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Thread: Absolute refernce frame ???

  1. #1 Absolute refernce frame ??? 
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    Didn't know wether to post this on the physics or cosmology forum.

    According to relativity there are no absolute frames of refernce other than the totality of global Minkowsky space/time. But consider the 2.7 deg. CMB radiation which permiates the universe. It is also present in all time from the decoupling era ( when the universe became transparent ) to the eternal ( ? ) future, although at reduced temperature. Any motion in a particular direction will see the CMB temperature shifted towards the blue, higher frquency, in the direction of travel. Similarily there will be a reduction in temperature, red shift, lower frequency, behind you. This would seem to give an absolute direction and possibly speed depending on the temperature shift.

    My question is, can the CMB be use as an absolute frame of reference ? And if not strictly by definition, then as a practical absolute reference frame ?


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  3. #2 Re: Absolute refernce frame ??? 
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    Quote Originally Posted by MigL
    Didn't know wether to post this on the physics or cosmology forum.

    According to relativity there are no absolute frames of refernce other than the totality of global Minkowsky space/time. But consider the 2.7 deg. CMB radiation which permiates the universe. It is also present in all time from the decoupling era ( when the universe became transparent ) to the eternal ( ? ) future, although at reduced temperature. Any motion in a particular direction will see the CMB temperature shifted towards the blue, higher frquency, in the direction of travel. Similarily there will be a reduction in temperature, red shift, lower frequency, behind you. This would seem to give an absolute direction and possibly speed depending on the temperature shift.

    My question is, can the CMB be use as an absolute frame of reference ? And if not strictly by definition, then as a practical absolute reference frame ?
    The CMB is a convenient reference frame, the so-called "co-moving" frame of cosmology.

    Relativity simply states that no reference frame has any distinguished status with respect to dynamics, or the expression of physical laws. You are still free to select any reference frame that you wish, for convenience or any other reason.

    The notion of a "reference frame" applies topecial relativity, but not to general relativity. In GR reference frames are local, except in special cases that are not really representative of the universe other than as very large scale approximations.


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    OK, I am well out of my depth, but what I have read thus far about CMB tells me that is so greatly red shifted that it appears as microwave radiation. Where, or how, does the blue shift come into it ?
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  5. #4 Re: Absolute refernce frame ??? 
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    Quote Originally Posted by MigL
    Didn't know wether to post this on the physics or cosmology forum.

    According to relativity there are no absolute frames of refernce other than the totality of global Minkowsky space/time. But consider the 2.7 deg. CMB radiation which permiates the universe. It is also present in all time from the decoupling era ( when the universe became transparent ) to the eternal ( ? ) future, although at reduced temperature. Any motion in a particular direction will see the CMB temperature shifted towards the blue, higher frquency, in the direction of travel. Similarily there will be a reduction in temperature, red shift, lower frequency, behind you. This would seem to give an absolute direction and possibly speed depending on the temperature shift.

    My question is, can the CMB be use as an absolute frame of reference ? And if not strictly by definition, then as a practical absolute reference frame ?
    Yes. It isn't quite an "absolute" reference frame to the purist, but see CMBR dipole anisotropy and note "relative to the reference frame of the CMB". That's the reference frame of the universe, and you can't get any more absolute than that.
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  6. #5 Re: Absolute refernce frame ??? 
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    Quote Originally Posted by Farsight
    Yes. It isn't quite an "absolute" reference frame to the purist, but see CMBR dipole anisotropy and note "relative to the reference frame of the CMB". That's the reference frame of the universe, and you can't get any more absolute than that.
    Once again you illustrate a facility with semantics, and a glibness in presentatio, but a total lack of understanding of basic physics. At best it defines a convenient local chart for a point in deep space in the spacetime manifold.

    1. There is nothing absolute about the "reference frame of the CMB".

    2. It isn't even a global reference frame, since there is no such thing as a global reference frame for a universe with varying curvature.

    3. "The reference frame of the universe" is a meaningless phrase without a lot of equivocation and qualification that you have proved yourself incapable of understanding.

    Crank
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    Quote Originally Posted by Dave Wilson
    OK, I am well out of my depth, but what I have read thus far about CMB tells me that is so greatly red shifted that it appears as microwave radiation. Where, or how, does the blue shift come into it ?
    If the CMB that is hitting us at any given time was all released in the same event, 13.7 billion years ago, and the expansion of the universe has redshifted it into microwaves, then it should all reach us having the same redshift, assuming we are at rest in relation to the expansion of the universe.

    But we are not at rest in relation to that expansion, and it shows up as a lesser redshift in the CMB in a certain direction. A lesser redshift can be considered as a relative shift towards the blue.

    The terms redshift and blueshift can be applied in different ways:
    In absolute terms - a galaxy is blueshifted if it is moving towards us and redshifted if it is moving away from us.
    In relative terms - a redshifted spiral galaxy has one arm rotating towards us whilst the other is rotating away. The arm rotating towards us will be less redshifted than the centre of the galaxy, whilst the arm rotating away will show a higher redshift. We say the arm rotating towards us is showing a blueshift in relation to the centre of the galaxy, although the whole galaxy is redshifted.
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    Quote Originally Posted by SpeedFreek
    Quote Originally Posted by Dave Wilson
    OK, I am well out of my depth, but what I have read thus far about CMB tells me that is so greatly red shifted that it appears as microwave radiation. Where, or how, does the blue shift come into it ?
    If the CMB that is hitting us at any given time was all released in the same event, 13.7 billion years ago, and the expansion of the universe has redshifted it into microwaves, then it should all reach us having the same redshift, assuming we are at rest in relation to the expansion of the universe.

    But we are not at rest in relation to that expansion, and it shows up as a lesser redshift in the CMB in a certain direction. A lesser redshift can be considered as a relative shift towards the blue.

