so the whole thread may become moot.)

[Dubbelosix]

2 minutes ago, Strange said:

 

And I am simply pointing out where the limitations are and why they make your answers irrelevant. (I have reported him as a likely sock puppet, so the whole thread may become moot.)

Maybe ... but I think laymen tend to get more confused thinking outside the traditional realms they tend to read on pop science articles. 

 

If it is shut down, that's a shame. Questions like this are popular with the laymen and they don't quite understand it for good reasons. 

[Mordred]

50 minutes ago, Dubbelosix said:

It's an old philosophical question... it's even hard enough to imagine trying to squeeze 3×1080 particles into a point, let alone infinity.

 

 

 

valid point here it is a very common question with tons of pop media misdirection

 

 

[Strange]

1 minute ago, Mordred said:

valid point here it is a very common question with tons of pop media misdirection

That the Big Bang was an "event" at t=0 where the universe was created seems to be one of those pop-sci distractions.

[Dubbelosix]

Agreed, I hate the pop media, it tries to do good, but makes it harder for the rest of us - laymen included. 

[Mordred]

6 minutes ago, Strange said:

That the Big Bang was an "event" at t=0 where the universe was created seems to be one of those pop-sci distractions.

Yes and depending on the treatment applied the T=0 can be correlated to last scattering or the singularity 10^-43. Though your cosmological horizon singularities also apply under the particulars of the treatment under the FRW metric. ie Hubble Law.

12 minutes ago, Dubbelosix said:

Agreed, I hate the pop media, it tries to do good, but makes it harder for the rest of us - laymen included. 

does help with forum membership though lol, generates posts of "this doesn't make sense I must reinvent so I can understand it"

[beecee]

13 hours ago, Dubbelosix said:

Maybe ... but I think laymen tend to get more confused thinking outside the traditional realms they tend to read on pop science articles. 

 

If it is shut down, that's a shame. Questions like this are popular with the laymen and they don't quite understand it for good reasons. 

I'm also only a lay person, and a retired one at that. But I do pride myself with having read plenty of reputable books on cosmology, and asked plenty of pertinent questions off professional experts that I respect, particularly on a now defunct forum run by the ABC, (Australian Broadcasting Service) one being an astronomer named Geraint Lewis.

But let me also say that in my time I have experienced plenty of other lay and non lay people that actually have no intention of accepting any answer, if that answer conflicts with any existing agenda they may have.

13 hours ago, Strange said:

That the Big Bang was an "event" at t=0 where the universe was created seems to be one of those pop-sci distractions.

 The "pop science media" as many call it, do do a job: It was the "pop science media" a long time ago that got me interested in astronomy and cosmology and the associated awe and mystery. The BB was of course the evolution of the universe/space/time (as we know them) from a hotter, denser state, is the way I like to put it...Emphasis on the bracketed "as we know them"

In essence, the "pop science media" is totally necessary particularly in creating interest in the awesome subjects of cosmology and astronomy. If a person is particularly interested, or has queries about what he has heard from the media, he will I believe do what I did a long time ago.( I only wish it was even earlier,  ) Read, (My first book that spiked my interest was Hawking's "A Brief History of Time" and I am going now to reread Kip Thorne's "Black Holes and Time Warps", listen to reputable professional people such as the late great Carl Sagan, and his recent protege Neil DeGrasse Tyson. Even concepts from these experts that I have listened to, I will nearly always take further and check out any relevant scientific papers. Anyway I'm off topic and could go on forever about the numbers of reputable books I have read and even the excellent pop science presenters.

 

 

 

 

[MigL]

Most books I get these days are E-books, but I do have K Thorne's book in softcover, and I often use for quick BH related reference.
If you don't mind a little math, Gravitation by Misner, Thorne and Wheeler is very handy to have ( hasn't been packed in a box yet ); It offers plenty of verbal explanations as well as mathematical ones, but can be rather pricy.
Another excellent reference is Principles of Physical Cosmology by Peebles, also a little math heavy, but offering plenty of verbal guidance so I don't get 'lost'.
( its been a while since I did any 'real' math )

[Mordred]

My favorite pocket reference has nothing to do with any set theory under physics but instead teaches the tools to understand the mathematics.

