Exploring the Expanding Universe: The Concept of Empty Space

[RustyBullet]

The Universe is expanding. Expanding to where ? There must be an empty space where the universe will expand itself to, right ? Think about a baloon. Let's say the universe is everything inside the baloon. The baloon expands, because it has room to expand. If the universe is infinit, the empty space it has around it to expand to is also infinit. What is this empty space ?

Thoughts ?

 

[russ_watters]

The inverse is not shaped like the space inside a balloon, it is shaped more like the surface of the balloon, but in 3d instead of 2d. Hence, there is no edge - no boudary for there to be something "outside" of.

 

[RustyBullet]

You have a point... but I still think that for it to be able to expand, there must be somewhere to expand to. How can something get bigger if it doesn't have enough room to get bigger ?

 

[Jack21222]

The inverse is not shaped like the space inside a balloon, it is shaped more like the surface of the balloon, but in 3d instead of 2d. Hence, there is no edge - no boudary for there to be something "outside" of.

I've never been able to grasp this argument. Even the surface of the balloon expands into something else.

If you're trying to say we have no way to measure an "outside" of the universe, so it might as well not exist for our purposes, that's fine. But, that isn't what you're saying.

Here's a related mental exercise. Imagine the expansion of the universe was halted, everything frozen in time where it is right now. Then, go in a straight line in any direction you wish. Would you end up back where you started eventually? Would you run into a boundry? What would happen?

Some say the big bang came to be because of a random fluctuation in vacuum energy, or that "something" is more stable than "nothing." If that is the case, what is to stop (some time in the distant future, even by cosmological timescales) another "big bang" to develop inside of our universe? Would the hypothetical denizens of that universe claim that they aren't expanding into anything? That there is no "outside?"

 

[cristo]

I've never been able to grasp this argument. Even the surface of the balloon expands into something else.

It's an analogy which, of course, is not exact.

Imagine the expansion of the universe was halted, everything frozen in time where it is right now. Then, go in a straight line in any direction you wish. Would you end up back where you started eventually? Would you run into a boundry? What would happen?

If the universe is closed, then yes, you will at some time go back to where you started. If the universe is flat, then you would continue forever. Current observations do not enable us to say which of the above is true. One of the bonuses of the balloon analogy is it gives us an example of a finite unbounded universe.

 

[DaveC426913]

If the universe is closed, then yes, you will at some time go back to where you started. If the universe is flat, then you would continue forever.

Even if the universe is only 14Gy old? How could you travel forever? It has a finite width.

 

[v2kkim]

I think the vacuum is not a simple empty one, but it has a property of inertia that is expanding activity wants to continue, like moving objects move continuously. And I am satisfied limiting myself in the universe.

 

[Waveform]

I think this borders more on the philosophical.

The Universe is not expanding to ‘where’. Rather it makes the ‘where’ as it expands.

The expansion creates time and space as it expands. To ask what is on the other side means nothing.

To paraphrase; to ask what is on the other side is like asking what is 15 kilometers South of the South Pole. It sounds like a good question but in essence really does not have a legitimate answer because of the question in the first place.

As put it, freeze or stop time. This sounds good, but think about it. If time exists at all then in flows in a direction and is measurable. This evokes a problem. If time flows, then it can not stop.
The premise means nothing.

Simple example;

If I were to stop time, then I would have to stop it for a measurable period. Perhaps a week, month, year, what ever. Yet if I stopped it, there is no appreciable time then to measure the stopped period.

I think these kinds of problems deal more with us than the universe. Our comprehension of dimensional space is closely related to our evolution. We did not require higher dimensional evolution. There for we are not ‘wired’ for it.

We have problems with understanding quantum mechanics, entangled particles, universal expansion and such, and probably always will.

So, the best thing is try to grasp the concept (which I have a difficult job with) there is no other side. There is no wall, no barrier, no time, no other side, no nothing.
It does not exist. The existence is made as the universe expands.

