What Is the Universe Expanding Into?

[Chronos]

Let's talk about those observers one more time.

This is a tough crowd, JesseM, with lots of moves. I would like to try one more time with pure logic - stated very simply so questions regarding semantics cannot cloud the issue.

The standard model assumes that the Big Bang occurred ~13.7Gy ago, and it attributes three very basic qualities to the universe, that it is homogeneous and isotropic, and that there is NO privileged or special frame of reference in this universe. These are non-controversial aspects of the standard model, and I will confine the logical proof to these qualities.

Stipulation 1: We observe ourselves and our surroundings, including things beyond Earth. We are Observer "A".

We are observer A in our here and now. Correct?

Stipulation 2: Due to the finite speed of light, we see things as they were when light impinging our instruments left those objects. For instance, we see a star 10 Ly distant as it was 10 years ago. If it goes nova NOW, we will not know it for 10 more years. The most mature point in our observable universe is right here, in the very center of our observable universe, 13.7Gy from the surface of last scattering as it appears to us.

Stipulation 3: Judging from their redshifts, we see some distant objects as they were 13Gy ago, less than a billion years after the surface of last scattering.

Now for the logical proof:
Choose a quasar or galaxy at an apparent distance of 13Gly. Given the concordance assumptions of homogeneity, isotropy, and no special frame of reference, what can we say with certainty about a theoretical observer "B" who exists at that distant position right NOW?

They observe the universe as we will observe it 13Gly in our future. What they see in our 'now' will not be visible to us for 13Gly, correct?.

We can say:

1. Since the universe is homogeneous and isotropic, and because "B's" frame of reference is no more or less special than ours, our theoretical observer looks out at his universe and sees a universe that is identical in its basic qualities to the one we see. He sees his own neighborhood, and due to the finite speed of light, he sees distant objects as they appeared in the past. Like us, he can only see objects out to about 13 billion light years distant. Anything much further, and he is looking at his surface of last scattering, just like we look out at our own. Just like us, "B" has a visible universe about 27 billion light years in diameter. We are on one edge of his visible universe, just as he is on one edge of our visible universe.

2. Over half of the volume of our visible universe (a ~27Gly diameter sphere) is outside the observer "B's" visible universe and is invisible to him. Over half the volume of "B's" visible universe is outside our visible universe and cannot be detected by us. It may help to imagine these visible universes as a pair of interconnected spheres that overlap one another just a bit more than one radius (~13.7Gy)

This is the fatal flaw in your argument. The only reason half the volume of B's visible universe is outside our [A's] visible universe is because the light B sees has not had time to reach A [us].

3. If observer "B" looks in the direction opposite that of our galaxy, he will be able to see other galaxies ~13Gly distant, and a hypothetical observer "C" in one of those galaxies will be able to look out and see a universe that is identical in its basic properties to the universes that observers "A" and "B" see. This is guaranteed by the three basic properties of the BB universe assumed in the introduction. Except for a very tiny intersecting volume centered on the location of observer "B", no part of the visible universe of observer "C" is in our visible universe (we are at observer position "A"), and except for same that tiny (lenticular, obviously) slice of space, observer "C" can see no part of our visible universe.

Observer B and C have the same problem as observer A and B, the finite speed of light.

4. In a BB universe that is homogeneous, isotropic, and devoid of preferred reference frames, this logical iteration can be carried out forever, projecting to an infinite number of "visible universes" each centered on a unique observer. Therefore, if the BB universe is flat or open (and most adherents of standard cosmology are solidly wedded to flat at a minimum, and perhaps open), it must also be spacially infinite.

This is a logical proof derived from the principles of the standard model. I would attempt to simplify it further, but refrain for fear of loss of coherence.

How could the BB universe possibly be finite? To model a finite BB universe, either at least one the three assumptions made by the standard model about the basic qualities of the universe must be wrong, OR the universe must assume a complex topology that somehow both keeps the universe flat/Euclidean locally AND bends space in such a way that one can set off in one direction and come back upon one's previous location without deviating from a straight path. Such theoretical topologies are apparently not falsifiable by any means, and absent any compelling reason to embrace them (apart from sheer revulsion at the thought of infinities ) there is presently no need to regard them as anything more than mathematical curiosities.

