The Direction of Space: Is Light Traveling Around the Periphery?

[Eh]

Originally posted by LW Sleeth
I suspect you mean spacetime for our universe didn't exist pre-big bang, but may for other universes (since that would rule out your suggestion of possible infinity)

No, I mean all of spacetime did not exist. At least, that is the theory.

 

[Les Sleeth]

Originally posted by Eh
No, I mean all of spacetime did not exist. At least, that is the theory.

Well, if it is the theory, then you can see how time and space cannot possibly be eternal/infinite (though I guess one could say time and space might continue on eternally).

 

[Mentat]

Originally posted by Eh
It's not a matter of opinion, but fact. What physicists have labeled as a void in some pre big bang theories, is a state where no classic notions of space or time exist. I'm not arguing that the idea is valid or even coherent, only that it is the definition being used.

Then a true "void" cannot exist.

 

[Eh]

Originally posted by LW Sleeth
Well, if it is the theory, then you can see how time and space cannot possibly be eternal/infinite (though I guess one could say time and space might continue on eternally).

Remember, it's only one theory. In other models, spacetime is fundamental and exists forever.

 

[heusdens]

Originally posted by Draco
Thats true.
Scientists already know that the Universe expands. They can see galaxy's spreading far apart, they move out into space. So i guess this means that the Universe does expand.

I doubt whether the Universe if infinite...When i think of it, i get all weird inside for some reason.

I don't think that the Universe if a sphere, if it is, then what is on the other side? Nothing? Some sort of wall? Hmmm!
Or is the Universe just a black hole going in reverse. Well that's what Stephen Hawking said, a massive black hole that's in reverse...you know, time starts to go...and eventually it dies. Well i don't know if it will result in the supposedly 'big crunch'

You can only talk in a sensical way about space and time in the context of moving matter (anything "material", i.e. particles, energy, fields, etc.)

Space and time just denote the "mode of existence" of matter.

Matter is to be seen as infinite. The infinity of matter means that, while every material form has a finite extend in space and time, it is always preceded and followed by another material form. Nowhere we see "creation" of matter as such, we can only see the transformation of one material form into another, and this transformations go on endlesly, without begin or end.

 

[Les Sleeth]

Originally posted by heusdens
Matter is to be seen as infinite.

You assume too much. As far as what we actually know, matter and the universe is finite and temporal. To assume any more is pure speculation.

Originally posted by heusdens
The infinity of matter means that, while every material form has a finite extend in space and time, it is always preceded and followed by another material form. Nowhere we see "creation" of matter as such, we can only see the transformation of one material form into another, and this transformations go on endlesly, without begin or end.

Right now the universe appears firmly in the grip of entropy, and if that continues one day it will just fizzle out. It seems if you were right, entropic change would not be dominating, but rather we'd see a balance of entropic and anti-entropic change.

Also, how does your idea get around the same problem people have with a god that is infinite and has always existed? They always ask, "but where did god come from?"

 

[Mentat]

Originally posted by Eh
No, I mean all of spacetime did not exist. At least, that is the theory.

But how is it that they can refer to it, using the term "didn't exist". That's a concept of time.

 

[marcus]

Mentat somewhere recently I read a discussion where
someone was discussing with an astronomer and they
compared a black hole to the beginning of the universe.

You might like how the astronomer replied---he drew a
clear logical distinction that bears thinking about. He said no
the two are very different because

a black hole is a singularity that is localized in space but not in time


whereas the beginning is a singularity that is localized in time
but not in space

you know the big bang occurred everwhere, not at some point.

often people think of it wrongly as an explosion outwards from some point

but the universe is infinite as far as we know (altho can only see a finite part) and so the big bang or whatever is imagined as a beginning must be thought of as extending infinitely in all directions also

but nevertheless (in contrast to a black hole singularity) localized to a particular instant.

Now I personally do not declare this. Make of it what you will. I am just reporting how this guy (maybe it was in one of those Cosmology FAQ things on the internet) made this neat logical distinction between Everything and a Black Hole. Explain it I cannot!

 

[meteor]

So Marcus, you dont't think that Big Bang is a quantum fluctuation?
If you say,Big Bang started in all space at the same time being infinite in size at the same begining, you have to provide a mechanism that permit this to happens. I think that even Big Bang has to have a physical explanation

 

[Draco]

Originally posted by heusdens

Matter is to be seen as infinite. The infinity of matter means that, while every material form has a finite extend in space and time, it is always preceded and followed by another material form. Nowhere we see "creation" of matter as such, we can only see the transformation of one material form into another, and this transformations go on endlesly, without begin or end.

