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Author Topic:   What's the Fabric of space made out of?
Sylas
Member (Idle past 5250 days)
Posts: 766
From: Newcastle, Australia
Joined: 11-17-2002


Message 226 of 284 (197600)
04-08-2005 1:01 AM
Reply to: Message 225 by Percy
04-05-2005 9:49 AM


Re: yes and no
One of the most effective ways of convincing yourself of this is to contrast motion through space with motion due to the expansion of space. If you're an observer watching someone whiz by at .866 times the speed of light (.866c), then you'll see the second hand of his watch ticking off the seconds at half the rate of your own. But if you observe a watch in a distant galaxy receding from us at the same rate of .866c then you'll see the second hand ticking off seconds at the same rate as your own.
Caution... if you speak about what is "seen", then actually you do see the second hand ticking more slowly. Suppose a photon leaves the watch at a certain instant. Another photon leaves when the second hand has ticked off another second. The second photon has further to travel than the first, and so arrives more than a second after the first. You see the clock ticking off seconds more slowly.
In fact, this is one of the lines of evidence that redshift really is due to expansion of space, and not due to loss of energy by some tired light effect. Supernova light curves have a characteristic decay time; but those which have a high redshift decay much more slowly. This is due to the same slowing effect as with the watch.
You also get a similar effect with recession due to local motions in space, and for the same reason. Photons leaving later have further to travel, and take longer to get here. This is actually a reasonable correspondence over small scales (small in comological terms!) but this does break down over billions of parsecs.
Redshift can be seen in this way as well. A photon is emitted with a certain frequency. We see it "slowed down" (reduced frequency) which is the redshift.
One thing to bear in mind that in general relativity, notions of distance and of velocity over large scales are not well defined. Comparing cosmological expansion to local motions is a good approximation at small scales -- and this makes it hard to explain the difference between local motions and expanding spaces in terms of observation. A full explanation in terms of local motion does fail, as you say; and we do need to use expansion of space to fit the observations.
Cheers -- Sylas

This message is a reply to:
 Message 225 by Percy, posted 04-05-2005 9:49 AM Percy has replied

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Percy
Member
Posts: 22359
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.8


Message 227 of 284 (197640)
04-08-2005 9:00 AM
Reply to: Message 226 by Sylas
04-08-2005 1:01 AM


Re: yes and no
Sylas writes:
Caution... if you speak about what is "seen", then actually you do see the second hand ticking more slowly. Suppose a photon leaves the watch at a certain instant. Another photon leaves when the second hand has ticked off another second. The second photon has further to travel than the first, and so arrives more than a second after the first. You see the clock ticking off seconds more slowly.
I wanted to keep it simple, but I've been assuming there are really two contributions. One is the effect of recession, the other is the effect of relativity. Relativity doesn't care about the direction of relative motion, only the magnitude. With recession/approach effects the direction matters a great deal. Does that sound right to you?
One thing to bear in mind that in general relativity, notions of distance and of velocity over large scales are not well defined. Comparing cosmological expansion to local motions is a good approximation at small scales -- and this makes it hard to explain the difference between local motions and expanding spaces in terms of observation. A full explanation in terms of local motion does fail, as you say; and we do need to use expansion of space to fit the observations.
This was a confusing paragraph for me. I've been assuming that we couldn't reach any conclusions based on supernova light curves without knowing the relative contributions to the red shift of both relativity and recession . I'm having trouble figuring out, on an intuitive level, how studying supernova in distant galaxies, even at many different distances, and even given that one effect is linear and the other isn't, could enable one to conclude expanding space if we didn't have a pretty good handle on distances. These distances are measured by other means, such as studying supernova of a type which produce a standard brightness.
--Percy

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 Message 228 by NosyNed, posted 04-08-2005 10:33 AM Percy has replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 228 of 284 (197662)
04-08-2005 10:33 AM
Reply to: Message 227 by Percy
04-08-2005 9:00 AM


direction of motion
One is the effect of recession, the other is the effect of relativity. Relativity doesn't care about the direction of relative motion, only the magnitude.
I believe this is incorrect. From reading Greene's "The Fabric of the Cosmos" I understand that the changes due to relative motion are the equivalent to the rotation of spacetime. Different directions produce a rotation in different directions.
Thus if something (one) is moving away from the observer it's space-time is shifted one way and if moving toward it is shifted the other way. This procuces different ideas of which is future and past between the two.
I could quote material from the book if you want. It is a interesting read.