Mathematical methods for Physicists by Arfken. An essential tool to understand group theory without dealing directly with group theory but covers the basis.  It is an invaluable tool in any physics related field covering topics such as Greene's, Louiville, Gaussian, distributions etc focussing on the vectorial aspects.

The book is fully applicable in Engineering as well.

 From personal experience since studying the book I have found a vast majority of physics related topics far easier to understand. (Though much of the book were of topics I was already aware of, in my case. The layout of the book places the pieces together in a clear fashion)

 

Edited October 1, 2017 by Mordred

[Orcus]

On 8/1/2017 at 3:27 PM, Dart15 said:

YES ....... and  .....NO,        Maybe !

I don't know... Can you repeat the question?

[Dan B.]

On 26.9.2017 at 7:34 PM, Strange said:

This seems to answer lots of common questions: https://www.cfa.harvard.edu/seuforum/faq.htm

Thanks Strange

It took me some time, but finally the BB process for infinite Universe is quite clear to me.

The explanation is as follow:

If the Universe is Infinite, then it was infinite before the Big bang.

The BB took place everywhere in space.

"To put it another way, the current evidence indicates only that the early universe - the WHOLE universe - was extremely DENSE - but not necessarily extremely small. Thus the Big Bang took place everywhere in space, not at a particular point in space."

So, 13.5 BY ago, the whole Universe (Even if it was infinite) was extremely hot and dense.

The CMB is decreasing over time. Hence, from about 5000 K, it went down to 2.7 K.

However, I still have few questions -

1.  What is the expected CMB decrease in the next one hundred years? Can we detect even small level decrease over our life time?

2. If the Universe is infinite today and it was infinite 13.5 BY ago, then how technically it could decrease its temp after limited time frame?

    As an example, let's look at infinite Oven at 5000K. If the door is open at the infinity, would we get any temp reduction at the center after some time? 

    Can we show/prove any temp reduction in infinite oven?

 

Edited October 2, 2017 by Dan B.

[Airbrush]

Since the universe means "all there is" that is probably infinite.  The big bang, however, is not necessarily "all there is".  Nothing that I have learned about cosmology leads me to think the big bang is infinite.  It could be, but that is a tall order for a big bang.  Only the "universe" is probably infinite, by definition.

[Strange]

Although David has been banned, here are a few comments:

The initial summary in David's post is (amazingly) pretty much correct. (I'm sure he will claim not to know any of that when he pops up again.)

As to the questions:

1. Immeasurably small. The universe will double in size in 13.8 billion years (ignoring the acceleration) so in 100 years it will cool by a factor of 100/13.8x10⁹ or about 20 billionths of a degree. (Maybe someone better at the relevant maths will correct that if necessary.) And no.

2. The oven is an inappropriate analogy. The universe is not cooling because the heat is leaving the universe. It is cooling because it is expanding (the volume is increasing). This is described by basic thermodynamics.

[Strange]

Excellent FAQ on some of the questions that have come up in this thread: https://medium.com/starts-with-a-bang/5-questions-you-were-too-embarrassed-to-ask-about-the-expanding-universe-9433c4906a29

And this one on whether the "Big Bang" is the beginning or not: https://medium.com/starts-with-a-bang/the-big-bang-wasnt-the-beginning-after-all-81844b973333

[beecee]

38 minutes ago, Strange said:

And this one on whether the "Big Bang" is the beginning or not: https://medium.com/starts-with-a-bang/the-big-bang-wasnt-the-beginning-after-all-81844b973333

That particular link is quite revealing and interesting, which is why I like saying in any explanation, (and in my lay person's style) that the BB is a theory of the evolution of space and time (spacetime) as we know it. 

Also interesting is the support for the "Superforce" reasonably speculative scenario, and being inherent to spacetime itself. Makes a heap of sense, at least to me. 

 

Also interesting and quite profound is the quote in your first link  https://medium.com/starts-with-a-bang/5-questions-you-were-too-embarrassed-to-ask-about-the-expanding-universe-9433c4906a29 thus.....

“The more clearly we can focus our attention on the wonders and realities of the universe about us, the less taste we shall have for destruction.” 
-Rachel Carson

[scherado]

On 10/2/2017 at 0:44 PM, Airbrush said:

Only the "universe" is probably infinite, by definition.

That might be called a probable definition. On what basis would one define the bounds of the universe using the word "probable?"

Hey, that just might be called a "quantum conundrum"!!!!!!