PDA

View Full Version : I dont understand how space expands?



GoshawkJV
2007-Feb-23, 03:46 AM
Hello Everyone,
I recently took an astronomy course and have also just read Patterns in the Void by Odenwald.
I cannot grasp the concept that space is expanding no matter how anyone explains it. If everything we see, galaxies etc etc are just along for the ride, then what is space expanding into?
I try to think in other dimensions but this does not help. I just always think there has to be something outside of something.

So if space is expanding, what is it expanding into? what is outside of space?

thanks gang

James Vellozzi

01101001
2007-Feb-23, 04:12 AM
I cannot grasp the concept that space is expanding no matter how anyone explains it.

So why do you think we can explain it? Language like that doesn't offer much encouragment.

Well, maybe it's a chance to try out the new factual Preposterous Universe Cosmology Primer (http://preposterousuniverse.com/writings/cosmologyprimer/index.html).

What bothers you about that Expanding Universe (http://preposterousuniverse.com/writings/cosmologyprimer/expanding.html) explanation?

Or, one specific issue you have, from the FAQ (http://preposterousuniverse.com/writings/cosmologyprimer/faq.html):


What is the universe expanding into?
As far as we know, the universe isn't expanding "into" anything. When we say the universe is expanding, we have a very precise operational concept in mind: the amount of space in between distant galaxies is growing. (Individual galaxies are not growing, as they are bound together by gravity.) But the universe is all there is (again, as far as we know), so there's nothing outside into which it could be expanding. This is hard to visualize, since we are used to thinking of objects as being located somewhere in space; but the universe includes all of space.

Welcome to the BAUT Forum.

astromark
2007-Feb-23, 06:59 AM
For me this is simple. Or is it me that is simple?
Space is nothing. Nothing can not expand. It is nothing. The gaps between things can expand. What is it expanding into? here we go again...Nothing. There is nothing there to expand into. The universe is expanding. That simply put means it is getting bigger. It would appear that the use of the word expanding is confusing. Nothing can not expand as it has no substance to do that with. Objects that are not gravitationally bound to other objects are getting farther away from each other, expanding the universe. Try to see space as nothing at all. It works for me.

Cougar
2007-Feb-23, 05:46 PM
I cannot grasp the concept that space is expanding no matter how anyone explains it. If everything we see, galaxies etc etc are just along for the ride, then what is space expanding into?
In the old balloon analogy, the two-dimensional surface of the balloon is the entire universe. There is no interior or exterior of the balloon, just the surface. As it expands, what is it expanding into? Well, it's not expanding into anything! The surface area is just growing.

If you can keep focused on just the balloon surface as everything-that-there-is and disregard the inside & outside of the balloon, maybe that will help.

Ken G
2007-Feb-23, 05:59 PM
You can try two other pictures that you can use, to see if any of these help you feel like you understand. The first is if you imagine a number line of integers, where each integer is a room number in an infinitely large hotel. Now imagine that everyone in the hotel is asked to move from their room into a room with double the room number. That is possible in an infinite hotel, and the hotel itself is not expanding, but suddenly there's an empty room in between every full room. So it is with expanding space.

Or, if you don't like the infinity that the hotel represents, here's an equivalent way to think of expansion of space-- picture it as a shrinking of matter and gravitationally bound systems. Note that all we ever really have is a comparison of the size of galaxies to the size in between galaxies, so shrinking the former (along with the rulers that measure it) is indistinguishable from expanding the latter (leaving the rulers fixed in that case). But if you imagine that matter is shrinking, then nothing at all is happening to "space"-- and the question becomes "what is matter shrinking into". But no one asks that question, if matter is shrinking, it's just shrinking-- it doesn't have to shrink "into" anything. So it is with expanding space, those are two sides of the same coin.

satori
2007-Feb-23, 06:28 PM
wellll Ken G........I can follow your first argument .........
what concerns your second attempt....even if you may be logicaly on the save side, the shrinking of matter and me and all.....no that would not constitute a conceptual progress for my taste.
Actualy, it rather sounds as if you were still under the impression of your conversation with Dons our new Law Man !

bigsplit
2007-Feb-23, 06:56 PM
The gravitational potentions of space expand and contract, it is called space/time. I think.

speedfreek
2007-Feb-23, 07:26 PM
The way I think of it is like this:

The metric expansion of space means that the whole of space is expanding. This isn't the same as other types of expansion. If you were to assign points in space a coordinate system, the matter is not expanding past different coordinates, it is the coordinates that are expanding.