    The terms redshift and blueshift can be applied in different ways:
    In absolute terms - a galaxy is blueshifted if it is moving towards us and redshifted if it is moving away from us.
    In relative terms - a redshifted spiral galaxy has one arm rotating towards us whilst the other is rotating away. The arm rotating towards us will be less redshifted than the centre of the galaxy, whilst the arm rotating away will show a higher redshift. We say the arm rotating towards us is showing a blueshift in relation to the centre of the galaxy, although the whole galaxy is redshifted.
    Thank you for your reply, that is certainly something to chew over.
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  9. #8 Re: Absolute refernce frame ??? 
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    Quote Originally Posted by DrRocket
    1. There is nothing absolute about the "reference frame of the CMB".
    It provides a reference frame that allows you to determine you motion through the universe. The universe is everything. Absolutely everything. So there's plenty that's absolute about it, even though it isn't quite an "absolute" reference frame to the purist. Hence as ever, you're wrong.

    Quote Originally Posted by DrRocket
    2. It isn't even a global reference frame, since there is no such thing as a global reference frame for a universe with varying curvature.
    The universe is flat on the large scale, as per the scientific evidence provided by WMAP. See http://wmap.gsfc.nasa.gov/universe/uni_shape.html. So on that large scale there is a global reference frame. And you're wrong again.

    Quote Originally Posted by DrRocket
    3. "The reference frame of the universe" is a meaningless phrase without a lot of equivocation and qualification that you have proved yourself incapable of understanding.
    You don't understand any of this, do you, you obnoxious troll?

    Quote Originally Posted by DrRocket
    Crank
    I give links to robust scientific evidence and references that back up the explanations I offer. You just hang around sneering at junior members and squawking outraged abuse when somebody explains something that you didn't deign to. You're no scientist, you're a mathematician, as you say here. So as far as physics is concerned, you're no doctor, you're a quack.
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  10. #9 Re: Absolute refernce frame ??? 
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    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    1. There is nothing absolute about the "reference frame of the CMB".
    It provides a reference frame that allows you to determine you motion through the universe. The universe is everything. Absolutely everything. So there's plenty that's absolute about it, even though it isn't quite an "absolute" reference frame to the purist. Hence as ever, you're wrong.
    Nope.

    You have no idea what you are talking about.

    As I stated, it is a convenient LOCAL frame for many purposes. Nothing more. Nothing less.

    Quote Originally Posted by DrRocket
    2. It isn't even a global reference frame, since there is no such thing as a global reference frame for a universe with varying curvature.
    The universe is flat on the large scale, as per the scientific evidence provided by WMAP. See http://wmap.gsfc.nasa.gov/universe/uni_shape.html. So on that large scale there is a global reference frame. And you're wrong again. [/quote]

    Wrong.

    The universe is not flat. If it were there would be no such thing as gravity. In particular it is not flat on the scale of galaxies, local groups or super groups, and we are certainly in that regime here on Earth, or in the Milky way or ...

    Even on the largest scale is not known that the universe is flat, only that it has very small curvature, and close is not good enough in this case. There is a large geometric difference, and in the case of positive curvature a topological difference, between 0 curvature, small positive curvature and slight negative curvature -- and the available data cannot differentiate among these cases.

    You obviously do not understand the data.



    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    3. "The reference frame of the universe" is a meaningless phrase without a lot of equivocation and qualification that you have proved yourself incapable of understanding.
    You don't understand any of this, do you, you obnoxious troll?
    I understand it rather well. It is quite obvious that you do not.

    You need to read a real physics book and put your own nonsensical self-published book in the trash. There is a reason why responsible publishers don't handle such trash.

    Quote Originally Posted by Farsight
    Quote Originally Posted by DrRocket
    ]Crank
    I give links to robust scientific evidence and references that back up the explanations I offer. You just hang around sneering at junior members and squawking outraged abuse when somebody explains something that you didn't deign to. You're no scientist, you're a mathematician, as you say here. So as far as physics is concerned, you're no doctor, you're a quack.

    Wrong fool. You don't begin to understand the science behind your own links.

    Just what one expects from some who self-publishes a book of nonsense on relativity.

    Yep, my PhD is in mathematics. So what ? I have more than one degree, and a hell of a lot of varied high-level experience.

    Yours does not exist. Just a failed computer guy. Badly deluded. So badly deluded that you actually believe the tripe in your own book. Part of your lack of understanding is a direct result of your ignorance of and incompetence in mathematics. Relativity requires some mathematical sophistication -- bad for you.

    You are a menace on public forums -- which you ought to recognize, having been debunked on a plethora of such venues. A well-known internet nut. A hot property for interviews on conspiracy theory shows. A danger to the intellectual development of young people interested in real science. A stereotypical wacko. Your basic crank.
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    Apologies all. Above is a typical mathematician, lost in abstraction, with no regard for the scientific method and totally dismissive of scientific evidence such as that provided by WMAP:

    "WMAP determined that the universe is flat, from which it follows that the mean energy density in the universe is equal to the critical density (within a 1% margin of error). This is equivalent to a mass density of 9.9 x 10-30 g/cm3, which is equivalent to only 5.9 protons per cubic meter".

    Offer such evidence, furnished by NASA, and what you get is feather-spitting outrage and a torrent of ad-hominem abuse. Offer evidence in future narrowing it down to .1%, or even .001%, and it'll be the same. Because this cuckoo-in-the-nest pretending to be an expert physicist is absolutely utterly convinced that the universe is curved. A little thing like scientific evidence isn't going to get in the way of that, and he will deliberately trash this thread to try to obscure it. The name in the game for this is what's euphemistically called a beautiful mind.

    Back to CMBR.
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  12. #11  
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    Quote Originally Posted by Farsight
    Apologies all. Above is a typical mathematician, lost in abstraction, with no regard for the scientific method and totally dismissive of scientific evidence such as that provided by WMAP:

    "WMAP determined that the universe is flat, from which it follows that the mean energy density in the universe is equal to the critical density (within a 1% margin of error). This is equivalent to a mass density of 9.9 x 10-30 g/cm3, which is equivalent to only 5.9 protons per cubic meter".

