Universe Expanding

[silverpig]

Originally posted by: Smilin
uh. The way I explained it WOULD look is "redshifted in every direction". What is it you want me to explain?

Ah! You want me to explain that the number of blue shifted objects in an infinitely thin slice of space = 0. Hence everything is red shifted. Was that the confusion? Mind you "infinitely thin" doesn't really mean the plane doesn't intersect an object. It's possible at close distances but at great distances the probability per object approaches zero. Of course that pretty much fits observation as well (only blue shifted objects in universe are nearby)

I say CMB crap because like in the other thread (where you said CMB was uniform btw) it was used in a context that has no relation to this explanation I've given.

As this is a theory I pulled out of my butt some years ago I'm certainly open to a rational reason why it couldn't be. Why do you think would we see a much larger dipole effect?

Just because this was pulled out ma butt doesn't mean it wasn't well thought out. I'm not going to say that I necessarily believe it, but I've discussed it quite a bit and haven't found a problem yet.

No it wouldn't. Your setup would show a redshift in one dimension. Look at my drawing.

universe

So on the left we have the universe at time t_0. The singularity is the big blob, the two smaller ones are test particles. We set all distances between the particles to be r. Letting the system evolve for a time t we have the image on the right. Both particles accelerate along their own respective r-vectors an equal amount as they are both the same distance from the singularity. The net result is that we have just shrunk this equilateral triangle. What's to note here is that the vector separating the two test particles has also shrunk. This would result in a blueshift along this direction.

And this is just one direction. The amount of shift and in what direction is a complicated function of distance and angle. If you consider a constant surface, then the amount of shift is a function of angle.

It just doesn't work. The CMB is redshifted equally in all directions and is nearly perfectly isotropic. The only way this can happen is if all parts of the universe were once in causal contact and all expanded away. With your universe, if there was a big bang leaving a singularity at the center, everything would have been in causal contact, but you would require that everything expanded, stopped, and is now re-accelerating back towards the center. Not only would we then see much of the sky blueshifted (not along the line of sight to the singularity, but in practically every other direction), but we would also see stars that are on the other side of the singularity as blueshifted. If you explain this as saying that the universe isn't old enough for this to be (say we had matter-radiation decoupling at a time such that the distance to the LSS is less than that to the singularity), then we wouldn't see the stars on the other side of the singularity, but we would still get the directional dependence on amount and direction of spectral shift. But we don't. Everything is redshifted.

You can convince me of your universe's validity if you can derive the 3-dimensional functional form of the amount of redshift we would see.

 

[Smilin]

Yeah, your drawing is a representation of the universe in the plane perpendicular to the direction of acceleration.

I can tell you're still not getting the basic concept of it. Once you do we can start picking it apart if you would like.

Let's try two dimensions - this will be ugly in an attempt to get formatting right.

Time 1:
---------------------------------------E-----F------G
-
-
-
A-------------------------------------B-----C------D
-
-
-
---------------------------------------H-----I-------J



Time 2:
----------------------------E---------F----------G
-
-
A------------------------B----------C--------D
-
-
----------------------------H---------I-----------J


ok, yea it's crude.

Things to note:
1. Everything at time 2 has moved towards point A.
2. E, B, H have accelerated the most since they are closest.
3. F, C, I are next. G,D,J have moved but barely.
4. Although crude we definately have motion in two dimensions. The EFG and HIJ lines have move inward towards the BCD line.
5. F and I will be slightly blue shifted when viewed from C.
6. everything else will appear red shifted to C...count the dashes to see the distance has grown.


The problem with your diagram is that it shows things shrinking. Do not confuse a collapsing universe with simple "shrinking".

If you fall into a black hole do you shrink as you fall in? No, you get stretched out into spaghetti. Your feet and head will appear red shifted if viewed from your torso. Your shoulders will blue shift to each other but red shift to every other part of your body. How can a bunch of body parts red shift (implies move away) from each other when they are all collapsing to the same point?!?! Simple, accleration.


If the universe were simply moving towards a singularity at an infinite distance then yes, things would appear blue shifted since the universe is "shrinking" towards a point (like in your diagram) I say the universe is "falling" into a singularity at an infinite distance. This implies acceleration. Although the net result is everything ends up in the same point, things get stretched as they go there. If you drop an observer into the middle of it all he can't tell the difference between redshift from expansion, or redshift from stretching.