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 Message 227 by Percy, posted 04-08-2005 9:00 AM Percy has replied

Replies to this message:
 Message 229 by Percy, posted 04-08-2005 11:10 AM NosyNed has replied

  
Percy
Member
Posts: 22359
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.8


Message 229 of 284 (197668)
04-08-2005 11:10 AM
Reply to: Message 228 by NosyNed
04-08-2005 10:33 AM


Re: direction of motion
NosyNed writes:
Thus if something (one) is moving away from the observer it's space-time is shifted one way and if moving toward it is shifted the other way. This procuces different ideas of which is future and past between the two.
You're right, but you're probably thinking of Green's description of the dramatic impact of relative motion on our perception of "now", particularly for distant objects. My point was more about the relative pace of observed time of a moving object, which shouldn't be a function of the direction of relative motion. In other words, the clock of someone moving at .866c through space relative to us will tick half as fast, whether they're receding, approaching or moving in a perpendicular direction. Of course, you have to adjust for Doppler (for want of a better word) effects.
If I understand this correctly (always questionable), then there are a couple interesting effects. A distant galaxy with no red shift and therefore neither receding from nor approaching us would be moving through space at high speed and should therefore experience severe relativistic effects, like clock slowing (I think Sylas was questioning this conclusion, but I'll await confirmation). If the galaxy actually were approaching us then there would be a speed relative to us where the Doppler and relativistic effects cancelled as far as red shift, though that speed would be a function of distance due to the expansion of space and therefore the amount of expanding space between us and the galaxy.
Of course, I never underestimate my ability to bollux this kind of thing completely. I'm just trying to make clear how I see this, and any corrections are welcome.
--Percy

This message is a reply to:
 Message 228 by NosyNed, posted 04-08-2005 10:33 AM NosyNed has replied

Replies to this message:
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 Message 231 by jar, posted 04-08-2005 3:45 PM Percy has replied

  
NosyNed
Member
Posts: 8996
From: Canada
Joined: 04-04-2003


Message 230 of 284 (197670)
04-08-2005 11:13 AM
Reply to: Message 229 by Percy
04-08-2005 11:10 AM


Re: direction of motion
Yes, sorry for nitpicking and complicating things.

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jar
Member (Idle past 384 days)
Posts: 34026
From: Texas!!
Joined: 04-20-2004


Message 231 of 284 (197704)
04-08-2005 3:45 PM
Reply to: Message 229 by Percy
04-08-2005 11:10 AM


Likely another dumb question from the old and slow.
A distant galaxy with no red shift and therefore neither receding from nor approaching us would be moving through space at high speed and should therefore experience severe relativistic effects, like clock slowing (I think Sylas was questioning this conclusion, but I'll await confirmation).
Two people are on seperate trains. Each looks out the window and finds he is looking into the eyes of the other. The line of site between the two pair of eyes is constant, neither approaching or moving away.
Is that the same scenario as looking at a distant galaxy with no shift, neither red or blue?
If that is the case, would it not require that the two objects, train vs. train or us vs. distant galaxy, be traveling at exactly the same speed and vector in relation to each other?
Can one object move at a different speed in relation to a second object without either approaching or receding?

Aslan is not a Tame Lion

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 Message 229 by Percy, posted 04-08-2005 11:10 AM Percy has replied

Replies to this message:
 Message 232 by Percy, posted 04-08-2005 5:14 PM jar has not replied

  
Percy
Member
Posts: 22359
From: New Hampshire
Joined: 12-23-2000
Member Rating: 4.8


Message 232 of 284 (197717)
04-08-2005 5:14 PM
Reply to: Message 231 by jar
04-08-2005 3:45 PM


Re: Likely another dumb question from the old and slow.
Until Sylas chimes back in take this all with a grain of salt, but the way I'm looking at this is that distant galaxies have only small relative motions relative to us through space. That's because their apparent motion away from us is due to the expansion of all the intervening space, not because they're really moving relative to us through space. Because relativity only applies to objects moving relative to us through space, the relativistic effects are very tiny.
If we were to see a distant galaxy with no red shift, one that was neither receding or approaching, it would mean that it would have a hefty relative velocity toward us through space. This is because while it maintains a constant distance from us, the intevening space is expanding and zipping past it at high velocity. There is a bit of similarity to the Red Queen. Though dx/dt is 0 for us and the distant galaxy, the distant galaxy would have to "run" as fast as it could toward us just to maintain that distance.
The elastic band analogy works pretty well here. Imagine that our galaxy and the distant galaxy are far apart on an elastic band which is infinitely stretchable (the elastic band could also be infinite in length, but since we're only considering the portion of the elastic band between our two galaxies it isn't important). The elastic band is being continually stretched longer and longer by the forces of darkness, and so our galaxies not only become separated by a greater and greater distance, but our speed of recession grows larger and larger, too.
One curious thing about this situation is that neither our galaxy nor the distant galaxy is moving with respect to the local piece of elastic band to which it is attached, and so though the distant galaxy is receding away from us at great speed, our relative motion as measured against the elastic band, i.e., our relative motion through space, is 0. With no relative motion through space there can be no measurable relativistic effects.
In order for the distant galaxy to maintain the same distance from us, it would have to begin moving toward us along the elastic band at the same rate that the elastic band is stretching in its region of the elastic band. If the galaxies were instead little radio controlled cars and the elastic band were actually one of those elastic ace bandages oriented so the cars could rest on it, then the distant car would have to really rev up its engines and go for broke in order to maintain the same distance from us.
--Percy

