Expanding space needs surroundings to expand into. T or F.

[Nick_Spanich]

Yes, I think there's a misunderstanding. I only meant to use the "Outside" to explain that the universe doesn't end. That even past all of the stars and plants and galaxy'[s that there is still "sapce" Even though there is no matter. Hopefully this clarify's

[losfomot]

Yes, I think there's a misunderstanding. I only meant to use the "Outside" to explain that the universe doesn't end. That even past all of the stars and plants and galaxy'[s that there is still "sapce" Even though there is no matter. Hopefully this clarify's

 

There is no 'outside' in that sense either. You can choose any point in the entire universe, and it should look (on average) just like right here... with galaxies all around, in the same numbers and density that we see from here.

[bascule]

SO you believe the universe is a house.

 

No, I believe "universe" defines the totality of all existence, therefore by definition there is nothing outside the universe.

 

But what about outside of those walls. There has to be something. Space is never ending. Even if the there is no matter there is still something there "lifeless" space

 

We don't know if space is never-ending or not. Perhaps the universe is spatially curved, and hence closed, i.e. if you go far enough in any one direction you will eventually (after a journey of incomprehensible length) find yourself back where you started.

[dichotomy]

Perhaps the universe is spatially curved, and hence closed, i.e. if you go far enough in any one direction you will eventually (after a journey of incomprehensible length) find yourself back where you started.

 

I think you've been playing Asteroids too long.

 

http://msdn.microsoft.com/coding4fun/images/gameDev/kpl_asteroids/kpl_asteroids_1_thumb.gif

 

That is to say, in Asteroids it doesn't matter what direction you fly your craft off the screen, you will immediately return to the same screen frame you are viewing.

 

I think I'll stick with the infinite space theory.

[Martin]

 

I think I'll stick with the infinite space theory.

 

You can prefer whichever. The main two alternatives are

1. infinite, boundaryless, with no surrounding space to expand into

2. finite, boundaryless, with no surrounding space to expand into

 

so far the data slightly favors what bascule says. The most recent errorbar for Omega that i've seen was 68 percent [1.010, 1.041].

 

that is, with 68 percent probability Bascule's pick is right.

 

Your pick requires that Omega be exactly 1, or less, and it would fall outside the errorbar---in the region with 32 percent probability.

 

Sixtyeight percent is still not conclusive, so they tell us that the data is still consistent with the infinite case----that is the infinite case has not been ruled out, at least so far. But the trend, since about 2002 and 2003 has been towards increasing certainty on the positive (greater than one) side.

 

If this trend continues, say until we have a 95 percent errorbar on the upside of 1, or better, on the upside of 1.01, then the experts will start assuming a paradigm of finite volume, boundaryless, no surrounding space.

 

A lot of the reason they assume what they do is preference for what is mathematically simplest. The simplest model that fits the data well. Why add frills that you don't need? Idea of spareness.

[Bettina]

...There is no outside of the universe, since the universe is everything. It doesn't make intuitive sense, but it's true.

 

The universe is everything, so the concept of an "outside" is meaningless.

 

 

Asking the question "what's outside of the universe" is logically equivalent to asking "how loud is the direction down?" It just doesn't make any sense.

 

 

Does this help?

 

No it doesn't. Hi iNow I still have problems with this and despite Martin tweaking my brain, I can't get past it.

 

How do scientists know enough to say "There is nothing outside our universe" instead of "We don't know what is outside". What is the key that makes this so absolute in all the discussions I've seen.

 

Bee

[iNow]

How do scientists know enough to say "There is nothing outside our universe" instead of "We don't know what is outside". What is the key that makes this so absolute in all the discussions I've seen.

Hi Bee,

 

My first impression is that it's more of a semantic issue. If the universe, by it's very definition, is THE absolute, then nothing can be outside of it.

 

Admittedly, this is just my intuitive logic, and I very well could be wrong, but if my previous experiences are indicative of my ability to be correct, then I'm correct here too.

