Speed relative to expansion

[PJay_A]

Take any two galaxy clusters in the Universe that are outside the gravitional influence of all other objects outside itselves. These objects, for argument purposes are relatively stationary in the Universe. Now, factor in expansion of the Universe. The two objects would "appear" to be moving away from each other due to space that is created between them. Is the appearance of movement an illusion caused by new space created and these objects are really stationary non-moving fixed positions in relating to the whole Universe? Would the last question be true, but the two objects in relating to each other be in movement? Or does the creation of space between the objects and the perceived movement of these objects away from each other created by the creation of new space between the objects actually is movement? And if the last question is true, then to make the two objects "stationary" then movement towards each other to counter separation caused by expansion would be the only way to keep these objects "still", but by applying movement so that there is no movement at the same time is a pardox.

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Take any two galaxy clusters in the Universe that are outside the gravitional influence of all other objects outside itselves. These objects, for argument purposes are relatively stationary in the Universe. Now, factor in expansion of the Universe. The two objects would "appear" to be moving away from each other due to space that is created between them.&nbsp; Is the appearance of movement an illusion caused by new space created and these objects are really stationary non-moving fixed positions in relating to the whole Universe? Would the last question be true, but the two objects in relating to each other be in movement? Or does the creation of space between the objects and the perceived movement of these objects away from each other created by the creation of new space between the objects actually is movement? And if the last question is true, then to make the two objects "stationary" then movement towards each other to counter separation caused by expansion would be the only way to keep these objects "still", but by applying movement so that there is no movement at the same time is a pardox. <br /> Posted by PJay_A</DIV></p><p>First, I prefer not to think of space as something that is being 'created' between two clusters.&nbsp; Stuff moves through space, but space neither expands nor is it created. &nbsp; It can be confusing to say space is expanding without discussing the metric.&nbsp; It leads to the notion that space is something physical.</p><p>It might be better to think about the volume of the universe laden with a coordinate system.&nbsp; As the volume increases, the coordinates maintain a proportional distance in relation to each other.&nbsp; A distant cluster from us is not changing coordinates on the manifold, rather the distance between the two static coordinates on the manifold is increasing.&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>

 

