A space expansion question

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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Is it possible that space is quantifiable and is subdividing rather than expanding?&nbsp; Sort of like&nbsp;a&nbsp;commute from the&nbsp;country&nbsp;to the city taking longer&nbsp;than it used to, but&nbsp;not because the distance changed, rather because there are now twice as many roads, intersections,&nbsp;and traffic lights that you must pass on the way. <br />Posted by i_think</DIV></p><p>There is some speculation that space is quantized, but nobody yet knows how to expand on that idea.&nbsp; However, even were that the case, if what you propose is that it is sort of "breeding" new quanta of space, that would be in essence an expansion.&nbsp; In other words if the measure of distance were how many intersections and traffic lights you passed, then an increase in intersections and traffic lights would actually be an increase in distance.&nbsp;What you are dealing with here is the very definition of "distance", so you have to think somewhat abstractly.</p> <div class="Discussion_UserSignature"> </div>
 
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i_think

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>There is some speculation that space is quantized, but nobody yet knows how to expand on that idea.&nbsp; However, even were that the case, if what you propose is that it is sort of "breeding" new quanta of space, that would be in essence an expansion.&nbsp; In other words if the measure of distance were how many intersections and traffic lights you passed, then an increase in intersections and traffic lights would actually be an increase in distance.&nbsp;What you are dealing with here is the very definition of "distance", so you have to think somewhat abstractly. <br />Posted by DrRocket</DIV><br /><br /><font size="2">Thanks for the reply and understanding my abstract question!&nbsp;&nbsp;I realize the end result is the same; distance increases.&nbsp;&nbsp;I just thought it was inconsistent that space-time simply "expands" while&nbsp;I can't think of anything else in nature that does so.&nbsp; Please indulge my line of thought one whit&nbsp;further... </font></p><p><font size="2">If&nbsp;the expansion of&nbsp;space&nbsp;is&nbsp;actually the&nbsp;multiplication of space quanta,&nbsp;in order to be consistent with the observed lack of "expansion" near the&nbsp;vicinity of matter, the rate of multiplication must be proportional&nbsp;to the distance from matter.&nbsp;&nbsp;As the distance between&nbsp;clusters of matter/galaxies increases, the rate of&nbsp;quanta multiplication would increase,&nbsp;which is consistent with our observed acceleration of the expansion.</font></p><p><font size="2">Finally, perhaps space quanta do not only stop multliplying near matter, but matter actually consumes space quanta, and this is what we observe as gravity.&nbsp;&nbsp;Why would matter consume space quanta?&nbsp; I have no idea!&nbsp; Hmm...&nbsp;hope no one&nbsp;thows that phrase&nbsp;back at me.</font></p><p><font size="2">Best regards!</font></p>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Thanks for the reply and understanding my abstract question!&nbsp;&nbsp;I realize the end result is the same; distance increases.&nbsp;&nbsp;I just thought it was inconsistent that space-time simply "expands" while&nbsp;I can't think of anything else in nature that does so.&nbsp; Please indulge my line of thought one whit&nbsp;further... If&nbsp;the expansion of&nbsp;space&nbsp;is&nbsp;actually the&nbsp;multiplication of space quanta,&nbsp;in order to be consistent with the observed lack of "expansion" near the&nbsp;vicinity of matter, the rate of multiplication must be proportional&nbsp;to the distance from matter.&nbsp;&nbsp;As the distance between&nbsp;clusters of matter/galaxies increases, the rate of&nbsp;quanta multiplication would increase,&nbsp;which is consistent with our observed acceleration of the expansion.Finally, perhaps space quanta do not only stop multliplying near matter, but matter actually consumes space quanta, and this is what we observe as gravity.&nbsp;&nbsp;Why would matter consume space quanta?&nbsp; I have no idea!&nbsp; Hmm...&nbsp;hope no one&nbsp;thows that phrase&nbsp;back at me.Best regards! <br />Posted by i_think</DIV></p><p>Again, nobody really knows if space is quantized or not, so recognize that this is pure speculation.&nbsp; If matter were consuming space quanta, then would&nbsp;you not expect distances near massive objects to be decreasing?&nbsp; Distances between cities on Earth don't seem to be changing, so I think the evidence tends not to support that hypothesis.</p> <div class="Discussion_UserSignature"> </div>
 
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EJA

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What is space expanding out of...and into...and how do you tell-from a great distance-which red shifted items are galaxies moving away from us, and which are actually moving towards us but apparently red-shifted due to a gravitational lens being between us and them making their otherwise blue shifed light appear red shifted due to the bending by the gravitationakl lens?
 