    Offer such evidence, furnished by NASA, and what you get is feather-spitting outrage and a torrent of ad-hominem abuse. Offer evidence in future narrowing it down to .1%, or even .001%, and it'll be the same. Because this cuckoo-in-the-nest pretending to be an expert physicist is absolutely utterly convinced that the universe is curved. A little thing like scientific evidence isn't going to get in the way of that, and he will deliberately trash this thread to try to obscure it. The name in the game for this is what's euphemistically called a beautiful mind.

    Back to CMBR.

    Wrong.

    I am not convinced of anything with regard to the large-scale structure of the universe, and neither is the scientific community. The question remains open.

    The universe is quite clearly curved on smaller scales -- without non-zero local curvature theree would be no gravitation. It is also quite clearly of small curvature, nearly flat on large scales. But "nearly flat" is not nearly good enough.

    The question of large scale curvature is closely related to the topology of space, and there are only 3 cases for a homogeneous and isotropic spacetime: positive curvature (a sphere), negative curvature (hyperbolic space) and zero curvature (Euclidean space). It matters not a whit how positive or how neative, and you clearly fail to understand this crucial point.

    Relax the assumptions of homogeneity and global isotropy, and other possibilities arise.

    Crank. Your incompetence in mathmatics translates to your inability to understand what the data really means. NASA is a good source for obtaining raw data, but not nearly so definitive when one is interested in the meaning of the data. For that you need to beyond NASA PR pieces and relate the data to the underlying mathematical models.
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    Just for fun, a friend on another forum sent me this. This seems to be Farsight in action, or so I am told (maybe I am wrong!)

    Don't skip the first few minutes, as they they may convince you of the fact, that is well known here (UK), that this is a nutter show, specialising in conspiracy theories.

    They seem rather keen on their interviewee's opinions. Hmm
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    I have been following this research for the past decade or so and I can say that the Doc is, as usual, correct.

    From Cornish et. al., 2006:

    An important question answered by the WMAP mission is that of the curvature of space. The matter and energy density of the Universe indicate that space is very nearly flat. The WMAP data point to a universe with a total energy density within 2% of critical. This means that even if space is not quite flat, the radius of curvature of the Universe is at least of order the size of the observable Universe, and space can be considered to be nearly flat.
    So, we can consider our observable universe to be close to being flat, but we cannot say for sure whether the whole universe is close to being flat - it might be curved on a scale far larger than our observable universe.
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  15. #14  
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    Quote Originally Posted by Guitarist
    Just for fun, a friend on another forum sent me this. This seems to be Farsight in action, or so I am told (maybe I am wrong!)

    Don't skip the first few minutes, as they they may convince you of the fact, that is well known here (UK), that this is a nutter show, specialising in conspiracy theories.

    They seem rather keen on their interviewee's opinions. Hmm
    That's him. He has billed hmself as the author of Duffield's Relativity+ in other forums. A nutter show, filled with nuts.
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    The classical Big Bang theory described an observable universe which was nearly as large as the total universe because of the time elapsed since the Big Bang and the finite speed of light.
    The inflationary Big Bang on the other hand, because of the exponential inflation, describes a universe of which only an infinitesimal portion is observable. Some of the numbers thrown about ( by Whitten, sting theorist ) are of the order of 10^10^12 , this is immense. It is so immense in fact that any measured local curvature is as close as can be to zero. BUT, this is only a scale effect, just like if the Earth was a thousand times larger, you would never see a ship dip below the horizon as it sails away, and you woild think the earth to be flat.

    But back to the original topic, before this latest pi**ing contest started. Can the CMB be used as an absolute reference frame for at least the observable universe. And can we determine our absolute motion through the observable universe. I have read, for example, about a large mass of galactic superclusters in the form of a wall, dubbed the great attractor. Is this at rest relative to the observable universe ?Is anything at rest ?
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  17. #16  
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    Quote Originally Posted by MigL
    But back to the original topic, before this latest pi**ing contest started. Can the CMB be used as an absolute reference frame for at least the observable universe. And can we determine our absolute motion through the observable universe. I have read, for example, about a large mass of galactic superclusters in the form of a wall, dubbed the great attractor. Is this at rest relative to the observable universe ?Is anything at rest ?
    You can arbitrarily choose any reference frame and refer everything to it. That does not make it "absolute".

    The notion of an absolute reference frame, the aether frame, was based on the assumption of some physical medium through which light was assumed to propagate. But it is now understood that light requires no physical medium and there is no preferred reference frame that can be singled out by the known laws of physics.

    The CMB defines a convenient (local) reference frame, but not an absolute reference frame.

    The real, observable universe is lumpy and curved. It does not admit a single chart/reference frame. Also, the definition of "observable" depends on the location of the observer.
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  18. #17  
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    Quote Originally Posted by MigL
    ...But back to the original topic, before this latest pi**ing contest started. Can the CMB be used as an absolute reference frame for at least the observable universe. And can we determine our absolute motion through the observable universe. I have read, for example, about a large mass of galactic superclusters in the form of a wall, dubbed the great attractor. Is this at rest relative to the observable universe ?Is anything at rest ?
    To answer your last question - as I understand it, things can, indeed, be "at rest" relative to each other. Technically, they're said to be in the same inertial frame of reference.

    As DrRocket pointed out, the CMB can be used as a frame of reference for our local area because it's comoving with our local volume of space. It is light (microwaves) that's coming evenly from all directions in our local area. Our planet and our galaxy are moving relative to this evenly distributed "incoming" microwave radiation. As a result, if we look in the direction of our motion relative to this background radiation it appears slightly blue-shifted. If we look in the opposite direction, it appears slightly red-shifted. Someone in another nearby solar system would notice the same effect. We could, in theory, compare our numbers with theirs and decide how we're moving relative to each other (approximately). In order to do this we would, of course, have to agree on which direction was up, down, forward, backward, left and right.