[copperstream]

If you say that it's a lifelees space..............How long does it continue?...............If it continues for a certain level , then will big crunch occur??????????????/

[ajb]

If you consider space-time in stead of space then the whole issue of space expanding into something disappears.

 

If space-time is [math]M =M_{3}\times \mathbb{R}[/math] (at least locally) then by space we mean a "slice" of [math]M[/math] at time [math]t \in \mathbb{R}[/math].

 

By expanding/contracting all we mean is that the metric (how we define distance) on [math]M[/math] is a function of [math]t[/math]. That is it is not the same on all "slices".

 

So, nothing "outside" is needed. No need to talk about metaphysics!

 

 

However, I have avoided the possibility that space-time is embedded in a larger space.

[lucaspa]

How do scientists know enough to say "There is nothing outside our universe" instead of "We don't know what is outside". What is the key that makes this so absolute in all the discussions I've seen.

 

Because to be "outside" in the normal sense means to have spacetime beyond the boundary. And spacetime means the 3 dimensions of length, width, and height. However, since the universe contains ALL the length, width, and height, there are none of those dimensions "outside" it.

[Bettina]

Because to be "outside" in the normal sense means to have spacetime beyond the boundary. And spacetime means the 3 dimensions of length, width, and height. However, since the universe contains ALL the length, width, and height, there are none of those dimensions "outside" it.

 

So you're saying that our spacetime could never exist in a larger spacetime with it's own 3 dimensions? Why do some scientists speculate that our universe could be just one bubble of many.

 

Bee

[Martin]

Why do some scientists speculate that our universe could be just one bubble of many.

...

 

 

... Hi iNow

 

How do scientists know enough to say "There is nothing outside our universe" instead of "We don't know what is outside". What is the key that makes this so absolute in all the discussions I've seen.

 

Hi Bee,

 

My first impression is that it's more of a semantic issue. If the universe, by it's very definition, is THE absolute, then nothing can be outside of it.

 

Bee, let's make an effort to use words the same way. Discussion will go better. I think iNow is citing the majority definition. Would you be willing to go with that?

 

You may be thinking of Andrei Linde at Stanford, who has a universe idea which contains many regions expanding at different rates----keywords are "eternal inflation" and "bubble". For instance these 1986 papers:

A. Linde (1986). "Eternal chaotic inflation". Mod. Phys. Lett. A1.

A. Linde (1986). "Eternally existing self-reproducing chaotic inflationary universe". Phys. Lett. B175. 

Other names associated with this are Vilenkin, Aguirre, Carroll...(just a sample.)

 

It would be an abuse of language for Linde to say that he pictures many universes. He pictures one universe, expanding irregularly, organized in various different bubbles or regions. The whole thing expands, on average, and it doesn't need any larger room to expand into.

 

My point in the poll is that expanding space, however you picture it, doesn't NEED any surroundings to expand into. I don't think Linde would disagree, do you?

 

You can, of course, decide to adopt what I think is a minority usage and call each separate one of Linde's regions or bubbles a "universe". But when he writes technical articles where he wants to be clear I don't think he himself does this. In journalistic popularizations they refer to separate bubbles as separate "universes". But that is a separate issue---journalists use words in a special way in order to stimulate the imagination. In professional articles I think someone would be more likely to say "domain". But there is less and less being written about it these days in any case. Paul Steinhardt (one of the inventors of inflation) had some words about this lately. The Landscape is on the way out---or words to that effect.

http://www.math.columbia.edu/~woit/wordpress/?p=647

 

I could be wrong but I think the semantic confusion is dying down. The universe (my impression is) is still the whole thing, which some people conjecture might be divided into different regions. Just give us fair warning if you are going to use words in a special sense.

 

I think this may be the main gist of what you are saying, so I will repeat it:

How do scientists know enough to say "There is nothing outside our [region of the universe]" instead of "We don't know what is outside".