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derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What is space expanding out of...and into...and how do you tell-from a great distance-which red shifted items are galaxies moving away from us, and which are actually moving towards us but apparently red-shifted due to a gravitational lens being between us and them making their otherwise blue shifed light appear red shifted due to the bending by the gravitationakl lens? <br /> Posted by EJA</DIV></p><p>Space isn't expanding into or out of anything but itself.&nbsp; The universe is everything.&nbsp; There is no inside or outside the universe.&nbsp; An ant on the 2d surface of a balloon has no concept of inside or outside the balloon as we, in or 3d universe, have no concept of inside our outside of our 3d existence.</p><p>Redshift is caused by the wavelength of a photon being stretched either via doppler effects, gravity, or the expansion of space.&nbsp; Gravitational lensing with not cause a redshift, per se, rather gravitational redshift is noticeable when a photon leaves a strong gravitational field.&nbsp; If it simply passes by a strong gravitational field, it will blue shift from its initial state because it is gaining energy as it approaches.&nbsp; That energy wil, in turn, be lost as it leaves the graviational field returning it back to it's original (or nearly original) redshift. </p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>It makes my head hurt too, but it has to be there. I'm using Occam's Razor. If there's nothing readily available "within" the 4 dimensional space-time of our Universe to explain accelerating expansion, then there must be something acting from either "inside" or "outside".Do me a favor. You know those beige colored rubber bands? The fat ones you use in the office?Take one, lay it flat, and with an ink pen, draw vertical lines across it from end to end. Now, stretch it with your finger or a pencil tip holding it down in the very middle, and observe the lines.&nbsp;&nbsp; <br />Posted by dragon04</DIV></p><p>I assume that what you are getting at is that the lines come together.</p><p>If you look in the other direction, the ribber band also gets thinner.&nbsp; The contraction in the two directions normal to the applied stress&nbsp;is a manifestation of Poisson's ratio, often denoted with the Greek letter nu.&nbsp; Nu is a term that relates, in a small strain continuum mechanics model, the ratio of&nbsp;stress in one axis to strain in the other two axes&nbsp; and is related to the compressibility or bulk modulus of a material.&nbsp; Rubber is nearly incompressible.&nbsp; A perfectly incompressible solid material has a value of 1/2 for nu.</p><p>I don't think this effect has much to do with expansion of space-time, but perhaps&nbsp;I am failing to see a connection that you see.</p><p>To take this a little further, you might want to consider a&nbsp;state of hydrostatic loading -- equal loading in all directions.&nbsp; If you first consider hydrostatic compression -- the load that results from submerging the object in a fluid to some depth -- you can probably imagine that an incompressible object (such as one made of rubber) does not deform at all.&nbsp;&nbsp;With totally uniform loading, the only deformation mode available is a shrinking under compression and being incompressible no deformation occurs.&nbsp; If you could apply a completely uniform load outward on the surface of such an object (like compression in reverse) the same thing would happen -- no deformation.</p><p>All of this applies at normally encountered stress levels.&nbsp; If you apply enough compression, materials break down and you can still get a neutron star.&nbsp; </p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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i_think