    If you go several tens of millions light years away in any direction, the CMB will be comoving with that local patch of space - but not with ours. We couldn't use their motion through their local CMB to directly compare our relative motion to them based on our motion through our local CMB.

    The CMB can't be use as an absolute frame of reference for the observable universe because the local CMB's for different widely separated volumes of space are different (they're comoving with each local volume of space).

    As far as our absolute motion through the observable universe - you might say that we're dead center. Everything in our observable universe is moving away from us in accordance the Hubble's law. The trick is to remember that for every other galaxy in the universe, they think that everything is moving away from them in accordance with Hubble's law.

    That's cosmic expansion.

    Chris
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    Quote Originally Posted by CSMYTH3025
    As DrRocket pointed out, the CMB can be used as a frame of reference for our local area because it's comoving with our local volume of space.
    It depends how you define "local". Our galaxy is moving relative to the frame associated with the CMB. This frame is convenient for the description of cosmological expansion, however.
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    Quote Originally Posted by PhysBang
    Quote Originally Posted by CSMYTH3025
    As DrRocket pointed out, the CMB can be used as a frame of reference for our local area because it's comoving with our local volume of space.
    It depends how you define "local". Our galaxy is moving relative to the frame associated with the CMB. This frame is convenient for the description of cosmological expansion, however.
    CMB is accelerating.

    If you are at rest with CMB then you are at rest with acceleration.

    This is not an inertial frame.
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    Quote Originally Posted by chinglu
    CMB is accelerating.

    If you are at rest with CMB then you are at rest with acceleration.

    This is not an inertial frame.
    Note that I, like many who write carefully about this topic, did not write that we were or were not at rest with respect to the CMB. I wrote that we were not at rest with the frame associated with the CMB. There is a frame of reference that we consider to be naturally associated with the CMB. The CMB itself is a collection of radiation and as such it is a collection of particles moving at a constant speed, the speed of llight.
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    Quote Originally Posted by chinglu
    Quote Originally Posted by PhysBang
    Quote Originally Posted by CSMYTH3025
    As DrRocket pointed out, the CMB can be used as a frame of reference for our local area because it's comoving with our local volume of space.
    It depends how you define "local". Our galaxy is moving relative to the frame associated with the CMB. This frame is convenient for the description of cosmological expansion, however.
    CMB is accelerating.

    If you are at rest with CMB then you are at rest with acceleration.

    This is not an inertial frame.
    The reference frame associated with the CMB has nothing to do with the accelerating expansion of the universe. It is space, not the CMB which is expanding. The CMB is a bunch of photons.

    In any case the reference frame in question is simply the reference frame in which the CMB is isotropic.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by chinglu
    Quote Originally Posted by PhysBang
    Quote Originally Posted by CSMYTH3025
    As DrRocket pointed out, the CMB can be used as a frame of reference for our local area because it's comoving with our local volume of space.
    It depends how you define "local". Our galaxy is moving relative to the frame associated with the CMB. This frame is convenient for the description of cosmological expansion, however.
    CMB is accelerating.

    If you are at rest with CMB then you are at rest with acceleration.

    This is not an inertial frame.
    The reference frame associated with the CMB has nothing to do with the accelerating expansion of the universe. It is space, not the CMB which is expanding. The CMB is a bunch of photons.

    In any case the reference frame in question is simply the reference frame in which the CMB is isotropic.
    Wrong.

    Comoving and proper distances are not the same concept of distance as the concept of distance in special relativity. This can be seen by considering the hypothetical case of a universe empty of mass, where both sorts of distance can be measured. When the density of mass in the FLRW metric is set to zero (an empty 'Milne universe'), then the cosmological coordinate system used to write this metric becomes a non-inertial coordinate system in the flat Minkowski spacetime of special relativity, one where surfaces of constant time-coordinate appear as hyperbolas when drawn in a Minkowski diagram from the perspective of an inertial frame of reference.[4] In this case, for two events which are simultaneous according the cosmological time coordinate, the value of the cosmological proper distance is not equal to the value of the proper length between these same events,(Wright) which would just be the distance along a straight line between the events in a Minkowski diagram (and a straight line is a geodesic in flat Minkowski spacetime), or the coordinate distance between the events in the inertial frame where they are simultaneous.
    http://en.wikipedia.org/wiki/Comovin...ng_coordinates
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    I would say the CMB is expanding and cooling ( or shifting to a longer wavelength ). but I don't see how it can be accelerating. Accelerating with respect to what ???
    The CMB is the vastly red-shifted remains of the radiation which permeated the universe before it became transparent , about 300,000 yrs after the big bang. I realise it came into existence after the inflationary period so it may not be present in the WHOLE universe but it is certainly present everywhere in our observable, causally connected universe.
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    Quote Originally Posted by chinglu
    CMB is accelerating.

    If you are at rest with CMB then you are at rest with acceleration.
    Perhaps this is a language issue we have?

    The CMB is radiation, moving through space at the speed of light. It is not accelerating - it has been moving at c since it was released, 13.7 billion years ago.

    The frame of reference in which that CMB was released is known as the CMB "rest frame" which is often considered to be a frame at rest in relation to the expansion of the universe. It is the expansion of the universe that is accelerating.

    The CMB rest frame might be the closest thing we have to an absolute frame, as it is co-moving with the expansion - the frame expands with the universe, so it remains at rest in relation to the expansion.

    Due to the peculiar motion of our galaxy in our local group, relative to the CMB rest frame, we measure an anisotropy in the temperature of the CMB in a certain direction - it is estimated we are moving at roughly 600 km/s in relation to the CMB rest frame.
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    The way I 'see' the CMB is using our typical ballon example of our universe with dots on it representing galaxies. Assume that the universe (Ballon) is filled with a gas ( of photons). Once, just after the big bang, this gas was so compressed that it was a solid. As expansion increased the volume of the universe ( balloon ) the gas became more rarified and lost pressure ( energy ). This loss of energy is the equivalent of photons losing energy by being red-shifted.

