Does the UNIVERSE have a boundary or OUTER LIMIT?

Re: does the universe ever end?

wat wrote:

i think the universe has no beginning or end because nothing is impossible nothing has to be something so there was no start and there will be no end and the universe doesn't end because if you got to the finnish well what's there???

Well, that is possible. However, we do have a lot of evidence for the big bang theory, which suggests that our universe did have a beginning. However, you are right that it could not be created from nothing, and this would imply that there is something...some kind of framework more basic than matter and space... before the universe that has, and will continue to exist, forever.

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Re: does the universe ever end?

stuh505 wrote:

However, you are right that it could not be created from nothing

We can't say that with any degree of certainty, or even probability. Our concept of time, and therefor cause and effect, is not even certain outside of the event we call the Big Bang (our Universe).

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Gee- it just shows the value of being in the company of experts who can give definitive answers to questions of momentous importance. This isn't called Able To Know for nothing folks.

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Re: does the universe ever end?

rosborne979 wrote:

stuh505 wrote:
However, you are right that it could not be created from nothing

We can't say that with any degree of certainty, or even probability. Our concept of time, and therefor cause and effect, is not even certain outside of the event we call the Big Bang (our Universe).

We assume that the concepts of time and causality were still in effect yesterday (as they are today) by simple induction, and by the fact that it is a much simpler and hence more likely explanation than all of history being some kind of fantasy illusion that was created by yourself this very moment. We should continue to make this induction back as far as possible until we have reason to doubt that it is no longer true. Indeed before the big bang theory was proposed, the theory was that the universe had an infinite nature going back.

Special relativity has shown us that time is (apparently) only defined relative to energy (although it should be noted that it does not provide any conflicts when it comes to causality....). This provides the ONLY reason to doubt the concept of time before the big bang. However, a simple proof by contradiction can be used to show that this does not actually provide any logical reason to doubt that the concept of time held before that instant.

The big bang is a theory to explain the existence of energy. If there was no such thing as energy before the big bang, and the results of special relativity still held, then indeed there would be no such thing as time...because by definition of the system, time is relative, and there would be nothing to measure time by.

However, this cannot be true, because the very occurrence of the big bang IS a change occurring (either spontaneously or gradually) when there was no energy and no time. Therefore, by contradiction, the above assumption is false...and having removed all reasons to possibly doubt that time held before the big bang, by induction, it is most logical to assume that it did.

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That's right stuh. You won't go far wrong sticking to that.

With no energy and no time something must have happened to cause the chain of events that led to this lot. The "Big Bang" seems a quite appropriate term to describe it in one go if you are in a hurry to catch a bus.

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spendius wrote:

That's right stuh. You won't go far wrong sticking to that.

With no energy and no time something must have happened to cause the chain of events that led to this lot. The "Big Bang" seems a quite appropriate term to describe it in one go if you are in a hurry to catch a bus.

Actually, my post was disproving what you are saying now...

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Re: does the universe ever end?

stuh505 wrote:

We assume that the concepts of time and causality were still in effect yesterday (as they are today) by simple induction, and by the fact that it is a much simpler and hence more likely explanation than all of history being some kind of fantasy illusion that was created by yourself this very moment. We should continue to make this induction back as far as possible until we have reason to doubt that it is no longer true.

We already have a reason not to use your proposed (as logical, yet incorrect) conclusion.

The Big Bang theory encapsulates physics as we know it within the bounds of our Universe. We know that our spacetime is part of our physical Universe. We know nothing about what is outside of this Universe, there may be Universes contained within Universes all with isolated spacetime realities similar to ours, or they may be non-spacetime realities in which causality is meaningless. All we know for sure is that based on the mathematics used to describe Big Bang theory and physics, our Universe is isolated and encapsulated, it is completely prescribed by internal physics.

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rosborne, I agree that we cannot see outside of the bounds of our own universe, and it could be just about anything. However, I believe my proof does correctly restrict the set of possibilities to those which have some notion of time and causality, because the proof itself is not based on the physics of our universe but only on the principles of logic, which do apply outside of the domain of our universe.

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stuh505 wrote:

rosborne, I agree that we cannot see outside of the bounds of our own universe, and it could be just about anything. However, I believe my proof does correctly restrict the set of possibilities to those which have some notion of time and causality, because the proof itself is not based on the physics of our universe but only on the principles of logic, which do apply outside of the domain of our universe.

If we know that our spacetime is contained within our Universe (which we do), then how is it logical to conclude that the same conditions extend outside the system?

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For what it's worth, the universe--as I define it--is not a "place" in which things happen. It IS those happenings.
I recall an A2K thought experiment regarding the outcome of our being able to travel for whatever time was needed beyond the limit of the universe. My answer was that we can't. Since we ARE our universe, where ever we go we take the universe with us.

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rosborne979 wrote:

If we know that our spacetime is contained within our Universe (which we do), then how is it logical to conclude that the same conditions extend outside the system?

I have specifically made a point of NOT assuming the same conditions outside of the universe in my previous two posts, so I'm not sure why you are even saying this.