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nipok
Inactive Member


Message 233 of 284 (202499)
04-26-2005 2:51 AM
Reply to: Message 1 by Fabric
02-27-2005 3:29 PM


Someday, hopefully in my lifetime the right person will be able to explain the answer to your question better than I can. You would think in this day and age with so much intelligence and knowledge that there would be more people able to grasp the underlying nature of the Universe. The fabric of space is energy. Energy is everywhere with varying degrees of relative density. From the almost pure vacuum that is note quite pure to the center of the largest stars there is energy. Some manifested as matter, some as heat, some as light, some as motion, some as attraction, some as kinetic, and some as potential.
It is upon this fabric of energy that there exists the visual representations of measurable units. Measurable units of time, measurable units of distance, and measurable units of energy (be it heat, or light, or motion, or matter) all providing our eyes and brains with an ability to perceive the visual universe.
It is these measurable units and visual perceptions of the manifestations of energy that give us the reality we call life. But these measurable units are not finite, only our small tiny minds and their inability to think on a grander plane create the false impression of the finite. In reality these measurements are made up of an infinite number of smaller measurements each making up an infinite chain of smaller measurements all as part of an infinite chain of larger measurements.
What we call our space time continuum that we feel originated with a big bang is nothing but a point in the true fabric of space and time. It is a point because in the grand scheme of the true Universe our known universe is a massless, timeless, energyless speck of nothingness.
Relativistic physics however makes our known universe much more than a point in time and space because we can place visual measurements upon both the super large and super small. It is only our current limitations on the degree of scientific precision we are able to obtain with our current technical instruments that prevent us from really understanding the true fabric of space and time.

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Replies to this message:
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randman 
Suspended Member (Idle past 4889 days)
Posts: 6367
Joined: 05-26-2005


Message 234 of 284 (237142)
08-26-2005 1:47 AM
Reply to: Message 233 by nipok
04-26-2005 2:51 AM


interesting post
good post....so you are saying it's all energy, and the form we see as our universe is just comparitive analysis of the massive fields of energy?

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prodigious by design
Junior Member (Idle past 5767 days)
Posts: 2
From: Louisiana USA
Joined: 06-03-2008


Message 235 of 284 (469037)
06-03-2008 5:58 AM


A different theory
The universe is NOT expanding and it is FINITE. Our known (visible) universe is encased (surrounded) by another dimension. Although space appears to extend to infinity, it actually has a 'curtain' which separates it from this other dimension. This other dimension can be called a parallel universe. It is possible to rip this fabric of space apart, allowing travel between these separate dimensions. Black holes are actually wormholes through this curtain which allow travel between these parallel worlds.
What this means, in essence, is that the universe is toroidal by design. In order to better understand the nature of the universe, read about Moebius strips, toroids, wormholes, black holes, and the 5th dimension. These are not fantastical, science fiction-type ideas but the stuff of serious, scientific research in attempts to understand our amazing and mysterious world. For example see here:
MSN | Outlook, Office, Skype, Bing, Breaking News, and Latest Videos
Although most scientists perceive worm/black holes as shortcuts across great distances of (folded) space, I see them as doors to the alternate (parallel) universe...i.e., the OTHER SIDE.
So, yes, there really is a 'fabric' of space.
That's my story and I'm sticking to it...
...until proved otherwise.

Serve my faith stirred but not shaken.
Truth is an island (often deserted) in a sea of lies.
I said it....BELIEVE IT!
(Hey, somebody's got to be right)

Replies to this message:
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onifre
Member (Idle past 2941 days)
Posts: 4854
From: Dark Side of the Moon
Joined: 02-20-2008


Message 236 of 284 (469121)
06-03-2008 11:04 PM
Reply to: Message 235 by prodigious by design
06-03-2008 5:58 AM


Re: A different theory
The universe is NOT expanding and it is FINITE.
Please give me a reference to this statement from a scientific source.
I see them as doors to the alternate (parallel) universe...i.e., the OTHER SIDE.
Also provide evidence for this statement please...what qualifies you to make this claim?