I know my explanation ‘sucks’ but I have to keep it philosophical because there are no formulas to analogize it in.
A philosophical question is best answered with a philosophical answer.

 

[Jack21222]

Waveform:

Ok, instead of "freezing time" just imagine the state of things at present at further and further distances from you. You see the sun as it was 8 minutes ago, but it exists now. Imagine how it is now. Now, imagine a further away star. Continue along in a linear fashion. Keep going out to where we see quasars right now. They will look dramatically different than we currently see them. Keep going out.

No ad hoc "time freezing" needed, it is just a mental excercise.

It seems to me we'd either hit a boundry or go around in a big circle.

I may be completely wrong here, but I think the more correct answer to the original question is something like "Nobody knows for sure... Furthermore, it may not even be a meaningful question to begin with. We're still working out the details. "

 

[RustyBullet]

Maybe we are forgetting something guys...

We all know the universe is composed of 90% Dark Matter. and the other 10% is everything else. Maybe the 'void', the empty space (if it exists), is Dark Matter.

 

[v2kkim]

Maybe we are forgetting something guys...

We all know the universe is composed of 90% Dark Matter. and the other 10% is everything else. Maybe the 'void', the empty space (if it exists), is Dark Matter.

Are you implying that the dark matter is being created from nothing as space expands ?

 

[Waveform]

Ok, instead of "freezing time" just imagine the state of things at present at further and further distances from you. You see the sun as it was 8 minutes ago, but it exists now. Imagine how it is now.

You see, this is the problem. I can't imagine it now. I have absolutely no way of knowing it 'now'.
Any information form the sun is only pertinent to me in my frame of reference.

This is like a mathematical anomaly; if I launch a projectile against a wall the distance is always divisible by 2, yet the projectile will hit the wall.

Then, what is the definition of 'now'. If you are looking at the moon, if you are looking at a tree across the street, if you are looking at an object just before your eyes. The answer is 'no' to all of these.

That is why these type of conversations are fruitless. There is point, counter point, that will eventually get into a loop, and excuse the pun turn back on itself.

This reminds me of a question someone asked me a few days ago. "Why does light travel at a particular speed and not a kilometer / hr more or less".
My answer was simple, " I have no idea. Things just work in a particular way".

Furthermore, it may not even be a meaningful question to begin with.

This is exactly what I said!

Answers to some things can be meaningless, which poses the premise, some questions can be meaningless.

I am not being obnoxious or fecicious here but perhaps ask the same question on a philosophical or religious forum. Perhaps they can give you a better answer.

However, I still do appreciate your problem with the universe 'size' or barrier.

However, unless there is some new radical discovery, you just have to get use to the idea.
There is no other side, your perceived 'other side' is here.
"What you see is what you get".



As for dark matter or energy, probably a legitimate question. But probably should be started in a new thread. Doesn't quite fit into this thread.

But, that is the moderators decision.

 

[Jack21222]

I'm reading Carl Sagan's "Cosmos," and I like how he phrases it in that book.

"By definition, nothing we can ever know about was outside. It is better to think of it from the inside..."

I like the qualifier "...we can ever know about." That way, an "outside" hasn't been disproven, but rather, its unprovable. It's kinda like God in that way, I guess.

 

[RustyBullet]

Are you implying that the dark matter is being created from nothing as space expands ?

Maybe... No one knows how dark matter is created... So maybe dark matter is the void. who knows ? For all we know, our entire universe can be inside a tiny atom of a whole other bigger universe.

 

[v2kkim]

Yes, I like to accommodate all kinds of possible imagination, until disproved or obvious better ones come up.

 

[whybother]

Anyone who asks "what is outside of the universe" knows nothing about... the universe. It is an entirely meaningless question. Just like asking "what happened 'before' the universe'". Meaningless garbage. The universe is all there is. No outside of it.

If we are talking about inflationary multiverses, we can define "outside" differently, but that is a different matter.

If you want to believe the universe is expanding, fine, but it's just expanding. Not expanding into something. It's expanding in the sense that things are getting further apart. Period.