I hope s

 

[marcus]

Originally posted by meteor
So Marcus, you dont't think that Big Bang is a quantum fluctuation?
If you say,Big Bang started in all space at the same time being infinite in size at the same begining, you have to provide a mechanism that permit this to happens. I think that even Big Bang has to have a physical explanation

As I said in my post, I wasn't declaring my personal opinion, or offering to explain. Just reporting what somebody else said. I thought you might find it interesting. I checked in ned wright's cosmology FAQ and it was there, in answer to "Is the BB like a BH?" I don't remember where I first came across this pithy utterance, could have been somewhere else, but anyway one place you find it is at Ned Wright's.

I do think that people are getting closer to a reasonable theory of quantum geometry and gravity-------and one thing such a theory ought to do is model the universe back then. The only model we have now----GR----doesnt work. What was it Wittgenstein said? "Of that whereof one cannot speak, thereof one must remain silent."
A good model would allow us to speak about things that, lacking a model, we can't yet talk about coherently.

Abhay Ashtekar has some good analogies about this and talks about-----well the title of his 2001 paper "Quantum Geometry and Gravity: Recent Advances" says what it is about.

the first thing he discusses in the first paragraph of the introduction is this very problem-----how to model the BB, making it not a singularity any more.

His paper is a non-mathematical overview, with references it is 24 pages long, but (curiously enough) it is not a popularization. Even fellow math/physics folk need to have things explained intuitively and figuratively, without equations, now and then and this is one of those rare cases of a non-popularizing non-mathematical survey of a research area.

arXiv:gr-qc/0112038

if you decide to download it and have any trouble getting the PDF to print please let me know. I didnt have any trouble. He is a famous guy because he invented the "new variables" of general relativity which have transformed the subject and he is clearly interested in the same singularity that you are, so maybe there is something to get from it.

 

[Mentat]

Originally posted by meteor
So Marcus, you dont't think that Big Bang is a quantum fluctuation?
If you say,Big Bang started in all space at the same time being infinite in size at the same begining, you have to provide a mechanism that permit this to happens. I think that even Big Bang has to have a physical explanation

But there are many possible explanations (with a quantum fluctuation of empty space being one of them). One of my favorites is the string theory approach, that all of space is not expanding or contracting, but both, at the same time (this is explained through the inverse nature of the use of wound and vibrational strings).

 

[Mentat]

Originally posted by marcus
As I said in my post, I wasn't declaring my personal opinion, or offering to explain. Just reporting what somebody else said. I thought you might find it interesting. I checked in ned wright's cosmology FAQ and it was there, in answer to "Is the BB like a BH?" I don't remember where I first came across this pithy utterance, could have been somewhere else, but anyway one place you find it is at Ned Wright's.

I do think that people are getting closer to a reasonable theory of quantum geometry and gravity-------and one thing such a theory ought to do is model the universe back then. The only model we have now----GR----doesnt work. What was it Wittgenstein said? "Of that whereof one cannot speak, thereof one must remain silent."
A good model would allow us to speak about things that, lacking a model, we can't yet talk about coherently.

Abhay Ashtekar has some good analogies about this and talks about-----well the title of his 2001 paper "Quantum Geometry and Gravity: Recent Advances" says what it is about.

the first thing he discusses in the first paragraph of the introduction is this very problem-----how to model the BB, making it not a singularity any more.

His paper is a non-mathematical overview, with references it is 24 pages long, but (curiously enough) it is not a popularization. Even fellow math/physics folk need to have things explained intuitively and figuratively, without equations, now and then and this is one of those rare cases of a non-popularizing non-mathematical survey of a research area.

arXiv:gr-qc/0112038

if you decide to download it and have any trouble getting the PDF to print please let me know. I didnt have any trouble. He is a famous guy because he invented the "new variables" of general relativity which have transformed the subject and he is clearly interested in the same singularity that you are, so maybe there is something to get from it.

Actually, marcus, I will have to slightly disagree with you about GR. It can be used to explain the origin of the Universe, but it has to be "taken up a few notches". The real problem (according to Hyperspacial theorists, like Michio Kaku) is that Einstein didn't use enough dimensions. He restricted himself to the 3 spatial dimensions and 1 temporal dimension - which is fine to explain gravity (provided one figures out how to unify it's approach with QM (which I think string theory does rather well)), but it isn't enough to explain the other "forces".

