Is the Universe Infinite or Finite?

[Jake4]

If you cannot see or measure something, it is undetectable, it is that simple

You can make a bunch of fancy experiments and interpret the results in a way that suits you, but it is still all based on hypothesis and even if the whole world is forced to conform to that so they can get good grades at school - that does not make it any more real

IMO theoretical cosmology has long lost it's way, and that's the reason we have almost zero innovation in actual space exploration, the rockets today use the same engines they used 40 years ago, despite the enormous advancement in all other areas

I hate to use a layperson's simplified example.. but..

we can't see or measure black holes directly... but only it's effect on surrounding bodies.


Also, one thing. Is infinity a constant? If infinity, even though not a specific number, is a constant, then the space between things cannot be increasing. If the universe is already infinite, how can it get bigger? (thus it would have to get bigger if the space between things is increasing, and there is no evidence of any other place compacting)

I guess, I don't understand how logically it can work to have an infinite universe. And I also agree that not much can truthfully be said for anything outside of the observable universe. For all we know there can be a door, that exits out of a Macy's bathroom stall in another dimension (harharhar) while it wouldn't be consistent with the rest of the universe, who's to say it couldn't be.

Our physical laws, are only laws, until we find an exception.

 

[tiny-tim]

Is infinity a constant?

Infinity, like any other number, is a constant.

Infinity and zero, unlike any other numbers, have the property that when multiplied by any other number, they are unchanged (eg 2 times ∞ = ∞, 2 times 0 = 0).

Does that help? ​

 

[Jake4]

yes, that helps.. but then my question still stands.

if infinite, is a constant. how can something that is infinite, get bigger (as I said, it must get bigger if there is no evidence of shrinkage anywhere else)

 

[bapowell]

yes, that helps.. but then my question still stands.

if infinite, is a constant. how can something that is infinite, get bigger (as I said, it must get bigger if there is no evidence of shrinkage anywhere else)

Imagine the universe to be an infinite rubber sheet with a grid marked on it. The expansion of the universe is then modeled as a stretching of the sheet -- the grid marks grow in size. That's what is meant by the expansion of the universe -- points locally at rest are pulled apart by the expanding space. The space can be (or not) infinite. It grows in size in the sense that the distance between points increases.

 

[Jake4]

Imagine the universe to be an infinite rubber sheet with a grid marked on it. The expansion of the universe is then modeled as a stretching of the sheet -- the grid marks grow in size. That's what is meant by the expansion of the universe -- points locally at rest are pulled apart by the expanding space. The space can be (or not) infinite. It grows in size in the sense that the distance between points increases.

this, I 100% understand. It makes perfect sense to me if the space is finite. The points on the sheet(as you put it) would be growing farther apart, but is that not connected to the sheet growing?

Unless there is a point of shrinkage, then it has to expand "somewhere"

if it is infinite (which logically, I can't see how it could be) then what is it growing in? You can't have something that is infinite in a space.

If these points are spreading in an infinite space, then there has to be a place where the points are coming together.


infinite universe=infinite bodies

if there are infinite bodies, taking up an infinite amount of space, then how can they spread without a point of shrinkage?

 

[Redbelly98]

If these points are spreading in an infinite space, then there has to be a place where the points are coming together.

No, there doesn't. Are you serious?

 

[Jake4]

No, there doesn't. Are you serious?

yes?...

Unless there is some high level law of physics or math that I don't know about:

if there is a constant size, and space between points is increasing, there has to be a location where the points are coming together.

if however (like I said) there is a finite size, that is variable. then yes, the spreading of points can be that the whole is increasing in size.

but as I asked and was answered, infinity is a constant.

There is nothing larger.

I don't see why this is so controversial.

I'm looking to be proved wrong here, I didn't just come here to flaunt my lay person's opinions. Tell me what, in what I have stated, is incorrect.

 

[Redbelly98]

There is no requirement for a constant size that I'm aware of. It is rather bizarre to even think about constant size when considering an infinite space.

