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Is new space created?

SarcasticIndeed
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1/6/2013 6:29:33 PM
Posted: 3 years ago
Just a quick question... The universe is supposed to be expanding, so it must be creating new space, right? Out of what is this space generated then?
<SIGNATURE CENSORED> nac
RyuuKyuzo
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1/6/2013 7:05:22 PM
Posted: 3 years ago
Higher spatial dimensions (4D brains and the like). Read up on superstring theory.
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Ramshutu
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1/7/2013 2:12:22 PM
Posted: 3 years ago
It's not necessarily "getting created", as much as it could be existing space stretching. All we know, is that the universe appears to be expanding; and the exact nature of what is expanding into what is an interesting topic covered by a number of potential theories, including Superstring theory as mentioned.
tBoonePickens
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1/7/2013 3:43:08 PM
Posted: 3 years ago
At 1/6/2013 6:29:33 PM, SarcasticIndeed wrote:
Just a quick question... The universe is supposed to be expanding, so it must be creating new space, right?
Depends on what you mean by "creating". If you mean "creating" as in "something out of nothing", then the answer is no; if you mean creating as in "space is expanding, unfolding, becoming" then yes.

Out of what is this space generated then?
It is unfolding from the existing order.
WOS
: At 10/3/2012 4:28:52 AM, Wallstreetatheist wrote:
: Without nothing existing, you couldn't have something.
DoubtingDave
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1/7/2013 3:52:36 PM
Posted: 3 years ago
At 1/6/2013 6:29:33 PM, SarcasticIndeed wrote:
Just a quick question... The universe is supposed to be expanding, so it must be creating new space, right? Out of what is this space generated then?

What do you mean by "being created"? Rather, space itself is expanding - it's like blowing up a balloon - you are not "creating" new air, rather, you are expanding it.
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tBoonePickens
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1/7/2013 4:05:34 PM
Posted: 3 years ago
At 1/7/2013 3:52:36 PM, DoubtingDave wrote:
At 1/6/2013 6:29:33 PM, SarcasticIndeed wrote:
Just a quick question... The universe is supposed to be expanding, so it must be creating new space, right? Out of what is this space generated then?

What do you mean by "being created"? Rather, space itself is expanding - it's like blowing up a balloon - you are not "creating" new air, rather, you are expanding it.
Well, the analogy would be that you're not creating "new balloon" but you're expanding it; HOWEVER, you are introducing NEW air into the balloon. This balloon analogy is better used to illustrate the fact the Universe appears to expanding regardless of where you are located within it (dots on the balloon surface are moving away from each other, etc.)

There really is no analogy that illustrates a principle that can address his question/doubt. The only thing that would is the Universe itself! You see, what the OP is suggesting is that if the Universe is expanding then it must be expanding out of something (itself) into something else (outside itself) thus becoming a bigger self. If one considers the Universe to be "all that exists" (which I believe is the proper definition) then there IS NO outside it because there is nothing that exists that ISN'T the Universe. This is why I prefer to say that the Universe is UNFOLDING: it means that what is already THERE is CHANGING. It's not that there is any MORE Universe than there was before, it is that the ARRANGEMENT of what was already there has changed.
WOS
: At 10/3/2012 4:28:52 AM, Wallstreetatheist wrote:
: Without nothing existing, you couldn't have something.
phantom
Posts: 6,774
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1/7/2013 4:07:58 PM
Posted: 3 years ago
At 1/7/2013 3:52:36 PM, DoubtingDave wrote:
At 1/6/2013 6:29:33 PM, SarcasticIndeed wrote:
Just a quick question... The universe is supposed to be expanding, so it must be creating new space, right? Out of what is this space generated then?

What do you mean by "being created"? Rather, space itself is expanding - it's like blowing up a balloon - you are not "creating" new air, rather, you are expanding it.

I think he means what it's expanding in to, not space in itself.
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Ramshutu
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1/7/2013 5:07:57 PM
Posted: 3 years ago
As a side note; one hypothesis to consider, as well as string theory and others (which are very interesting, but are not really validated so need to be treated with the pinch of salt they need) is as follows:

The universe is expanding. However, it is quite possible, neglicting other hypothesis, is that space exists WITHIN the universe; the universe does not exist WITHIN space (that we know of, can prove or test otherwise).