This doesn't mean objects are moving through space due to expansion, it is the space itself that is expanding, which moves the galaxies apart from each other (objects also interact locally due to inertial movement through gravity, but the whole system is being pulled apart by the metric expansion of space).

For space to be expanding into something, that implies an 'edge' where space stops and the something begins. But an 'edge' needs something beyond it, to define it. This something could actually be nothing (void - no dimensions, no time etc) or maybe a dimension outside our universe that we cannot, by definition, know anything about.

If the universe is, for instance, a region of space expanding in a void, there would be no edge between space and void. We are talking about an expanding dimensional space, with no dimensions anywhere but in that space. We cannot visualise this as a shape to help us understand.

A good model for this would be a 4 dimensional manifold, as used to model spacetime in general relativity.

A manifold is an abstract mathematical space in which every point has a neighbourhood which resembles Euclidean space, but in which the global structure may be more complicated. In discussing manifolds, the idea of dimension is important. For example, lines are one-dimensional, and planes two-dimensional.

In a one-dimensional manifold (or one-manifold), every point has a neighborhood that looks like a segment of a line. Examples of one-manifolds include a line or a circle. In a two-manifold, every point has a neighborhood that looks like a disk. Examples include a plane, the surface of a sphere, and the surface of a torus.

So, if the universe were a four-manifold, every point would have a neighborhood that looks 4 dimensional (i.e. space-time). That being the case, try coming up with an example of this shape (to understand where the edge might be!), bearing in mind that an example of a two-manifold is the surface of a sphere!

Einstein said that universe was finite but unbounded, to me that does not mean the matter ends and some form of space continues, it means all of space is within itself - there is no boundary and it somehow curves dimensionally back on itself.

satori
2007-Feb-23, 07:43 PM
"stupid-name-but-bright-mind" , wellcome to the forum !

bigsplit
2007-Feb-23, 07:50 PM
The way I think of it is like this:

If you were to assign points in space a coordinate system, the matter is not expanding past different coordinates, it is the coordinates that are expanding.


This is decieving, if the coordinates are based on the 3 spacial dimensions fix space like a land map the coordinates would not expand. But, because of matters movement streching the gravitational pontials we assign the coordinate based on space/time. This is the prefered visual physicist like to use and very practicle conceptual imagery .

Other debates about an infinate space matrix and space beyond the universe are all outside of our current knowledge and untestable at best. So the question of a fixed 3D infinate space matrix without time is not resolved and may be unresolvable.

speedfreek
2007-Feb-23, 07:55 PM
Hi there Satori, and thanks for the, err, welcome! :dance:

The nickname (note the spelling) may be less or more stupid than you think, depending on your viewpoint. It comes from the HULK marvel comic, Speedfreek was one of the Hulks enemies! And it applies to me due to my love of motorsports, but I digress.

speedfreek
2007-Feb-23, 08:13 PM
This is decieving, if the coordinates are based on the 3 spacial dimensions fix space like a land map the coordinates would not expand. But, because of matters movement streching the gravitational pontials we assign the coordinate based on space/time. This is the prefered visual physicist like to use and very practicle conceptual imagery .

Other debates about an infinate space matrix and space beyond the universe are all outside of our current knowledge and untestable at best. So the question of a fixed 3D infinate space matrix without time is not resolved and may be unresolvable.

True, I didn't explain that part very well for it is not easy to explain. The metric expansion of space means that space itself is expanding by a metric which changes over time. If we imagine points 1 unit apart in space, the metric expansion means over a certain period of time 1 unit expands to what was 2 units.

So over a time of length X, 1 meter becomes what was 2 meters, 100 km becomes what was 200 km, 1 light year becomes 2 light years - the diameter of the universe doubles! This explains why we see little evidence of expansion at close distances, but the most distant objects seem to be receding from us extremely fast. But the same is true anywhere! In those distant galaxies, expansion seems slow close up, but our galaxy is receding from them at a great speed. Any given unit will expand at the same rate as any other unit, over a given time. This is unlike any other kind of expansion we usually deal with, which is possibly why it can be so difficult to understand.

