Is space infinite?

[evmar]

hello, im new here and i would love to make friends:) i also wonder if space is infinite or finite? thanks 💜

[Paul M]

The easy answer that, for most human endeavors is adequate, is "yes".

Then there are postulates that would suggest:

1) No

2) Maybe

3) depends

4) all the above

Here to help! 😁 

[saac]

welcome to SGL @evmar. I think the jury is still undecided re state of the universe, really depends on its shape and mass/volume (critical density).  Here's some thoughts from somebody more knowledgeable than me. 

https://www.esa.int/Science_Exploration/Space_Science/Is_the_Universe_finite_or_infinite_An_interview_with_Joseph_Silk

Jim

Edited July 4 by saac

[cloudsweeper]

From Sky At Night, April 2023:

The Universe is believed to be infinite, flat, without edges, and expanding.

Doug.

[TiffsAndAstro]

31 minutes ago, cloudsweeper said:

From Sky At Night, April 2023:

The Universe is believed to be infinite, flat, without edges, and expanding.

Doug.

And full of clouds

[Ags]

It's getting smaller. When I was a kid I could see all the way to the milky way. Today I can't see further than the nearest security light.

[saac]

The catchy named COMPACT  (Collaboration for Observations Models and Predictions of Anomalies and Cosmological Topology) modeled a hyperdimensional doughnut (3 Torus) resulting in a line of sight in which endless images of the universe would unfold on itself like a hall of mirror effect. Usefully they concede that the shape of the universe remains entirely wide open.  One wonders if due to these bizarre "observational  effects" the true shape of the universe will forever be outwith our reach!

The Universe's Topology May Not Be Simple

 

Jim 

Edited July 4 by saac

[Paul M]

In my lifetime, and I'm 60 soon, no real progress has been made on the answer to this question. Yeah, lots of science and physics, lots of output, but no progress.

Indeed, it just got more complicated. 

Last time I read anything on the subject, the mass of the Universe seemed to be just so that the universe would expand for ever but slowing at a rate that tended to zero at time = infinity., or something like that.

Way too flat for any coincidence. Are we overthinking it? 

I've seen a few "headlines" lately suggesting that the Big Bang is in crisis, or the Universe is a "reflection". I don't know, but I think the fist full of straws being grasped at just keeps getting fatter. 

Is cosmology in crisis? I've never like Dark Matter or Dark Energy concepts. Look like fudges to me... (as a sewage worker 🤣)

[saac]

12 hours ago, Paul M said:

In my lifetime, and I'm 60 soon, no real progress has been made on the answer to this question. Yeah, lots of science and physics, lots of output, but no progress.

Indeed, it just got more complicated. 

 

I'm not sure I'd agree with that Paul, in fact I think the opposite is true. In the short jump from Hubble establishing that the universe was far larger than the originally envisaged confines of the Milky Way and Lemaitre's theory of the "Big Bang", to the phenomenal work of WMAP (2010) in providing the most detailed study of the CMBR which cemented the Standard Model (Lamda CDM) I'd say we have made pretty amazing insights to the nature of the universe.  I wouldn't be surprised if the nature of the universe is so complicated that it will remain beyond our ability to offer a full description but that does not detract from the profundity of our knowledge to date - all the more remarkable that it was acquired in such short order. In truth, I think every cosmologists worth their PhDs would hope for a never ending complexity. We don't want the mystery and fun to end  

Jim 

 

Edited July 5 by saac

[RT65CB-SWL]

6 hours ago, Ags said:

It's getting smaller. When I was a kid I could see all the way to the milky way. Today I can't see further than the nearest security light.

For me it’s LED streetlights! 

[Paul M]

On 04/07/2024 at 23:50, saac said:

I wouldn't be surprised if the nature of the universe is so complicated that it will remain beyond our ability to offer a full description but that does not detract from the profundity of our knowledge to date

I feel think that too. 

But there have been numerous "dead-ends" along the way and the only thing that has increased along with our (their) knowledge is complexity. Like in the old horror films where someone is running down a corridor to escape a bug-eyed monster, and the corridor just gets longer and longer as they run. That's cosmology. just when you think you see the end, you don't.

So I'll double down on my earlier statement. That the answer to the OP's question is still no nearer being answered now than it was when I was a boy. The story has just got more complex. I'm just waiting, expecting, Dark Matter and/or Dark Energy to be declared fudge factors or to be neither energy or matter. Waves, innit

[vlaiv]

Here is an interesting question:

Is infinity purely mathematical construct or do we have something in nature that is infinite?