Because of this, the question "what is universe expanding into" may not make any logical make sense; as to be expanding "into" something requires you to assume that there is space in existance outside of the universe.
tBoonePickens
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1/7/2013 5:23:33 PM
Posted: 3 years ago
At 1/7/2013 5:07:57 PM, Ramshutu wrote:
As a side note; one hypothesis to consider, as well as string theory and others (which are very interesting, but are not really validated so need to be treated with the pinch of salt they need) is as follows:

The universe is expanding. However, it is quite possible, neglicting other hypothesis, is that space exists WITHIN the universe; the universe does not exist WITHIN space (that we know of, can prove or test otherwise).

Because of this, the question "what is universe expanding into" may not make any logical make sense; as to be expanding "into" something requires you to assume that there is space in existance outside of the universe.

Thanks for repeating what I said.
WOS
: At 10/3/2012 4:28:52 AM, Wallstreetatheist wrote:
: Without nothing existing, you couldn't have something.
tBoonePickens
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1/7/2013 5:24:15 PM
Posted: 3 years ago
At 1/7/2013 5:23:33 PM, tBoonePickens wrote:
At 1/7/2013 5:07:57 PM, Ramshutu wrote:
As a side note; one hypothesis to consider, as well as string theory and others (which are very interesting, but are not really validated so need to be treated with the pinch of salt they need) is as follows:

The universe is expanding. However, it is quite possible, neglicting other hypothesis, is that space exists WITHIN the universe; the universe does not exist WITHIN space (that we know of, can prove or test otherwise).

Because of this, the question "what is universe expanding into" may not make any logical make sense; as to be expanding "into" something requires you to assume that there is space in existance outside of the universe.

Thanks for repeating what I said.

And now that it's been repeated 3 times, then it HAS to be true!
WOS
: At 10/3/2012 4:28:52 AM, Wallstreetatheist wrote:
: Without nothing existing, you couldn't have something.
SarcasticIndeed
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1/7/2013 9:19:18 PM
Posted: 3 years ago
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.
<SIGNATURE CENSORED> nac
Floid
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1/7/2013 11:15:41 PM
Posted: 3 years ago
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

The distance between major objects (like galaxies) in the universe is increasing with time. You could correlate that with density and say the density of space is decreasing with time.
Sidewalker
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1/8/2013 2:30:04 AM
Posted: 3 years ago
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.
"It is one of the commonest of mistakes to consider that the limit of our power of perception is also the limit of all there is to perceive." " C. W. Leadbeater
Sidewalker
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1/8/2013 2:31:00 AM
Posted: 3 years ago
At 1/7/2013 5:24:15 PM, tBoonePickens wrote:
At 1/7/2013 5:23:33 PM, tBoonePickens wrote:
At 1/7/2013 5:07:57 PM, Ramshutu wrote:
As a side note; one hypothesis to consider, as well as string theory and others (which are very interesting, but are not really validated so need to be treated with the pinch of salt they need) is as follows:

The universe is expanding. However, it is quite possible, neglicting other hypothesis, is that space exists WITHIN the universe; the universe does not exist WITHIN space (that we know of, can prove or test otherwise).

Because of this, the question "what is universe expanding into" may not make any logical make sense; as to be expanding "into" something requires you to assume that there is space in existance outside of the universe.

Thanks for repeating what I said.

And now that it's been repeated 3 times, then it HAS to be true!

Can I just agree, or do I have to say it again?
"It is one of the commonest of mistakes to consider that the limit of our power of perception is also the limit of all there is to perceive." " C. W. Leadbeater
SarcasticIndeed
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1/8/2013 7:41:08 AM
Posted: 3 years ago
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?
<SIGNATURE CENSORED> nac
drafterman
Posts: 18,870
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1/8/2013 9:09:35 AM
Posted: 3 years ago
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?

http://en.wikipedia.org...
tBoonePickens
Posts: 3,266
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1/8/2013 1:53:17 PM
Posted: 3 years ago
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?
The Universe (space included) has a limited number of possible "arrangements"; time occurs as the Universe transforms from one "arrangement" extreme to the other. It's not indefinite in the sense that when time runs out, there will definitely not be any more possible arrangements!
WOS
: At 10/3/2012 4:28:52 AM, Wallstreetatheist wrote:
: Without nothing existing, you couldn't have something.
SarcasticIndeed
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1/8/2013 3:56:59 PM
Posted: 3 years ago
At 1/8/2013 1:53:17 PM, tBoonePickens wrote:
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?
The Universe (space included) has a limited number of possible "arrangements"; time occurs as the Universe transforms from one "arrangement" extreme to the other. It's not indefinite in the sense that when time runs out, there will definitely not be any more possible arrangements!