 

In brackets is a translation so I can understand better and avoid semantic confusion.

 

I think you left out a possbility: "We don't know IF there is anything outside."

That is, we don't know if Linde's or Vilenkin's pictures with the many bubbles expanding at different rates is correct! I think more people would choose to say that instead of the alternatives you offered.

 

I think you also put in a touch of strawman here. I don't know of any cosmologist who flatly denies Linde's bubble picture, or "eternal inflation" picture. I think there was some interest in it as a possibility 5 or 10 years ago. I think interest has WANED somewhat in the past 2 or 3 years.

 

That doesn't mean it's wrong, or that anyone would flatly rule it out. It just isn't as fashionable as it was a while back. It was omitted from the agenda of the last big cosmology conference (GR18 in Sydney last summer).

 

Maybe the key thing here is Occam Razor. Ideas like "eternal inflation" and "chaotic inflation" and many-bubbles have been around for some 10 years, maybe more, and nobody has succeeded in showing that we NEED them.

 

they are beginning to look like unnecessary complication. Intriguing speculation but not a lot more. So people don't contradict the enthusiasts, they just have lost interest in hearing about it.

 

We'll see how it goes.

 

None of this impacts the question about whether expanding space needs surroundings to expand into, do you agree? (Linde uses General Relativity like everybody else, he just has patches with different inflaton fields. And in GR you don't need surroundings in order to have expansion.)

[Bettina]

Martin, please answer this wild question the best way you can..... Don't throw anything at me, just answer.

 

You are a God who cannot be destroyed. If you could snap your finger and make the universe disappear, what would you see as you looked around.

 

Bee

[Realitycheck]

It sounds like he has a good handle on this pre-BB baryonic matter thing. Why would there be any reason to believe in additional universes other than an old man's ramblings? I believe that there is no scientific merit to it whatsoever.

[iNow]

Martin, please answer this wild question the best way you can..... Don't throw anything at me, just answer.

 

You are a God who cannot be destroyed. If you could snap your finger and make the universe disappear, what would you see as you looked around.

 

Where exactly is this God (let's call him "Martin" due to the really great god-like post above) sitting as they look around? If the universe suddenly doesn't exist, then where is the thing which popped it out of existence located exactly?

[Realitycheck]

It was a seed of the Bodhi tree, from which all existence flowed.

 

If you consider space-time in stead of space then the whole issue of space expanding into something disappears.

 

If space-time is [math]M =M_{3}\times \mathbb{R}[/math] (at least locally) then by space we mean a "slice" of [math]M[/math] at time [math]t \in \mathbb{R}[/math].

 

By expanding/contracting all we mean is that the metric (how we define distance) on [math]M[/math] is a function of [math]t[/math]. That is it is not the same on all "slices".

 

So, nothing "outside" is needed. No need to talk about metaphysics!

 

 

However, I have avoided the possibility that space-time is embedded in a larger space.

 

However, this is too bungled up in math, because space, as we know it, has 3 dimensions. Adding a 4th dimension, time, is just some fancy way of describing a reality that is not realist.

[iNow]

However, this is too bungled up in math, because space, as we know it, has 3 dimensions. Adding a 4th dimension, time, is just some fancy way of describing a reality that is not realist.

 

You know, you can't just make stuff up and pretend it's true, right?

[Realitycheck]

Are you trying to tell me that space has 11 dimensions? It's just semantics.

[Bettina]

Martin, please answer this wild question the best way you can..... Don't throw anything at me, just answer.

 

You are a God who cannot be destroyed. If you could snap your finger and make the universe disappear, what would you see as you looked around.

 

Bee

 

I wanted to clarify, that by "universe", I meant ours.

 

Bee

 

P.S... http://www.world-science.net/exclusives/060330_multiversefrm.htm

[lucaspa]

Martin, please answer this wild question the best way you can..... Don't throw anything at me, just answer.

 

You are a God who cannot be destroyed. If you could snap your finger and make the universe disappear, what would you see as you looked around.