I welcome any logical refutation of this proof. "Carpet-bombing" this post with citations that do not address the logic of the proof and simple nay-saying will be cheerfully ignored. Is there a logical failure in this proof? I would love to see it.

It is not logical. I will see exactly the same thing observer B or C sees once the light cone reaches me [A].

 

[JesseM]

They observe the universe as we will observe it 13Gly in our future. What they see in our 'now' will not be visible to us for 13Gly, correct?

You are assuming that the space between A and B is not expanding. If it is, it will take longer than 13 Gy for the light from their location to reach us, and it may never reach us at all depending on how the expansion rate varies over time.

This is the fatal flaw in your argument. The only reason half the volume of B's visible universe is outside our [A's] visible universe is because the light B sees has not had time to reach A [us].

Again, you are ignoring the possibility of event horizons due to expansion. Depending on the curvature of space and the value of the cosmological constant, there may be events whose light will never reach us.

Even if you ignore this possibility, how is that a "fatal flaw" in his argument? His argument was meant to establish that in a flat or open universe with the simplest topology, space would be infinite, so if the expansion rate is such that there is no upper limit on the distance of events happening "now" which we will eventually be able to see in the future, doesn't that confirm his claim that the size of the universe "now" must be infinite?

 

[Chronos]

The logic is flawed.

You are assuming that the space between A and B is not expanding. If it is, it will take longer than 13 Gy for the light from their location to reach us, and it may never reach us at all depending on how the expansion rate varies over time. Again, you are ignoring the possibility of event horizons due to expansion. Depending on the curvature of space and the value of the cosmological constant, there may be events whose light will never reach us.

Expansion has nothing to do with this issue. If the light B observed can never reach A, neither can the message B attempts to send. B cannot say 'I see more than you ever will' because by the time B sees that light and sends the message, the light B saw will arrive at A, and A will agree having seen the same light that B did. To say otherwise suggests the message B sent reached A sooner than than the light B observed passing by on its way to A.

Even if you ignore this possibility, how is that a "fatal flaw" in his argument?

I'm not ignoring anything except the possibility that B can transmit a message that travels faster than light passing by B.

His argument was meant to establish that in a flat or open universe with the simplest topology, space would be infinite, so if the expansion rate is such that there is no upper limit on the distance of events happening "now" which we will eventually be able to see in the future, doesn't that confirm his claim that the size of the universe "now" must be infinite?

No.

 

[JesseM]

The logic is flawed. Expansion has nothing to do with this issue. If the light B observed can never reach A, neither can the message B attempts to send.

turbo-1 never said anything about B sending A a message, there is no need for this to happen.

B cannot say 'I see more than you ever will'

Yes, if the rate of expansion is such that light from B will never reach A, then B can't send any such message to A, and turbo-1 didn't say he could. But in this case, it will be true that B will see things (including the state of his own local region in his present) which A never will.

His argument was meant to establish that in a flat or open universe with the simplest topology, space would be infinite, so if the expansion rate is such that there is no upper limit on the distance of events happening "now" which we will eventually be able to see in the future, doesn't that confirm his claim that the size of the universe "now" must be infinite?

No.

OK, do you agree that "the size of the universe now is infinite" is equivalent to the statement "for every finite distance d, there is some event which is happening now at a distance d"?

 

[Jackson1942]

Antimatter

The Big Bang stipulates an initial condition of a highly compressed state of Matter and Space with the ensuing rapid expansion of Space. Can a case be made for the concept [going back to the Aether Theory] that the process was one of converting Matter into Antimatter called Aether. All the Matter not being converted during this rapid initial expansion was dispersed. An analogy might be that of a expanding reservoir absorbing matter. The two states co-exist and affect one another. If you input enough energy into the reservoir [making a hole] Matter will react to filll the hole and give off the same energy. This does not require the concept of Anti-Mass Worlds existing in the Universe. The concept would be one of two opposing gravitational forces, which possiibly are not constants.

