Is the universe infinite?

[modest]

Originally Posted by tatwood106

And no I don't think the universe is a sphere, current theory says it is either flat or saddle shaped. Both of which would make it finite. Unimaginably LARGE but still finite and expanding.

The open universes (flat or saddle shaped) are generally considered to be infinite in spatial extent. This is not necessarily provable as we can never see beyond our local observable universe, but it is deductively true assuming the rest of the universe is pretty much like our local universe. This is commented on here:

Is the Universe really infinite or just really big?

We have observations that say that the radius of curvature of the Universe is bigger than 70 billion light years. But the observations allow for either a positive or negative curvature, and this range includes the flat Universe with infinite radius of curvature. The negatively curved space is also infinite in volume even though it is curved. So we know empirically that the volume of the Universe is more than 20 times bigger than volume of the observable Universe. Since we can only look at small piece of an object that has a large radius of curvature, it looks flat. The simplest mathematical model for computing the observed properties of the Universe is then flat Euclidean space. This model is infinite, but what we know about the Universe is that it is really big.

Frequently Asked Questions in Cosmology

And your question about what the universe is expanding into is commented on at the same site:

What is the Universe expanding into?

This question is based on the ever popular misconception that the Universe is some curved object embedded in a higher dimensional space, and that the Universe is expanding into this space. This misconception is probably fostered by the balloon analogy which shows a 2-D spherical model of the Universe expanding in a 3-D space. While it is possible to think of the Universe this way, it is not necessary, and there is nothing whatsoever that we have measured or can measure that will show us anything about the larger space. Everything that we measure is within the Universe, and we see no edge or boundary or center of expansion. Thus the Universe is not expanding into anything that we can see, and this is not a profitable thing to think about. Just as Dali's Corpus Hypercubicus is just a 2-D picture of a 3-D object that represents the surface of a 4-D cube, remember that the balloon analogy is just a 2-D picture of a 3-D situation that is supposed to help you think about a curved 3-D space, but it does not mean that there is really a 4-D space that the Universe is expanding into.

Do these quotes make sense? Is there anything that can be elaborated on?

~modest

[freeztar]

Originally Posted by tatwood106

So again, is there any theory for what is beyond the universe's boundaries?

No.

It's like asking "What is on the outside of the inside?". It doesn't make sense.
This isn't to discourage philosophy on the subject, but it should be known that science does not deal with intangible things such as no-space. The best answers coming from science, to the best of my knowledge, involve finite structures that "wrap around" to create an infinity. This is similiar to the balloon analogy. We can travel in any direction at any speed on the surface of the balloon and at no point can we claim a central location or an end point.

Since almost all of our information about the universe is based on light signals, we can never hope to know the truth at the "edge" of the universe. It's simply inaccessible.

[maddog]

Originally Posted by OneArmedScissor

Ok... I just got into a long discussion with a friend of mine as to whether or not the universe is infinite or finite.
I said it was sort of a mixture of both. Like a sphere inside itself. Or something you see off in the distance, but no matter how fast you run or travel, you'll never get to it.
His argument was that the universe was infinite... That it goes forever with no ends, etc.
Basically, my whole point was that it was neither, but shared properties of each (infinite and finite). His whole argument was that, "since you can never get to the end of it, that means it's infinite." Anyways, any inputs would be appreciated!

This is a convoluted problem as this thread implies.

1. First off, there has been a lot of "evolution" of thought regarding universe's size, BBT, etc. A lot of what has been said is from all sides.
2. Data from WMAP has been a reversal if not an overall revolution of thought of how the
universe is composed (new types of matter has been created - paradigm shift to account for it).

Said in the simplest of form, I think your answer might be closest to the truth (if there is a truth).

In the original BBT from Gamov, Bondi, et al was the presumption "everything" started
from one event (point). Implicit assumption with this was that the universe was
"closed". That there was enough matter to close the universe and eventually as Hawking
says "end in the Big Crunch". The original BBT back was finite-like.

