outside the universe

[Mr Skeptic]

As a language Reformer (I suffer from both conservative and reform urges), I would focus on your word Visible and incline towards a made-up term like "Visiverse" pronounced vizzy-verse. It has a lively brisk sound, like ginger ale.

 

Visiverse, I like it.

 

I still can't think of something to call "our" universe, the stuff contained in all spacetime connected to ours. It would include the visiverse and also the stuff that is forever cut off from us due to the expansion of space.

[Martin]

... So, could I get away with saying that the BB was an event that "created" our region of the greater universe that was NOT created along with our BB?...

 

Well I for one agree with that so you wouldn't get any static from me.

 

You have to be prepared for people disliking what you say and criticizing, tomorrow you might take a position on some other issue and I or Edtharan or somebody might dispute it. but in this case it sounds all right, at least to me.

 

the thing is you put it the verb create in the context of a larger universe presumably governed by the same or similar laws. So you let me interpret your statement in a way that I am comfortable with, and that is recognizable to me as science. You leave HOPE that the larger universe you mention can somehow be understood wholly or partially by us humans. Intellectual hope is important to people.

 

It is not a thing where you get other people to agree with you so much as that you put your own belief in a way that leaves open to me or somebody else to interpret it comfortably, and indeed hopefully.

 

I see now I have been quibbling needlessly about some things.

I probably got disturbed when somebody said "the big bang created the universe so therefore what was before it is outside the universe."

That was like being confronted by a wall of mystery. You cant hope to understand because it is outside the universe. Maybe I was disturbed and didn't realize how much it bothered me.

 

I think our human history shows that walls of mystery don't stand up. eventually we get past or thru them somehow.

 

But you put it in a completely unmysterious unforbidding way. I can even imagine making testable conjectures about models along those lines.

 

Funny how the context and wording can make a difference.

[maxlongo]

but how our microverse, region-verse, visiverse interact with the rest of the Universe?

 

is it like a drop of oil in a glass of water which remains completely isolated from the rest or like a drop of ink that "dissolves" into the bigger "verse"?

 

because in the first case "there is something outside". Something we can't even remotely understand and therefore from our perspective it would be "nothing". it would be like a flat 2d being trying to grasp, and therefore measure and give a name to the 3rd dimension we call height.

 

in the second case there would be nothing, anyway.

[Air]

So if the universe has a finite size, which i had previously, previously meaning way in the past, heard it didnt, what is outside the universe? Is there any mathematical proof or such or just wild speculation? It seems very confusing that there is something outside the universe, i mean what would it be like and such? It must just be my tiny incompetent early 21st century mind........

 

This really depends on what you define as the "universe". If you are talking about the Observable Universe, then it simply expands into more of the same (more stars, more galaxies) - because it is defined by the distance of the most remote light we can see (imagine a sphere with a radious of some 13,7 billion years).

 

If you define the "universe" as everything that can possibly be, then there is nothing into which the Universe can expand. This would make the Universe infinite (but not necessarily occupying an infinite space - simply all the space that is available!).

 

Another way to view our Universe is to consider that it might be a part of a larger universe in which ours is only a small part (like an island in the ocean). This is actually just a modification of the first point above. However, depending on how each of the universes came into being, their physical laws and properties may be different.

Edited September 1, 2008 by Air
Adding quote so users are aware of the post at which I'm responding to.

[iNow]

Hi Air - I think it's very possible that you hadn't yet read the past few pages of this thread before making your response.

[Martin]

but how our microverse, region-verse, visiverse interact with the rest of the Universe?

 

is it like a drop of oil in a glass of water which remains completely isolated from the rest or like a drop of ink that "dissolves" into the bigger "verse"?

 

because in the first case "there is something outside". Something we can't even remotely understand and therefore from our perspective it would be "nothing". it would be like a flat 2d being trying to grasp, and therefore measure and give a name to the 3rd dimension we call height.

 

in the second case there would be nothing, anyway.

 

Max, don't you find that making up all these dumb-sounding synonyms for universe gets OLD rather quickly. I do, even though I'm guilty of trying to coin terms like that myelf. Jargon neologisms like "multiverse" can get really boring fast. Why can't people just say universe for the whole business, whatever it is, however they picture it?

 

The problem you are struggling with has been with us for 100+ years. There is the universe, and there is the part of it that we can see.

 

And for at least a hundred years some people have always been wondering what is beyond what we can see? What is the overall structure, that we might see if we could see further?

 

The new terminology (words like "multiverse") that people have made up in the past 5 or 10 years is basically just clutter, or garbage. It doesn't help clarify the problem. If you try you can state the essential questions cleanly in classical terms.