Anyway, we do not know that "spacetime is contained within our universe either"...a fact that is evidenced by several different "layers" of alternate theories that divide the scientific community, as well as a preposterously low confidence in some of the basic assumptions underlying all theories at present, such as the homogeneous and isotropic properties of space made from local observations which are assumed to eliminate the possibility of the universe having any kind of an edge. I could just as easily take a zoomed in photograph of a dinner plate and conclude that, since the entire image was white, the plate must be infinite.

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Does your conceptualization/idealization extend to our sensory amplifications of such things as space probes and/or electron microscopes let alone out indirect sensory amplifications via such disciplines as physics? If so the pretext of "wherever we go we take the universe with us" is open to question.

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JLNobody wrote:

For what it's worth, the universe--as I define it--is not a "place" in which things happen. It IS those happenings.
I recall an A2K thought experiment regarding the outcome of our being able to travel for whatever time was needed beyond the limit of the universe. My answer was that we can't. Since we ARE our universe, where ever we go we take the universe with us.

Well, technically it would not be possible to travel beyond the limit of the universe given infinite time anyway because it expands much faster than the speed of light, and special relativity prevents matter from traveling faster than the speed of light...

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He's referring to the perceptual.

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Chumly wrote:

He's referring to the perceptual.

Well then, I guess he is just saying that his definition of universe extends to the space that contains matter and energy...which is in perfect agreement with the formal definition!

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Stuh,

You started off by referencing the Big Bang theory, which is a mathematical model which carries certain rules (such as spacetime being contained in this Universe)...

stuh505 wrote:

Well, that is possible. However, we do have a lot of evidence for the big bang theory, which suggests that our universe did have a beginning. However, you are right that it could not be created from nothing

You concluded that the Universe could not be created from nothing, which is an incorrect conclusion based on the Big Bang theory. I pointed out that spacetime was not an assumption outside of our Universe.

You responded with...

stuh505 wrote:

We assume that the concepts of time and causality were still in effect yesterday (as they are today) by simple induction, and by the fact that it is a much simpler and hence more likely explanation than all of history being some kind of fantasy illusion that was created by yourself this very moment. We should continue to make this induction back as far as possible until we have reason to doubt that it is no longer true.

Implying that you thought it was logical to break the bounds of the mathematical model to extend the conditions within our Universe outside of our Universe. I pointed out that this is non sequitir.

You responded with...

stuh505 wrote:

rosborne, I agree that we cannot see outside of the bounds of our own universe, and it could be just about anything. However, I believe my proof does correctly restrict the set of possibilities to those which have some notion of time and causality, because the proof itself is not based on the physics of our universe but only on the principles of logic, which do apply outside of the domain of our universe.

You have not restricted any set of possibilities. You have made a wild assumtion. Why do you think it is more reasonable to assume present conditions exist outside of our Universe than to think that different conditions exist outside our Universe, especially when the model you started with (Big Bang) clearly encapsulates this Universe.

Then you say...

stuh505 wrote:

I have specifically made a point of NOT assuming the same conditions outside of the universe in my previous two posts, so I'm not sure why you are even saying this.

Then I must be misunderstanding your posts.

stuh505 wrote:

Anyway, we do not know that "spacetime is contained within our universe either"

Yes we do. You started this discussion by referencing the Big Bang model (see first quoted post). That theory is a mathematical model. If you want to switch your argument and talk about some other model, then maybe things are not contained, but within the Big Bang model, spacetime defines our Universe.

stuh505 wrote:

I could just as easily take a zoomed in photograph of a dinner plate and conclude that, since the entire image was white, the plate must be infinite.

We are talking about a mathematical model of the Universe here (the Big Bang), not about the Universe itself.

If you want to talk about the Universe based on purely observational intuition (like a plate), then I guess you can make up any assupmtion you like, but then you can't make 'logical' conclusions.

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rosborne979 wrote:

Big Bang theory, which is a mathematical model which carries certain rules (such as spacetime being contained in this Universe)...

Please clarify what you mean by the word "contained within." Do you mean that spacetime exists within the universe, or that spacetime does not exist outside of the universe? Because the big bang theory only talks about what is inside the universe, it cannot be used to make statements about what is outside the universe.

stuh505 wrote:

You concluded that the Universe could not be created from nothing, which is an incorrect conclusion based on the Big Bang theory. I pointed out that spacetime was not an assumption outside of our Universe.

In my proof I started without making any assumption of time before the big bang. I showed that is an oxymoron in my proof by contradiction, proving that in fact time (in some form) must have existed before the big bang. So no, I did not assume the presence of spacetime -- I proved it.

Quote:

stuh505 wrote:
We assume that the concepts of time and causality were still in effect yesterday (as they are today) by simple induction, and by the fact that it is a much simpler and hence more likely explanation than all of history being some kind of fantasy illusion that was created by yourself this very moment. We should continue to make this induction back as far as possible until we have reason to doubt that it is no longer true.

Implying that you thought it was logical to break the bounds of the mathematical model to extend the conditions within our Universe outside of our Universe.