[UncertainH]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>First, I prefer not to think of space as something that is being 'created' between two clusters.&nbsp; Stuff moves through space, but space neither expands nor is it created. &nbsp; It can be confusing to say space is expanding without discussing the metric.&nbsp; It leads to the notion that space is something physical.It might be better to think about the volume of the universe laden with a coordinate system.&nbsp; As the volume increases, the coordinates maintain a proportional distance in relation to each other.&nbsp; A distant cluster from us is not changing coordinates on the manifold, rather the distance between the two static coordinates on the manifold is increasing.&nbsp; <br />Posted by derekmcd</DIV></p><p>Isn't saying that the coordinate system is expanding the same thing as saying that space is expanding? In either choice of wording, the implication is that the objects are staying in the same 'place' but the distance between them is growing. In fact we must say that the distant galaxy is staying in the same coordinates otherwise those galaxies would be travelling faster than light relative to us and that would violate our current understanding. Seems like a bit of a paradox. Another paradox, to me anyway, is when in some models it is stated that there is a critical mass density of the universe which when reached will start to reverse the expansion. Wasn't the mass density in the early universe far greater than it is now and it didn't prevent the expansion then what make us think that it would in the future. The forces at work (expansion, gravity) seems to be separate things. I don't think there is any known way to either expand or contract the manifold.</p>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Isn't saying that the coordinate system is expanding the same thing as saying that space is expanding? In either choice of wording, the implication is that the objects are staying in the same 'place' but the distance between them is growing. In fact we must say that the distant galaxy is staying in the same coordinates otherwise those galaxies would be travelling faster than light relative to us and that would violate our current understanding. Seems like a bit of a paradox. Another paradox, to me anyway, is when in some models it is stated that there is a critical mass density of the universe which when reached will start to reverse the expansion. Wasn't the mass density in the early universe far greater than it is now and it didn't prevent the expansion then what make us think that it would in the future. The forces at work (expansion, gravity) seems to be separate things. I don't think there is any known way to either expand or contract the manifold. <br />Posted by UncertainH</DIV></p><p>&nbsp;You can think of expansion in either of two ways.&nbsp; You can think of the manifold itself expanding locally (the expansion is not uniform and that is one reason that it is said that the space within a galaxy or a local group is not expanding).&nbsp; You can also think of the expansion as being a change in the metric, so that distance increases because the way in which it is measured is changing.&nbsp; These are really the same thing since you need both the metric and the underlying manifold to speak sensibly of distance.</p><p>You need to think about this rather abstractly.&nbsp; You can't really say that the galaxies are "in the same place" and the distance between them is growing, although that is a valid perspective.&nbsp; The reason that you need to be careful with such a statement is that there is no good definition of "absolute space" or "absolute rest".&nbsp; If you arbitrarily fix your coordinate system on a particular galaxy then you can say that it is "fixed" but that is simply an artifact of your selection of a reference frame.&nbsp; It is OK to do that, but you need to recognize that you have indeed selected a specific reference frame for your discussion.</p><p>But basically saying that the coordinate system is expancing, saying that the metric is changing, and saying that space is expanding are all different ways of verbalizing the same thing.&nbsp; And there are ways to expand or contract the manifold in these senses -- that is what a cosmological constant does.</p><p>One also ought to be a little careful with the terminology of "metric".&nbsp; The term "metric" is used in two ways in mathematics, and sometimes the useage is confused in discussions of physics.&nbsp; A metric space is a topological space in which the topology arises from a distance function.&nbsp; A distance function is a function that assigned to each pair of points (x,y) a non-negative real number d(x,y) that satisfies the intuitive properties of distance:&nbsp; d(x,y)=0 if and only if x=y, and d(x,z) is less than or equal to d(x,y) + d(y,z).&nbsp; The functin d is called the metric of a metric space.&nbsp; In the case of manifolds, and in special relativity, the word metric is meant to provide an inner product that is defined on tangent vectors,&nbsp; From that inner product one can define a notion of distance along a path, via a line integral, and from that obtain a notion of distance.