If space can be differently arranged that means there must be more space at one point than space in another point. So are there really places in the universe where there is more "space" in a certain volume? If the universe is streching, that would mean there is less and less space per a certain volume every second.
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Franz_Reynard
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1/8/2013 4:11:23 PM
Posted: 3 years ago
At 1/6/2013 6:29:33 PM, SarcasticIndeed wrote:
Just a quick question... The universe is supposed to be expanding, so it must be creating new space, right? Out of what is this space generated then?

Space isn't generated, per se. The Universe is an active explosion. So, think more the expansion of air when it's heated.
Franz_Reynard
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1/8/2013 4:13:22 PM
Posted: 3 years ago
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?

Redshift, galactic rip, etc.
1dustpelt
Posts: 1,970
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1/8/2013 5:22:36 PM
Posted: 3 years ago
Our human minds are too feeble to understand.
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SarcasticIndeed
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1/8/2013 8:26:26 PM
Posted: 3 years ago
At 1/8/2013 4:11:23 PM, Franz_Reynard wrote:
At 1/6/2013 6:29:33 PM, SarcasticIndeed wrote:
Just a quick question... The universe is supposed to be expanding, so it must be creating new space, right? Out of what is this space generated then?

Space isn't generated, per se. The Universe is an active explosion. So, think more the expansion of air when it's heated.

So space is getting just thinner and thinner?
<SIGNATURE CENSORED> nac
Franz_Reynard
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1/8/2013 9:34:28 PM
Posted: 3 years ago
At 1/8/2013 8:26:26 PM, SarcasticIndeed wrote:
At 1/8/2013 4:11:23 PM, Franz_Reynard wrote:
At 1/6/2013 6:29:33 PM, SarcasticIndeed wrote:
Just a quick question... The universe is supposed to be expanding, so it must be creating new space, right? Out of what is this space generated then?

Space isn't generated, per se. The Universe is an active explosion. So, think more the expansion of air when it's heated.

So space is getting just thinner and thinner?

That should be a fair way of looking at it... I mean, when it all began, it was in a state of singularity, which is about as dense as it comes. Thus, from there, it can only become progressively less dense.

But, think of it this way. When you zoom in just so far into molecules of air, it's less how "thin" it is, and more, the space between each molecule. So, from the vantage of something cosmically enormous, like a a galaxy, perhaps the universe is becoming progressively thinner, but for things that are unimaginably small in comparison, like us, it's only expanding.
Sidewalker
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1/9/2013 6:52:20 AM
Posted: 3 years ago
At 1/8/2013 3:56:59 PM, SarcasticIndeed wrote:
At 1/8/2013 1:53:17 PM, tBoonePickens wrote:
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unit of volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergalactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?
The Universe (space included) has a limited number of possible "arrangements"; time occurs as the Universe transforms from one "arrangement" extreme to the other. It's not indefinite in the sense that when time runs out, there will definitely not be any more possible arrangements!

If space can be differently arranged that means there must be more space at one point than space in another point. So are there really places in the universe where there is more "space" in a certain volume? If the universe is stretching, that would mean there is less and less space per a certain volume every second.

It's more appropriate to think of it as there is more and more volume for the same amount of space. The expansion of space is a metric expansion, which means the distance between distant objects in space is increasing, but they are not moving in space. Space is the dimensional framework within which measurements occur. It is measured by recognizing that distance between distant objects is increasing, so in effect they are moving away from us, but it isn't like the traditional concept of motion because the objects are not moving in space, it is the space between the objects that is expanding.

Think of it this way, imagine three dots an inch apart and in a row on the surface of a balloon. The dots are objects, the surface of the balloon is space. If the balloon doubles in size, the distance between the dots is greater but their position on the balloon, in space, hasn't changed. Measured from dot 1, dot 2 has moved an inch away, and dot 3 has moved two inches away. This is how we would measure the change in distance from dot 1, but dot 3 is not moving any faster than dot 2, it only will be measured that way from dot 1 because it is space that is expanding, the objects are not moving in space, the dots are still in the same place on the balloon that they started from.