 

[RustyBullet]

Anyone who asks "what is outside of the universe" knows nothing about... the universe.

Are you serious ?

The only people who question, imagine, wonder about 'meaningless garbage' are the ones who understand the universe. People used to think that there was nothing outside our solar sistem, that our solar sistem was all there was. Exactly what you just said, "meaningless garbage" was also told to Galileo and all the other pioneers of astronomy when they started wondering what was outside our planet.

 

[whybother]

Exactly what you just said, "meaningless garbage" was also told to Galileo and all the other pioneers of astronomy when they started wondering what was outside our planet.

If we assume that the basic things we know about the universe/cosmology/and general relativity are correct (and frankly, we all do), then the comparison there is pretty bad.

If you want to assume that we know absolutely nothing about physics, then sure, let's talk about what's outside the universe and pretend that it's the 1600s.

Unless you are willing to through out general relativity, it is meaningless to talk about what's outside the universe. Throwing out GR is not cool. It was cool for Galleio to through out magic and witchcraft and whatever the hell else they believed then though.

 

[cam875]

If we assume that the basic things we know about the universe/cosmology/and general relativity are correct (and frankly, we all do), then the comparison there is pretty bad.

If you want to assume that we know absolutely nothing about physics, then sure, let's talk about what's outside the universe and pretend that it's the 1600s.

Unless you are willing to through out general relativity, it is meaningless to talk about what's outside the universe. Throwing out GR is not cool. It was cool for Galleio to through out magic and witchcraft and whatever the hell else they believed then though.

theories change all the time, and to say that anyone who thinks about anything outside the universe does not understand the universe at all is garbage in its own right, because right now not one person understands the universe exactly, this includes you, in 100 years they might have reformulated current cosmology into a model which has things outside of our universe, not saying its probable but don't undermine someones opinion out of ignorance.

 

[whybother]

If they reformulate cosmology to "have things outside our universe" then they are just redefining "universe".

 

[cam875]

who knows there may be no limit, there could be universe's inside universe's (just an example, not a real opinion) the point is, unless you publish a TOE for the entire universe with everything figured out don't undermine someone else's curiousity.

 

[whybother]

dont undermine someone else's curiousity.

I'm pretty sure that's a lot of what the internet is for, actually.

 

[MathematicalPhysicist]

You have a point... but I still think that for it to be able to expand, there must be somewhere to expand to. How can something get bigger if it doesn't have enough room to get bigger ?

Perhaps there's a mechanism which makes the universe keep expanding, i.e the universe creates its own space by anhilating and extracting virtual particles which become as real as any other tangible particles.

 

[Jack21222]

It is an entirely meaningless question.

Clashes with

The universe is all there is. No outside of it.

I'm going to steal a "meaningless question" from Neil deGrasse Tyson. If somebody asks you "What is the square root of a pork chop?" you cannot answer "That's a meaningless question. The square root of a pork chop is imaginary." You can just stop at "that's a meaningless question."

In this case, talking about the universe, I don't think it's accurate to say "there is no outside of the universe." It's more accurate to say "We have no way of defining what 'outside' means in this case" or some such thing.

Later, you say it much better.

it is meaningless to talk about what's outside the universe

That is NOT the same as "There is no 'outside' of the universe."

As I mentioned before, if a flux in the vacuum of space in our universe were to create another "big bang" within our universe, and it followed the same course of evolution ours did, would the future intelligent creatures in that universe also say "There is no outside of the universe?" Clearly, wouldn't OUR universe (or what remains of it) be "outside" their universe?

It may be a meaningless question for them to ask, because their universe would obliterate any trace of what is "outside" of it. They'd have no way to know what, if anything, is "outside." They'd have no way to know if it was a meaningful question or not. Defining "outside" would be problematic.

Throwing out GR is not cool.

Sure it is. General relativity and quantum mechanics cannot both be 100% correct. One or both may need to be "thrown out" as you put it.