As for other debates about what may or may not be outside our universe, or if it even has an outside, well that was the original posters question, and I just mentioned some possibilities, but the main point is that unbounded doesn't have to mean endless, or that it has an end!

DyerWolf
2007-Feb-23, 09:57 PM
For me this is simple. Or is it me that is simple?
Space is nothing. Nothing can not expand. It is nothing. The gaps between things can expand. What is it expanding into? here we go again...Nothing. There is nothing there to expand into. The universe is expanding. That simply put means it is getting bigger. It would appear that the use of the word expanding is confusing. Nothing can not expand as it has no substance to do that with. Objects that are not gravitationally bound to other objects are getting farther away from each other, expanding the universe. Try to see space as nothing at all. It works for me.

This sounds like a good example to me. Folks had a hard time with the concept of the number zero in antiquity. Perhaps this is similarly hard for some today.

thecolorofash
2007-Feb-23, 10:01 PM
bigsplit
Senior Member

"This is decieving, if the coordinates are based on the 3 spacial dimensions fix space like a land map the coordinates would not expand. But, because of matters movement streching the gravitational pontials we assign the coordinate based on space/time. This is the prefered visual physicist like to use and very practicle conceptual imagery ."

I do not understand this ? ....

transreality
2007-Feb-23, 11:17 PM
Matter more or less consists of particles embedded in space, gravity controls the movement and local density of these particles.

In a vaccuum, or any where the gap between individual particles falls below a particular density, virtual particles can then manifest. They seem to do so by stretching the gap so they fit, and then annihilate each other, leaving the space stretched.

Particles on each side of the expanded gap are now measureably more distant. This process happening on a very small scale occurs continuously throughout the universe, so the separation rate between particles increases with distance between them.

Since the gaps are all opening up, more space exists for vaccuum fluctuations to occur in, so the expansion of the universe is accelerating.

GoshawkJV
2007-Feb-24, 08:00 AM
thanks everyone!

dhd40
2007-Feb-24, 06:41 PM
Well, it's not expanding into anything! The surface area is just growing.

Hmmm, what´s the difference between >expanding< and >growing< in this context?

The Patriot
2007-Feb-28, 01:20 AM
Hello Everyone,
I recently took an astronomy course and have also just read Patterns in the Void by Odenwald.
I cannot grasp the concept that space is expanding no matter how anyone explains it. If everything we see, galaxies etc etc are just along for the ride, then what is space expanding into?
I try to think in other dimensions but this does not help. I just always think there has to be something outside of something.

So if space is expanding, what is it expanding into? what is outside of space?

thanks gang

James Vellozzi

Space is already infinite so it can't expand.

In the Bible, God saind that he would cast off Israel if man ever saw the edge of space. In another section of the bible, God said that he would never cast off Israel. So obviously space is infinite.

Yes, I'm a Christian. No, I'm not a clueless nut. Contrary to what some people think, they're two different things (lest you think this is an insult, I'm NOT thinking of anyone in particular).

PLEASE, don't get me modded by using that above paragraph as an excuse to start a flamewar!

Ken G
2007-Feb-28, 03:10 AM
I'll keep it simple: you can't cite a religious text as if it were scientific evidence on a science board. It may not necessarily be the act of a "nut", but it is certainly the act of someone who understands neither science nor the rules of this forum.

cjl
2007-Feb-28, 05:01 AM
Not to mention (and this also can get confusing) is that even if it is infinite, it can still expand.

eburacum45
2007-Feb-28, 08:39 AM
cjl is apparently right. The Infinite Hotel thought experiment seems to show that even in an apparently full infinite space there is also an infinite amount of room;
http://en.wikipedia.org/wiki/Hilbert's_paradox_of_the_Grand_Hotel
this paradox was noted by the famous and influential mathematician David Hilbert. Basically, it seems that an infinite universe can expand for an arbitrary length of time and still be infinite.

The Patriot
2007-Mar-01, 12:45 AM
I'll keep it simple: you can't cite a religious text as if it were scientific evidence on a science board. It may not necessarily be the act of a "nut", but it is certainly the act of someone who understands neither science nor the rules of this forum.

The Blible has never been proven wrong scientifically, and many parts of it have actually been proven right.

Those "life on planets besides Earth" hypotheses (word?) don't rely on scientific evidence any more than the Bible does.