Jack

 

[SOH CRATES]

I am a philosopher and always have been. When one considers the constant of time and the mathematical equations that prove this and that, the evidence is compelling. However, philosophically speaking one must consider the esoteric and spiritual side of the question of the origin of the universe. These Christians, for instance, who believe in God believe in a God that is "outside" of time. If time is removed from the equations, the question of how long and how far are irrelevant, instead we are left with the concept that perhaps te only constant in the universe is how much we continue NOT to know. For if there is no time, then the big bang occurred moments ago. This view is compelling to a philosopher anyway. If science isn't about the "what ifs" then what is the function of science? Perhaps science is simply the meager attempt of miniscule man attempting to explain the vastness of an eternal mind. Dave

 

[Chris Hillman]

Necropost alert!

Hi, SOH CRATES, welcome to PF.

I see you resurrected a thread which has been dormant since Jan 2005; if you can avoid this in future, that would probably be a good idea. (Resurrecting a thread dormant for a year or more is often called "necroposting" and it can be disorienting for frequent posters.)

When one considers the constant of time

The what? Constant as in "not varying"?!

and the mathematical equations that prove this and that, the evidence is compelling.

Did you have some specific equations and some specific conclusion in mind? (Something mentioned in this thread, perhaps?)

However, philosophically speaking one must consider the esoteric and spiritual side of the question of the origin of the universe. These Christians, for instance, who believe in God believe in a God that is "outside" of time.

Hang on a second, this subforum at PF is really for discussions of cosmology, not Christianity. You might want to try posting in the Philosophy subforum, but see [thread=93343]this sticky[/thread] first. Please also read the PF rules and note the cautions about discussing religion in general and specific religious doctrines in particular.

For if there is no time, then the big bang occurred moments ago. This view is compelling to a philosopher anyway.

I believe this might be better discussed in the Philosophy subforum, since this subforum is intended for discussions of modern physical cosomology, but you can see Lawrence Sklar, Space, Time, and Spacetime for a very readable book by a philosopher which discusses the profound impact which gtr and cosmology have had philosophical discourse concerning the nature of space and time. From my reading of the philosophical literature from 1950 on, I don't think I would agree with your claim that all philosophers would find the suggestion that the Big Bang occurred moments ago to be "compelling", but I think that would be better discussed in the philosophy forum, since it seems to have little to do with modern physical cosmology.

 

[adx24001]

Sorry to jump in here, I have little knowledge but read the posts. Just wanted to add this -
If there are other universes/dimensions beyond our own, surely we can't see them as their physics are different. What if our universe was created by some kind of matter/antimatter explosion, is this possible? As for black holes, could they be holes in (if) fabric of spacetime?

 

[glondor]

how about this...

I have been trying to wrap my head around this universe size thing.I have to try to express a point of view.
I read recently that for a considerable time after the big bang, that the universe expanded at a rate faster than the speed of light.
If this rate were to be considerably faster and for a long enough duration,(I believe the time mentioned was 3000000 years) Would this not account for our "Center of the universe view"
The point is that the universe may be much larger than we can see because it really is 13.7 billion years old, which is all we can see, However it is larger than we can see because for a certain amount of time it expanded faster than light, and as time passes on a major scale we will see more "of the stuff that outran the light it generated"
I do not recall the amount of speed faster than light, but may this account for anything if the factor were large?
ie if the speed were 100 times "c' for 3000000 years that makes 3 billion light years in each direction we cannot observe. Makes the universe 34 billion light years or so across. Tell me if this is crap. lol

 

[Pippo]

I realize this topic has probably been beaten to death on here but I've never had the fortune of coming across it so I made my own.

Now, if you believe the whole Big Bang theory, the universe is exanding. In order for anything to expand, there must be something for it to expand into. Now, if we define the universe as "everything", just what the heck is the universe exanding out into, nothing??

Any thoughts?

By saying that the universe is expanding it is included the space as well, space defined as a distance between two masses, so no mass no space as well. The point could be where the space terminates, you must go there to know but if you get there your mass will be there as well.

 

[p764rds]

Lost the plot..

