A difficult question.....

[MeteorWayne]

This thread has produced very little scientific discussion. Mostly wild and uninformed speculation. If it doesn't get more closely aligned within the subject matter of this forum (Space Science and Astronomy) it is destined for a trip to The Unexplained. Please lets talk real science here.

Thanx

Meteor Wayne

i must be missing something... it wouldn't be the first time...

i arrived at this thread from the space.com news headlines... reading the initial message, more than once, i don't see anything indicating that "real science" was a requirement for replying to the original message or participating in this thread... in fact, the original message even states something to the effect of letting the imagination flow...

Well, the Space Science and Astronomy forum is a REAL SCIENCE part of Space.com. For unsubstantiated speculation, we have other forums.

 

[Saife]

Certainly space has certain boundariens, but to our amazement its vastness is so much that it is still expanding at an accelerating rate and yet we havenot reached the limits. And the catch is speed of ligh,t we can only see that from where light had reached us and we cant say that if we cant see something its not there. I do firmly believe that one day we will discover the boundaries and then we will reconcile all the theoreis we had made about it infinite universe.

 

[metastring]

DELETED

Right...?

 

[rubicondsrv]

(More) Scientific speculations about boundaries of Universe?
(Physicallist, metaphysic or phylosophic...
modelling, free speculating or to pare balloon...)
------------------------------------------------------------------------------------------------------------------
To push reset button, refresh or survey of ideas (and requirements):

- What's Universe, universe, boundaries of it and observable vs. nonobservable regions of.
(definitions, statements, arguments, consequences)

- Over there
(assumptions, thought experiments, interpretations)

- Limits of our mind: perception, senses, meaning
(complementary discussion through reflection)
----------------------------
Let me think!

Universe - whole existing everything, that is ain't over / outside Universe
(Set theorists murmur slightly: Set of Everything lead to paradoxes)

universe - observable (by ourselves) regions of Universe
(observable, that is causally relationship between ourselves and things in regions...
who, when, whereby? human, tense-present-future, what's causality?...
relationship between observable and nonobservable regions... /for example in set sense/)

boundaries - partial (according to direction or completness) or total causality separation of regions
(existence, classifications /for example: spacelike, spacetimelike, timelike, other: absolute zero temperature/)

...etc.
-----------------------------

That's what You want to get at, Mr. Quirk?

????????

 

[lafeesfalsa]

So space is basically endless. More or less. Well the way scientists portray it is that the Universe is so incredibly complex and infinite. This is probably true but I want to know whether or not the Universe has boundaries. And if you were to collide with those "boundaries" (if any exist) then what would happen if you popped out the other side. Just a nice happy endless void? What forces created the Universe (as in the matter and energy, not the explosion) and could there be a universe WITHIN a universe? Is it just an endless cause and effect relationship? (the Universe was a product of something bigger?) Don't worry, I don't expect a straight answer to this, just personal speculation. Have fun! :|

The Universe is not complex. It is however finite. Point of fact, nothing can be 'so' infinite. Because bipeds are incapable of comprehending this, even the most cabalistic geniuses among us, does not render the universe 'complex.' Hidden, indeed but complex; not in the least. You obviously are looking for answers on faith or are fair to spark an argument about it. Shakespeare does a better job at explaining our existence than some primordial nincompoop scribing on walls and animal skin two thousand years ago. Indeed, the Big Bang makes six days seem an eternity which according to biblical script makes God appear apathetic or lazy at best.

You, as sure as I breathe now, will never, ever know the answers to these questions. Perhaps this inescapable truth is what has driven you to faith.

 

[metastring]

If there were a boundary to space-time, it would be some sort of 3-manifold. But what would that be, locally? Two space dimensions and 1 time dimension, three space dimensions without time ? Nothing makes good sensefroma physical perspective.

Some say event horizon of black holes are good example for 2s+1t dimension boundary... :?:
Alas, come in my mind only bizarre wasp examples for 3s dimension boundary now, but possible...

Overstepped 3+1 dimension manifold (general relativity) model, that will fill the bill...

 

[metastring]

That's what You want to get at, Mr. Quirk?

????????

Mr. Quirk (MeteorWayne) would like to level up content in this topic.
Whether, He thought on above approach?

 

[MeteorWayne]

That makes about as much sense as what rubicondsrv replied to, so I will use his response.

?????????

BTW, calling people names (such as Mr Quirk) is not permitted in the SDC forums. Please read the Guidelines.

 

[metastring]

That makes about as much sense as what rubicondsrv replied to, so I will use his response.

?????????

BTW, calling people names (such as Mr Quirk) is not permitted in the SDC forums. Please read the Guidelines.

OK. Posteriorly.

I'm sorry for Mr. Quirk. (I might have known about touchy users...)

Instead of quirk at least I have a try to conclude some (in my opinion valuable) ideas from content of topic.
(in short sketch because of readable size and my poor english)

If You make public something here, then your criticism will be rightly. (I'm sorry, I'm rough.)

Do we look into my reply...? (in clearable)

 

[MeteorWayne]

I'm not a touchy user. As a moderator, it's my job to educate the new users to the rules and decorum expected here.