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Again, nobody really knows if space is quantized or not, so recognize that this is pure speculation.&nbsp; If matter were consuming space quanta, then would&nbsp;you not expect distances near massive objects to be decreasing?&nbsp; Distances between cities on Earth don't seem to be changing, so I think the evidence tends not to support that hypothesis. <br />Posted by DrRocket</DIV></p><p><font size="2">The way I see it, since 1 is a quantity,&nbsp;space <em>must</em> be quantized, and the only remaining question is does space exist in units greater than 1.&nbsp; IMHO, greater than 1 is more plausible&nbsp;than a "single-celled" rubber balloon stretching&nbsp;in all directions to astronomical proportions&nbsp;while simultaneously being "warped" by matter.</font></p><p><font size="2">If one accepts the possibility that space is quantized, and realizing that space is expanding,&nbsp;it is a small leap to&nbsp;envision "currents" of space.&nbsp; I&nbsp;picture quanta of space&nbsp;creating currents&nbsp;(gravity) as they get sucked&nbsp;toward matter,&nbsp;&nbsp;and&nbsp;our cities would indeed be swept&nbsp;closer to&nbsp;each other under&nbsp;any&nbsp;explanation of gravity were it not for other intervening forces, like the Earth's gravity, the land beneath and atmosphere above the cities, friction, etc.</font></p><p><font size="2">Quantized space and currents&nbsp;provide a single explanation for two observations currently explained&nbsp;two different ways.&nbsp; Time slows as the velocity of matter&nbsp;through space increases.&nbsp; Time also&nbsp;slows&nbsp;as&nbsp;the&nbsp;proximity to&nbsp;and mass of matter increases.&nbsp;&nbsp;Perhaps the same mechanism is at work.&nbsp;&nbsp;There is no relative difference between matter moving through "stationary" space, and&nbsp;"stationary"&nbsp;matter&nbsp;within a moving current of&nbsp;space quanta.&nbsp; (I realize that stationary is a relative term in this context.)&nbsp;&nbsp;</font></p><p><br /></p>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The way I see it, since 1 is a quantity,&nbsp;space must be quantized, and the only remaining question is does space exist in units greater than 1.&nbsp;...Posted by i_think</DIV></p><p>I think you are confusing "quantification" with "quantization".&nbsp; They are not at all the same thing.</p><p>1&nbsp; is a number.&nbsp; It is meaningless as a quantity, unless you are either counting discrete things or unless you use it in the context of some unit of measure.&nbsp; Thus 1 mile is a distance, and 1 parsec is a distance.</p><p>The question in the quantification of space, is whether in fact there is some smallest unit of distance and if all distances are just&nbsp;accumulations of this smallest distance.&nbsp; In other words do we move smoothly along a continuum or do we actually move in a series of very small jumps.&nbsp; If space is quantized, then 1 could actually become a distance, 1 distance quanta, whatever that might be.</p><p>I can make neither heads nor tails of the rest of your post.<br /></p> <div class="Discussion_UserSignature"> </div>
 
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vitalstatistic63

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<p>I have some observations to add to this discussion.</p><p>&nbsp;</p><p>If space is expanding, wouldn't our tools used to measure that expansion also be expanding, therefore rendering their measurement invalid? Could the existence or not of this phenomenon clarify the question of local versus global expansion?</p><p>&nbsp;</p><p>Why is there an assumption that the universe is 14 billion light years wide?&nbsp; That is the estimated age of the universe, and therefore light travelling from 14 billion light years away is just reaching us, but that does not mean there is nothing outside that area. It just means we can't see it.</p><p>&nbsp;</p><p>There has been a question about whether the universe is in a state of continual expansion or will eventually run out of steam and collapse in on itself, then re-expand starting the whole process over again.&nbsp; If we are in an endless cycle of expansion, collapse, re-expansion, re-collapse, etc... is there any reason to believe we are in the first cycle, or has it happened countless times previously?&nbsp; </p><p>&nbsp;Is there any reason to believe the expansion is uniform in all directions?&nbsp; Imagine the Earth represents the universe.&nbsp; Is it possible for the equator of the universe to still be expanding as the poles collapse together, or the areas represented by Indonesia and Venezuela be contracting while the Middle East expands away from Polynesia?&nbsp; Is it possible for the whole universe to flatten down to an infinitely thin pancake shaped disk before suddenly being engulfed in a one dimensional Z-axis big-bang that sees the pancake suddenly rise and start expanding again, independent of the behaviour of the edges in the X and Y planes? </p><p>If the rate of expansion was measured to be different depending on the direction we look, that would be a good argument that we are not within the first cycle of expansion.</p><p>&nbsp;</p><p>Further, is it possible that the collapse of the universe continues past the zero point and continues with momentum into a negative direction, that we would possibly be unaware of being negatively sized entities within that negative sized space?</p> <div class="Discussion_UserSignature"> </div>
 