If it were possible to 'be' a photon then for us time would stand still. For example, think of a photon that records a person falling from a building at the instant of starting the fall. This photon (or 'me' in this thought experiment) would travel through the Universe for many millions of years. When the photon (me) steps out into reality (a plastic photo film of an amateur astronemer guy in the alpha centaura galaxy) millions of years later, no time would have passed for me (the photon). I would still be starting my fall off the building. When I was stopped in my tracks by this plastic photo film I would then whizz round and round an atom because I am trapped in a chemical substance loop (probably silver nitrate). But still no time is passing for me, and I would whizz round my gauge symmetry U(1) in the film until its (the photo's) destruction. Then I would continue on my way. I assume, I must connect, in such a way to the infinite future and likewise to the origin of me at the BB. Light seems to have no length or time of itself and exists 'beneath' our space-time Universe, I am losing the plot now...why are we here at all? Someone take me down pls.

 

[SdogV]

The end.

Just a skim through all the schemes to answer the question of "How big is big?" Obviously the answer is BIG.
Seriously, to start from zero (a beginning) and get to 1 (the present) makes what we know as "unity", in this case called the "universe". But Bucky Fuller has said that "unity" is plural, and at a minimum, 2. There's the problem, 2 is beyond us.

 

[a_g]

If there was a second universe what is in between us and them? Heaven? Hell? Ect?

your on the wrong message board

 

[zankaon]

Complement of the universe

In a mathematical sense, using a domain of discourse, one could consider the universe, and it's complement i.e. that which is not part of universe. Visualizing in terms of Venn diagram might be helpful.

 

[Amp1]

Chronos said …

…The volume occupied by galaxies and such are otherwise meaningless. There is no space outside of space. Space can only be described in terms of the distance between physical objects.

I like Garth’s post and JesseM’s was most enlightening. I haven’t read all the posts yet and those that I mentioned are among the first replies to Ulnarian’s post.

Even the brief brush with the ‘R’ word by SOH CRATES -I’m reading the last few- brings together something I’ve pondered.

I get the sense that setAI is on to what I’m thinking in a way. The universe isn’t expending into anything in the physical sense – I think that like the symbolic use used in this thread of imagining the universe as a sphere expanding in a plane, one can think of the universe as being analogous to intangible quality of electricity used measure to impedence, reactance being complex along with the resistance being real combine into impedence. So that the concept, existence could be a combination of spirit which isn’t physical or tangible and reality which analogous to resistance is physically real and tangible (measurable-detectable).

Existence would then be dimensionless or the totality of indefinitely/infinite dimensions.

If the universe is ‘… expanding into its future’ as Garth proposed, running time in reverse would give null time just before the BB. Concepually and sequentially, existence was before eternity - (all time). So, Garth the universe expands into Existence as well. ;)

 

[H.M. Murdock]

I don't know much about cosmology, but string theory has proposed the hypotezis that there are huge branes outside the space of the universe. and they were the ones that made posible the explotion of the big bang. I personately don't take seriously the brane hypotezes, but apparently millions of dollars are being spend right now in order to detect huge gravitational waves that could prove their existens.

 

[nanoWatt]

If the Universe is expanding, then why don't our atoms in our bodies expand apart?

Also, before the Big Bang, if there was such a thing, wouldn't there have been an infinite amount of time? Or am I thinking too linearly?

 

[Garth]

I don't know much about cosmology, but string theory has proposed the hypotezis that there are huge branes outside the space of the universe. and they were the ones that made posible the explotion of the big bang. I personately don't take seriously the brane hypotezes, but apparently millions of dollars are being spend right now in order to detect huge gravitational waves that could prove their existens.

Welcome to these Forums HMM!

Brane (as in membrane)Theory is one possibility that seems to come up with the correct numbers. As you say large detectable gravitational waves are predicted by the theory.
If they are detected then we will know more!

Garth

 

[Garth]

If the Universe is expanding, then why don't our atoms in our bodies expand apart?

Also, before the Big Bang, if there was such a thing, wouldn't there have been an infinite amount of time? Or am I thinking too linearly?

nanoWatt you might find a basic introduction to cosmology useful, such as the website by Ned Wright.

In the standard model the universe on the largest scales is described by the Friedmann-Lemaître-Robertson-Walker metric, often abbreviated to the R-W or FRW metric, and space either expands or contracts on the largest scales.

Hubble red shift shows that we are in an expanding phase of the universe.