The rest of your post makes no sense, so I have no comment. I get that could be because of the language issue. We do our best to understand.

Wayne

 

[DrRocket]

If there were a boundary to space-time, it would be some sort of 3-manifold. But what would that be, locally? Two space dimensions and 1 time dimension, three space dimensions without time ? Nothing makes good sensefroma physical perspective.

Some say event horizon of black holes are good example for 2s+1t dimension boundary... :?:
Alas, come in my mind only bizarre wasp examples for 3s dimension boundary now, but possible...

Overstepped 3+1 dimension manifold (general relativity) model, that will fill the bill...

I am sure that some do say that even horizons are an example of a boundary. You can fiind someone to say almost anything. All that you need do to prove that is to read some of the nonsense posted on bulletin boards. But anyone who says such a thing has no idea what a manifold is or what a manifold with boundary is.

Itis pretty clear that the event horizon is not a boundary in the sense of the manifold of space-time -- things cross it.

Also, space-time is NOT a 3+1 dimensional manifold it is a Lorentzian 4-manifold. There is NO global "time" and there is no global "space" except as approximations in an idealized model used by cosmologists. That model fails to model the observed universe except at the largest of scales. It is quite clear that space-time incorporates curvature as an important quality, and that the curvature is quite variable over small scales (if it were not then we would not have gravity as we know it on earth).

 

[metastring]

If there were a boundary to space-time, it would be some sort of 3-manifold. But what would that be, locally? Two space dimensions and 1 time dimension, three space dimensions without time ? Nothing makes good sensefroma physical perspective.

Some say event horizon of black holes are good example for 2s+1t dimension boundary... :?:
Alas, come in my mind only bizarre wasp examples for 3s dimension boundary now, but possible...

Overstepped 3+1 dimension manifold (general relativity) model, that will fill the bill...

I am sure that some do say that even horizons are an example of a boundary. You can fiind someone to say almost anything. All that you need do to prove that is to read some of the nonsense posted on bulletin boards. But anyone who says such a thing has no idea what a manifold is or what a manifold with boundary is.

manifold - set of points, which have an relationship (called neighborhood or surrounding?)
(that is manifold, like in accordance topology space)
definitions of manifolds interior points: http://en.wikipedia.org/wiki/Interior_(topology)#Interior_point
boundary of manifold - subset of NOT interior points of manifold

In technical language, a manifold with boundary is a space containing both interior points and boundary points.

...etc. (before it proliferate)

In my opinion: be possible / we can consider boundary of manifold or (lack of it) closure-of-manifold-minus-interior-points-of-manifold (limit points) in context with boundary of universe. (If universe is NOT closed manifold. If closed, then closure is equal to entire universe, that is limit points empty set, but closed / compactness of universe is open question, isn't it so?)
What's wrong in above?

Itis pretty clear that the event horizon is not a boundary in the sense of the manifold of space-time -- things cross it.

It depends on whether things capable of cross event horizon in finite time (and for whom: thing or distant observer) and
it depends on whether how defined boundary of universe. (for example only one direction crossing is maybe weak boundary)

Event horizon is boundary of universe rather belong to black hole topic?
I would like to point to boundaries of universe (or environment of it) still observable, in spite of expanding...

Also, space-time is NOT a 3+1 dimensional manifold it is a Lorentzian 4-manifold. There is NO global "time" and there is no global "space" except as approximations in an idealized model used by cosmologists. That model fails to model the observed universe except at the largest of scales. It is quite clear that space-time incorporates curvature as an important quality, and that the curvature is quite variable over small scales (if it were not then we would not have gravity as we know it on earth).

OK. (Riding on words and sign)
My 3+1 dimension note is NOT topological qualifying, much rather is loose folk notation.
Obviously, this is NOT the scientific sign convention, that is (1,3) or (3,1)...
Other is correct.

 

[DrRocket]

manifold - set of points, which have an relationship (called neighborhood or surrounding?)
(that is manifold, like in accordance topology space)
definitions of manifolds interior points: http://en.wikipedia.org/wiki/Interior_(topology)#Interior_point
boundary of manifold - subset of NOT interior points of manifold

In technical language, a manifold with boundary is a space containing both interior points and boundary points.

...etc. (before it proliferate)

In my opinion: be possible / we can consider boundary of manifold or (lack of it) closure-of-manifold-minus-interior-points-of-manifold (limit points) in context with boundary of universe. (If universe is NOT closed manifold. If closed, then closure is equal to entire universe, that is limit points empty set, but closed / compactness of universe is open question, isn't it so?)
What's wrong in above?

What's wrong is that you don't know what you are talking about, and apparently are quoting Wikipedia quite out of context to boot.

1. The Wikipedia link is to a discussion of interior points relative to a subset of a topological space, a topic in elementary point-set topology. That discussion has NOTHING to do with the notion of a boundary for a manifold. The concept of a manifold with boundary is applicable to an intrinsic manifold, and related to points in which the is a neighborhood that is homeormorphic to a half-hyperplane, rather than to an entire Euclidean space. ALL points in a full topological space, which an intrinsic manifold is, are interior points. And if a manifold is embedded in a higher-dimensional space, then as a subspace, all points are in the boundary. In short, your "definition" of a boundary is meaningless in the case of a manifold.