&nbsp; That definition of distance satisfies the requirements of the "d" funtion of a metric space if the inner product is positive-definite.&nbsp; In the case of relativity the inner product is not positive definite but rather is Lorentzian, and that is the source of the classification of points into "timelike" and "spacelike" separation from a fixed point.&nbsp; One still gets a generalized notion of distance but it does not fit all of your intuitive ideas regarding Euclidean distance, although in a coordinate patch, one can separate time and space coordinates and the metric is positive definite with respect to the space coordinates, and the geometry is locally Euclidean there.</p><p>You are correct in the assumption that the Big Bang model predicts a very high density of matter and energy in the early universe.&nbsp; And yes that ought to cause a contraction under ordinary circumstances and with appropriate initial conditions.&nbsp; But the initial conditions of the Big Bang were apparently not ordinary, and we are not sure what physical laws dominated that early universe either.&nbsp; The scalar field of inflatin theory would have driven rapid expansion for the first fraction of a second, and imposition of appropriate boundary conditions would cause expansion to continue in any case until something (like gravity) slowed or even reversed it.&nbsp; We simply do not know enough to explain the mechanism, so we must rely on the observations of the current behavior of the universe and then use general relativity in reverse to determiine what happened earlier.<br /></p> <div class="Discussion_UserSignature"> </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Isn't saying that the coordinate system is expanding the same thing as saying that space is expanding? In either choice of wording, the implication is that the objects are staying in the same 'place' but the distance between them is growing. In fact we must say that the distant galaxy is staying in the same coordinates otherwise those galaxies would be travelling faster than light relative to us and that would violate our current understanding. Seems like a bit of a paradox.</DIV></p><p>Seems more like a *huge* paradox if you're a skeptic of the concept. </p><p>I don't have much trouble accepting an "objects in motion stay in motion" type of 'expansion', but that would in no way explain a superluminal expansion process.&nbsp; Superluminal expansion seems hard to explain especially if you assume that the whole system was once gravitionally bound together at some point. </p><p>FYI, these paradoxes tend to be why I personally haven't ruled out "tired light" theories entirely.</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Another paradox, to me anyway, is when in some models it is stated that there is a critical mass density of the universe which when reached will start to reverse the expansion. Wasn't the mass density in the early universe far greater than it is now and it didn't prevent the expansion then what make us think that it would in the future. The forces at work (expansion, gravity) seems to be separate things. I don't think there is any known way to either expand or contract the manifold. <br /> Posted by UncertainH</DIV></p><p>There isn't. &nbsp; Inflation is presumed to have overcome the force of gravity somehow, but inflation has never been shown to emprically exist.&nbsp; Dark energy is also presumed to have a similar effect on the manifold, and it too lacks empirical support. </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Isn't saying that the coordinate system is expanding the same thing as saying that space is expanding? In either choice of wording, the implication is that the objects are staying in the same 'place' but the distance between them is growing. In fact we must say that the distant galaxy is staying in the same coordinates otherwise those galaxies would be travelling faster than light relative to us and that would violate our current understanding. Seems like a bit of a paradox. Another paradox, to me anyway, is when in some models it is stated that there is a critical mass density of the universe which when reached will start to reverse the expansion. Wasn't the mass density in the early universe far greater than it is now and it didn't prevent the expansion then what make us think that it would in the future. The forces at work (expansion, gravity) seems to be separate things. I don't think there is any known way to either expand or contract the manifold. <br /> Posted by UncertainH</DIV></p><p>Saying that "space expands" is ok depending on the context in which you are making the statement.&nbsp; I was just trying to avoid objectifying space as a physical entity as the OP was implying by stating "creating new space".</p><p>If I'm not mistaken, the critical density if found by dividing an expected mass of universe to keep the expansion from completely stopping by the Hubble constant.&nbsp; If the density of the universe is higher than the critical density, that expansion will eventually stop and reverse.&nbsp; It's related to the Hubble constant divided by the overall density at any given time.&nbsp; The universe was more dense in the past, but the Hubble constant was also far higher. </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>