 

And within a science context there are limitations on what one can say. In science, the propositions must always be empirically testable.

This is a traditional requirement---an old rule that still matters although some people who claim to be scientists have shown a willingness to break it.

The rule is:

To be scientific, any mathematical model of the universe must make distinct predictions that can be tested.

 

Besides that, there is a traditional scientific preference for simplicity called Occam's Razor. If you have two mathematical models of the universe that result in the same measurable predictions---always choose the simpler and discard the more complicated. Occam put it this way: Don't put more entities in your theory than you need. Einstein rephrased it: Everything should be as simple as possible but not simpler.

 

Related to that is an assumption cosmologists normally make, called the cosmological principle, or cosmological assumption----they adopt the simplifying premise that since the universe obviously extends out beyond what we can see, it is essentially the SAME out there. They typically assume uniformity unless they see compelling reasons to postulate something different. Uniformity---assuming the same physical laws operating and the same average distribution of matter, wherever you look in all directions---makes things simple. So it obeys Occam. Compelling reasons is a judgment call. So far I see no compelling reason not to assume uniformity---and that includes looking past what used to be considered as singularities, beyond which one was not supposed to look. I assume the universe plays by the same rules back before the big bang and down thru a collapsed star's black hole. That's the simplest to assume, and it works.

 

I can't tell you how to picture the universe, and I don't think anyone can. In part because I don't think mainstream science has anything more than a provisional mathematical model---something that works, and fits the data remarkably well, but leaves some things unanswered and is subject to revision.

 

I can tell you my attitude---the universe is all physical existence. New words for it just confuse and clutter. We see a part, and we can infer somewhat out beyond that (because of the regular way our visible part is behaving). Beyond that the simplest way to extend the model is to assume uniformity.

 

Mathematically, the universe can work fine with no extra spatial dimensions (the need for more has not been demonstrated.) Mathematically it can have either finite or infinite spatial volume. Finite spatial volume does not require any outside.

 

I think you have to decide yourself how to picture the universe. I can tell you the most common mainstream model, and I can tell you my own attitudes or preferences but you decide. One thing is it is highly advisable to understand the common mainstream model first before you try to branch out.

 

For that, the Lineweaver article in March 2005 Scientific American is the best place to start.

[Air]

Hi Air - I think it's very possible that you hadn't yet read the past few pages of this thread before making your response.

 

It was aimed at the OP. I've added his quote to avoid confusion. Sorry for any confusion that it may have caused.

[iNow]

No worries at all. I just hoped that you'd had the opportunity to learn from all of the responses already. Be well.

[Aterna]

This is an interesting thread. I've always thought about these types of things.

 

We all know they say that if we were to travel the universe, we'd end up where we started. And that there's no "outside" because if there was, that would also be part of our universe. That still doesn't help answer the question though, not that it CAN be answered.

 

One thing to think about is that if we were to shoot out the earth in one direction and kept going straight up (I know it's impossible but imagine for the sake of the example) what would we eventually reach? The "edge"? (assuming there was one after assuming the universe is finite) What's after the edge? Nothing? What would happen to us? Would be just "bump" into the edge not being able to go any further?

 

It's not that I'm looking for an answer as nobody knows for certain (and we'll NEVER know) but it's interesting to think about.

Edited September 1, 2008 by Aterna

[Martin]

It's not that I'm looking for an answer as nobody knows for certain (and we'll NEVER know) but it's interesting to think about.

 

don't close yourself off so fast from the possibilities of knowledge:D

Can you prove we will never know? Humans occasionally surprise themselves at how much they can figure out.

 

 

...

One thing to think about is that if we were to shoot out [from] the earth in one direction and kept going straight up (I know it's impossible but imagine for the sake of the example) what would we eventually reach? ...

 

It sounds like you want to keep going at a constant speed. That is fine. You don't want to just boost off at some high speed and then have the earth gravity gradually slow you down---you want it guaranteed that you don't slow down. This is OK! (Pretend you have extra rockets.) But what speed would you like to go? It makes a difference.

 

We can easily answer your question if you tell us what speed. Say you choose to travel at the limit----the speed of light.

 

Then you could eventually just barely approach any galaxy which is currently 16 billion LY from us. But you could not reach any galaxy which is currently 17 billion LY from here. We can see lots of galaxies that are farther than that, that you could never get to, no matter how long you traveled at the speed of light. Even if you were immortal and had infinite time to travel.

 

There are lots of galaxies which are 15 billion LY from here. We can find some for you if you want. You could get to any of them in a finite time.

 

16 billion LY is known as the cosmological event horizon. It exists because of the observed accelerating expansion.