WMAP changed all that. The data from WMAP now implies that the universe is accelerating
outward not "just" expanding. This forces a Hyperbolic geometry not Riemannian.

Another "monkey-wrench" was in late 60s - 70s when Wheeler proposed the notion of
"Bubble" universes expanding in a Multiverse, so that even if our universe were finite,
the Multiverse would be infinite. -- Beginning of his Quantum Foam idea.

From then on BBT models didn't make the assumption of finite expansion. Instead what
papers I've read talked of an arbitrary expansion. In some of the papers in the concluding remarks
were speculation of this expansion embedded whithin something else. Even Hoyle's
reinvented Steady State Theory (I got to meet him in a talk at Indiana University 1976)
before he retired spoke of such an embedding (ie, finite & infinite). I am speaking of the
period before Alan Guth's work on Cosmological Inflation (pre-1980).

So EWright is somewhat correct that BBT doesn't require finite (not any more). It just
doesn't state either way anymore. Current discussion of finite was thrown out with the
proverbial "bath-water" when Closure is no longer considered likely.

To also speculate what is "beyond the boundary" (of expansion) is on unfounded turf.
You can not really go there with any authority. So whether is even there or not is beyond
your purview. With that I kinda' go along with JA Wheeler and consider Bubble Universes, Multiverse, etc.

maddog

[tatwood106]

Thank you everyone for your replies, I learned a few things and as you pointed out if there is no way to observe, measure or quantify something then there can only be speculation and science does not operate on speculation. I should have deduced as much myself.

It also seems paradoxical that the universe could be infinite and yet have a definable shape, unless the point I am missing is that it is only infinite in certain directions.

Anyway thanks again, I only recently began to ponder what might be beyond the universe and the finite/infinite nature of the universe and sought the knowledge and advice of those that would know and it appears I came to the right place.

And finally I am not a very educated person and want to thank everyone for explaining things in a nontechnical way without sounding condescending. Your answers were intelligent but easily understood by a layperson such as myself. All who replied have proven not only there intelligence but also there humanity.

Live each day as the first and last, for they truly are.
Todd

[arkain101]

I thought that you might enjoy reading a bit through this topic. I took some time to explain some things to consider when thinking about the universe

http://hypography.com/forums/266691-post55.html

[HydrogenBond]

There are several things that need to be understood to better answer this question. There is a difference between a mental construct and tangible reality. For example, science works under the assumption that time is a reference variable and not a thing. While space is not a thing like the aether, but the void between things. Infinity is a mathematical construct and not a thing since how can you measure something without any boundaries. But on the other hand, there are many real and tangible things like mass and energy due to effects these cause.

Mental constructs only exist in the human mind. They are useful because they can be used to orientate the mind, so we can correlate and explain the behavior and the interactivity of the real and tangible things. In a real and tangible sense, the universe is the tangible stuff. But when we combine the real stuff with constructs we are mixing the tangible with the intangible.

Let me give an example of this mind effect. Don't take this example the wrong way, but it will help one see the mind effect creating by mixing real and tangible with constructs which exist only in the mind. A unicorn is not real, but it could be used as a mental construct to give a particular structure to flesh and bones. If I then say the unicorn is running, one can visualize this in the imagination. I am combining running, which is real, with something that is a construct. So what I am describing is now partially real, even though it is still imaginary. The effect is analogous to the cute babe near the magician (running) distracts the mind with something real, while the magician uses his construct (unicorn) to create magic. But if you look behind the scenes, it is the construct of the mechanism that creates the final effect. It is not the disappearing hat that is generating the construct mechanism.

That being said, to define the size of only the tangible universe and not the construct-tangible universe, we need to use only real and tangible things and leave out all or most of the constructs. It is a boring magic show without construct mechanisms.