 

Bee

 

No space, no time, no matter, no energy. What would that "look" like? Beats me. I can state it, but not really imagine it. Since there would be no electromagnetic energy (light), you wouldnt be able to "see" anything. No photons to interact with your eyes.

 

I wanted to clarify, that by "universe", I meant ours.

 

Bee

 

P.S... http://www.world-science.net/exclusives/060330_multiversefrm.htm

 

Bettina, this is different than "bubble universe".

 

"“The multiverse is like a bubble bath,” with a bubble representing each universe, he added. There are “multiple universes bubbling, colliding and budding off each other” all the time.

 

Another panelist backed the multiverse idea, but three more insisted there’s virtually no evidence for the highly speculative concept."

 

In multiverse, each universe with space, time, matter, energy is self contained. A "bubble" would be the universe we see around us.

 

In bubble universe, there is only one universe with space, time, matter, and energy. Instead, there are "pockets" within that big universe that are invisible to the others -- because space is expanding faster than the speed of light.

 

In multiverse, there is no way to contact any of the other universes. Notice that comment that multiverse is VERY speculative. It's a fun idea to play with mathematically but there is no observational data to support or refute it.

[Bettina]

Hi Lucaspa,

 

What I'm about to say really belongs in the speculation or trash section and I feel a bit stupid saying this but I just want to share what has been on my mind ever since I began reading books on Cosmology. It may be child like so I want to apologize up front and be done with this once and for all but I just have to say it. No flames please...

 

OK, when the god entity snapped his finger (in my question to Martin) and made our universe with all it's matter, space and time, disappear, he wasn't left in an empty dark void unable to see anything. What he did see, with his god like eyes, were other universes each with their own space, time, and matter. Some were separate from others but some were joined together, and there were universes as far as his eyes could see.

 

To carry this further, he snaps his finger again and removes all of the other universes until there is nothing left. Now, he is really alone, floating in the mother universe that is infinite and without end. Travel in a straight line and you will never come back to where you started. You go on forever. This is the last doll of the Russian set and it's where everything comes from. It was never created nor was there any expansion. It was always there. It's the final nothing that is, when everything is removed.

 

Now, with everything gone, the god entity waits. He sees something pop into existence and pop out just as fast. As he looks around, he sees more of these god particles popping in an out until finally, after what appears to be an eternity, one pops in, stays longer than it was supposed to, becomes unstable, then bang.... a bubble takes shape and a universe is born. In time, another bubble is born, then another. Some spawn from one another while some remain singular in a different part of the mother universe.

 

The mother universe is without end. Carry this out as far as you would like....

 

I like physicists like Linde and especially Kaku.. who has been my favorite for some time now. His imagination is awesome. Oh well.... I said what I had to say.

 

Bee

[YT2095]

No space, no time, no matter, no energy. What would that "look" like? Beats me. I can state it, but not really imagine it. Since there would be no electromagnetic energy (light), you wouldnt be able to "see" anything. No photons to interact with your eyes.

 

an almost Perfect description of Void Space.

[Dark matter]

Question: if the universe was expanding into something, wouldn't that just be part of the universe?

[Bettina]

Question: if the universe was expanding into something, wouldn't that just be part of the universe?

 

Depends on what you mean by universe. When I hear the word universe, I take it to be our observable universe and nothing else. This would be expanding into something which is infinite and was always there. Call it the "void", "multiverse", the "nothing", etc.

 

Pure speculation on my part. but it's what I believe.

 

Bee

[Dark matter]

Depends on what you mean by universe. When I hear the word universe, I take it to be our observable universe and nothing else. This would be expanding into something which is infinite and was always there. Call it the "void", "multiverse", the "nothing", etc.

 

Pure speculation on my part. but it's what I believe.

 

Bee

 

When you mean observable universe, do you mean what we can see with waves, or what anything can see.

 

Woa, major headache from reading this.