 

There is nothing unusual out there at the 16 billion LY limit, we observe the galaxies there, everything looks normal---the universe is rather uniform as far as we can tell.

 

there certainly is no chance of your reaching any kind of edge

but you asked, so I did the best I could to answer the question

[maxlongo]

...

 

that was exactly the point i was trying to make, although you put it in a much more detailed way

 

our ability to know is as vast as our ability to understand.

 

and we can't understant what we can't perceive, because for us it doesn't exist.

 

it would be like to explain the difference between green and red to a blind.

 

the universe is finite only because finite is the power of our intellect.

[Mr Skeptic]

it would be like to explain the difference between green and red to a blind.

 

Or like explaining the difference between infrared and ultraviolet to someone who cannot see those colors!

[Baby Astronaut]

One thing to think about is that if we were to shoot out the earth in one direction and kept going straight up (I know it's impossible but imagine for the sake of the example) what would we eventually reach? The "edge"? (assuming there was one after assuming the universe is finite) What's after the edge? Nothing? What would happen to us? Would be just "bump" into the edge not being able to go any further?

 

We can easily answer your question if you tell us what speed. Say you choose to travel at the limit----the speed of light.

 

Then you could eventually just barely approach any galaxy which is currently 16 billion LY from us. But you could not reach any galaxy which is currently 17 billion LY from here. We can see lots of galaxies that are farther than that, that you could never get to, no matter how long you traveled at the speed of light. Even if you were immortal and had infinite time to travel.

Let's continue to imagine (as per Aterna's suggestion), for the sake of getting the question answered.

 

Imagine that the universe froze in motion, allowing you to reach your destination if you had infinite time and were immortal. Or even that only the universe's expansion stopped (with no dire or perceptible consequences).

 

What of Aterna's question then?

[Martin]

Let's continue to imagine (as per Aterna's suggestion), for the sake of getting the question answered.

 

Imagine that the universe froze in motion, allowing you to reach your destination if you had infinite time and were immortal. Or even that only the universe's expansion stopped (with no dire or perceptible consequences).

 

What of Aterna's question then?

 

 

I didn't see your post earlier. So missed answering.

If you froze expansion that would make everything different. I guess there are two cases. Either space extends indefinitely and Aterna would just cruise on for ever and ever.

Or space is finite like the 3D sphere analog. In that case she would eventually get back approximately to where she started.

 

As long as she didn't get too badly deflected by random stars and black holes---their gravity can bend lightrays. So nothing is perfect, she is trying to travel a straight line but space has warts that will tend to deflect her path. Or she might run smack into something. But barring random imperfections like that, say on a perfect 3-sphere, she would get back to starting place.

 

To me that is not too interesting. What is interesting is that with the universe expanding the way it does----plus a little acceleration thrown in----you really can point to a galaxy that has a definite redshift, like z = 1.7, and say "that is the farthest thing you can get to if you depart today and travel at speed of light."

 

And 1.7 is not the farthest thing we can see by any means. People are reporting galaxies with redshift z > 6 all the time. z = 1.7 is comparatively near. It corresponds to about present distance 15.5 billion lightyears. The way things are going that is about the limit to the farthest galaxy she could get to. Of course by the time she got there the galaxy would be way way way farther from us than 15.5 billion lightyears because it would have been receding all the time she was traveling towards it.

[Mr Skeptic]

If you stopped the expansion of the universe, wouldn't that also remove gravity? Or is my understanding of general relativity even more limited than I thought?

[joshuam168]

martin, what do you mean that we could not travel to a galaxy that is 17 billion light years away? Is it because of the rate of expansion of the universe? But if that were the case we would not be able to move from our earth at all......please explain

[Martin]

If you stopped the expansion of the universe, wouldn't that also remove gravity? Or is my understanding of general relativity even more limited than I thought?

 

Baby Astronaut proposed a hypothetical case where you think of the galaxies and everything arranged just as they are today with their own small local motions etc, just without the general Hubble Law expansion of largescale distance. then the galaxy that WAS 17 billion LY from here will always STAY at about that distance.

 

and then naturally with Aterna's spaceship that can travel at speed c for as long as you need, YOU CAN GET THERE. Obviously it will take 17 billion years.

 

That is too artificial an example for us to discuss. Nobody could actually stop the expansion. It is useless to think about what would be involved physically.

 

At least I don't see the point. so I will just leave it for somebody else to speculate about

 

martin, what do you mean that we could not travel to a galaxy that is 17 billion light years away? Is it because of the rate of expansion of the universe?...

 

Yes that's right. The critical thing is the very slight acceleration.

 

There is a critical distance of around 15.5 to 16 billion LY which is called the cosmological horizon.