The thinking that are other planets (espicially life-bearing planets) in other solar systems in other galaxies is no more science than the Bible is.

Isaac Newton used the Bible in his studies quite a lot.

NO, I am NOT trying to start a religious flamewar or violate the rules.

Doodler
2007-Mar-01, 12:58 AM
Man, I'm good, didn't even read this thread before responding to him in the other thread in Life in Space, and I knew he learned everything he knew from a Bible.

I'm gonna get some popcorn, this meltdown should be amusing.

Kaptain K
2007-Mar-01, 01:00 AM
The Blible has never been proven wrong scientifically...
How about where it states that pi is exactly equal to 3?


NO, I am NOT trying to start a religious flamewar or violate the rules.
Could have fooled me (on both counts)!

Doodler
2007-Mar-01, 01:01 AM
http://www.bautforum.com/showthread.php?p=936809#post936809

For those curious as to my reference.

Hamlet
2007-Mar-01, 01:25 AM
The Blible has never been proven wrong scientifically, and many parts of it have actually been proven right.

Really? How about that there is no evidence of a world-wide flood? How about the ridiculous notion that you can stuff an entire global ecosystem onto a wooden boat? Those are some examples among many.



Those "life on planets besides Earth" hypotheses (word?) don't rely on scientific evidence any more than the Bible does.

The thinking that are other planets (espicially life-bearing planets) in other solar systems in other galaxies is no more science than the Bible is.

Yes, the Bible doesn't have any science in it. However, the science of exobiology has many lines of reasoning going for it.

We know that the chemicals necessary for life on Earth are found in abundance throughout the universe.
We know that life can exist in more extreme environments than we once thought.
We have evidence of at least 200 other planets outside of our solar system. The odd are that there are many, many more. It doesn't take much of an imagination to see that there could be some planets that are hospitable to life.




Isaac Newton used the Bible in his studies quite a lot.

Do tell. What parts of the Bible did Newton use to develop his theories on optics and gravitation?



NO, I am NOT trying to start a religious flamewar or violate the rules.

Then what exactly are you trying to do?

Occam
2007-Mar-01, 02:32 AM
Ignoring the bible twaddle...
You cannot relate the properties of the universe to anything in your everyday experience, so don't try.
The universe is infinite, because it is all there is.
Space, time and mass are all part of the same parcel.
Space is created by matter. In the expanding universe theory, the universe is is not expanding INTO anything. Matter is only moving relative to other matter, creating the space as it goes along.
Therefore, as odd as it may seem, the universe can be said to be infinite AND expanding.

dhd40
2007-Mar-01, 07:33 PM
The Blible has never been proven wrong scientifically, and many parts of it have actually been proven right. (SNIP)


Sorry, but that sounds extremely naive. Just one example, and I have to paste the German text as well (and my poor translation to English):
Offenbarung 12,3 - 4
Ein anderes Zeichen erschien am Himmel: ein Drache, gro&#223; und feuerrot, mit sieben K&#246;pfen und zehn H&#246;rnern und mit sieben Diademen auf seinen K&#246;pfen. Sein Schwanz fegte ein Drittel der Sterne vom Himmel und warf sie auf die Erde herab.
Revelation 12,3 – 4
A new sign appeared in the sky: A dragon, tall and blazing red, with seven heads and ten horns and with seven diadems on its heads. His tail wiped away one third of all stars in the skys and threw them down on earth

This should not be understood as an argument against the Bible but against those who don&#180;t understand the Bible

speedfreek
2007-Mar-02, 12:50 AM
The universe is infinite, because it is all there is.
Hang on, if it is all there is, it cannot be infinite. For something to be infinite, there has to be more than there is! I'm with Einstein on this one, it's finite but unbounded.


Space is created by matter.
See below.


In the expanding universe theory, the universe is is not expanding INTO anything.
Yes, the metric expansion does not have to proceed "into" anything. The universe that we inhabit does expand and distances get larger, but that does not mean that there is a larger space into which it is expanding.


Matter is only moving relative to other matter, creating the space as it goes along.
The metric expansion of space means it is the metric defining distance that is changing. This makes objects move apart, but this is not due to inertial movement. The metric expansion of space moves matter apart, not the other way round.