On local scales objects such as galaxies, solar systems, and atoms are gravitationally bound and do not expand.

Actually it depends on what you use to measure length, if you use a steel rule, then by definition the atoms it is made of, and by extension all other atoms, do not expand. A steel rule is 'rigid' (of fixed length to a co-moving observer) and the universe on the largest scales expands around it.The standard model may be projected back in time to about 13.7 billion years ago to the Big Bang. Whether or not the BB itself was a genuine beginning of time in our universe, or just a 'pinch-point' from a universe beyond is a subject of active debate, not least on these Forums!

Garth

 

[marcus]

Also, before the Big Bang, if there was such a thing, wouldn't there have been an infinite amount of time? Or am I thinking too linearly?

Not too linearly for me anyway! I don't know if I'd call it linear, but it's how I think too. I agree with everything Garth just said and also I don't know of any scientific reason to suppose that time-evolution doesn't extend back indefinitely

Time is a dimension, not a substance----so it is a little odd to think of it as an "amount".
But I think what you are saying is basically right. People used to think that the fact that the classical vintage 1915 version of General Relativity broke down at a certain point PROVED that time stopped there. But that's not a proof, it just shows that classic GR breaks down, not that Nature does. So a lot of researchers have made it their business to model the Big Bang, get rid of the classic "singularity", and investigate what could have been happening prior. they just had a conference at Cambridge where this was discussed a lot. And in January 2007 there was a 3-week international workshop on it in Santa Barbara.

the extent of time----or the extent of the PROCESS governed by physical law, which we associate with the passage of time----is something we don't know.

To sum it up, you could say that the backwards extent of time could be unlimited or cut off-----the classical model breaks down but some other model do not----so we can't say. For now we have to entertain both possibiliities, including that the process of time-evolution may extend back indefinitely.

 

[marcus]

According to the Big Bang Theory, at the time of the Big Bang, all forces, matter, dimensions, etc.. were created...

Is this your own theory or do you have a LINK to a source that you can share with us?
It doesn't sound like a contemporary professional mainstream consensus view, so it makes me curious as to where you are getting it.

It seems premature to me to be talking about THE Big Bang Theory as if we already knew the right model to replace the classic singularity. As you probably realize, classic General Relativity breaks down right at the Big Bang, so it does not give us a theory.
the only theories that describe the Big Bang itself are quantum cosmology models which extend back in time BEFORE.

I think your use of the word "created" seems a bit pretentious, since it is not generally the case in today's models that all forces, matter, and space begin at that point.
As far as I know, it has not yet been established in modern quantum cosmology that these things (forces, matter, space) have any beginning at all! Indeed they may have always existed. This simply isn't known.

Even if they do have beginnings, I know of no scientific reason to believe that their beginnings would coincide with what is called the big bang.

 

[dvy001]

Just wanted to point out that the ever quoted balloon analogy has flaws. Here is a previous comment from someone:

"Livio is up to the task. He dredges up the old expanding balloon as his prop. "An ant traveling on the surface of a balloon will never reach an edge," Livio explains. "In the worst case it will return to its starting point."

The fallacy is that the ant has reached the edge of the balloon and is in fact standing on it. The surface is the edge.

 

[Garth]

Just wanted to point out that the ever quoted balloon analogy has flaws. Here is a previous comment from someone:

"Livio is up to the task. He dredges up the old expanding balloon as his prop. "An ant traveling on the surface of a balloon will never reach an edge," Livio explains. "In the worst case it will return to its starting point."

The fallacy is that the ant has reached the edge of the balloon and is in fact standing on it. The surface is the edge.

To make the analogy work you have to specify that it is a two dimensional ant living in the two dimensional surface of the sphere, represented by the (thin) membrane of the balloon.

The whole point is that it is possible, if it is helpful, to visualize a representation of four dimensional space-time by suppressing one space dimension.

Garth

 

[nanoWatt]

And all this time I thought the Universe was 13 dimensions.

 

[Garth]

And four dimensional space-time is four dimensional!

Garth

 

[petm1]

On local scales objects such as galaxies, solar systems, and atoms are gravitationally bound and do not expand.