 

If something is less than that far, like 15 billion LY, then a light signal sent today could eventually get there. But by the time it got there it would have traveled much much farther than 15 billion LY and it would take much longer than 15 billion years, because while it is traveling towards the goal the goal is also receding. Still eventually it gets there.

 

If a galaxay is farther than that, like 17 billion LY, then a light signal sent today would never get there, because while it was going the first billion LY the damned galaxy would have receded still more. No matter if it traveled a trillion trillion trillion years it would never reach the galaxy, because expansion would keep carrying it further away.

 

If anybody likes math, there is some algebra you can do to get a rough estimate of what this critical distance is. If anyone is interested in the math, let me know. You wont get a full-course dinner of it, just a quick back of the envelope calculation to get a rough estimate, which as I recall is about 15.5.

[Baby Astronaut]

I don't believe that will happen. No proof, but just observation of observations

 

(and of hypothesis)

 

If it's true the universe had slowed down previously, and if Einstein's claim that space can expand, shrink, etc is true, I don't see how its expansion couldn't reverse in the future.

 

It would be more logical that scientists do not claim an ultimatum of ever increasing space, but rather, they make a projection of what'll happen if (and only if) current trends persist.

 

Aside from that, if dark energy were accelerating space, then isn't it feasible that after some point there wouldn't be enough dark energy to keep increasing the expansion, unless more dark energy were somehow created -- because the dark energy might be thinned out in the immensely expanded universe?

[Sisyphus]

I'm wondering how appropriate it is to think of the scale of the observable universe as the "big" analogy to the "small" planck length. Something which is so far away as to be "causally disconnected" from us effectively doesn't exist as far as science is concerned, right? Just like something smaller than the planck length, even though the immeasurability is for a totally different reason. Between them is the "size range of physical significance" or something.

 

Of course, that's very weird, since what "exists" or not depends on where and when you are. Oy. Then again, the analogy (which, BTW, I'm suggesting with more whimsy than confidence, so restrain your snark) might be useful in illustrating what each does and does not mean, particularly in mentally separating our ontology from our epistemology.

[pioneer]

I still think the difference between the observeable universe and what is beyond is the observable uses space-time and the beyond is just space. Without time none of the forces can not actt there is no speed less than C, since only at C is time stopped using SR. Enegy although moving at C as a time aspect called frequency. This requires time to act so energy can not exit in space without time. Due to E=MC2, matter also needs time due to the equvilency of energy which needs time.

[I_Pwn_Crackpots]

I still think the difference between the observeable universe and what is beyond is the observable uses space-time and the beyond is just space. Without time none of the forces can not actt there is no speed less than C, since only at C is time stopped using SR. Enegy although moving at C as a time aspect called frequency. This requires time to act so energy can not exit in space without time. Due to E=MC2, matter also needs time due to the equvilency of energy which needs time.

 

I don't get the feeling that you read or understood this thread.

 

 

Doesn't the universe already contain everything that exists? Which would mean that to talk about what is outside the universe is meaningless. We might as well talk about what is north of the North Pole.

 

I doubt what is outside the observable universe is any different than inside of it.

[Arch2008]

Actually, there still persists a misunderstanding of the question made by Joshuam168. If one says that the universe is everything, this isn’t commonly understood to mean anything before the Big Bang or beyond our space-time. Scientists are going to use WMAP to attempt to determine events before the BB and Lisa Randall has an unproven theory for dimensions beyond our space-time. So this is what is meant by “outside the universe”. If these efforts indeed turn out to be unfalsifiable, then the question becomes meaningless…but not until then. Remember, it’s the question that drives us.

[I_Pwn_Crackpots]

Actually, there still persists a misunderstanding of the question made by Joshuam168. If one says that the universe is everything, this isn’t commonly understood to mean anything before the Big Bang or beyond our space-time. Scientists are going to use WMAP to attempt to determine events before the BB and Lisa Randall has an unproven theory for dimensions beyond our space-time. So this is what is meant by “outside the universe”. If these efforts indeed turn out to be unfalsifiable, then the question becomes meaningless…but not until then. Remember, it’s the question that drives us.

 

He asked specifically what was outside the universe as his first post.

 

Also, we don't know what happened during the Big Bang, or if there was a time before it. If not, then that is also a meaningless question.

 

I think the persistent misunderstanding going on over here is that (and this applies to the public in general) there are some questions in the universe that simply don't have answers, or have any meaning.

[throng]

The outside has no volume, volume is space.

 

Considering its all little movements of energy the universe is the existence of energy forms.

 

A singular elementary state and a shifting form state. Not inside and outside