 

[derekmcd]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Seems more like a *huge* paradox if you're a skeptic of the concept. I don't have a much trouble accepting an "objects in motion stay in motion" type of 'expansion', but that would in no way explain a superluminal expansion process.&nbsp; Superluminal expansion seems hard to explain especially if you assume that the whole system was once gravitionally bound together at some point. FYI, these paradoxes tend to be why I personally haven't ruled out "tired light" theories entirely.There isn't. &nbsp; Inflation is presumed to have overcome the force of gravity somehow, but inflation has never been shown to emprically exist.&nbsp; Dark energy is also presumed to have a similar effect on the manifold, and it too lacks empirical support. <br /> Posted by michaelmozina</DIV></p><p>I'm not sure I even have the energy to address this crap again.&nbsp; You will forever remain in a cloud of skepticism due to your refusal to understand the mechanics behind it.&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>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I'm not sure I even have the energy to address this crap again.&nbsp; You will forever remain in a cloud of skepticism due to your refusal to understand the mechanics behind it.&nbsp; <br /> Posted by derekmcd</DIV></p><p>Well, it wouldn't be like that if you could demonstrate that inflation and/or DE have an empirical effect on matter in controlled experiments.&nbsp;&nbsp; It's only because I have to take it on "faith" that these things exist and have a real effect on nature that I remain a skeptic.&nbsp;&nbsp; It's not my fault that you can't explain how you got from a gravitationally bound singularity thing to a comoving coordinate system without invoking things that don't exist in nature.&nbsp;&nbsp; Inflation isn't even like any other known and identified vector or scalar field, because all other vector and scalar fields will experience a signficant decrease in desnity during multiple exponential increases in volume.&nbsp; It's literally a "supernatural" construct.&nbsp; Is that my fault too? </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[DrRocket]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Well, it wouldn't be like that if you could demonstrate that inflation and/or DE have an empirical effect on matter in controlled experiments.&nbsp;&nbsp; It's only because I have to take it on "faith" that these things exist and have a real effect on nature that I remain a skeptic.&nbsp;&nbsp; It's not my fault that you can't explain how you got from a gravitationally bound singularity thing to a comoving coordinate system without invoking things that don't exist in nature.&nbsp;&nbsp; Inflation isn't even like any other known and identified vector or scalar field, because all other vector and scalar fields will experience a signficant decrease in desnity during multiple exponential increases in volume.&nbsp; It's literally a "supernatural" construct.&nbsp; Is that my fault too? <br />Posted by michaelmozina</DIV></p><p>EVERYBODY&nbsp;is a skeptic about inflation, including Alan Guth.&nbsp; But some are skeptical for logical reasons, and simply need more data and more understanding before they accept&nbsp;a pending hypothesis&nbsp;as valid.&nbsp; There is a difference between someone who understands the theory and maintains a healthy skepticism while awaiting data and further theoretical development of gravitational and quantum theories, and someone who simply rejects the hypothesis outright with no understanding whatever of what that theory means, what the data says, or what questions remains to be answered.</p><p>Your last sentence is rather baffling since the major effects of inflation were over long before the first second following the Big Bang.&nbsp; Are you under the misconception that inflation and expansion are synonymous ?&nbsp; That is not the case.&nbsp; </p><p>Inflation is an add-on to the basic Big Bang hypothesis, but it is at the moment the&nbsp;best available hypothesis that&nbsp; accounts for the horizon problem, that explains the apparent flatness of the universe and&nbsp;that provides a particle theory explanation for the observed absence of magnetic monopoles, and that accurately predicts some of the details of the anisotropy of the cosmic microwave background.&nbsp; But there are also a lot of questions to be answered and provlems with the theory to be ironed out, ot the least of which is the origin and nature of the inflation field.&nbsp; I suspect that it will remain a tentative hypothesis until there is a viable theory that includes both quantum mechanics and gravity that will hopefully either include inflation or refute it.&nbsp; </p><p>http://en.wikipedia.org/wiki/Cosmic_inflation</p><p>http://www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/inflation.html</p> <div class="Discussion_UserSignature"> </div>