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centsworth_II

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<p><font color="#666699"><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>....If space is expanding, wouldn't our tools used to measure that expansion also be expanding...<br /> Posted by vitalstatistic63</DIV></font><br />If it's true, as we've been saying, that gravitationally bound objects like the galaxies of our local group are not affected by the expansion, then our tools which are held together by electromagnetic forces that are much stronger than gravity will surely not be affected.</p><p>What is affected by the expansion are the measurements made of very distant galaxies, because the distance between us and them has changed at a rate not consistent with previous theory.&nbsp; That's how the increasing rate of expansion was discovered (as far as I know).&nbsp;</p><p>&nbsp;</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> </div>
 
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derekmcd

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<p>Welcome to the boards and good questions...&nbsp;</p><p><strong>"Why is there an assumption that the universe is 14 billion light years wide?&nbsp; That is the estimated age of the universe, and therefore light travelling from 14 billion light years away is just reaching us, but that does not mean there is nothing outside that area. It just means we can't see it."</strong></p><p>The observable universe is actually thought to have a radius of 46 billion light years (Gly) making it 92gly wide in diameter.&nbsp; The light from a galaxy that is 12gly distant actually emitted it's light when it was much, much closer to us, but due to the metric expansion of space that light is only now just reaching us giving the appearance of being 12gly away.&nbsp; That galaxy is realistically in terms of our 'now' time some 40+gly away in physical distance.</p><p>There's a thread in Ask the Astronomer (click for link) that goes into a bit more detail.&nbsp;</p><p><strong>"There has been a question about whether the universe is in a state of continual expansion or will eventually run out of steam and collapse in on itself, then re-expand starting the whole process over again."</strong></p><p>This is determined by measuring the density of the universe.&nbsp; If the critical density divided by the energy density are the same, Omega = 1.&nbsp; Too dense and it collapses (closed universe having positive curverature).&nbsp; Not enough it expands forever (open universe having negative curverature).&nbsp; If it just right (critical density/energy density=1) it expands forever (flat universe with zero curverature), but is always slowing down but never quite stopping.&nbsp; Lastest measurement from WMAP have put Omega at 1.02 +/- .02 making the universe flat or very nearly flat.</p><p>With that said, despite the universe possibly having positive curverature, it is still thought to expand forever due to hypothetical dark energy.</p><p><strong>"If we are in an endless cycle of expansion, collapse, re-expansion, re-collapse, etc... is there any reason to believe we are in the first cycle, or has it happened countless times previously?"</strong></p><p>If we were in this cycle, would there be any possible way of knowing?&nbsp; There would be a total disconnect from the previous universe rendering the discussion fruitless.&nbsp;</p><p><strong>"Is there any reason to believe the expansion is uniform in all directions?"</strong></p><p>There may be minor perterbations in the expansion, but it's not like an expanding balloon with bulges in it.&nbsp; The universe has no edges which is were I think you were aluding to with the rest of your post.</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>... If the critical density divided by the energy density are the same, Omega = 1.&nbsp; Too dense and it collapses (closed universe having positive curverature).&nbsp; Not enough it expands forever (open universe having negative curverature).&nbsp; If it just right (critical density/energy density=1) it expands forever (flat universe with zero curverature), but is always slowing down but never quite stopping.&nbsp;...Posted by derekmcd</DIV></p><p>&nbsp;</p><p>I believe that the case used to be as you described it.&nbsp; But then the physicists learned a little more mathematics, particularly some work of Bill Thurston, and discovered that there are such things as negatively curved compact manifolds.&nbsp; There is a brief description in this Wiki article as to where the confusion has come from.</p><p>http://en.wikipedia.org/wiki/Shape_of_the_universe<br /></p> <div class="Discussion_UserSignature"> </div>
 