You can't think of space as a substance that is stretching, getting thinner or wider, or less dense, to understand you have to recognize that space itself is a dimensional framework in which objects exist and have relative positions to each other. Think of it as a coordinate system that allows one to locate items in space, from the reference point of an object, there are three coordinates that allow one to locate their position as it relates to your position. It's somewhat misleading to say space is expanding because that implies that there is a thing that is expanding, but in a metric expansion, it is only the coordinate variables that are expanding, and since all three linear coordinates in a three dimensional coordinate system are expanding at the same rate, the relative positions of objects aren't changing in space, they remain where they are relative to each other, it's the metric of the coordinates that is expanding.

It's certainly counter intuitive, but that's just the way physics is since relativity theory changed all the rules. Our intuitive sensibilities result from experience at a certain scale, but in this context, relativity applies to scales far beyond the scales that our intuition can grasp. When you go to a very small scale, where quantum physics applies, or very large scales, where relativity applies, the physics is very different than they are on the scale we are accustomed to, which can be seen as a different kind of logic, and consequently, you are dealing with scales that are immensely counter intuitive.
"It is one of the commonest of mistakes to consider that the limit of our power of perception is also the limit of all there is to perceive." " C. W. Leadbeater
Sidewalker
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1/9/2013 7:02:03 AM
Posted: 3 years ago
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?

No, space is not nothing, but in this context, it isn't really something either, the only thing it is is that dimensional framework within which we can measure the distance between things, so you can't think of it as space is something that is expanding, you have to think of the expansion of space as a metric expansion, which is to say, nothing is happening to the space itself, but the rulers we measure with are getting longer.
"It is one of the commonest of mistakes to consider that the limit of our power of perception is also the limit of all there is to perceive." " C. W. Leadbeater
Sidewalker
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1/9/2013 7:29:43 AM
Posted: 3 years ago
At 1/9/2013 7:02:03 AM, Sidewalker wrote:
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?

No, space is not nothing, but in this context, it isn't really something either, the only thing it is is that dimensional framework within which we can measure the distance between things, so you can't think of it as space is something that is expanding, you have to think of the expansion of space as a metric expansion, which is to say, nothing is happening to the space itself, but the rulers we measure with are getting longer.

Correction: The rulers are getting shorter, it's the measurements that are getting longer.
"It is one of the commonest of mistakes to consider that the limit of our power of perception is also the limit of all there is to perceive." " C. W. Leadbeater
SarcasticIndeed
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1/9/2013 7:53:49 AM
Posted: 3 years ago
At 1/9/2013 7:29:43 AM, Sidewalker wrote:
At 1/9/2013 7:02:03 AM, Sidewalker wrote:
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?

No, space is not nothing, but in this context, it isn't really something either, the only thing it is is that dimensional framework within which we can measure the distance between things, so you can't think of it as space is something that is expanding, you have to think of the expansion of space as a metric expansion, which is to say, nothing is happening to the space itself, but the rulers we measure with are getting longer.

Correction: The rulers are getting shorter, it's the measurements that are getting longer.

This is pretty hard to grasp... So the framework within which we measure things is getting larger.. Then it must be expanding. And if it is expanding, it must get more of itself to make the expansion happen. This is rather confusing...
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tBoonePickens
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1/9/2013 12:42:05 PM
Posted: 3 years ago
At 1/8/2013 3:56:59 PM, SarcasticIndeed wrote:
At 1/8/2013 1:53:17 PM, tBoonePickens wrote:
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?
The Universe (space included) has a limited number of possible "arrangements"; time occurs as the Universe transforms from one "arrangement" extreme to the other. It's not indefinite in the sense that when time runs out, there will definitely not be any more possible arrangements!

If space can be differently arranged that means there must be more space at one point than space in another point.
It's not just "space" that's differently arranged, it's the entire Universe that's differently arrange. Think of it as a rearrangement of existence.

So are there really places in the universe where there is more "space" in a certain volume?
One could say such a thing about variations in CMBR I suppose, as well as variations in curvatures in spacetime, etc.

If the universe is streching, that would mean there is less and less space per a certain volume every second.
Well, that's why I wouldn't use "stretching" use to describe this. I would just say that the "total contents" of the Universe is unchanged but that it is arranged differently in that there is now more space and less time. Or as Sidewalker put it: "It's more appropriate to think of it as there is more and more volume for the same amount of space."