 

[Gibsons]

Originally posted by: Smilin
Yeah, your drawing is a representation of the universe in the plane perpendicular to the direction of acceleration.

I can tell you're still not getting the basic concept of it. Once you do we can start picking it apart if you would like.

Let's try two dimensions - this will be ugly in an attempt to get formatting right.

Time 1:
---------------------------------------E-----F------G
-
-
-
A-------------------------------------B-----C------D
-
-
-
---------------------------------------H-----I-------J



Time 2:
----------------------------E---------F----------G
-
-
A------------------------B----------C--------D
-
-
----------------------------H---------I-----------J


ok, yea it's crude.

Things to note:
1. Everything at time 2 has moved towards point A.
2. E, B, H have accelerated the most since they are closest.
3. F, C, I are next. G,D,J have moved but barely.
4. Although crude we definately have motion in two dimensions. The EFG and HIJ lines have move inward towards the BCD line.
5. F and I will be slightly blue shifted when viewed from C.
6. everything else will appear red shifted to C...count the dashes to see the distance has grown.


The problem with your diagram is that it shows things shrinking. Do not confuse a collapsing universe with simple "shrinking".

If you fall into a black hole do you shrink as you fall in? No, you get stretched out into spaghetti. Your feet and head will appear red shifted if viewed from your torso. Your shoulders will blue shift to each other but red shift to every other part of your body. How can a bunch of body parts red shift (implies move away) from each other when they are all collapsing to the same point?!?! Simple, accleration.


If the universe were simply moving towards a singularity at an infinite distance then yes, things would appear blue shifted since the universe is "shrinking" towards a point (like in your diagram) I say the universe is "falling" into a singularity at an infinite distance. This implies acceleration. Although the net result is everything ends up in the same point, things get stretched as they go there. If you drop an observer into the middle of it all he can't tell the difference between redshift from expansion, or redshift from stretching.

If we were at point C in your diagram, F and I would be blueshifted, right? B and D would be redshifted.

 

[msparish]

Originally posted by: Smilin
Yeah, your drawing is a representation of the universe in the plane perpendicular to the direction of acceleration.

I can tell you're still not getting the basic concept of it. Once you do we can start picking it apart if you would like.

Let's try two dimensions - this will be ugly in an attempt to get formatting right.

Time 1:
---------------------------------------E-----F------G
-
-
-
A-------------------------------------B-----C------D
-
-
-
---------------------------------------H-----I-------J



Time 2:
----------------------------E---------F----------G
-
-
A------------------------B----------C--------D
-
-
----------------------------H---------I-----------J


ok, yea it's crude.

Things to note:
1. Everything at time 2 has moved towards point A.
2. E, B, H have accelerated the most since they are closest.
3. F, C, I are next. G,D,J have moved but barely.
4. Although crude we definately have motion in two dimensions. The EFG and HIJ lines have move inward towards the BCD line.
5. F and I will be slightly blue shifted when viewed from C.
6. everything else will appear red shifted to C...count the dashes to see the distance has grown.


The problem with your diagram is that it shows things shrinking. Do not confuse a collapsing universe with simple "shrinking".

If you fall into a black hole do you shrink as you fall in? No, you get stretched out into spaghetti. Your feet and head will appear red shifted if viewed from your torso. Your shoulders will blue shift to each other but red shift to every other part of your body. How can a bunch of body parts red shift (implies move away) from each other when they are all collapsing to the same point?!?! Simple, accleration.


If the universe were simply moving towards a singularity at an infinite distance then yes, things would appear blue shifted since the universe is "shrinking" towards a point (like in your diagram) I say the universe is "falling" into a singularity at an infinite distance. This implies acceleration. Although the net result is everything ends up in the same point, things get stretched as they go there. If you drop an observer into the middle of it all he can't tell the difference between redshift from expansion, or redshift from stretching.

The problem with your argument:
Even if the sigularity were an infinite distance away (so that your plane of blue shift = 0), as viewing near this plane would result in a smaller and smaller redshift. As you viewed further away from it, redshift would get larger.

We don't see that. Sorry, but you're wrong.