 

[PJay_A]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Isn't saying that the coordinate system is expanding the same thing as saying that space is expanding? In either choice of wording, the implication is that the objects are staying in the same 'place' but the distance between them is growing. In fact we must say that the distant galaxy is staying in the same coordinates otherwise those galaxies would be travelling faster than light relative to us and that would violate our current understanding. Seems like a bit of a paradox. Another paradox, to me anyway, is when in some models it is stated that there is a critical mass density of the universe which when reached will start to reverse the expansion. Wasn't the mass density in the early universe far greater than it is now and it didn't prevent the expansion then what make us think that it would in the future. The forces at work (expansion, gravity) seems to be separate things. I don't think there is any known way to either expand or contract the manifold. <br /> Posted by UncertainH</DIV></p><p>Thank you. You made the points I was indirectly implying to with my post. But you got me thinking when you mentioned expansion and force in the same sentence. Would expansion then be considered as our Universe' 5th force?</p>

 

[UncertainH]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Thank you. You made the points I was indirectly implying to with my post. But you got me thinking when you mentioned expansion and force in the same sentence. Would expansion then be considered as our Universe' 5th force? <br />Posted by PJay_A</DIV><br /><br />I thought that there was no force strong enough to accelerate anything faster than the speed of light so expansion cannot be a force in the sense that we think of it now (F=ma) and from what the learned contributors above have said in the frame of reference of some galaxy its coordinates on the manifold remain the same during expansion. So to me expansion is not a force&nbsp;and so should not be affected or reversed by any force that we know of. Sometimes dark energy is talked about as being a repulsive force contributing to expansion yet we know that no force is capable of accelerating an object faster than the speed of light so how can it or any other force contribute to expansion. If I push you away from me we are not expanding the space between us (changing the metric) we are just moving away from each other.</p><p>The other thing mentioned above is that space does not expand in a gravity bound system. Is there any proof of this and how would the boundary of that system be defined ?</p>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Thank you. You made the points I was indirectly implying to with my post. But you got me thinking when you mentioned expansion and force in the same sentence. Would expansion then be considered as our Universe' 5th force? <br /> Posted by PJay_A</DIV></p><p>That depends on how one defines "expansion" actually.&nbsp; If one assumes that objects in motion stay in motion, then some amount of "expansion" could related to whatever event took place initially at the instant of the "bang". &nbsp;&nbsp; No additional forces would be required to drive a sort of "coasting" (decelerating) expansion as the objects that makeup spacetime expand and move away from each other.&nbsp; If you assume that the unvierse is accelerating for some reason, then you'll need a "force" to overcome the tendency of gravity to slow things down over time.&nbsp; EM fields are known to accelerate plasma, and we know most of the universe is made of plasma.&nbsp; We don't need any new forces of nature to even explain an eccelerating form of expansion.&nbsp; Superluminal expansion on the other hand is a horse of a different color. </p><p>&nbsp;</p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>EVERYBODY&nbsp;is a skeptic about inflation, including Alan Guth.</DIV></p><p>I'm afraid you'll need to define the term "skeptic" then since I'm a skeptic and Guth and I have very different opinions on this topic.&nbsp; He doesn't seem very "skeptical" at all from my perspective.</p><p>The way I see it, inflation is the ultimate "supernatural" invokation.&nbsp; No known vector or scalar field will retain near constant density over several exponential increases in volume.&nbsp; I'm skeptical that any such force of nature exists or ever existed. </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> I suspect that it will remain a tentative hypothesis until there is a viable theory that includes both quantum mechanics and gravity that will hopefully either include inflation or refute it.&nbsp; http://en.wikipedia.org/wiki/Cosmic_inflationhttp://www4.ncsu.edu/unity/lockers/users/f/felder/public/kenny/papers/inflation.html <br /> Posted by DrRocket</DIV></p><p>Well, we actually agree on that point.&nbsp; I'm sure that inflation theory and dark energy theory are not going to go away anytime soon, but I doubt I'll accept anything other than an emprical test that demonstrates that these items are real forces of nature.&nbsp;&nbsp;&nbsp; I too would have to assume that such explanations would resolve themselves to the level of QM. </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Inflation is an add-on to the basic Big Bang hypothesis,</DIV></p><p>Yes, I know.&nbsp; Expansion was explained to me in the absense of inflation.&nbsp; Guth didn't popularlize inflation theory till a couple years later.&nbsp; I've seen how it's been "added on".&nbsp; I also watch "dark energy" added on to the expansion cycle too, and that addition was much more recent. </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>but it is at the moment the&nbsp;best available hypothesis that&nbsp; accounts for the horizon problem, that explains the apparent flatness of the universe and&nbsp;that provides a particle theory explanation for the observed absence of magnetic monopoles,</DIV></p><p>While I might be inclined to give you the first two, the last one is a total bust.&nbsp;&nbsp; There has never been any type of 'monopole' found in nature so attributing it's absense to inflation is like attributing the absense of elves to inflation.&nbsp; I can't check or corroborate any of these things in a lab.&nbsp; I have to take inflation and DE on pure faith in a math formula. </p><p><br /></p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[UFmbutler]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That depends on how one defines "expansion" actually.&nbsp; If one assumes that objects in motion stay in motion, then some amount of "expansion" could related to whatever event took place initially at the instant of the "bang". &nbsp;&nbsp; No additional forces would be required to drive a sort of "coasting" (decelerating) expansion as the objects that makeup spacetime expand and move away from each other.&nbsp; If you assume that the unvierse is accelerating for some reason, then you'll need a "force" to overcome the tendency of gravity to slow things down over time.&nbsp; EM fields are known to accelerate plasma, and we know most of the universe is made of plasma.&nbsp; We don't need any new forces of nature to even explain an eccelerating form of expansion.&nbsp; Superluminal expansion on the other hand is a horse of a different color. &nbsp; <br /> Posted by michaelmozina</DIV></p><p>You speak of assumptions like "the expansion of the universe is accelerating" negatively, even though it is backed up by observation.&nbsp; Then you go on to assume that because EM fields "can" accelerate plasma, then they must be what is accelerating the universe.&nbsp; You can't do a simple lab experiment like the ones I know you are referring to and say "this is how the whole universe works".&nbsp; If such fields were operating on a cosmological scale, there would be predicted signatures that could be observed to test the theory.&nbsp; Where's the observational evidence?&nbsp; Lab experiments are useful for characterizing a process, but you cannot just apply it to such huge scales with no justification.&nbsp; For example, we knew about the ideal gas law for quite some time and it was studied extensively in the lab, but until observational evidence backed it up we could not say for certain whether the gas in stars behaves ideally. &nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[UFmbutler]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>There has never been any type of 'monopole' found in nature so attributing it's absense to inflation is like attributing the absense of elves to inflation.&nbsp; I can't check or corroborate any of these things in a lab.&nbsp; I have to take inflation and DE on pure faith in a math formula. <br /> Posted by michaelmozina</DIV></p><p>No types of monopoles found in nature?&nbsp; What about...electric monopoles?&nbsp; You know, point charges?&nbsp; The electrical analogue to the idea of magnetic monopoles?&nbsp; I believe what he was saying is that inflation can explain the existence of electrical point charges, while also explaining why the&nbsp; magnetic version is absent.&nbsp; </p> <div class="Discussion_UserSignature"> </div>