As far as I can see (there is a pun there somewhere I'm sure ) - everything that we've observed so far in this universe is finite.

Even some "philosophical" examples can be shown to be finite or rather depend on something that will be finite - take for example following argument:

Take a circle and marble and move marble on a circle - it can trace "infinite" length around the circle if it repeats itself. That would be physical infinity, right? Well - it implies that time needs to run to infinity and physical processes need to be undisturbed for duration of run - but we know that in expanding universe - that won't be the case. In fact, I don't think we need expanding universe - we just need second law of thermodynamics and fact that all will end in heat death to show that there is no infinite motion as described.

Which ever angle you adopt - you'll see that there simply is not infinity in physical world - so this begs a question - why would space be infinite?

[saac]

1 hour ago, Paul M said:

I feel think that too. 

But there have been numerous "dead-ends" along the way and the only thing that has increased along with our (their) knowledge is complexity. 

 Dark Matter and/or Dark Energy to be declared fudge factors or to be neither energy or matter. Waves, innit

I'll join you in doubling down Paul    Should we not expect greater complexity, if that is what we are finding then that is encouraging. 

As for dark matter/energy. Why do you think they are fudge factors?  In their absence what do you believe will explain the missing mass and what is causing the accelerated expansion and why would that be more credible than dark mater and dark energy?

Jim 

Edited July 6 by saac

[saac]

19 minutes ago, vlaiv said:

Here is an interesting question:

Is infinity purely mathematical construct or do we have something in nature that is infinite?

As far as I can see (there is a pun there somewhere I'm sure ) - everything that we've observed so far in this universe is finite.

Even some "philosophical" examples can be shown to be finite or rather depend on something that will be finite - take for example following argument:

Take a circle and marble and move marble on a circle - it can trace "infinite" length around the circle if it repeats itself. That would be physical infinity, right? Well - it implies that time needs to run to infinity and physical processes need to be undisturbed for duration of run - but we know that in expanding universe - that won't be the case. In fact, I don't think we need expanding universe - we just need second law of thermodynamics and fact that all will end in heat death to show that there is no infinite motion as described.

Which ever angle you adopt - you'll see that there simply is not infinity in physical world - so this begs a question - why would space be infinite?

Infinities in mathematics are sources of fun and frustration. Infinities in nature are just places waiting to be known   I believe the general consensus in physics is that infinities in nature do not exist in the common definition. 

Jim 

 

Edited July 6 by saac

[Mr Spock]

Hi, welcome to SGL 

If I knew the size or origin of the universe I'd be giving a nudge to the Nobel committee 
Everything we have is just opinion based on our perception of any evidence there may be however small that evidence may be.

Humans as we know them are not knowledgeable or intelligent enough to determine the origin of matter. 

[Nik271]

Infinity is only an abstract concept, everything that we can see or measure in the universe is finite, even the number of elementary particles in every galaxy that our instruments have ever seen. But we  can still speculate what is out there that we cannot detect.  

Here is the following thought experiment: imagine a race of two dimenionsional beings which live on some surface and are wondering: is it finite or infinite. There are some tests they can do to check. For example they can draw a large triangle and measure its angles. If the sum of the three angles is less than pi (and assuming their universe looks the same at every point), mathematics tells them that they live on a finite surface. If the angles add up to less than pi conversely they can deduce that they live on an infinite surface. And if the angles always add up to pi the test is inconclusive: the surface can be either finite or infinite. Here by infinite I mean in terms of area, or equivalently there is no bound on how many houses they can build all of distance at least 1 unit measure from each other.

We have performed such measurements in our universe and to the best of our ability they tell us that space is flat. So the jury is still out if the universe is finite or infinite at this moment of time. 

[TiffsAndAstro]

35 minutes ago, Nik271 said:

Infinity is only an abstract concept, everything that we can see or measure in the universe is finite, even the number of elementary particles in every galaxy that our instruments have ever seen. But we  can still speculate what is out there that we cannot detect.  

Here is the following thought experiment: imagine a race of two dimenionsional beings which live on some surface and are wondering: is it finite or infinite. There are some tests they can do to check. For example they can draw a large triangle and measure its angles. If the sum of the three angles is less than pi (and assuming their universe looks the same at every point), mathematics tells them that they live on a finite surface. If the angles add up to less than pi conversely they can deduce that they live on an infinite surface. And if the angles always add up to pi the test is inconclusive: the surface can be either finite or infinite. Here by infinite I mean in terms of area, or equivalently there is no bound on how many houses they can build all of distance at least 1 unit measure from each other.