 

[Smilin]

Yes, from C's perspective:

1. F,I would be blueshifted (we are assuming they are EXACTLY vertically aligned).
2. B,D,E,G,H,J would be redshifted.

 

[Smilin]

Originally posted by: msparish

The problem with your argument:
Even if the sigularity were an infinite distance away (so that your plane of blue shift = 0), as viewing near this plane would result in a smaller and smaller redshift. As you viewed further away from it, redshift would get larger.

We don't see that. Sorry, but you're wrong.

Ah yes. We would see a reduced redshift (but not blueshift) near the plane. That would probably break the idea, you're right.

Back to the drawing board.

 

[silverpig]

No that still doesn't work. And there's no problem with my drawing. If you *really* want, I can come up with the functional dependence on theta and phi for you, or I could probably use the gravitational simulator I wrote for a computational physics project. Okay, just think about it like this:

You admit that there will be a blueshift in a certain plane (actually it's maximized in a sphere centered around the singularity I believe). You can probably also agree that there is a maximum redshift along the line of acceleration. Now, it seems as though your interpretation is that there is an even redshift independent of angle, and then a single slice of blueshift in the one plane. Does that really make sense to you?

What happens is there is a maximum redshift along the direction of acceleration, and then this redshift lessens as you look away from the line, and then turns to a blueshift. There is also a complicated function of distance involved as well, and then you have to use 2 angles to work in 3-dimensions. It's quite complicated, and definitely will not give a simple uniform redshift.

 

[Agent11]

Good forum for big questions

Go here

I'm waiting for somone to bust out string theory

The problem is your saying that the universe is a sphere accelerating to be gobbled up from all directions by a larger sphere of black hole..

How would such a singularity be created, and why is it that the black holes that we see do not behave in any way like this... Also black holes eject radiation that we would be able to detect..

Is your theory one of a finite or infinite universe?
Also I dislike the baloon illustration, do we percieve ourselves on the inside of the baloon? If so there is a finite wall to come to, it assumes that space is curved at that point(a positive curvature),and you would find yourself back where you started. If we are outside the baloon it doesn't work at all.

Friedmann described three possible models in which the universe would appear homogeneous and isotropic, yet be seen as expanding, by all observers in it at the present time:

(1) The open universe, in which the rate of expansion everywhere exceeds the velocity of escape from the rest of the matter in the universe. Such an expansion would continue forever; and space in such a universe can be described as negatively curved.

(2) The closed universe, in which the expansion is eventually halted by gravity and becomes a collapse back to the origin. Such a universe has a finite lifetime unless it bounces and continues expanding and recollapsing forever. Space in this type of universe has positive curvature. As on a sphere, a straight line in any direction eventually returns to its starting point.

(3) The flat universe, in which the expansion is critically balanced at the threshold between open and closed. The expansion goes on forever, asymptotically approaching zero velocity after infinite time has elapsed and the universe has become infinitely large. Space therein has no curvature.

In principle, observations should allow us to determine which type of Friedmann expanding universe we inhabit. We simply measure the cosmic deceleration parameter, q. In a flat universe, the total matter in the universe is just enough to halt the expansion after an infinite time. This corresponds to a cosmic deceleration q0 = 0.5. If the observed value of q0 is larger than 0.5, the universe is closed. If q0 is less than 0.5, the universe is open. If there were no cosmic deceleration, q0 = 0; or if the expansion accelerates due to some hypothetical force of repulsion, q0 < 0. The most widely accepted form of the big bang theory predicts that q0 = 0.5.

 

[xeno2060]

Why?
When?
How?

None of you can answer it , because. YOU DO NOT KNOW!!@!!!

 

[silverpig]

Originally posted by: Agent11
Good forum for big questions

Go here

I'm waiting for somone to bust out string theory

The problem is your saying that the universe is a sphere accelerating to be gobbled up from all directions by a larger sphere of black hole..

How would such a singularity be created, and why is it that the black holes that we see do not behave in any way like this... Also black holes eject radiation that we would be able to detect..

Is your theory one of a finite or infinite universe?
Also I dislike the baloon illustration, do we percieve ourselves on the inside of the baloon? If so there is a finite wall to come to, it assumes that space is curved at that point(a positive curvature),and you would find yourself back where you started. If we are outside the baloon it doesn't work at all.

