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Is the universe infinite?


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Ok, here is the definition of infinite I mean. I am located on earth, I leave earth and travel in any direction in the universe and I am traveling far faster than the universe is expanding. No matter how fast I travel or how far I would never reach an edge or boundary of the universe; I would keep traveling forever there would be no end to the universe, it would be infinite. I would however still be in space and there would still be time.

Now if the universe if finite and I make the same trip I would eventually reach the edge of the universe's expansion. If I keep traveling out past that boundary, what would I pass into? Or without the construct of space/time is there no way either physically or mathematically to predict what I would encounter?

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Ok, here is the definition of infinite I mean. I am located on earth, I leave earth and travel in any direction in the universe and I am traveling far faster than the universe is expanding. No matter how fast I travel or how far I would never reach an edge or boundary of the universe; I would keep traveling forever there would be no end to the universe, it would be infinite. I would however still be in space and there would still be time.

Now if the universe if finite and I make the same trip I would eventually reach the edge of the universe's expansion. If I keep traveling out past that boundary, what would I pass into? Or without the construct of space/time is there no way either physically or mathematically to predict what I would encounter?

 

I tried to communicate that you idea of what the universe is like is based on your senses. This is the trouble.

 

I am gathering You expect that the universe is like a sphere, because you are using your world view acquired by your senses..

 

How do you know you are not on the edge of the universe already?

 

Do you think you are at the center?

 

Where is your location?

 

Accroding to scientific theory, special relativity would describe that if you were to travel in a real ship, trying to "reach the edge of the universe", as you speed up more and more and more getting ever closer to the speed of light, the universe would become shorter and shorter in the direction that you are traveling. So as you travel, very fast it would take barely any time relative to your observation to travel this earlier percieved vast distance.

 

 

 

Muon Experiment: Relativistic, Muon-Frame Observer

 

 

However, what you see before you start your journey is a very very old representation, and it is not what you are going to observe when you reach those destinations.

 

I actually need to brush up on all of this myself... :eek_big:

 

 

I don't expect you would ever reach any sort of end to a universe, in the sense that stars and suddenly started dissapearing and you headed off into the void.

 

I really dont expect that nature works like we imagine it 3 dimensionally.

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I didn't mean to get into a discussion on the physics of space travel, just presenting a simplified example to illustrate the definitions of infinite and finite. If analyzed the major flaw with the example as that as the speed increases so does the mass and if you could actually obtain light speed your mass would be infinite and would require all the energy in the known universe just to keep moving.

 

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.

 

As there are galaxies moving away from us in all directions It is unlikely that we are at the edge of the universe. At the edge if space/time is being created then there would likely be fluctuations and deformations of both, can't say that I have noticed either.

 

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

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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

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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.

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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. :hihi:

 

maddog

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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

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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.

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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!

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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. :naughty:

 

maddog

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  • 4 months later...

Hmmm... :rolleyes: ;) Good question. After avidly watching "The Universe" on the History Channel for sometime now, I think it's safe to say that the 'local' universe is, in fact, finite & very likely flat to some degree--yes, flat (mind you, this is only what I've learned by watching the programme--it is not plucked out of thin air). However, beyond our 'local' universe, the entire cosmos, per se (& beyond), I'd like to assume hopefully correctly, that it is infinite, say, for instance, once all matter (gasses/chemicals, asteroids, moons, planets, stars, galaxies, clusters, etc., etc...) disperses to where there really is nothing left but black or blank space, being made up of what is known to astronomers as "dark matter." This is the space between moons, planets, stars, galaxies, clusters, etc., which appear to have nothing in it...just black space. "Most of the stuff in clusters of galaxies is invisible and, since these are the largest structures in the Universe held together by gravity, scientists then conclude that most of the matter in the entire Universe is invisible. This invisible stuff is called 'dark matter'." (found here :D : Dark Matter - Introduction) & a lot of interesting stuff about our universe can be found w/in this site, "NASA's Imagine the Universe!" (Imagine The Universe! Home Page). Scientists' studies are also infinite (ha-ha), & they continue to contemplate & deliberate on exactly what this "dark matter" really is or what it's made up of (or NOT made up of). But so far, it would seem that this is the closest yet they've found to, at least, describing it. So, yes, I would agree that questions may never be fully answered w/ any certainty, & I would subscribe to the possible fact that the Bigger Universe beyond our tiny universe is at least forever if not infinite. :phones:

 

These questions may never be answered with any absolute precision but the standard model views our local universe as a finite sphere. Nevertheless, our local universe may be contained within a larger megauniverse which may be infinite in nature. Hopefully this definition does not confuse things for you.
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The size of the universe depends on what we call the universe. If we are talking about the matter/energy or substance of the universe, that substance appears to occupy finite size or else we could not be able to set an age to the universe. If we take the largest number we have, to approximate infinite size, and divide by the age of the universe, we would get a speed much greater than C, which is not possible. The age is describing something finite.

 

If we were living in a C reference, an infinite distance universe would be possible because it would appear to be contracted in a point, that would take an instant to traverse at the speed of light. In that reference, an infinite universe would be possible since it does not violate C. A finite universe would then have to be smaller than a point/instant. If we were on this forum in the C reference, the debate would be, could there be a universe that exists that is smaller than the limiting point instant? The answer is yes, but it would be hard to prove at C.

 

To be able to prove this theoretically universe, that is smaller than a point (C reference) we will need to slow the C reference to below C (expand space-time) so the point appears to expand and break apart into detail. It would look sort of like a point singularity, expanding as we zoom to maximum space-time expansion. Now we can see the finite universe that had been contained in the point within the C reference. Since only the microscope magnified space-time reference, and we are still at C, we know infinite is still there as well as places smaller than that point called infinite.

 

Conversely, if we start in our current finite reference and telescope our reference by contracting space-time (moving toward C reference) the outer boundary of the visible universe would get closer. But since matter can't go all the way to C, we would stop at a finite line of sight, with infinite always just out of reach. Matter can not extend to infinity precluding an infinite universe that contains matter all the way to infinity.

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Of course the answer depends on the definition of "universe."

Mine is: "All there is both within and beyond or cosmic event horizon."

But "all things that exist" is a different set than the "space" in which all things exist.

Space must be infinite. Why? Because the alternative, an "end of space" is a no-brainer absurdity. Think about it. What boundary could possibly be an "end of space" in the universal sense? (Not speaking of geometric shapes defined by their "walls" etc.)

So if you do posit such a wall/boundary to space, what is it made of and what lies on the other side? See what I mean? An ill conceived concept!

 

Michael

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Think about it. What boundary could possibly be an "end of space" in the universal sense? (Not speaking of geometric shapes defined by their "walls" etc.)

So if you do posit such a wall/boundary to space, what is it made of and what lies on the other side? See what I mean? An ill conceived concept!

Michael, there is no "physical boundary" to space in the 3D universe you imagine. There is a boundary, however, but that boundary exist in time, not in space. If you look at the furthest reaches of space, you'll see that boundary at a distance of around fifteen billion light years. And even if you were to magically be instantly transported to that boundary, the universe will look exactly as it does from Earth in all directions, with a boundary of fifteen billion light years from that point. If you look at where the Earth is supposed to be, the Earth's location will appear to you as the Edge of the Universe, with only CMBR emanating from that spot. A little closer, and you will see pulsars and all kinds of weird stuff existing in the early universe coming from close to Earth. This is clearly not the case. And it is not the case, because the universe is an unfolding hypersphere, not a flat 3D structure with a physical boundary.

 

Yes, the universe has a boundary. But that boundary exist in time, not in space. And there's no getting away from that. However hard you try, however fast your spaceship travels, that boundary will always be fifteen billion light years away from you, and it will recede from you at the speed of precisely one light-year per year. Imagining what that boundary will look like is fruitless, because from that very same spot, the universe will look the same as it does from here, or any other spot in the universe you'd care to sample. There's an easy way to get there, though. You don't even have to move an inch. You can sit right there in your chair, behind your computer. All you have to do is to invent time-travel, and travel 15 billion years back in time. Because that border you see, that fifteen-billion light-year distant edge from whence you see the CMBR, was actually each and every spot in the universe, simultaneously.

 

I'm sorry if you don't get it, though. I admit that it is a bit of a mind-bender. But its the only explanation currently fitting the data.

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