All great truths begin as blasphemies
I smoke pot. If this bothers anyone, I suggest you look around at the world in which we live and shut your fuckin' mouth.

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IamJoseph
Member (Idle past 3658 days)
Posts: 2822
Joined: 06-30-2007


Message 237 of 284 (469338)
06-05-2008 4:52 AM
Reply to: Message 235 by prodigious by design
06-03-2008 5:58 AM


Re: A different theory
If the BBT is accepted, it says there was a point, which expanded to the current status of the universe. This also says, there was nothing else aside from the first point - else the entire BBT becomes superfluous. Here, we can surmise the possibilities applicable:
1. Space, or its prototype status, was compressed within the first primal point, and spewed out, expansively, in proportion to all other products from within that point.
2. Space was independent of the BB point, and was poured into the universe from another dimension or realm. This factor violates the finite premise.
3. Space is a post-BB product, as are all other universe products, and occured after and outside the BB point.
4. Both the BB point and the universe was the result of an external impacting.
I see no other possibilities, and I favor the 1st one from a scientific pov, and the 4th from a belief pov. The first [1] says there was a program which anticipated and fostered the universe and all its content, alligning with the logical premise whatever came about was resultant on a corresponding program which fostered it. Here, space would be no dfferent from the other products, and can be seen as anticipatory and accomodating, akin to a builder or a program, which would obviously cater to bed or floor to contain a house and its contents.
Thus space is a matrix to rest the universe products - else the products would not/could not exist. The confusion results from space resembling nothingness, but in fact, space is an inert factor, which can cater to all the varied products, without causing confusion. If space was made of terminable material and elements, we would not be able to distinquish the other materials, so we can see why space was made without any material traits, and is a neutral factor. We can see space - it is not nothingness; space can also bend, and it's independent temperature be determined.

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JJP
Junior Member (Idle past 5679 days)
Posts: 14
From: Northern Ireland
Joined: 08-28-2008


Message 238 of 284 (479515)
08-28-2008 12:25 AM


Space Fabric
It's a funny old thing isn't it?
imagine this for a second,,, we say that space fabric is non excistant but oly to obey the 4th demention of space,
when you thnk of it this way, who has ever proved that space doesn't excist? for some other reason, if you open a capsule of air in space it dispates really fast with what we call the space vacume, why does this not happen to the earh on a day to day besis then? surely if the space vacume is so vast and strong then you would think all the air would have been sucked out a long time ago, but it has't been.
i'll tell you what,,, go up to space and open a capsule in the vacumous space then close it, the same vacume of space should be contained in this, then bring it back to earth and let it go, just like when you trap air in a ball under water, if space is made up of anything it should shoot straight back out to where it belongs. if that hapens then space must be made out of something.
Anybody care to elaborate on that?
Edited by JJP, : No reason given.

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 Message 245 by lyx2no, posted 08-28-2008 1:09 PM JJP has replied

  
JJP
Junior Member (Idle past 5679 days)
Posts: 14
From: Northern Ireland
Joined: 08-28-2008


Message 239 of 284 (479516)
08-28-2008 12:41 AM


oh by the way
Stop talking about light bending, you can bend light with mirrors, plus time travelling is impossible, why you ask? in order to time travel you need to be able to control every natural state of ordinance within excistance, this is something that cannot be achieved by anything, no massive stars or black holes. worm holes? no such thing and evenif there were it would lead back to the same place. if we ever mastered the power of a black hole then i believe we could pull on it's gravity, an thenwe would be able to bring to points in the universe together, but lets face it, what's heavier gravity?
if you want to travel at the speed of light then good luck trying to piece your molecules back together, and even if you could keep your moecules together with some sort of inertial dampners you still wouldn't be able to see anything as the human eye can only see what it's used to.
Edited by JJP, : No reason given.

  
lyx2no
Member (Idle past 4706 days)
Posts: 1277
From: A vast, undifferentiated plane.
Joined: 02-28-2008


Message 240 of 284 (479543)
08-28-2008 8:26 AM
Reply to: Message 238 by JJP
08-28-2008 12:25 AM


Read a Book
why does this not happen to the earh on a day to day besis then?
Gravity.
Edited by lyx2no, : 8

Kindly
When I was young I loved everything about cigarettes: the smell, the taste, the feel . everything. Now that I’m older I’ve had a change of heart. Want to see the scar?

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