Friedmann described three possible models in which the universe would appear homogeneous and isotropic, yet be seen as expanding, by all observers in it at the present time:

(1) The open universe, in which the rate of expansion everywhere exceeds the velocity of escape from the rest of the matter in the universe. Such an expansion would continue forever; and space in such a universe can be described as negatively curved.

(2) The closed universe, in which the expansion is eventually halted by gravity and becomes a collapse back to the origin. Such a universe has a finite lifetime unless it bounces and continues expanding and recollapsing forever. Space in this type of universe has positive curvature. As on a sphere, a straight line in any direction eventually returns to its starting point.

(3) The flat universe, in which the expansion is critically balanced at the threshold between open and closed. The expansion goes on forever, asymptotically approaching zero velocity after infinite time has elapsed and the universe has become infinitely large. Space therein has no curvature.

In principle, observations should allow us to determine which type of Friedmann expanding universe we inhabit. We simply measure the cosmic deceleration parameter, q. In a flat universe, the total matter in the universe is just enough to halt the expansion after an infinite time. This corresponds to a cosmic deceleration q0 = 0.5. If the observed value of q0 is larger than 0.5, the universe is closed. If q0 is less than 0.5, the universe is open. If there were no cosmic deceleration, q0 = 0; or if the expansion accelerates due to some hypothetical force of repulsion, q0 < 0. The most widely accepted form of the big bang theory predicts that q0 = 0.5.

Except that inside a spherical shell gravity would be zero, so it wouldn't make you accelerate at all in any direction. A "larger spherical black hole" would not exist, and even if it did, would not have any effect on us.

The balloon illustration is great. We live on the surface of the balloon. It's a 2-d/3-d analog to our 3-d/4-d possible reality. You are to consider living on a 2-d surface embedded in 3-d space. The surface expands in 3-d space but is still 2 dimensional. It is finite yet expanding in every direction. This is a lower dimensional analog to our possible finite 3-d surface that expands. It can be visualized if we could perceive 4-d space.

And your Friedmann stuff is a little out of date. It is now known that we live in a 4th type of universe, one where the expansion accelerates.

 

[Looney]

Originally posted by: RichardE

Originally posted by: suszterpatt
Infinite space?


I don't really understand the question.

Well, I understand I am just starting University next year, so I do not have knowledge on this subject at all, but solely from reading on physics ect, I wondered what exactly the universe is expending into?

IE, if you blow up a baloon it displaces the air around it as it expands, what is the universe displacing?

Time.

 

[Agent11]

Yes a large spherical (yet hollow)black hole could not exist.
The idea of all space outside the baloon of the universe being a black hole powering the acceleration of the universe seems to be what he is trying to describe.

Redshift

Science isn't about proving a theory, it's about proving theories false.

I don't assume that there was a big bang, it's a theory. I don't assume that redshift proves anything, it should be our objective to disprove a theory in order to validate it.

thats called 'science'



edit:
by the way I like your first quote there looney.

 

[imported_BigT383]

Agent11, science is about proving things false. However, evidence CAN support theories. For instance, all evidence supports the theory of General Relativity being the way that gravity behaves. Evidence supports the theory of Natural Selection being one of the ways that living things evolve. Evidence supports the Big Bang model being the way the universe once existed (redshift and the CMB being two large pieces of that evidence). Of course, science is about disproving theories as well. If any one of these theories were to be disproved, a new one would have to be drawn up (or the old one modified). But, since they are all supported by so much evidence, whatever new theory would be created can't be too far from the old one, since it would have to make the same predictions about the observed evidence. Thus, the incorrect theories are weeded out and those supported by evidence survive. Basically the more evidence you have that agrees with a theory the more sure you can be that it is correct, and it is just a part of the language we use to say that theories that have survived many attempts at disproving them are "proven" or "law". But just because we call them that doesn't mean we don't still try to disprove them.