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At 1/9/2013 6:52:20 AM, Sidewalker wrote:
It's more appropriate to think of it as there is more and more volume for the same amount of space. The expansion of space is a metric expansion, which means the distance between distant objects in space is increasing, but they are not moving in space. Space is the dimensional framework within which measurements occur. It is measured by recognizing that distance between distant objects is increasing, so in effect they are moving away from us, but it isn't like the traditional concept of motion because the objects are not moving in space, it is the space between the objects that is expanding.
Excellent explanation! So I scratch my head and think: is there a reason why space itself (or the "metric expansion") need to obey the limit of c?

Think of it this way, imagine three dots an inch apart and in a row on the surface of a balloon. The dots are objects, the surface of the balloon is space. If the balloon doubles in size, the distance between the dots is greater but their position on the balloon, in space, hasn't changed. Measured from dot 1, dot 2 has moved an inch away, and dot 3 has moved two inches away. This is how we would measure the change in distance from dot 1, but dot 3 is not moving any faster than dot 2, it only will be measured that way from dot 1 because it is space that is expanding, the objects are not moving in space, the dots are still in the same place on the balloon that they started from.

You can't think of space as a substance that is stretching, getting thinner or wider, or less dense, to understand you have to recognize that space itself is a dimensional framework in which objects exist and have relative positions to each other. Think of it as a coordinate system that allows one to locate items in space, from the reference point of an object, there are three coordinates that allow one to locate their position as it relates to your position. It's somewhat misleading to say space is expanding because that implies that there is a thing that is expanding, but in a metric expansion, it is only the coordinate variables that are expanding, and since all three linear coordinates in a three dimensional coordinate system are expanding at the same rate, the relative positions of objects aren't changing in space, they remain where they are relative to each other, it's the metric of the coordinates that is expanding.
Yet why isn't this metric coordinate system expanding between the earth and the moon? The earth and the sun? Our solar system and the Milkyway? It seems to only be happening between the Milkyway and MOST other galaxies. I say "most" because Andromeda is heading strait for us!

It's certainly counter intuitive, but that's just the way physics is since relativity theory changed all the rules. Our intuitive sensibilities result from experience at a certain scale, but in this context, relativity applies to scales far beyond the scales that our intuition can grasp. When you go to a very small scale, where quantum physics applies, or very large scales, where relativity applies, the physics is very different than they are on the scale we are accustomed to, which can be seen as a different kind of logic, and consequently, you are dealing with scales that are immensely counter intuitive.
And how!
WOS
: At 10/3/2012 4:28:52 AM, Wallstreetatheist wrote:
: Without nothing existing, you couldn't have something.
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1/9/2013 7:37:53 PM
Posted: 3 years ago
At 1/9/2013 7:53:49 AM, SarcasticIndeed wrote:
At 1/9/2013 7:29:43 AM, Sidewalker wrote:
At 1/9/2013 7:02:03 AM, Sidewalker wrote:
At 1/8/2013 7:41:08 AM, SarcasticIndeed wrote:
At 1/8/2013 2:30:04 AM, Sidewalker wrote:
At 1/7/2013 9:19:18 PM, SarcasticIndeed wrote:
So if the space is streching (or however you call it), it is becoming less and less dense, right? I mean, I never heard about the density of space itself, but what you said kinda implies that.

Density is mass per unitof volume, space has no mass so density doesn't apply.

If you are talking about the mass in a volume of space, then the expansion of space would correlate to a lower density measurement, but then you are talking very large volumes of space on an intergallactic scale. On the scale of say, our solar system, density isn't decreasing.

But space can't stretch indefinitely, right? I mean, space is not nothing, it cannot just become wider without having some impact on it, right?

No, space is not nothing, but in this context, it isn't really something either, the only thing it is is that dimensional framework within which we can measure the distance between things, so you can't think of it as space is something that is expanding, you have to think of the expansion of space as a metric expansion, which is to say, nothing is happening to the space itself, but the rulers we measure with are getting longer.

Correction: The rulers are getting shorter, it's the measurements that are getting longer.

This is pretty hard to grasp... So the framework within which we measure things is getting larger.. Then it must be expanding. And if it is expanding, it must get more of itself to make the expansion happen. This is rather confusing...

Space isn't a thing, it's the framewok of spatial relation between objects, it's what things exist in, it isn't a substance that you get more of when the spatial relations between objects increases.

That said, it expands, it curves, and it has a shape....so yes, it's confusing.
"It is one of the commonest of mistakes to consider that the limit of our power of perception is also the limit of all there is to perceive." " C. W. Leadbeater