We have performed such measurements in our universe and to the best of our ability they tell us that space is flat. So the jury is still out if the universe is finite or infinite at this moment of time. 

doesn't flat space suggest its infinite though? curved space would suggest its finite.

[Kev M]

It can't possibly be infinite....or at least not as we define infinite under our understanding of spacetime.

You cannot have an infinite number of entities...basically real things, galaxies, stars, atoms etc....there are many undisputable reasons why this is so....start with gravity.

However if it was finite....then the question becomes what is outside the boundaries.....which then means it is not finite...as we understand finite to mean.

In our 4 dimensional understanding of spacetime the universe cannot be either infinite or finite......which means that 4 dimensional spacetime is incorrect

 

 

 

 

 

[Earl]

What is Infinity... I think we can only speculate

 

Edited July 6 by Earl

[vlaiv]

1 hour ago, TiffsAndAstro said:

doesn't flat space suggest its infinite though? curved space would suggest its finite.

No.

Flat space that is simply connected is infinite.

There are geometries that are flat but are finite. Surface of 3D Torus is 2D space that is both flat and finite - but is not simply connected - you have a choice of different trajectories between two points - for example along minor or major circle.

"Surface" of 4D would be equivalent structure to represent 3D space with similar properties - however, it would void our assumption of cosmological principle - space would no longer be isotropic - meaning the same in all directions - again consider minor and major circle equivalent. Distance to return to starting point would depend on direction and that would void anisotropy.

[iantaylor2uk]

By definition, the observable universe is finite in size, since the big bang model shows that the universe started at a finite time in the past, and the furthest out we can see is limited by the speed of light. 

You can argue that science is only associated with observable things, so speculating what happens outside the observable universe is more philosophy than science (unless the unobservable universe has some impact on the observable universe which can be measured). 

[iantaylor2uk]

3 hours ago, saac said:

I'll join you in doubling down Paul    Should we not expect greater complexity, if that is what we are finding then that is encouraging. 

As for dark matter/energy. Why do you think they are fudge factors?  In their absence what do you believe will explain the missing mass and what is causing the accelerated expansion and why would that be more credible than dark mater and dark energy?

Jim 

Complex behaviour generally occurs ultimately from very simple rules. There is a good paper from Turing on how patterns on animal skins (stripes, spots etc) occur due to very simple rules on chemical reactions when animals are young. There is also a good book on cellular automata by Wolf ram which explains how complex behavior can arise from very simple rules. 

[saac]

4 minutes ago, iantaylor2uk said:

Complex behaviour generally occurs ultimately from very simple rules. There is a good paper from Turing on how patterns on animal skins (stripes, spots etc) occur due to very simple rules on chemical reactions when animals are young. There is also a good book on cellular automata by Wolf ram which explains how complex behavior can arise from very simple rules. 

I don't think we could argue that the universe is anything less than complex to our understanding Ian.  That the atom comprises a nucleus surrounded by an electron cloud appears non complex - the path to it's understanding was anything but simple. Similarly the equation to describe everything (when we arrive at it) will also appear simple because we will have understood it. 

Jim 

Edited July 6 by saac

[vlaiv]

7 minutes ago, iantaylor2uk said:

ou can argue that science is only associated with observable things, so speculating what happens outside the observable universe is more philosophy than science (unless the unobservable universe has some impact on the observable universe which can be measured). 

That is in fact the case.

What is currently unobservable to us - is actually observable to our nearest neighbor and as such has impact on our observable universe.

In fact, due to way universe expands - there are parts of the universe which are currently unobservable but will become observable in some future time before becoming unobservable again.

[vlaiv]

@iantaylor2uk

You've actually pointed out to a phenomena that leads to very freaky conclusions - now that I think about it more deeply.

You are quite right to raise the question - if something is outside of our Hubble sphere and will never ever influence us - does it exists at all (for all intents and purposes)? However - fact that our Hubble sphere is expanding and that something will enter it - makes me wonder which of the following is true / makes sense:

1. Will it pop into existence as our Hubble sphere expands

2. Why will precisely that pop into existence - one which is so much like everything else. Why don't we see purple unicorns pop into existence

3. If we can postulate that beyond our Hubble sphere there is real existence - can we postulate that there is real existence "everywhere" - which means that all that can exist - does exist.

and so on

Freaky stuff ...