So, basically, the General Relativity approach can be used to explain the origin of the Universe, and all of the "forces", but you need to add more dimensions (which makes the math almost impossible for me to comprehend ).

 

[meteor]

But there are many possible explanations (with a quantum fluctuation of empty space being one of them).

Like Eh said before, a quantum fluctuation can't have an infinite size

One of my favorites is the string theory approach, that all of space is not expanding or contracting, but both, at the same time

How can space be expanding and contracting at the same time? That's not possible. Anyways, redshifts of galaxies indicate that space is expanding.
And remember that string theory can't deal with the problem of the cosmological constant

 

[Eh]

Originally posted by Mentat
But there are many possible explanations (with a quantum fluctuation of empty space being one of them). One of my favorites is the string theory approach, that all of space is not expanding or contracting, but both, at the same time (this is explained through the inverse nature of the use of wound and vibrational strings).

I don't think string theory predicts that. If it were the case, the net expansion/contraction of the universe would be zero. The light from distant galaxies would not be redshifted.

From what I've read, it seems that string theory merely puts a minimum size on the universe. Any attempts to define the universe shrinking smaller than the Planck scale, would be equivalent to defining a universe expanding from that scale. So instead of collapsing down to a singularity, the universe bounces at the Planck scale. But I'm not entirely certain on this.

 

[Mentat]

Originally posted by meteor
How can space be expanding and contracting at the same time? That's not possible. Anyways, redshifts of galaxies indicate that space is expanding.

Yes, space most definitely is expanding. But it is also contracting. Like I said, it's because of our use of vibrational strings in measurement.

A basic explanation would first require that I define "vibrational" and "wound" strings. A "vibrational" string is a string that moves along our 3-d space. A "wound" string is a string that is "wrapped around" our 3-d space. Let me use the "Flatland" illustration to try and better explain this:

Imagine a universe of "flat" people. A 2 dimensional universe, kind of like a bunch of drawings on a piece of paper. They have the directions of North, South, East, and West, but they have absolutely no concept of "up" or "down". These things make no sense to them. Now, imagine that their space was actually "curled up" (as if someone had curled the piece of paper they are on into a hollow tube). Now, they still can't concieve of the "up" direction, but it must exist (otherwise, their dimensions couldn't "curl up"). Finally, imagine that they are all made up of 1-dimensional strings, and that they strings move along their space (their Flatland). These would be the "vibrational strings". But there are also "wound" strings, which are "wrapped around" the "hollow tube" that their reality really is.

It is the same with us (according to string theory). We live our lives in 3 dimensions of space, and can't concieve of any higher space dimensions. As far as common sense goes, our space cannot be "curled up" in another direction. But what if it were so? Then there could be strings that were "wound" and strings that were "vibrational", right?

Now, if we measure using vibrational strings, the Universe is expanding (and all of the stars, planets, people, etc are made up of vibrational strings). However, the measurement using wound strings is always inversely proportional to the measurement using vibrational strings, and thus - depending on which you use to measure it - space is both expanding and contracting.

I don't know if I made that clear enough (and I probably didn't), but I hope you got the gist. I suggest Brian Greene's "The Elegant Universe", as it explains it better, and uses illustrations to help you conceptualize it.

And remember that string theory can't deal with the problem of the cosmological constant

You mean the coupling constant, don't you? This was a big problem for string theory, but the operative word is "was", as M-Theory deals with it rather nicely (it's just much to complicated, mathematically, for anyone to actually solve it's equations, and thus it can't be proven yet).

 

[Mentat]

Originally posted by Eh
I don't think string theory predicts that. If it were the case, the net expansion/contraction of the universe would be zero. The light from distant galaxies would not be redshifted.

Please read my previous post, in response to "meteor" (I'd hate to have to re-post all of that).

From what I've read, it seems that string theory merely puts a minimum size on the universe. Any attempts to define the universe shrinking smaller than the Planck scale, would be equivalent to defining a universe expanding from that scale. So instead of collapsing down to a singularity, the universe bounces at the Planck scale. But I'm not entirely certain on this.

This is pretty much correct (you often astound me with the depth and breadth of you knowledge ), however there is a reason why things appear to "bounce back" at the Plank scale. And that reason is that, at those scales, one measure using "wound" strings, instead of "vibrational" ones.

 

[Eh]

Mentat, are you sure about that? Can you cite something? The closet thing it sounds like is the notion that our 3 dimensions expand while the others contract. Our 3D universe, is still expanding only.