 

[Jake4]

There is no requirement for a constant size that I'm aware of. It is rather bizarre to even think about constant size when considering an infinite space.

my point being, that infinite is a constant. which is what I asked before. Unless the person who answered was incorrect.

one infinity is the same as another (in fact logically, only one thing can be infinite right?)

so if infinity, is a constant itself. how could it get bigger.

a better question to ask is this: how would you define infinity.

 

[Redbelly98]

I'm pretty sure infinity cannot be considered a constant, but people more versed in mathematics than I may wish to respond.

 

[StandardsGuy]

People who think you can multiply infinity by something don't understand infinity.

 

[zomgwtf]

Ever hear of a countable infinite set? You can certainly multiply all the numbers in the set by a value... let's say a physical constant, and still have a countable infinite set of numbers.

1,2,3,4,5,6,7... is an example (I'm pretty sure) of a countable infinite set of numbes. Multiply that by two 2,4,6,8,10,12,14... they've gotten larger! WHAT THE HECK??!

I'm not sure if this applies to this discussion but I think the premise that distances within an infinite universe can't be expanding all over based on it being infinite is wrong.

 

[Jake4]

People who think you can multiply infinity by something don't understand infinity.

This was never even a part of the discussion.

Ever hear of a countable infinite set? You can certainly multiply all the numbers in the set by a value... let's say a physical constant, and still have a countable infinite set of numbers.

1,2,3,4,5,6,7... is an example (I'm pretty sure) of a countable infinite set of numbes. Multiply that by two 2,4,6,8,10,12,14... they've gotten larger! WHAT THE HECK??!

I'm not sure if this applies to this discussion but I think the premise that distances within an infinite universe can't be expanding all over based on it being infinite is wrong.

actually, that does kind of help.. That makes a little sense in this.

almost like, because it is infinite in nature, it already has enough space to expand the space between points. by definition, the infinite would have infinite space.

I have to say though, it still is a little puzzling. How it can have infinite space, with infinite bodies, yet can expand the space between these bodies.

infinite space, makes me think it has just enough room for an infinite amount of bodies.

 

[zomgwtf]

actually, that does kind of help.. That makes a little sense in this.

almost like, because it is infinite in nature, it already has enough space to expand the space between points. by definition, the infinite would have infinite space.

I have to say though, it still is a little puzzling. How it can have infinite space, with infinite bodies, yet can expand the space between these bodies.

infinite space, makes me think it has just enough room for an infinite amount of bodies.

This may help you:
http://www.math.vanderbilt.edu/~schectex/courses/infinity.pdf

I agree with you that at first it's quite puzzling.

As well this works for all sorts of functions, as long as there is a bijunction or cardinality involved (I think this is how you would word it), not just multiplication. Before accepting what I'm saying though you should wait for someone with higher understanding in maths to comment. I will admit I've only taken up to grade 12 calculus.

 

[Jake4]

This may help you:
http://www.math.vanderbilt.edu/~schectex/courses/infinity.pdf

I agree with you that at first it's quite puzzling.

As well this works for all sorts of functions, as long as there is a bijunction or cardinality involved (I think this is how you would word it), not just multiplication. Before accepting what I'm saying though you should wait for someone with higher understanding in maths to comment. I will admit I've only taken up to grade 12 calculus.

unfortunately I'l not yet math savvy enough to really understand most of that. but it does seem pretty interesting.

I'll look at it again in 6 months lol

 

[Hurkyl]

Rule #1 of infinity / the infinite -- take everything you've heard outside of a math class (and even some of what you hear inside of a math class) with a grain of salt.


There's a lot of bad knowledge out there, seemingly based on half-truths and the idea that the infinite is some mystical concept that eludes all hope of knowledge.

There's also a lot of good knowledge out there... but removed from context so that it becomes bad knowledge.

e.g. does 1/0 make sense?

In (ordinary) arithmetic, the answer is obviously not.

In complex analysis, 999 times out of 1000, the answer is that it obviously does, and is the element \infty of the Riemann sphere.