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Tissa_Perera

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The evidence indicates that space is expanding.On the local level we do not see that expansion due to gravity.My question:Is space expanding locally and gravity is holding the local group of galaxies together so that space is sort of sliding under our feet so to speak or is gravity not allowing space to expand in this local area?Another way to phrase it is to say&nbsp;if space is like a stretching&nbsp;rubber sheet&nbsp;and our galaxy is like a&nbsp;dinner&nbsp;plate - is the sheet stretching underneath the plate or is the plate glued to the sheet not allowing the sheet to expand under the plate?I have not been able to get a clear explanation of this.&nbsp; I hope what&nbsp;I wrote makes some sense.&nbsp; <br /> Posted by origin</DIV></p><p>Good thinking, good question. They say the dinner plate is glued to space-time. Per their explanations the dinner plate includes all systems held by gravity too. So the space sliding underneath is not applicable in local space. But then how big a gravitationaly bound system&nbsp; can we&nbsp; go to before expansion counts?&nbsp; If not solar system,&nbsp; is it galaxy, clusters or super clusters? before expansion kicks in?</p><p>I have another explanation, and a derivation of the size when expansion kicks in. It is purely a natural consequence of a new 4D space topology. Below a crtical distance(approximately&nbsp; 11Kpc) from the center of a system, space has positive gravitational potential energy and therefore is gravitationaly binding and wants to contract space. Beyond this crtical distance space potential energy is negative and space wants to expand. As a matter of fact the expansion potential enegy of space is also exponential in nature(explains dark energy). To summerize, from the center of any gravitating body till a distance of 11Kpc space will be binding, beyond that expansion takes over. </p><p>&nbsp;</p><p>&nbsp;</p>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Good thinking, good question. They say the dinner plate is glued to space-time. Per their explanations the dinner plate includes all systems held by gravity too. So the space sliding underneath is not applicable in local space. But then how big a gravitationaly bound system&nbsp; can we&nbsp; go to before expansion counts?&nbsp; If not solar system,&nbsp; is it galaxy, clusters or super clusters? before expansion kicks in?I have another explanation, and a derivation of the size when expansion kicks in. It is purely a natural consequence of a new 4D space topology. Below a crtical distance(approximately&nbsp; 11Kpc) from the center of a system, space has positive gravitational potential energy and therefore is gravitationaly binding and wants to contract space. Beyond this crtical distance space potential energy is negative and space wants to expand. As a matter of fact the expansion potential enegy of space is also exponential in nature(explains dark energy). To summerize, from the center of any gravitating body till a distance of 11Kpc space will be binding, beyond that expansion takes over. &nbsp;&nbsp; <br />Posted by Tissa_Perera</DIV></p><p>So, what is the new 4D space topology ?&nbsp; And do you mean space or space-time ?&nbsp; That is, is time included in your new 4D space or is there a 5th dimension needed to include time ?</p> <div class="Discussion_UserSignature"> </div>
 
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SpeedFreek

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Good thinking, good question. They say the dinner plate is glued to space-time. Per their explanations the dinner plate includes all systems held by gravity too. So the space sliding underneath is not applicable in local space. But then how big a gravitationaly bound system&nbsp; can we&nbsp; go to before expansion counts?&nbsp; If not solar system,&nbsp; is it galaxy, clusters or super clusters? before expansion kicks in?<br /> Posted by Tissa_Perera</DIV></p><p>Expansion happens where the force of gravity is too weak to keep two objects or systems bound together, i.e. it is only apparent in the large voids between separate clusters of galaxies. Galaxies cluster due to gravity, but are not gravitationally bound to other clusters and so those clusters separate due to the expansion of the universe. &nbsp;</p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>
 