To make the original example work requires putting the earth back in the center of everything and having things that can work pi times faster than the speed of light.
Suppose the expansion was caused by gravity from an invisible source outside the universe similar to what's described in the first post in this thread. The problem is that in order for things equidistant from the gravity source as you are to not have a blue shift, the source of gravity would have to be all around the entire visible universe. So it would have to be a "shell", but it would not necessarily have to be a black hole, as was suggested. A huge amount of normal matter, evenly dispersed, would do just fine. But a sphere of gravitational influence would cause an uneven redshift- stuff closer to it would be redder than stuff further away. So since we see even redshifts everywhere, the giant sphere of gravity-stuff must be centered on earth. Not likely, but I guess it's possible. However, a giant sphere of gravity-stuff would have 0 gravity inside it, as was pointed out. So that means that the giant sphere of gravity stuff must be so big, light hasn't had time (since gravity moves at the speed of light) to reach the other side and make the gravity 0. So, since it's a sphere and the distance straight across it is the diameter, the giant sphere must have popped into existance at least pi times faster than the speed of light (and that's if it's infinitely thin!), or else gravity from the point it started appearing at would have reached the other side before the appearing sphere got there. Since nothing can affect anything else at faster than the speed of light, this would be impossible.

 

[darkdemyze]

Originally posted by: RichardE

Unless it was spherical(which was shown to be false, and the current theory is the universe is flat), would you not see D moving towards you? Or, at least, D's distance would never change. The only thing I could think of is that we are anexing another matter, and the more we annex the easier it is, so in theory the expansion would increase.

funny how this was "shown" to be false just as the earth was once seen as being flat when everyone was scared of sailing off the edge of the planet

 

[Agent11]

I think the odds of the earth being the center for anything in something as large as the universe are kind of slim, to say the least.
The idea that gravity moves at the speed light is flawed, doesnt work in reality.

'The most amazing thing I was taught as a graduate student of celestial mechanics at Yale in the 1960s was that all gravitational interactions between bodies in all dynamical systems had to be taken as instantaneous. This seemed unacceptable on two counts. In the first place, it seemed to be a form of "action at a distance". Perhaps no one has so elegantly expressed the objection to such a concept better than Sir Isaac Newton: "That one body may act upon another at a distance through a vacuum, without the mediation of any thing else, by and through which their action and force may be conveyed from one to the other, is to me so great an absurdity, that I believe no man who has in philosophical matters a competent faculty of thinking, can ever fall into it." (See Hoffman, 1983.) But mediation requires propagation, and finite bodies should be incapable of propagation at infinite speeds since that would require infinite energy. So instantaneous gravity seemed to have an element of magic to it.

The second objection was that we had all been taught that Einstein's special relativity (SR), an experimentally well established theory, proved that nothing could propagate in forward time at a speed greater than that of light in a vacuum. Indeed, as astronomers we were taught to calculate orbits using instantaneous forces; then extract the position of some body along its orbit at a time of interest, and calculate where that position would appear as seen from Earth by allowing for the finite propagation speed of light from there to here. It seemed incongruous to allow for the finite speed of light from the body to the Earth, but to take the effect of Earth's gravity on that same body as propagating from here to there instantaneously. Yet that was the required procedure to get the correct answers.'
Tom Van Flandern Univ. of Maryland Physics, Army Research Lab

Why do total eclipses of the Sun by the Moon reach maximum eclipse about 40 seconds before the Sun and Moon's gravitational forces align? How do binary pulsars anticipate each other's future position, velocity, and acceleration faster than the light time between them would allow? How can black holes have gravity when nothing can get out because escape speed is greater than the speed of light?

We do not know too much about gravity right now.

string theory and gravity

Maybe that will change soon.

 

[Smilin]

Originally posted by: silverpig
No that still doesn't work. And there's no problem with my drawing. If you *really* want, I can come up with the functional dependence on theta and phi for you, or I could probably use the gravitational simulator I wrote for a computational physics project. Okay, just think about it like this:

You admit that there will be a blueshift in a certain plane (actually it's maximized in a sphere centered around the singularity I believe). You can probably also agree that there is a maximum redshift along the line of acceleration. Now, it seems as though your interpretation is that there is an even redshift independent of angle, and then a single slice of blueshift in the one plane. Does that really make sense to you?

What happens is there is a maximum redshift along the direction of acceleration, and then this redshift lessens as you look away from the line, and then turns to a blueshift. There is also a complicated function of distance involved as well, and then you have to use 2 angles to work in 3-dimensions. It's quite complicated, and definitely will not give a simple uniform redshift.