 

[UncertainH]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>That depends on how one defines "expansion" actually.&nbsp; If one assumes that objects in motion stay in motion, then some amount of "expansion" could related to whatever event took place initially at the instant of the "bang". &nbsp;&nbsp; No additional forces would be required to drive a sort of "coasting" (decelerating) expansion as the objects that makeup spacetime expand and move away from each other.&nbsp; Posted by michaelmozina</DIV></p><p>From what was discussed above, during expansion no force is actually acting upon the object and the object is not moving with respect to its local coordinate system.&nbsp;So if the expansion were to slow down, so would the object relative to a remote frame of reference. There would be no coasting or inertial expansion because supposedly nothing is moving in a classical way. I don't see how inertial expansion can be used to describe the expansion of space because two objects moving away from each other do not expand space, they move into pre-existing space.</p>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I thought that there was no force strong enough to accelerate anything faster than the speed of light so expansion cannot be a force in the sense that we think of it now (F=ma) </DIV></p><p>That's essentially correct.&nbsp; While EM fields might help explain a type of acceleration of plasma, EM fields would not explain a superliminal brand of expansion.&nbsp; No known force of nature could have that affect.&nbsp; This is why I still haven't written off tired light theories.&nbsp; The redshift may be related to overall distance, but not necessarily the speed of the object. </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>and from what the learned contributors above have said in the frame of reference of some galaxy its coordinates on the manifold remain the same during expansion.</DIV></p><p>BB theory has a particularly perplexing problem at the start because it assumes that all energy/matter had the same gravitational reference point.&nbsp;&nbsp;&nbsp; How then do we explain superliminal expansion from a single gravity well?&nbsp;&nbsp; </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>So to me expansion is not a force&nbsp;and so should not be affected or reversed by any force that we know of.</DIV></p><p>That seems like a logical assumption, but then "what is it"?&nbsp; How can we emprically demonstrate this idea in a lab?</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Sometimes dark energy is talked about as being a repulsive force contributing to expansion yet we know that no force is capable of accelerating an object faster than the speed of light so how can it or any other force contribute to expansion.</DIV></p><p>No known vector or scalar field found in nature is going to get stronger as expansion continues. </p><p> Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>If I push you away from me we are not expanding the space between us (changing the metric) we are just moving away from each other.</DIV></p><p>That would not lead to superluminal expansion. </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The other thing mentioned above is that space does not expand in a gravity bound system. Is there any proof of this and how would the boundary of that system be defined ? <br /> Posted by UncertainH</DIV></p><p>It's a little too "convenient" from my perspective that all attempts to emprically 'test' these ideas are impossible because evidently DE is shy around objects of mass.&nbsp;&nbsp; There seems to be no obvious way to empirically falsify or verify either inflation or DE. </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>No types of monopoles found in nature?&nbsp; What about...electric monopoles?&nbsp; You know, point charges? The electrical analogue to the idea of magnetic monopoles?&nbsp; </DIV></p><p>You mean like electrons and protons?&nbsp; They're already covered in normal physics and MHD theory.&nbsp; They are not "magnetic monopoles".</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I believe what he was saying is that inflation can explain the existence of electrical point charges, while also explaining why the&nbsp; magnetic version is absent.&nbsp; <br /> Posted by UFmbutler</DIV></p><p>As far as I know, nature has always contained electrical curernts and it has never contained any magnetic monopoles.&nbsp; Current flows are a known part of physics.&nbsp; Magnetic monopoles do not exist in nature and their absense is not empircially related to anything else, not inflation, not electrical current, not anything else.&nbsp;&nbsp; I have no emprical support that monopoles exist, or that their existence, or lack thereof is related to inflation or anything else.&nbsp; From a skeptics perspective, claiming that inflation is supported by a lack of monopoles is like saying inflation is supported by a lack of unicorns.&nbsp; There's no logical or emprical correlation established between these two issues.</p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[UFmbutler]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You mean like electrons and protons?&nbsp; They're already covered in normal physics and MHD theory.&nbsp; They are not "magnetic monopoles".<br /> Posted by michaelmozina</DIV></p><p>Didn't say that.&nbsp; You made a blanket statement of there being not "any kind of monopole in nature".&nbsp; There's a reason why people might expect magnetic monopoles, and that is because there ARE monopoles in electricity.&nbsp; So, at the basic level, the assumption that a force so intimately related to electricity, magnetism, should have monopoles/charge carriers as well is not invalid(before you quote this and say I'm trying to say magnetic monopoles exist...go back and read the sentence again...I'm only saying the hypothesis of magnetic monopoles is not totally off the wall).&nbsp; If a theory can explain why there are charge carriers for one force but not for another, how is that not valid?&nbsp; You again are not addressing the question, at all.&nbsp; If a theory says it explains the non-existence of a certain particle, they have a valid mathematical reason for saying so.&nbsp; You can't say the same thing about unicorns.&nbsp; There is no math that forbids their existence.&nbsp; So no, it is not the same thing.&nbsp; You just see the word "monopole" and use it to go off on an EU tangent that has little to do with the discussion.&nbsp;</p> <div class="Discussion_UserSignature"> </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You speak of assumptions like "the expansion of the universe is accelerating" negatively, even though it is backed up by observation. </DIV></p><p>The actual "observation" is redshifted photons.