In calculus, most of the times 1/0 comes up are:

• As a limit form, in which case it signifies that the form is indeterminate -- the limit, if it exists, could be either of the elements +\infty and -\infty of the extended real line, but looking at the form isn't enough to decide between the three cases.
• In a situation where you really should have been taking a limit, but tried not to
• In a situation where you don't actually care about the value -- e.g. in an integrand, values at individual points don't matter, so it's irrelevant if a denominator is zero at some points. (Unless you're doing something like using a discrete measure where that set of points has positive measure)

But if you are more specific -- e.g. a limit form like 1/0^+ which signifies that 0 was approached from the positive side, then you know 1/0^+ = +\infty.

In set theory, the arithmetic of ordinals/cardinals is far too ill-behaved to even make sense of a division operation -- so you wouldn't even get to the point of wondering if it can be defined at 1/0.


Often, you see knowledge that is correct in one of the above situations being pushed as if it is the absolute truth in every mathematical situation... and that is bad.

 

[emc2cracker]

May I ask if the universe is infinite, then wouldn't we be able to see more and more stars say by taking another deep field picture of space? An infinite universe will be provable in time because none of the matter in space is currently traveling faster than the speed of light.

I think we should know the answer to this question in due time... no idea how long a wait would be considered long enough.

One thing I have a hard time grasping for the infinite universe is the existence of the CMB itself. Wouldn't the afterglow of the big bang have expanded far beyond the observable universe? Maybe someone can help me grasp this I"m sure there is an explanation I must be missing.

 

[Jake4]

May I ask if the universe is infinite, then wouldn't we be able to see more and more stars say by taking another deep field picture of space? An infinite universe will be provable in time because none of the matter in space is currently traveling faster than the speed of light.

I think we should know the answer to this question in due time... no idea how long a wait would be considered long enough.

One thing I have a hard time grasping for the infinite universe is the existence of the CMB itself. Wouldn't the afterglow of the big bang have expanded far beyond the observable universe? Maybe someone can help me grasp this I"m sure there is an explanation I must be missing.

well, logically we would never 'know' no matter how far we look, we can't ever prove it is 'infinite'

 

[emc2cracker]

well, logically we would never 'know' no matter how far we look, we can't ever prove it is 'infinite'

Lets suppose mankind lasts here for another million years for a second, and let's suppose at that time the deep image pictures show exactly the same material we see today. Wouldn't that debunk the notion of infinite universe? It would seem discovering additional material beyond what we currently see would be crucial proof in my mind at least if inflation faster than the speed of light can hold water at all.

Unless what we see is as far as we will ever be able to see period in every direction, that is a very depressing notion!

 

[StandardsGuy]

An infinite universe will be provable in time because none of the matter in space is currently traveling faster than the speed of light.

Incorrect. Though nothing can travel faster than c through space, the "fabric" of space is expanding. Everything past the visible universe (13.7Gly) is expanding away from us faster than c relative to us.

 

[Calimero]

Incorrect. Though nothing can travel faster than c through space, the "fabric" of space is expanding. Everything past the visible universe (13.7Gly) is expanding away from us faster than c relative to us.

Correction. Everything above z=1.4 is receding now faster then light. Although that redshift corresponds to the distance now of 13.7 GLY, it is much smaller than OU, which "edges" are now at around 45 GLY from us.

 

[Calimero]

Lets suppose mankind lasts here for another million years for a second, and let's suppose at that time the deep image pictures show exactly the same material we see today. Wouldn't that debunk the notion of infinite universe? It would seem discovering additional material beyond what we currently see would be crucial proof in my mind at least if inflation faster than the speed of light can hold water at all.

Unless what we see is as far as we will ever be able to see period in every direction, that is a very depressing notion!

You shouldn't be concerned about expansion speeds exceeding speed of light. It is inevitable. The rule goes that informations can't travel faster than light, and they don't.