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Tissa_Perera

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>So, what is the new 4D space topology ?&nbsp; And do you mean space or space-time ?&nbsp; That is, is time included in your new 4D space or is there a 5th dimension needed to include time ? <br /> Posted by DrRocket</DIV></p><p>Apparently you misspelled my website name as I noticed in the reply on another subject forum, there you can get a better idea(cosmicdarkmatter.com). I mean, an additional cosmic size dimension i.e.&nbsp; 4 dimensions of space. This means 5D space time. As seen I have derived a formula for the fundamental baryon masses and the formula is published there which gives very accurate relative masses. This needed the existance of a 5D space time matrix. </p><p>This extra dimension is not compactified either, it is cosmic size large but more importantly bounded if anybody can fathom that. </p>
 
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derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Apparently you misspelled my website name as I noticed in the reply on another subject forum, there you can get a better idea(cosmicdarkmatter.com). I mean, an additional cosmic size dimension i.e.&nbsp; 4 dimensions of space. This means 5D space time. As seen I have derived a formula for the fundamental baryon masses and the formula is published there which gives very accurate relative masses. This needed the existance of a 5D space time matrix. This extra dimension is not compactified either, it is cosmic size large but more importantly bounded if anybody can fathom that. <br /> Posted by Tissa_Perera</DIV></p><p>There is a function, when composing a post, to provide a clickable link or you might provide us a synopsis or an abstract so it can be discussed here.</p><p>And I can't fathom anything you are saying as nothing makes sense.&nbsp; Sounds like you are just throwing words together and hoping something makes sense.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>
 
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SpeedFreek

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><font color="#0000ff">Apparently you misspelled my website name as I noticed in the reply on another subject forum, there you can get a better idea(cosmicdarkmatter.com). I mean, an additional cosmic size dimension i.e.&nbsp; 4 dimensions of space. This means 5D space time. As seen I have derived a formula for the fundamental baryon masses and the formula is published there which gives very accurate relative masses. This needed the existance of a 5D space time matrix. This extra dimension is not compactified either, it is cosmic size large but more importantly bounded if anybody can fathom that. </font><br /> Posted by Tissa_Perera</DIV></p><p>Have you studied General Relativity? I only ask as you seem to be going over old ground. Have you not heard of four dimensional manifold spaces?</p><p>A manifold describes a shape that can have one more spacial dimension than is apparent to any observer within that manifold.</p><p>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 the line that defines a circle, which is a two dimensional object.</p><p>In a two-manifold, every point has a neighborhood that looks like a flat disk. Examples include a plane, the surface of a sphere, and the surface of a torus.</p><p>In a three-manifold, every point has a neighbourhood that looks like a sphere. Examples include the surface of a 4 dimensional sphere.</p><p>In General Relativity, space-time is represented by a four-manifold. Are you sure you aren't trying to describe the same thing?&nbsp;</p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>
 
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derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Have you studied General Relativity? I only ask as you seem to be going over old ground. Have you not heard of four dimensional manifold spaces?A manifold describes a shape that can have one more spacial dimension than is apparent to any observer within that manifold.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 the line that defines a circle, which is a two dimensional object.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.In a three-manifold, every point has a neighbourhood that looks like a sphere. Examples include the surface of a 4 dimensional sphere.In General Relativity, space-time is represented by a four-manifold. Are you sure you aren't trying to describe the same thing?&nbsp; <br /> Posted by SpeedFreek</DIV></p><p>I'm guessing they are talking about having a 4th spatial dimension with the 5th being time... a 5-manifold.&nbsp; Describing this 4th spacial dimension as "not compactified" and "bounded", it appears as though this dimension should be physically realized and have an edge to it... not sure.&nbsp;&nbsp; Either it's completely over my head, or it is borderline word-salad. </p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>
 