I'm not necessarily disagreeing with most of what you say, but the way you phrase some things imparts a certain "finality" on some topics which may not necessarily exist.

 

[DaveC426913]

Tyson. If somebody asks you "What is the square root of a pork chop?" you cannot answer "That's a meaningless question. The square root of a pork chop is imaginary." You can just stop at "that's a meaningless question."

The comment "that's a meaningless question." is inevitably going to be countered with "Why is it meaningless?" So, you might as well just go ahead and anticipate that. You owe them a rationale for your claim.

 

[Waveform]

Since I also use the terminology of the “meaningless question” I’ll give my interpenetration.

A question has to have a viable premise. It has to be answerable or arguable or even an unanswerable, but yet still maintains the criteria of a question.

I look at my watch right now, it is 2:30pm. I can then ask; If it is 2:30 pm here what time is it in the middle of the closest black.
Not only is it unanswerable, the question is meaningless.

Another point, good questions are as important as good answers.

I think at times when people get into a very philosophical area they should carefully think about how to word a question rather than just ‘hip shot’ it.

I think the response would perhaps be more positive.

 

[DaveC426913]

I look at my watch right now, it is 2:30pm. I can then ask; If it is 2:30 pm here what time is it in the middle of the closest black.
Not only is it unanswerable, the question is meaningless.

Of course it is, but you have picked an obvious one (In fact, why did you invent an example that is obvious? Is it perhaps because the one under discussion wasn't obviously non-sensical, yes?).

The asker does not necessarily know what about the question does not make sense; if they did, they probably wouldn't have asked it.

 

[Integral]

Since our universe is that which can be observed, to be outside our universe would to be unobservable. In other words if we can observe it it is in our universe.

Note that since we have rules about what can be discussed on these forums, such a question brings up more then a few problems. We restrict our discussions to known and accepted physics, and specifically prohibit religion. It is my humble opinion that things that lie outside our universe fall into the realm of metaphysics and religion, therefore this topic falls into forbidden territory.

How can we discuss the unobservable while staying within the realm of known physics?

 

[Waveform]

In fact, why did you invent an example that is obvious? Is it perhaps because the one under discussion wasn't obviously non-sensical, yes?

I was certainly not going to present an example that was ambitious. There would have been no point in it. So, of courses I kept it obvious.

The asker does not necessarily know what about the question does not make sense; if they did, they probably wouldn't have asked it.

Yes, I can absolutely appreciate your point here and agree.

However, I will still imply this thread can go on indefinitely and still be no farther ahead than when it started.

 

[Dmitry67]

It is possible that what we call "Universe" is a just a brane in a highly dimensional world called "Multiverse".
In that sense question can be valid and the answer is "Multiverse".

 

[Cryptonic]

Anyone who asks "what is outside of the universe" knows nothing about... the universe. It is an entirely meaningless question. Just like asking "what happened 'before' the universe'". Meaningless garbage. The universe is all there is. No outside of it.

If we are talking about inflationary multiverses, we can define "outside" differently, but that is a different matter.

If you want to believe the universe is expanding, fine, but it's just expanding. Not expanding into something. It's expanding in the sense that things are getting further apart. Period.

This almost sounds like a quasi-religious stance to me heh! It's almost a stubborn refusal to question. Maybe there's fear lurking in such staunch conservatism, like a fear of the unknown or something?

Jack21222 makes valid points. Inside an event horizon of a black hole, you would be completely disengaged from the "outside universe", but that doesn't mean "nothing" exists "out there" somewhere!

Besides, Dmitry67 correctly points out our universe may be a subset of a larger multiverse. Defining "universe" as an "all-encompassing EVERYTHING" can be deceptive and is really nothing more than word-games!

 

[cristo]

This almost sounds like a quasi-religious stance to me heh! It's almost a stubborn refusal to question. Maybe there's fear lurking in such staunch conservatism, like a fear of the unknown or something?

Such statements have nothing to do with Cosmology, and thus this thread is done.