&nbsp; The mainstream "interpretation" of this redshift phenomenon is "expansion".&nbsp;&nbsp; Arp's work and tired light theories predict that there is more to the redshift phenomenon than simply expansion.&nbsp;&nbsp; Even maninstream theories recognize that it's a complicated process with many variables.&nbsp; Tired light theories tend to presume that there is some type of interaction between the photons and the plasma medium between objects in space. &nbsp; I tend to ride the fence a bit and lean toward some expansion.&nbsp; In some tired light theories however, there is no expansion required.</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Then you go on to assume that because EM fields "can" accelerate plasma, then they must be what is accelerating the universe. </DIV></p><p>I'm simply noting that EM fields are one force of nature is this is known to be 39 OOM more powerful than gravity.&nbsp; If anything known to us can accelerate a universe of plasma, EM fields are a likely option.&nbsp; It would'nt explain superliminal expansion however.</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You can't do a simple lab experiment like the ones I know you are referring to and say "this is how the whole universe works".&nbsp; If such fields were operating on a cosmological scale, there would be predicted signatures that could be observed to test the theory.</DIV></p><p>And I can think of at least a half dozen observations inside our solar system off the top of my head that fit the predictive signatures, including coronal loops, aurora, plasma "jets", etc.&nbsp; I therefore can justifiy at least some type of real "expansion".</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Where's the observational evidence?&nbsp; Lab experiments are useful for characterizing a process, but you cannot just apply it to such huge scales with no justification. </DIV></p><p>I personally believe that there is ample justification for suggesting there are EM fields in space. </p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>For example, we knew about the ideal gas law for quite some time and it was studied extensively in the lab, but until observational evidence backed it up we could not say for certain whether the gas in stars behaves ideally. &nbsp; <br /> Posted by UFmbutler</DIV></p><p>I'm not sure how plasma is going to behave at every level and MHD theory has "issues" as it relates to "scaling factors".&nbsp; There can probably never be a full emprical "test" done at cosmic scales, but that is where computer models can be useful.&nbsp; Peratt's work is rather extensive on that front. </p><p>FYI, I do actually favor some type of "expansion".&nbsp; I'm just not conviced that we can rule out all types of tired light theories just yet, and Arp's work needs to be considered. &nbsp;&nbsp; </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>Didn't say that.&nbsp; You made a blanket statement of there being not "any kind of monopole in nature". </DIV></p><p>I was specifcally refering to the 'magnetic" variety.</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>There's a reason why people might expect magnetic monopoles, and that is because there ARE monopoles in electricity.</DIV></p><p>Actually there are just charged particles inside of plasma.&nbsp; The term "monopole" is unncessary and misleading.&nbsp; Electrons and protons are well understood parts of MHD theory and need no other names.</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>So, at the basic level, the assumption that a force so intimately related to electricity, magnetism, should have monopoles/charge carriers as well is not invalid(before you quote this and say I'm trying to say magnetic monopoles exist...go back and read the sentence again...I'm only saying the hypothesis of magnetic monopoles is not totally off the wall).&nbsp; If a theory can explain why there are charge carriers for one force but not for another, how is that not valid?</DIV></p><p>It's not valid because it is the movement of electrons and charged ions that sustain the magnetic field.&nbsp; The magnetic field is simply a function of current flow, and magnetic fields do not ever pass along discrete units of magnetic monopoles. &nbsp;</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'> You again are not addressing the question, at all.&nbsp; If a theory says it explains the non-existence of a certain particle, they have a valid mathematical reason for saying so. </DIV></p><p>Suppose I came to you and tried to use my personal set of math equations about Michael's new energy source to prove the non existence of unicorns to you?&nbsp;&nbsp; How would you react to such a presentation, assuming the math was perfect?</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>You can't say the same thing about unicorns.&nbsp; There is no math that forbids their existence.</DIV></p><p>I can substitute the term "unicorn'' into Guth original "monopole' comments and then there is math that forbids their existence too.&nbsp;&nbsp; You don't figure someone could trump up some math?</p><p>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>&nbsp; So no, it is not the same thing.&nbsp; You just see the word "monopole" and use it to go off on an EU tangent that has little to do with the discussion.&nbsp; <br /> Posted by UFmbutler</DIV></p><p>I'm actually trying not to focus on anything but expansion.&nbsp; The monopole thing is irrelevent IMO, but it's not logical arguement in favor of inflation.&nbsp;&nbsp; As far as anyone knows they have never existed and their non existence is unrelated to anything else. </p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[SpeedFreek]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>The actual "observation" is redshifted photons.&nbsp; The mainstream "interpretation" of this redshift phenomenon is "expansion".&nbsp;&nbsp; Arp's work and tired light theories predict that there is more to the redshift phenomenon than simply expansion.&nbsp;&nbsp; Even maninstream theories recognize that it's a complicated process with many variables.&nbsp; Tired light theories tend to presume that there is some type of interaction between the photons and the plasma medium between objects in space. &nbsp; I tend to ride the fence a bit and lean toward some expansion.&nbsp; In some tired light theories however, there is no expansion required.<br /> Posted by michaelmozina</DIV></p><p>What is your opinion on the Angular Size - Redshift relationship? Or the Tolman Surface Brightness Test? </p> <div class="Discussion_UserSignature"> <p><font color="#ff0000">_______________________________________________<br /></font><font size="2"><em>SpeedFreek</em></font> </p> </div>