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SpeedFreek

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><font color="#0000ff">I'm guessing they are talking about having a 4th spatial dimension with the 5th being time... a 5-manifold.&nbsp; Describing this 4th spacial dimension as "not compactified" and "bounded", it appears as though this dimension should be physically realized and have an edge to it... not sure.&nbsp;&nbsp; Either it's completely over my head, or it is borderline word-salad. </font><br /> Posted by derekmcd</DIV></p><p>It looks a lot like that to me too, but I saw the phrase "an additional cosmic size dimension" and wondered if that might mean a dimension in which our 3 spacial dimensions were "embedded", i.e. the topology of the universe. For instance, our 3D universe might represent the surface of a 4D sphere and if you add time to that it may seem like you have 5 dimensions... perhaps Tissa is thinking that 4D sphere is bounded for some reason.</p><p>But I doubt it.&nbsp;</p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>It looks a lot like that to me too, but I saw the phrase "an additional cosmic size dimension" and wondered if that might mean a dimension in which our 3 spacial dimensions were "embedded", i.e. the topology of the universe. For instance, our 3D universe might represent the surface of a 4D sphere and if you add time to that it may seem like you have 5 dimensions... perhaps Tissa is thinking that 4D sphere is bounded for some reason.But I doubt it.&nbsp; <br />Posted by SpeedFreek</DIV></p><p>I don't have the patience to go through the web site in detail and figure out what is screwed up.&nbsp; But I saw enough to recognize that the extra dimension is macroscopic, as opposed to some of the "curled up" dimensions that have been contemplated in string theory.&nbsp; I think that is what is meant by "cosmic sized".&nbsp;&nbsp; In fact the model seems to be a 4-sphere crossed with the real line (time).</p><p>Go read it if you want, but I have seen enough to be sure that it won't work.<br /></p> <div class="Discussion_UserSignature"> </div>
 
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SpeedFreek

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'><font color="#0000ff">Go read it if you want, but I have seen enough to be sure that it won't work. </font><br /> Posted by DrRocket</DIV></p><p>I think I'll take your word for it!&nbsp; <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-smile.gif" border="0" alt="Smile" title="Smile" /> </p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>
 
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KernelSanders

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<p>"The observable universe is actually thought to have a radius of 46 billion light years (Gly) making it 92gly wide in diameter.&nbsp; The light from a galaxy that is 12gly distant actually emitted it's light when it was much, much closer to us, but due to the metric expansion of space that light is only now just reaching us giving the appearance of being 12gly away.&nbsp; That galaxy is realistically in terms of our 'now' time some 40+gly away in physical distance.There's a thread in Ask the Astronomer (click for link) that goes into a bit more detail."</p><p>&nbsp;</p><p><font color="#0000ff">&nbsp;<font size="2">Actually according to this link (</font></font><font size="2" color="#0000ff">http://www.space.com/scienceastronomy/mystery_monday_040524.html</font><font size="2" color="#0000ff">) the universe is 156 billion light-years wide</font></p> <div class="Discussion_UserSignature"> </div>
 
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derekmcd

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Actually according to this link (http://www.space.com/scienceastronomy/mystery_monday_040524.html) the universe is 156 billion light-years wide <br /> Posted by KernelSanders</DIV></p><p>That article is wrong.</p><p>http://en.wikipedia.org/wiki/Observable_universe</p><p>About 1/2 way down this page they give numbers that were reported incorrectly.&nbsp;</p> <div class="Discussion_UserSignature"> <div> </div><br /><div><span style="color:#0000ff" class="Apple-style-span">"If something's hard to do, then it's not worth doing." - Homer Simpson</span></div> </div>
 
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DrRocket

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<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>"The observable universe is actually thought to have a radius of 46 billion light years (Gly) making it 92gly wide in diameter.&nbsp; The light from a galaxy that is 12gly distant actually emitted it's light when it was much, much closer to us, but due to the metric expansion of space that light is only now just reaching us giving the appearance of being 12gly away.&nbsp; That galaxy is realistically in terms of our 'now' time some 40+gly away in physical distance.There's a thread in Ask the Astronomer (click for link) that goes into a bit more detail."&nbsp;&nbsp;Actually according to this link (http://www.space.com/scienceastronomy/mystery_monday_040524.html) the universe is 156 billion light-years wide <br />Posted by KernelSanders</DIV></p><p>I have seen some thought to the effect that the universe might have a radius of 46 billion light years, but that is NOT the observable universe.</p><p>The universe is thought to be about 13 billion years old (i.e. since the Big Bang) that would place the radius of the observable universe at no more than 13 billion light years.<br /></p> <div class="Discussion_UserSignature"> </div>
 
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