    The point is that this photon 'gas' permeats all the universe and runs through it as a framework not as a frame against which the universe is accelerating.
    My apologies if I haven't made myself very clear, Its a topic very difficult to describe using everyday things and experiences.
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    Quote Originally Posted by SpeedFreek
    Quote Originally Posted by chinglu
    CMB is accelerating.

    If you are at rest with CMB then you are at rest with acceleration.
    Perhaps this is a language issue we have?

    The CMB is radiation, moving through space at the speed of light. It is not accelerating - it has been moving at c since it was released, 13.7 billion years ago.

    The frame of reference in which that CMB was released is known as the CMB "rest frame" which is often considered to be a frame at rest in relation to the expansion of the universe. It is the expansion of the universe that is accelerating.

    The CMB rest frame might be the closest thing we have to an absolute frame, as it is co-moving with the expansion - the frame expands with the universe, so it remains at rest in relation to the expansion.

    Due to the peculiar motion of our galaxy in our local group, relative to the CMB rest frame, we measure an anisotropy in the temperature of the CMB in a certain direction - it is estimated we are moving at roughly 600 km/s in relation to the CMB rest frame.
    I am sorry I entered this debate.

    But, to be at rest with the comoving CMB frame, you are at rest with acceleration or an accelerating universe and that is the only way you can see light frequency isotropy in all directions.

    Otherwise, you are at rest with an absolute reference frame frame and SR is false.

    Take your pick.
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  28. #27  
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    Quote Originally Posted by DrRocket

    The universe is quite clearly curved on smaller scales -- without non-zero local curvature theree would be no gravitation. It is also quite clearly of small curvature, nearly flat on large scales. But "nearly flat" is not nearly good enough.
    Right, but the CMB can only be analyzed stochastically. Everything we know for sure about it is an approximation based on statistical patterns. Is the universe's curvature great enough that it would detectably influence those observations?



    Quote Originally Posted by CSMYTH3025
    Quote Originally Posted by MigL
    ...But back to the original topic, before this latest pi**ing contest started. Can the CMB be used as an absolute reference frame for at least the observable universe. And can we determine our absolute motion through the observable universe. I have read, for example, about a large mass of galactic superclusters in the form of a wall, dubbed the great attractor. Is this at rest relative to the observable universe ?Is anything at rest ?
    To answer your last question - as I understand it, things can, indeed, be "at rest" relative to each other. Technically, they're said to be in the same inertial frame of reference.

    As DrRocket pointed out, the CMB can be used as a frame of reference for our local area because it's comoving with our local volume of space. It is light (microwaves) that's coming evenly from all directions in our local area. Our planet and our galaxy are moving relative to this evenly distributed "incoming" microwave radiation. As a result, if we look in the direction of our motion relative to this background radiation it appears slightly blue-shifted. If we look in the opposite direction, it appears slightly red-shifted. Someone in another nearby solar system would notice the same effect. We could, in theory, compare our numbers with theirs and decide how we're moving relative to each other (approximately). In order to do this we would, of course, have to agree on which direction was up, down, forward, backward, left and right.
    Michelson and Morley wanted to measure absolute speed relative to an "Ether Wind" , but we get to measure it relative to a snapshot in time.

    The question is whether the cloud the emitted it was truly stationary? Intuitively, it's tempting to assume it was stationary, because it filled all of space and therefore had nowhere to go, but ...... it could still have been moving with a combined direction, because when you reach the edge of the universe it's like reaching the edge of the surface of planet Earth..... you're right back where you started.

    Is it likely that it had a combined direction? I'd say no. And if it had no combined direction then we are measuring our speed relative to a truly stationary object.




    If you go several tens of millions light years away in any direction, the CMB will be comoving with that local patch of space - but not with ours. We couldn't use their motion through their local CMB to directly compare our relative motion to them based on our motion through our local CMB.
    They also observe a different CMB than we do. We observe that light which was emitted Now -(time of emission) ago. It's point of origin is {Now -(time of emission)} * C away from us. (And we also have to account for inflation too.)

    If you were located in a different part of the universe, the CMB light you observe will honestly have originated from a different place.
    Some clocks are only right twice a day, but they are still right when they are right.
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    Quote Originally Posted by chinglu
    Wrong again.

    Read your own damn link. Read it slowly and try to understand it next time.
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    For a period of time, after the Big Bang the universe was filled only with radiation at extremely high temperature. After decoupling, permanent particles started to precipitate out, and they make up the matter we see in the universe today.
    The universe filling energy did not go away, however, but as the universe expanded, the wavelength of this energy also expanded, It has expanded so much in wavelength that instead of being energetic it is now at 2.7 deg K. But it still permeates all of space. It was not emitted from a cloud nor is it like a curtain, stationary at the edge of the universe. It would not be moving in any way unless the universe is expanding at differing rates in different, causally connected regions ( unlikely since it would lead to interesting and visible edge effects ).
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by chinglu
    Wrong again.

    Read your own damn link. Read it slowly and try to understand it next time.
    Let's see, I said to be at rest with CmB you are at rest with acceleration of the expanding universe. My link proves this.

    You claimed that is false. That means, when you are at rest with CMB you are at rest with an absolute at rest reference frame.

    Is that correct?
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    Quote Originally Posted by chinglu
    Let's see, I said to be at rest with CmB you are at rest with acceleration of the expanding universe
    Being "at rest" with an accelerating frame is logically incoherent.
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    Quote Originally Posted by inow
    Quote Originally Posted by chinglu
    Let's see, I said to be at rest with CmB you are at rest with acceleration of the expanding universe
    Being "at rest" with an accelerating frame is logically incoherent.
    It's also a non-inertial reference frame and is therefore not applicable to relativity, rest frame or not.
    Wise men speak because they have something to say; Fools, because they have to say something.
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  34. #33  
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    Quote Originally Posted by chinglu
    Quote Originally Posted by DrRocket
    Quote Originally Posted by chinglu
    Wrong again.