The real and tangible restraints implies the expansion of space-time can't be used because it has the property of a unicorn running. How can two none real things expand or contract? We need to restrict ourself to matter and/or energy because these are real and tangible. As a side note, matter is being turned, buy some, into space-time effects. This amount to horses becoming unicorns, which is a disturbing trend.

Let us get back to the universe. Energy travels at C, which is real. C is independent of reference, which is real. So far so good. The second premise, gets rid of space-time expansion or the unicorn running, because energy does not care when it comes to the unicorn's reference. We have energy chugging along at C, ignoring the unicorn, although wavelength will change. The question is how far can C go in the amount of time we have? Unfortunately, this question includes the concept of time which is a construct, sort of an unicorn horn being added to the horse we are trying to create. But it is mostly horse but we need to get rid of the horn.

The approach I took to remove the unicorn's horn of time, was to see if it was possible to define time in terms of tangibles. The idea was not simply translate the existing construct, into a new concept for a pixie, but redefine what is meant by time so it is tangible and subject to measurement. The very idea of trying to remove the unicorn's horn of time, to create a horse is met with resistance, because the unicorn can do many more things, even mutually exclusive things.

Here is one line of thinking for removing the unicorn's horn of time. Every photon carries with it a time associated effect; frequency. Photons did this even before humans developed the time concept, yet frequency is a tangible manifestation of the concept common to all photons. This is a way to turn the unicorn's horn, into something tangible, since now time is somehow connected to energy potential. I understand a unicorn without a horn looks funny but bare with me.

Getting back to the universe, we can use energy at C to define distance, because the speed of light is not effected by the changing reference as the unicorn runs. Although C is not effected, the frequency or time aspect of energy do show an effect. What we notice is energy red shifting or higher energy photons being turned into lower energy photons. This implies time's potential is being used up or lapsing. If time lapses quickly, the unicorn appears to running faster. It is the running that is key, in this case a tangible horse is what is running.

It is likely tangible time (energy related) charged out the gate and was galloping at the beginning of the universe, with time potential used up quickly, to create matter that is still around today. Time now appears to be walking, by comparison, although data suggests time appears to trotting opening its gait. The time potential curve is not linear. But C was chugging along paying no mind to the change in time potential.

The upper limit of the tangible universe's size is equal to its estimated age times the speed of light. But that estimate uses constructs. Time potential could have been burning the candle at both ends, especially at the beginning, using up the time potential quickly, thereby making the universe appear older than it looks.

[arkain101]

In a real and tangible sense, the universe is the tangible stuff.

What is tangible about wave-particle duality? At what point does the universe (beyond our stimuli interpretation) become tangible? (in your words?)

[lemit]

Hey, this is some kind of Zen question, isn't it?

Merriam-Webster seems to define universal as infinite: universal - Definition from the Merriam-Webster Online Dictionary

So, could we also ask if infinity is universal? I had lately fallen in love with the question, "If parallel lines meet in infinity, where do they go after that?" Researching this post, I found that has been approached as a serious question. We are approaching Homer Simpson's circular theological question, "Could Jesus microwave a burrito so hot even He couldn't eat it?"

Can we define the limits of knowledge in such a way that the definition can not be circumvented by theory?

Can we accept that our knowledge has boundaries? Those boundaries are not fixed. Each new discovery changes them. But an expanding boundary is still a boundary. I don't think the words "infinity" and "universe" mean more than that. Or less.

-lemit

p.s. Zen, Jesus, and theoretical physics in 150 words!

[maddog]

Originally Posted by tatwood106

So again, is there any theory for what is beyond the universe's boundaries?

The only theories I have heard of are by John A. Wheeler of Bubble Universes embedded
in a Higher Dimensional Multiverse (we are in one of those Bubble Universes).
Wheeler came up with this in the 70s I think.

maddog

[maddog]

Originally Posted by lemit

Zen, Jesus, and theoretical physics in 150 words!

Lemit,

Those words {Zen, Jesus, and theoretical physics}, go together don't they ???

maddog