I find it humorous that you arrive after msparish already found the flaw in the idea and continue your argument (horse is already dead, but you need to get one more whip in I guess). This is also the first post in which you actually seem to even understand the concept. Your previous posts including the one with that diagram have all tried to explain how the entire universe would be blueshifted under this model demonstrating that you didn't even follow the idea. I'm glad you seem to get it at least No CMB required!

 

[silverpig]

Originally posted by: Smilin

Originally posted by: silverpig
No that still doesn't work. And there's no problem with my drawing. If you *really* want, I can come up with the functional dependence on theta and phi for you, or I could probably use the gravitational simulator I wrote for a computational physics project. Okay, just think about it like this:

You admit that there will be a blueshift in a certain plane (actually it's maximized in a sphere centered around the singularity I believe). You can probably also agree that there is a maximum redshift along the line of acceleration. Now, it seems as though your interpretation is that there is an even redshift independent of angle, and then a single slice of blueshift in the one plane. Does that really make sense to you?

What happens is there is a maximum redshift along the direction of acceleration, and then this redshift lessens as you look away from the line, and then turns to a blueshift. There is also a complicated function of distance involved as well, and then you have to use 2 angles to work in 3-dimensions. It's quite complicated, and definitely will not give a simple uniform redshift.

I find it humorous that you arrive after msparish already found the flaw in the idea and continue your argument (horse is already dead, but you need to get one more whip in I guess). This is also the first post in which you actually seem to even understand the concept. Your previous posts including the one with that diagram have all tried to explain how the entire universe would be blueshifted under this model demonstrating that you didn't even follow the idea. I'm glad you seem to get it at least No CMB required!

Uh no. The entire universe would not be blueshifted in my drawing. I just chose three points that illustrated a single case of blueshift that provided a counterexample to your argument. I can re-draw it again if you like with more points. I fully understand what your argument is, and I fully understand from the beginning why it does not work. It is actually you who does not undertand my position.

But that's okay. I know what I'm talking about, and there are plenty of people who don't understand it. Nothing new to me. *shrug*

 

[imported_electron]

The universe doesn't expand into time. That deosn't make any sense whatsoever. The universe doesn't expand into anything. The universe itself IS what is expanding. It is all that there is. If you could venture outside of the universe, that would still be a part of our universe. There is no outside of the known universe. It is all that there is. Note this has nothing to do with being able to "prove" or to "see" anything outside of our universe. It's a function of it's definition. If you call it all that there is, then there can be nothing outside of it.

Also I'd like to point out why the universe expanding into time makes no sense at all. That is simply because "time" or the 4th dimension, is within our universe. It is a part of it. Expanding into a part of itself makes no sense at all. That charlatan of a poster just wanted to use a buzzword to grab your attention when he spouted "time" the way he did.

 

[Agent11]

I think some people just let their imagination go wild without enough information/

 

[Smilin]

Originally posted by: electron
The universe doesn't expand into time. That deosn't make any sense whatsoever. The universe doesn't expand into anything. The universe itself IS what is expanding. It is all that there is. If you could venture outside of the universe, that would still be a part of our universe. There is no outside of the known universe. It is all that there is. Note this has nothing to do with being able to "prove" or to "see" anything outside of our universe. It's a function of it's definition. If you call it all that there is, then there can be nothing outside of it.

Also I'd like to point out why the universe expanding into time makes no sense at all. That is simply because "time" or the 4th dimension, is within our universe. It is a part of it. Expanding into a part of itself makes no sense at all. That charlatan of a poster just wanted to use a buzzword to grab your attention when he spouted "time" the way he did.

Charlatan of a poster eh?

Very nice. A Personal attack, but nice. Ok since you clearly know what the universe is expanding into please enlighten us your highness. I have no proof my idea is right and you have no proof it is wrong. What is it exactly that makes you feel so superior? Have a little chitchat with God about this last week did ya?

Actually if you could just prove any one of the statements you made I would appreciate it:

1. The universe doesn't expand into anything
2. Time is within our universe. It is a part of it.

Although the word "Universe" may imply "everything" there are some that allow their minds to consider the possibility of something other than "everything". The original poster on this thread appears to be such a person. If you want to cling to this limited thinking you'll be able to spout "WRONG!" at every conceivable idea. If that's what you're after spare us the posts. If you have an alternate idea or thoughts on this mostly metaphysical topic please share.