    Read your own damn link. Read it slowly and try to understand it next time.
    Let's see, I said to be at rest with CmB you are at rest with acceleration of the expanding universe. My link proves this.

    You claimed that is false. That means, when you are at rest with CMB you are at rest with an absolute at rest reference frame.

    Is that correct?
    Nothing that have said is correct. Not even close. In fact it is totally nonsensical.

    Your link disproves your statement. You obviously do not even understand your link.

    Being "at rest with the acceleration of the universe" is a non-sequitar.

    The CMB is a bunch of photons. You cannot be at rest with respect to photons.

    What you can do, precisely as I stated, and as noted in your link, is to adopt a local reference frame in which the CMB is isotropic.
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    Quote Originally Posted by Arcane_Mathematician
    Quote Originally Posted by inow
    Quote Originally Posted by chinglu
    Let's see, I said to be at rest with CmB you are at rest with acceleration of the expanding universe
    Being "at rest" with an accelerating frame is logically incoherent.
    It's also a non-inertial reference frame and is therefore not applicable to relativity, rest frame or not.
    Yeah, but universal expansion doesn't count as "moving" for the purposes of relativity. If it did, then probably some objects very far from us would be moving faster than C.
    Some clocks are only right twice a day, but they are still right when they are right.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by chinglu
    Quote Originally Posted by DrRocket
    Quote Originally Posted by chinglu
    Wrong again.

    Read your own damn link. Read it slowly and try to understand it next time.
    Let's see, I said to be at rest with CmB you are at rest with acceleration of the expanding universe. My link proves this.

    You claimed that is false. That means, when you are at rest with CMB you are at rest with an absolute at rest reference frame.

    Is that correct?
    Nothing that have said is correct. Not even close. In fact it is totally nonsensical.

    Your link disproves your statement. You obviously do not even understand your link.

    Being "at rest with the acceleration of the universe" is a non-sequitar.

    The CMB is a bunch of photons. You cannot be at rest with respect to photons.

    What you can do, precisely as I stated, and as noted in your link, is to adopt a local reference frame in which the CMB is isotropic.
    When I say at rest with CMB, I mean frequency is isotropic in all directions.

    Now, I will ask you again.

    If you are at rest with CMB, are you at rest with the accelerating/expanding universe or are you at some absolute rest?

    Are you able to answer this simple question?
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  37. #36  
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    False dichotomy. The answer already given was neither.
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    Quote Originally Posted by MagiMaster
    False dichotomy. The answer already given was neither.
    Uh, no the answer is not given.

    So, it is a false dichotomy.

    If you are at rest with CMB, then it is false that you are at absolute rest and it is false you are at rest with the expanding universe based on the isotropic frequency of CMB in all directions.

    That implies you have a third alternative.
    What is it?
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    Quote Originally Posted by chinglu
    Quote Originally Posted by MagiMaster
    False dichotomy. The answer already given was neither.
    Uh, no the answer is not given.

    So, it is a false dichotomy.

    If you are at rest with CMB, then it is false that you are at absolute rest and it is false you are at rest with the expanding universe based on the isotropic frequency of CMB in all directions.

    That implies you have a third alternative.
    What is it?
    Quote Originally Posted by DrRocket
    What you can do, precisely as I stated, and as noted in your link, is to adopt a local reference frame in which the CMB is isotropic.
    This.
    Wise men speak because they have something to say; Fools, because they have to say something.
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    Quote Originally Posted by Arcane_Mathematician
    Quote Originally Posted by chinglu
    Quote Originally Posted by MagiMaster
    False dichotomy. The answer already given was neither.
    Uh, no the answer is not given.

    So, it is a false dichotomy.

    If you are at rest with CMB, then it is false that you are at absolute rest and it is false you are at rest with the expanding universe based on the isotropic frequency of CMB in all directions.

    That implies you have a third alternative.
    What is it?
    Quote Originally Posted by DrRocket
    What you can do, precisely as I stated, and as noted in your link, is to adopt a local reference frame in which the CMB is isotropic.
    This.
    Good.
    I assume you understand mathematical logic.

    We have to make a decision.

    If you claim being at rest locally is a reference frame, then I assume you are claiming a local at rest absolute frame.

    Is that correct?


    Now, let's apply mathematical logic.

    There is no such term as local. Either the frame is at rest in the absolute sense or it is at rest with the accelerating universe.

    So, in the view of logic, do you choose to answer?
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    Quote Originally Posted by chinglu
    Now, let's apply mathematical logic.

    There is no such term as local.
    False assumption there. Any conclusions drawn from that are invalid. Specifically, reference frames are local approximations of global spacetime, which isn't a reference frame itself.
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    Quote Originally Posted by chinglu
    Quote Originally Posted by Arcane_Mathematician
    Quote Originally Posted by chinglu
    Quote Originally Posted by MagiMaster
    False dichotomy. The answer already given was neither.
    Uh, no the answer is not given.

    So, it is a false dichotomy.

    If you are at rest with CMB, then it is false that you are at absolute rest and it is false you are at rest with the expanding universe based on the isotropic frequency of CMB in all directions.

    That implies you have a third alternative.
    What is it?
    Quote Originally Posted by DrRocket
    What you can do, precisely as I stated, and as noted in your link, is to adopt a local reference frame in which the CMB is isotropic.
    This.
    Good.
    I assume you understand mathematical logic.

    We have to make a decision.

    If you claim being at rest locally is a reference frame, then I assume you are claiming a local at rest absolute frame.

    Is that correct?


    Now, let's apply mathematical logic.

    There is no such term as local. Either the frame is at rest in the absolute sense or it is at rest with the accelerating universe.