No, the above paragraph was merely stating the importance of logical induction in regards to this type of discussion. I was making no specific claims at all.

Quote:

You have not restricted any set of possibilities. You have made a wild assumtion. Why do you think it is more reasonable to assume present conditions exist outside of our Universe than to think that different conditions exist outside our Universe, especially when the model you started with (Big Bang) clearly encapsulates this Universe.

Once again, that is not an assumption, it is a conclusion reached by a proof by contradiction.

Quote:

We are talking about a mathematical model of the Universe here (the Big Bang), not about the Universe itself.

If you want to talk about the Universe based on purely observational intuition (like a plate), then I guess you can make up any assupmtion you like, but then you can't make 'logical' conclusions.

A mathematical model IS based purely on assumptions! Sure, the math is correct, but the entire model is balanced on the initial assumptions that you assumed to make the model...assumptions which, as I have pointed out, have serious cause to be doubted.

For instance, let us take a look at some of the primary assumptions made by this mathematical model:

1) The existence of spacetime. We don't actually really know that spacetime exists. It's something we concocted to explain the bending of light. However, it is not the only explanation we have concocted to fit the bill -- there is also the theory of gravitons. The only evidence for either theory is the fact that light bends from gravity. In other words, there is no specific evidence for any theory. This is something I have pointed out to you numerous times in the past but has never been acknowledged.

2) The universe is homogeneous and isotropic. This means that there is no edge to the universe no matter how far you travel, and the distribution of energy (taken over a large local window) is exactly the same at all points in the universe. Note that this is an INITIAL ASSUMPTION and NOT a conclusion of the theory! We are simply ASSUMING that there is no edge to the universe to begin with. Considering that most people logically think it makes more sense that the universe DOES have an edge, I think it is pretty wacky to just ASSUME with confidence that it DOES NOT. Why do we make this observation? Simply, because when we look at the sky with big telescopes it appears to be the case. Well, I wouldn't expect us to be able to see any traces of the edge. In fact, if it is expanding faster than the sped of light, then it would be IMPOSSIBLE to observe anything but a homogeneous and isotropic universe even if we are not in one!

In fact, if you remove the homogeneous and isotropic constraints, a much simpler model of the universe emerges: an expanding VOLUME, rather than an expanding HYPERSPHERE. This makes a HECK of a lot more intuitive sense.

3) Do not forget to keep in perspective what evidence is used to design a theory. we simply observe that matter and energy appears to be moving apart. This does not give us rational cause to believe that it actually came out of an infinite singularity point. We cannot really saw how close together things once were. That part of the theory is faith-based, and is no different than believing in a god, because there is no evidence to support it. Also, it is faith-based to say that time did not exist before the big bang, because the theory does not extend to encompass events before the big bang, nor does it provide any explanation for how/why it occurred in the first place. Clearly there is a lot of ambiguity there, and if you choose to believe that it all makes sense and is understood perfectly correctly now, that is your religion -- not science.

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Rosborne, I AM talking about a model of the universe itself. And Stuh, you missed my point. I was talking about a "thought experiment" in which we COULD travel to the limits of the universe. My comment was that EVEN IF WE DID get there (which I agree with you: we can't) we could not make exit because we ARE the universe. To leave "the universe" would be tantamount to leaving ourselves.

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stuh505 wrote:

In my proof I started without making any assumption of time before the big bang. I showed that is an oxymoron in my proof by contradiction, proving that in fact time (in some form) must have existed before the big bang. So no, I did not assume the presence of spacetime -- I proved it.

Ha, very funny.

I'll have to tell the guys at the Harvard coffee shop the good news, extra-bang models have been proven. Smile

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Stuh,

Two points:

1) Technically it's not CMB being examined that is revealing structure where none should exist in our models - indicating that the presumption of the homegenity of the entire Universe at extremely large scales should be questioned. It's a survey of 150,000 gaxalies as part of the SLOAN sky study. Part of the 'great wall' has been shown to have fractal structure out to 200 million light years. Current theories compliant with the inflation relativity flowing on from the big bang limit structures to less than 30 million light years. The limit in size comes from an accepted age of the observable universe as being around 13.8 billion years and a relativistic expansion after inflation. Apparently the mathematics works out a hard limit on structures forming, unless there are hidden variables operating.

We see definite fractal structures which hard and fast implies there are more hidden variables at work to be explored. Stay tuned!

2) Technically you can't pass information faster than lightspeed in a relativistic framework. But who is to say either i) spacetime is entirely relativistic everywhere or that ii) using uber-science we may not be able to create a non-relativistic framework for a brief period of time in a finite location. That might make extraordinary travel as we percieve it possible outside the constraints of relativity today.

* * * * * * * * * * * * * * * * *

Personally spectulation about edges and boundaries, when the underlying topology of reality itself is still being fathomed, is a long bow to draw. There MAY be an infinity hidden somewhere - and they are always real problem children to deal with in any scientific framework. Models based on numbers rather than infinities work much better in science! Bury an infinity and you're only borrowing trouble...

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Does the UNIVERSE have a boundary or OUTER LIMIT?

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