Ken G
2007-Mar-02, 03:47 AM
Hang on, if it is all there is, it cannot be infinite. For something to be infinite, there has to be more than there is! I'm with Einstein on this one, it's finite but unbounded.
Einstein never claimed the universe is finite but unbounded, that sounds like the "closed universe" possibility that he would have only viewed as that-- one possibility. It now appears that we will never know if the universe is finite and unbounded, or truly infinite, it will likely always be beyond our ability to observe or measure. This is one of many limitations that science must simply live with.

The metric expansion of space means it is the metric defining distance that is changing. This makes objects move apart, but this is not due to inertial movement. The metric expansion of space moves matter apart, not the other way round.
Yes, that is right on target for the current way that the expansion is conceptualized in comoving-frame coordinates, which are the local coordinates where measurements can actually be made by any intelligent beings that happen to populate our universe. It is also the coordinate system that most seamlessly conforms to the "cosmological principle", so it is tempting to think of it as the "most real" interpretation, though others are certainly possible and also valid.

Bogie
2007-Mar-02, 04:01 AM
Hello Everyone,
I recently took an astronomy course and have also just read Patterns in the Void by Odenwald.
I cannot grasp the concept that space is expanding no matter how anyone explains it. If everything we see, galaxies etc etc are just along for the ride, then what is space expanding into?
I try to think in other dimensions but this does not help. I just always think there has to be something outside of something.

So if space is expanding, what is it expanding into? what is outside of space?

thanks gang

James VellozziNormally answers in the Q&A thread are to be limited to mainstream answers. This thread has already brought in several non mainstream ideas without comment from the moderators so I feel that it is in line to mention my answer to the question in the OP.

There are several new multiverse theories and "our" expanding universe fits with these alternate cosmologies. My idea in particular says that "our" universe is an expanding ball of high energy density, expanding into space that is of lower energy density.

As the high energy density spreads, its energy density is lowered. The lowered energy density of the spreading ball of high energy density is lowered equally throughout the entire ball because the density equalizes itself as it expands.

This same principle of equilization is the reason that the ball of high energy density expands in the first place. It is equalizing its density with the surrounding low energy density that it is expanding into.

Ken G
2007-Mar-02, 04:22 AM
Normally answers in the Q&A thread are to be limited to mainstream answers. This thread has already brought in several non mainstream ideas without comment from the moderators so I feel that it is in line to mention my answer to the question in the OP.In my perusal of the thread, I see only one post that is clearly ATM, the rest are at times a bit vague but rarely ATM, so I think you are misinterpreting some of the answers and concluding they are ATM when really they are just not terribly precisely worded.

There are several new multiverse theories and "our" expanding universe fits with these alternate cosmologies. My idea in particular says that "our" universe is an expanding ball of high energy density, expanding into space that is of lower energy density.Now there's an ATM idea. I see what you're saying, you feel that latitude has been granted to others so you will accept some yourself. But your idea is not just vague, it is actually quite unsupportable, in the sense that it is different from the Big Bang model in ways that have no observational support. (Who knows, it could end up being right, but we have to stick with what we've already observed.)
This same principle of equilization is the reason that the ball of high energy density expands in the first place. It is equalizing its density with the surrounding low energy density that it is expanding into.
Actually, this isn't really ATM, it's more just simple misconception. You are under the mistaken idea that the Big Bang can be modeled as an explosion, as occurs when you have a higher pressure surrounded by a low pressure. Perhaps this misconception is fueled by the horrible misnomer "Big Bang". In any event, your description of this model has never been a feature of it, and leads to questions like "what is the universe expanding into". For the benefit of the OPer and any lurkers on the thread, I feel I have to step in at this point and say your picture is inaccurate, misleading, and can cite zero observational support, relative to the more descriptive versions of the Big Bang already in this thread.

transreality
2007-Mar-02, 04:25 AM
Space is created by matter.

I don't think is against the mainstream to explain the expansion of space as the sum effect of vaccuum fluctuations aka casimir effect aka Dark Energy.

In this view matter inhibits the expansion of space.