 

[michaelmozina]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>What is your opinion on the Angular Size - Redshift relationship? Or the Tolman Surface Brightness Test? <br /> Posted by SpeedFreek</DIV></p><p>I would imagine that these issues would be explained as scattering effects over various distances.&nbsp;&nbsp; The best tired light work I'm aware of right now comes from Ari Brynlofsson.&nbsp; He's got a 95 page "whopper" of a paper that is loaded with math and gives me a gigantic headache everytime I read it. &nbsp; I cannot however find any errors in his presentation either mathematically or based on any known laws of physics.&nbsp; It's equally "unverified" at this point in time, but it seems like a reasonable alternative to superluminal expansion, and that is attractive from my perspective. </p><p>http://arxiv.org/find/astro-ph/1/au:+Brynjolfsson_A/0/1/0/all/0/1</p><p>&nbsp;</p> <div class="Discussion_UserSignature"> It seems to be a natural consequence of our points of view to assume that the whole of space is filled with electrons and flying electric ions of all kinds. - Kristian Birkeland </div>

 

[Mee_n_Mac]

<p><BR/>Replying to:<BR/><DIV CLASS='Discussion_PostQuote'>I'm just not conviced that we can rule out all types of tired light theories just yet, and Arp's work needs to be considered. &nbsp;&nbsp; <br />Posted by <strong>michaelmozina</strong></DIV></p><p>What type of tired light theory do you favor ? Where has this been demonstrated ?</p><p>EDIT : I see your answer predated my question by 1 minute ...&nbsp;&nbsp; Mebbe my electrons were tired.&nbsp; <img src="http://sitelife.space.com/ver1.0/content/scripts/tinymce/plugins/emotions/images/smiley-laughing.gif" border="0" alt="Laughing" title="Laughing" /></p> <div class="Discussion_UserSignature"> <p>-----------------------------------------------------</p><p><font color="#ff0000">Ask not what your Forum Software can do do on you,</font></p><p><font color="#ff0000">Ask it to, please for the love of all that's Holy, <strong>STOP</strong> !</font></p> </div>