    So, in the view of logic, do you choose to answer?
    I assume you are a mathematical laymen. There is such a concept as "local" in mathematics. There is no "absolute" here, everything is relative, and as such, you must deal with it all relative to some frame of reference. the whole of the universe does not have a reference frame for relativity, you need to think about a specific frame of reference, if your frame of reference is local CMB, then that is your local reference frame. CMB varies from place to place, though, and is not consistent for two arbitrary points in the universe. Because of this, it in and of itself, is non-inertial and can not be a global frame of reference in relativity.

    if i'm mistaken, Dr. R or Magi will correct me
    Wise men speak because they have something to say; Fools, because they have to say something.
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    Quote Originally Posted by chinglu

    Now, let's apply mathematical logic.

    There is no such term as local. Either the frame is at rest in the absolute sense or it is at rest with the accelerating universe.

    So, in the view of logic, do you choose to answer?
    Wrong. This is ridiculous. Your aggressive tone makes you look very foolish, while the content reveals you to be ignorant of both physics and mathematics.

    General relativity is based on pseudo-Riemannian geometry, and "local" is a rather standard term throughout differential geometry.

    It is quite clear that you have no idea what you are talking about. There is no point in addressing your questions. They don't make any sense, and you are obviously incapable of understanding answers in terms of rigorous mathematics or physics in any case.

    There is no such thing as "at rest in the absolute sense". Neither is there any meaning to "at rest with the accelerating universe". So not only is you dichotomy false, it is just plain nuts.

    You have no idea what you are talking about.
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    Quote Originally Posted by Arcane_Mathematician
    if i'm mistaken, Dr. R or Magi will correct me
    I probably wouldn't be able to correct any minor errors, since I'm not much of a physicist (I'm a mathematician and computer scientist, if it matters), but yeah, chinglu's errors aren't minor (and he's getting into logic, which is a big part of CS).
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    Quote Originally Posted by Arcane_Mathematician
    I assume you are a mathematical laymen. There is such a concept as "local" in mathematics. There is no "absolute" here, everything is relative, and as such, you must deal with it all relative to some frame of reference. the whole of the universe does not have a reference frame for relativity, you need to think about a specific frame of reference, if your frame of reference is local CMB, then that is your local reference frame. CMB varies from place to place, though, and is not consistent for two arbitrary points in the universe. Because of this, it in and of itself, is non-inertial and can not be a global frame of reference in relativity.

    if i'm mistaken, Dr. R or Magi will correct me
    The reason for lack of a global reference frame has to do with the fact that the universe is a manifold with curvature. GR represents the universe as a 4-dimensional Lorentzian manifold, and manifolds do not in general admit global reference frames (charts). They are in fact built up locally, with the differential structure built from compatible, overlapping charts, forming an "atlas".

    So far as is known the CMB is the same everywhere, on large scales and in selected charts -- this is the cosmological principle (assumption) that on the largest scales the universe is homogeneous and isotropic. It is obviously neither on smaller scales.
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    Quote Originally Posted by chinglu

    When I say at rest with CMB, I mean frequency is isotropic in all directions.

    Now, I will ask you again.

    If you are at rest with CMB, are you at rest with the accelerating/expanding universe or are you at some absolute rest?

    Are you able to answer this simple question?
    A better way to say it would be to say that you are at rest with respect to the phenomenon that gave rise to the CMB. At least, you would at rest with respect to it, if the CMB had no net red or blue shift in any direction when you observe it.

    The problem as I mentioned before is, there is no way to be certain that the photon cloud (or whatever the correct term may be) didn't have a net motion with respect to the universe as a whole. Maybe it did.
    Some clocks are only right twice a day, but they are still right when they are right.
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    Quote Originally Posted by kojax

    A better way to say it would be to say that you are at rest with respect to the phenomenon that gave rise to the CMB. At least, you would at rest with respect to it, if the CMB had no net red or blue shift in any direction when you observe it.
    That makes even less sense than chinglu's statements. What, precisely, would it mean to be at rest with something that happened over 13 billion years ago ?
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    The CMB rest frame is any frame of reference where you measure the CMB to be isotropic. Simple as that.

    Using WMAP is it estimated that we have a peculiar motion of ~630 km/s in relation to the CMB rest frame.

    This means you could travel in a certain direction through the Solar System, at ~630 km/s, and you would be in the CMB rest frame - you would measure the CMB to be isotropic. You would not, in any absolute sense, be at rest, though, and you would struggle to remain in that frame, whilst in the Solar System, due to your path being perturbed.
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    Thanks SpeedFreek, that was the most concise answer to my original question. I wanted to know if we had any motion relative to the CMB, which can under certain circumstances, be used as a quasi-absolute frame.

    As to chinglu's one of two choices, the assertion that the CMB is at rest with an accelerating universe, I still fail to see how exactly the universe is accelerating. Only its expansion is accelerating. If you blow up a balloon at an increasingly faster rate, so that it expands faster and faster, then you say its expansion is accelerating, BUT the balloon itself is NOT accelerating. I think he is confusing his terminology and not understanding the actual process.
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    Quote Originally Posted by MigL
    Thanks SpeedFreek, that was the most concise answer to my original question. I wanted to know if we had any motion relative to the CMB, which can under certain circumstances, be used as a quasi-absolute frame.

    As to chinglu's one of two choices, the assertion that the CMB is at rest with an accelerating universe, I still fail to see how exactly the universe is accelerating. Only its expansion is accelerating. If you blow up a balloon at an increasingly faster rate, so that it expands faster and faster, then you say its expansion is accelerating, BUT the balloon itself is NOT accelerating. I think he is confusing his terminology and not understanding the actual process.
    My point is this.
    Many think to be at rest with CMB means you are at absolute rest.
    In SpeedFreek's post, he indicated the earth's motion relative to CMB.

    Some would claim this implies you know your absolute motion.

    However, according to current theory, the universe is expanding and these photons are being carried with the expansion.

    Therefore, to be at rest with the CMB photons implies you are at rest with the expansion of the universe which again according to current theory you are at rest with acceleration. Therefore, to be at rest with CMB does not imply you are at absolute rest according to current theory.

    That is my point and this is the mainstream position.
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    I think part of what chinglu was saying earlier was correct, but lost in translation, and unfortunately he confuses things further with his references to an absolute frame.