The quote that you used from Wikipedia has nothing to do with the link that you provided. The quote comes from this Wiki article http://en.wikipedia.org/wiki/Manifold_w ... h_boundary. And that article repeats what I just told you, with a definition of "interior point" that is quite different from the link that you provided.

If you are going to quote Wiki articles it woudl behoove you to understand them first.

In short, get your brain in gear before you let out the clutch on your mouth.

Itis pretty clear that the event horizon is not a boundary in the sense of the manifold of space-time -- things cross it.

It depends on whether things capable of cross event horizon in finite time (and for whom: thing or distant observer) and
it depends on whether how defined boundary of universe. (for example only one direction crossing is maybe weak boundary)

To an observer moving toward the event horizon nothing particularly remarkable happens at the horizon. He simply crosses it, without noticing much of anything and then proceeds IN FINITE TIME to reach the singularity predicted by general relativity.

There is no "depends" involved. The event horizon is NOT a boundary in the sense of the theory of manifolds.

Event horizon is boundary of universe rather belong to black hole topic?
I would like to point to boundaries of universe (or environment of it) still observable, in spite of expanding...

Gibberish

Also, space-time is NOT a 3+1 dimensional manifold it is a Lorentzian 4-manifold. There is NO global "time" and there is no global "space" except as approximations in an idealized model used by cosmologists. That model fails to model the observed universe except at the largest of scales. It is quite clear that space-time incorporates curvature as an important quality, and that the curvature is quite variable over small scales (if it were not then we would not have gravity as we know it on earth).

OK. (Riding on words and sign)
My 3+1 dimension note is NOT topological qualifying, much rather is loose folk notation.
Obviously, this is NOT the scientific sign convention, that is (1,3) or (3,1)...
Other is correct.

More gibberish.

 

[wkitty42]

This thread has produced very little scientific discussion. Mostly wild and uninformed speculation. If it doesn't get more closely aligned within the subject matter of this forum (Space Science and Astronomy) it is destined for a trip to The Unexplained. Please lets talk real science here.

Thanx

Meteor Wayne

i must be missing something... it wouldn't be the first time...

i arrived at this thread from the space.com news headlines... reading the initial message, more than once, i don't see anything indicating that "real science" was a requirement for replying to the original message or participating in this thread... in fact, the original message even states something to the effect of letting the imagination flow...

Well, the Space Science and Astronomy forum is a REAL SCIENCE part of Space.com. For unsubstantiated speculation, we have other forums.

i can understand that... i was just pointing out that folk may arrive, like i did, via a method that gives no indication of the material that may be allowed... as i wrote, i only had the initial message to go by

as a moderator and admin of several other forums, i fully understand your position :mrgreen:

 

[metastring]

First:
Thanks for DrRocket to dialog. Thanks to he willing to understand my ideas from my poor english text...

Second:
Is well-modelled (without a mistake...) environment of event horizon with an full / complete topological space or an intrinsic manifold of General Relativity? At most with limits or boundaries...
It seems to me that

...a neighborhood that is homeomorphic to a half-hyperplane, rather than to an entire Euclidean space...

is better model for it.
Obviously, I'm not infallible. You can gain me over, if you feel so disposed...

Third:
Event horizon seems like aymptotic limit of several functions for every distant observer.
But who aren't distant observer (outside event horizon)?
(Observers beyond event horizon maybe trivial answer. Anybody else?)

Fourth:

http://www.faculty.iu-bremen.de/course/fall02/c210101/students/BlackHoles/Black%20holes%20and%20Schwartzschild%20geometry.htm[/url]":1kzusbbe]Finally, closer and closer to the event horizon, light cones are so tilted that no geodesic on the cones points towards the “outside;” all the light which is emitted unavoidably heads towards the center of the black hole, the singularity. Notice also that the axis of the cones, which started out as vertical – time axis – becomes almost horizontal nearer to the horizon. But horizontal axes represent spatial coordinates on our diagram!

(Note: 1s+1t or 2s+1t Minkowski-diagram)

http://www.as.utexas.edu/astronomy/education/spring06/komatsu/secure/lecture12.pdf[/url]":1kzusbbe]B’s View
• An observer B, who is freely falling into BH,
would not notice he would be falling into BH
(Equivalence Principle) except for tidal force.
– His feet are pulled more strongly than his head
• The sign of redshift and time dilation is reversed:
– B sees the wavelength of light coming from the
outside world being blueshifted.
– B sees time of the outside world flowing very fast.

This world flowing accelerates to infinity, when B falls to event horizont?
Then limit of causality (not effect) region of B, as B approaches event horizon is whole universe?


Finally:
Yes, of course: My knowledge about nature of event horizon is very little.
My skepticism about models of it is much bigger.
I'm sorry my poor english again, but please don't you take advantage of it!