Bogie
2007-Mar-02, 05:08 AM
In my perusal of the thread, I see only one post that is clearly ATM, the rest are at times a bit vague but rarely ATM, so I think you are misinterpreting some of the answers and concluding they are ATM when really they are just not terribly precisely worded. Now there's an ATM idea. I see what you're saying, you feel that latitude has been granted to others so you will accept some yourself. But your idea is not just vague, it is actually quite unsupportable, in the sense that it is different from the Big Bang model in ways that have no observational support. (Who knows, it could end up being right, but we have to stick with what we've already observed.)
Actually, this isn't really ATM, it's more just simple misconception. You are under the mistaken idea that the Big Bang can be modeled as an explosion, as occurs when you have a higher pressure surrounded by a low pressure. Perhaps this misconception is fueled by the horrible misnomer "Big Bang". In any event, your description of this model has never been a feature of it, and leads to questions like "what is the universe expanding into". For the benefit of the OPer and any lurkers on the thread, I feel I have to step in at this point and say your picture is inaccurate, misleading, and can cite zero observational support, relative to the more descriptive versions of the Big Bang already in this thread.You are very gallant to come to the rescue of those here who might not immediately see that my brief description of two energy environments merging as the one of higher energy density expands into the one of lower energy density is not supported by the evidence. I guess the only evidence we could have besides the observed expansion itself would be to get beyond the expanding ball of high energy density but of course that would require us leaving "our" universe and entering the greater universe. That is an event that is not likely to be possible for maybe trillions of years.

As for the misconception of the "Big Bang", I am not one of those who think of it as an explosion.

Ken G
2007-Mar-02, 08:57 AM
As for the misconception of the "Big Bang", I am not one of those who think of it as an explosion.

But a high pressure region, surrounded by a low pressure region, as you describe, is an explosion!

Bogie
2007-Mar-02, 12:40 PM
But a high pressure region, surrounded by a low pressure region, as you describe, is an explosion!
http://books.google.com/books?id=pePU3MRBaNwC&pg=RA1-PA59&lpg=RA1-PA59&dq=patterns+in+the+void+by+odenwald&source=web&ots=0-ZaWJc229&sig=oN2daecayS2UTvT2QpAt3w3tojc#PPP1,M1 (http://books.google.com/books?id=pePU3MRBaNwC&pg=RA1-PA59&lpg=RA1-PA59&dq=patterns+in+the+void+by+odenwald&source=web&ots=0-ZaWJc229&sig=oN2daecayS2UTvT2QpAt3w3tojc#PPP1,M1)

http://books.google.com/books?id=pePU3MRBaNwC&dq=patterns+in+the+void+by+odenwald (http://books.google.com/books?id=pePU3MRBaNwC&dq=patterns+in+the+void+by+odenwald)

I don’t know if it was just an oversight on James’ part but he left out any link to Patterns in the Void by Odenwald, and yet his reading inspired the question, “So if space is expanding, what is it expanding into? what is outside of space?”

I think that if you read Odenwald you may conclude that GoshawkJV, i.e. James was trying to reconcile the imaginative work of Odenwald with the very positions of science that you convey. I think he knows what science says and wonders why the scientific explanation is so much less imaginative that Odenwald’s work in regard to the possible alternatives that could cause an expanding universe.

Ken G
2007-Mar-02, 02:11 PM
I think he knows what science says and wonders why the scientific explanation is so much less imaginative that Odenwald’s work in regard to the possible alternatives that could cause an expanding universe.

Maybe, because "being imaginative" is less important to science than providing an accurate description supported by observations?

Bogie
2007-Mar-02, 03:18 PM
Maybe, because "being imaginative" is less important to science than providing an accurate description supported by observations?We always find a point of agreement :).

speedfreek
2007-Mar-02, 06:48 PM
Einstein never claimed the universe is finite but unbounded, that sounds like the "closed universe" possibility that he would have only viewed as that-- one possibility.

Well, it was his claim, but as you say, he claimed it to be a possibility. See chapter 31 of Relativity: The Special and General Theory. (1920).

I'll quote a little of the translation,.

XXXI. The Possibility of a ?Finite? and Yet ?Unbounded? Universe

"BUT speculations on the structure of the universe also move in quite another direction. The development of non-Euclidean geometry led to the recognition of the fact, that we can cast doubt on the infiniteness of our space without coming into conflict with the laws of thought or with experience (Riemann, Helmholtz). These questions have already been treated in detail and with unsurpassable lucidity by Helmholtz and Poincaré, whereas I can only touch on them briefly here."

The whole paper is available to read HERE (http://www.bartleby.com/173/)