If you stop our motion in time does the universe continue to expand? If time truly is a part of the universe then what is time (along with everything else) expanding into? Is a 5th dimension also part of our universe? 6th? At some point that which we can sense is moving into something we can't. Being unable to sense it may clearly drop it outside of "everything" but it doesn't mean it isn't out there.

 

[silverpig]

Originally posted by: Smilin

Originally posted by: electron
The universe doesn't expand into time. That deosn't make any sense whatsoever. The universe doesn't expand into anything. The universe itself IS what is expanding. It is all that there is. If you could venture outside of the universe, that would still be a part of our universe. There is no outside of the known universe. It is all that there is. Note this has nothing to do with being able to "prove" or to "see" anything outside of our universe. It's a function of it's definition. If you call it all that there is, then there can be nothing outside of it.

Also I'd like to point out why the universe expanding into time makes no sense at all. That is simply because "time" or the 4th dimension, is within our universe. It is a part of it. Expanding into a part of itself makes no sense at all. That charlatan of a poster just wanted to use a buzzword to grab your attention when he spouted "time" the way he did.

Charlatan of a poster eh?

Very nice. A Personal attack, but nice. Ok since you clearly know what the universe is expanding into please enlighten us your highness. I have no proof my idea is right and you have no proof it is wrong. What is it exactly that makes you feel so superior? Have a little chitchat with God about this last week did ya?

Actually if you could just prove any one of the statements you made I would appreciate it:

1. The universe doesn't expand into anything
2. Time is within our universe. It is a part of it.

Although the word "Universe" may imply "everything" there are some that allow their minds to consider the possibility of something other than "everything". The original poster on this thread appears to be such a person. If you want to cling to this limited thinking you'll be able to spout "WRONG!" at every conceivable idea. If that's what you're after spare us the posts. If you have an alternate idea or thoughts on this mostly metaphysical topic please share.

If you stop our motion in time does the universe continue to expand? If time truly is a part of the universe then what is time (along with everything else) expanding into? Is a 5th dimension also part of our universe? 6th? At some point that which we can sense is moving into something we can't. Being unable to sense it may clearly drop it outside of "everything" but it doesn't mean it isn't out there.

One of my profs is one of the world expert cosmologists on the CMB. He has a question page you might enjoy reading. Here's a selection which answers your questions:

I teach a historical geology class in which I give a lecture on the Big Bang. My students are often bothered by some of the issues raised in your "the Universe can't have an edge" answer ... Is the problem that we're using "universe" in two senses?

Submitted by rlsbk"AT"gly.uga.edu 5/00

I think you're right that there may be a problem with some people using "Universe" in two senses. But personally I try to stick to one use! This is partly why I like to capitalize the word Universe - to emphasize that I mean the entirety of stuff. In other words, one shouldn't think of the Universe as being a collection of things embedded in some larger object, for then that larger object should really be the thing that you label "Universe".

So first of all you should erase any ideas that you can talk about the Universe being "in" something else! This may help clear up the conceptual misunderstanding.

Secondly, the other problem people can have is with a mental image of the Universe expanding outwards. This obviously has no meaning unless there's something the Universe is in, and so we're back to the first problem. To solve this, many cosmologists try to avoid using the word "explosion" to describe the Big Bang. "Explosion" (as indeed the inappropriate term Big Bang itself) conjures up an image of something sitting there localised in space, which then explodes outwards.

Instead think of the Big Bang as being the model in which the Universe is getting less dense and cooler with time, and which can be extrapolated backwards to arbitrarily early times (with t=0 perhaps excluded). Expansion of space should be thought of as the distance between objects getting larger, rather than the volume of space growing as it expands into something.

And always remember that this is hard stuff to get your mind around!

Think of the universe as always infinite, even before the big bang. It's just at that time the distance between all points in space was zero.

Link

It's a good read. He keeps it interesting by inserting some funny responses here and there.

In many papers the equation of state for the dark energy is written as w= pressure/density. Then it is stated that pressure is proprtional to R ^(-n) where n=3(1+w). Is there a simple way to derive this?

Submitted by shantanu"AT"bu.edu 4/00

Yes there is.