 

[emc2cracker]

So with that great input I'm still slightly confused, are we going to be able to see more universe in the future or not? Surely the expansion isn't constant in every single vector? There must be some of the universe out there that will be exposed? I am reading Calimero's correction to mean that we will or should.

Thanks everyone this is like the wal mart of knowledge and I'm like a kid in the toy section lol.

 

[Calimero]

So with that great input I'm still slightly confused, are we going to be able to see more universe in the future or not? Surely the expansion isn't constant in every single vector? There must be some of the universe out there that will be exposed?

Nop, future is dark for astronomers. Less and less things to observe. Some astronomer in a very distant future may very well think that his universe consists of few galaxies. They will have hard time learning that their universe isn't static, and without apparent beginning.

 

[dgtech]

What makes you say that, the radius of the observable universe is constantly increasing the last years, and chances are this trend will continue. Here is a thought - the observable region may not be defined by time, but as an even increasing value might suggest it is defined only by the immense distances and the decay of photons. Better technology, as it arrives, gives more observational power and the radius of the observable universe is increasing.

 

[Dmitry67]

Even the radius of the observable universe is increasing the acceleration might be faster. So we will never see objects behind the so called cosmological horizon.

 

[dgtech]

It is curios that mainstream theoretical cosmology deems an incredibly unexciting future, no interstellar space travel, no intergalactic travel, no discoveries beyond the horizon, and yet enjoys so much popularity. I actually think that is one of the reasons - people have been trained to only believe in the ordinary, and as much as anyone would like endless possibilities in an endless universe, people still prefer the regular, the ordinary, the view we are a random occurrence, stranded on a rock, doomed to never escape and reach even the closest systems.

Thinking outside the box is regarded as something good, but when it comes to actually thinking outside the box, the mainstream quickly acts to protect itself and only people that think inside the box get support, while others, instead of support receive ridicule, which seems to have become an official scientific method of destroying others' credentials and boosting the mainstream, blindly ignoring all its flaws

Sometimes I wonder what would Einstein have say if he was still around, would he approve of the direction science has swung due to his personal contribution? Or would he criticize the narrow path science has taken, vigorously ignoring all other possibilities? And all the censoring out of anything that might suggest the faults of the standard model, which has deeply rooted into the mainstream scientific community. It is not a good thing when science becomes 100% theoretical and dogmatic in nature

 

[Calimero]

It is curios that mainstream theoretical cosmology deems an incredibly unexciting future, no interstellar space travel, no intergalactic travel, no discoveries beyond the horizon, and yet enjoys so much popularity.

I, on the other hand, think that it is very exciting. Think of it! Completely different universe for observers, but still the same one. For example, they can build model with static coordinates, and it will work fine for them. They would never be able to identify things like dark energy, big bang or even expansion itself, things that very much shaped their universe. So, it raises question, how many things are out there that had profound influence on us, but we have no way of knowing about them?

 

[CompuChip]

But this boring mainstream theoretical cosmology, as you call it, is currently the most convenient theory we have. It works well with the theories that we already have (and which are, contrary to the popular meaning of the word "theory" well tested up to great accuracy), enables us to make predictions, do measurements and fit data. And since the goal of your average scientiest is to describe, model and predict reality - not to dream about interstellar and time travel - this is very acceptable indeed. That it is too bad that it seems theoretically impossible to ever achieve this, even with advanced technology, is a completely different story.

 

[dgtech]

I happen to think there are more appealing directions in cosmology, theories that provide much simpler answers than the mainstream, crowded with hypothetical entities and assumptions theory, and also providing much more possibilities, unfortunately this is not the place to discuss them it seems :)

Mainstream means the prevailing current of thought, not necessary the right one. Historically, as I've already said, the masses have the tendency of being wrong :)

The mainstream is being heavily insisted upon, which shouldn't be needed if it was that much of a bullet proof theory. Also, alternative research hardly gets anything besides ridicule and colorful descriptions like crackpottery and such, hardly gets any support at all, and naturally will take a lot more time to evolve into a viable option.