This is the type of statement that I have to disagree with, the intrinsic motion of the celium atom that we use as the ruler in our atomic clocks, too me, appears to be in phase with time, Times only motion is dilation, therefore I've always thought that everything dilates.

Actually it depends on what you use to measure length, if you use a steel rule, then by definition the atoms it is made of, and by extension all other atoms, do not expand.

By definition I change the size of steel by adding energy, one of the reasons we set standards at elevation and temperature. Atoms with their intrisnic motion changes locally to phase with each other, does not mean that they are always the same globally.

A steel rule is 'rigid' (of fixed length to a co-moving observer) and the universe on the largest scales expands around it.[/

I see the rigid ruler expanding with the mostly empty universe expanding just a little bit faster around it.

The standard model may be projected back in time to about 13.7 billion years ago to the Big Bang. Whether or not the BB itself was a genuine beginning of time in our universe, or just a 'pinch-point' from a universe beyond is a subject of active debate, not least on these Forums!

Truth if I ever saw it.

 

[Garth]

This is the type of statement that I have to disagree with, the intrinsic motion of the celium atom that we use as the ruler in our atomic clocks, too me, appears to be in phase with time, Times only motion is dilation, therefore I've always thought that everything dilates.

The question is: "dilates relative to what?"

That is, the question is: "What is the standard unit of length that you measure this dilation with and how do you mentally transport that standard unit around the universe to make astrophysical and cosmological measurements?"

By definition I change the size of steel by adding energy, one of the reasons we set standards at elevation and temperature. Atoms with their intrisnic motion changes locally to phase with each other, does not mean that they are always the same globally.

You have to define the standard unit of length, mass and time.

You need a conservation prinicple, something that does not change by definition and show that this principle leads to results that are consistent with experiment and observation.

In GR the 'rest' mass of an atom is constant, this is a consequence of GR's conservation principle the conservation of stress-energy-momentum:

T^{\mu}_{\nu;\mu} = 0

I see the rigid ruler expanding with the mostly empty universe expanding just a little bit faster around it.

Again relative to what standard?

Note that we have been talking about GR, the standard theory that fits the data and leads to the mainstream \LambdaCDM cosmological model; there are alternative published theories out there.

In conformal gravity theories the standard atomic units may well change from place to place and over time, but these theories need to have alternative and clearly defined standard units of mass, length and time to replace the atomic ones.

One such published theory that you may be interested in, although in its present form it has just been falsified by the Gravity Probe B experiment, is http://en.wikipedia.org/wiki/Self_creation_cosmology .

Garth

 

[petm1]

"dilates relative to what?"

Intrinsic motion is relative to everything, as to this question I'm thinking more of relative to when and the where is itself.

"What is the standard unit of length that you measure this dilation with and how do you mentally transport that standard unit around the universe to make astrophysical and cosmological measurements?"

Don't we already do this using the meter and or the second? We measure this dilation as the difference between clocks, maybe this same dilation explains why things that we view via photons at the farthest reaches of our visible universe appear to be getting bigger.

You have to define the standard unit of length, mass and time.

I use webster's

You need a conservation prinicple, something that does not change by definition and show that this principle leads to results that are consistent with experiment and observation.

I'm not talking about changing the one we have. Relative we don't change, our dilation rate is always the same locally.

In GR the 'rest' mass of an atom is constant, this is a consequence of GR's conservation principle the conservation of stress-energy-momentum:

I am not saying that rest mass changes relative to anything, I see two types of motion that of time like or if you will intrinsic motion of matter and the other as space like or the motion of matter through space.

 

[petm1]

I've tried to think of matter as static for the last couple of days, and I can't get it. Thinking of a steel ruler in my mind, it is constantly dilating when you put heat to it you are changing the rate of its time dilation, we see it as the steel expanding, after you remove the heat it goes back to the local dilation rate. I'm watching the snow melt and I can feel the difference in the time dilation rates between in my house and the outside air. I see time dilation everywhere. How about this for a thought experiment: if you could step back far enough to see the entire light cone of our visible universe, and then reach out and place it under a microscope, what would you see?

Getting to the original subject, I think using the meter and the second, I would except that our visible universe is expanding into time and when we get there we will measure it as space.