    The CMB rest frame, where you measure the CMB to be isotropic in all directions, is often considered to be a frame at rest in relation to the Hubble flow, otherwise known as the expansion of the universe.

    But, the Hubble flow is based on the Hubble constant - the rate of expansion averaged over the co-moving volume of the universe during its history. In other words, it is an expansion rate based on the change in the scale factor of the universe. To put this into context, even though the rate of expansion is accelerating, the Hubble constant is still decreasing.

    So, in the CMB rest frame, what is it that you are at rest in relation to? Well, you can quite validly consider yourself at rest in relation to the place where all those CMB photons were released, 13.7 billion years ago. But how much sense does that make now?
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    Quote Originally Posted by SpeedFreek
    I think part of what chinglu was saying earlier was correct, but lost in translation, and unfortunately he confuses things further with his references to an absolute frame.

    The CMB rest frame, where you measure the CMB to be isotropic in all directions, is often considered to be a frame at rest in relation to the Hubble flow, otherwise known as the expansion of the universe.

    But, the Hubble flow is based on the Hubble constant - the rate of expansion averaged over the co-moving volume of the universe during its history. In other words, it is an expansion rate based on the change in the scale factor of the universe. To put this into context, even though the rate of expansion is accelerating, the Hubble constant is still decreasing.

    So, in the CMB rest frame, what is it that you are at rest in relation to? Well, you can quite validly consider yourself at rest in relation to the place where all those CMB photons were released, 13.7 billion years ago. But how much sense does that make now?
    Close but not quite there.

    The expansion of the universe is pulling apart the frequency of that light making it longer/cooler.

    You need a reason with the conservation of energy for the observed cooling.

    This is the current theory.

    So, to be at rest with CMB, you are at rest with the expansion.

    Otherwise,you are at absolute rest. Have you ever wondered why SR is still here?
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    Quote Originally Posted by chinglu
    Quote Originally Posted by SpeedFreek
    I think part of what chinglu was saying earlier was correct, but lost in translation, and unfortunately he confuses things further with his references to an absolute frame.

    The CMB rest frame, where you measure the CMB to be isotropic in all directions, is often considered to be a frame at rest in relation to the Hubble flow, otherwise known as the expansion of the universe.

    But, the Hubble flow is based on the Hubble constant - the rate of expansion averaged over the co-moving volume of the universe during its history. In other words, it is an expansion rate based on the change in the scale factor of the universe. To put this into context, even though the rate of expansion is accelerating, the Hubble constant is still decreasing.

    So, in the CMB rest frame, what is it that you are at rest in relation to? Well, you can quite validly consider yourself at rest in relation to the place where all those CMB photons were released, 13.7 billion years ago. But how much sense does that make now?
    Close but not quite there.

    The expansion of the universe is pulling apart the frequency of that light making it longer/cooler.

    You need a reason with the conservation of energy for the observed cooling.

    This is the current theory.

    So, to be at rest with CMB, you are at rest with the expansion.

    Otherwise,you are at absolute rest. Have you ever wondered why SR is still here?
    This is just bizarre. Are you really that ignorant of physics ? Or are you simply a troll stirring the pot ?
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    Quote Originally Posted by SpeedFreek
    ...But, the Hubble flow is based on the Hubble constant - the rate of expansion averaged over the co-moving volume of the universe during its history. In other words, it is an expansion rate based on the change in the scale factor of the universe. To put this into context, even though the rate of expansion is accelerating, the Hubble constant is still decreasing....
    So far, what I get is that for two distant comoving observers, if one of them observes the CMB to be isotropic relative to himself, the other observer will also observe the CMB in his local space to be isotropic to himself. Please correct me if I've misunderstood this concept.

    Your above quoted comment is hard for me to figure out, SpeedFreek. I understand that the rate of expansion has been increasing for about the past 5-6 billion years. We measure the Hubble constant to be ~70 km/s per Mpc this year. This is the average rate of expansion of the universe since the big bang as I understand it from your comment.

    In trying to understand your seemingly paradoxical statement I came across this passage in Wikipedia:

    Current evidence suggests the expansion of the universe is accelerating (see Accelerating universe), meaning that for any given galaxy, the recession velocity dD/dt is increasing over time as the galaxy moves to greater and greater distances; however, the Hubble parameter is actually thought to be decreasing with time, meaning that if we were to look at some fixed distance D and watch a series of different galaxies pass that distance, later galaxies would pass that distance at a smaller velocity than earlier ones...
    (ref. http://en.wikipedia.org/wiki/Hubble%...Interpretation )

    This passage essentially restates what you've said, but I don't understand why this should be so.

    I'm sure I'm missing something here, but I can't figure out what it is.

    Chris
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    Quote Originally Posted by CSMYTH3025
    We measure the Hubble constant to be ~70 km/s per Mpc this year. This is the average rate of expansion of the universe since the big bang as I understand it from your comment.
    The Hubble constant is (related to) the current rate of expansion. The Hubble constant parameter represents the apparent recession velocity of a distant galaxy as a function of distance at a give cosmological time. The Hubble constant is the current value of that parameter.

    However, the distance that we see a galaxy at is not necessarily the distance that it is currently at (given the reference frame that we usually use for these things). When we look at a really distant galaxy, we are seeing it in the past, so we see it at a time when the Hubble parameter was different from the current value of that parameter.

    We can use the detectable difference between the Hubble parameter then vs. the Hubble constant to make determinations about the kinematics of the universe.
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    While searching for information about the Hubble constant I ran across the following passage in Wikipedia:
    A comoving observer is the only observer that will perceive the universe, including the cosmic microwave background radiation, to be isotropic. Non-comoving observers will see regions of the sky systematically blue-shifted or red-shifted. Thus isotropy, particularly isotropy of the cosmic microwave background radiation, defines a special local frame of reference called the comoving frame. The velocity of an observer relative to the local comoving frame is called the peculiar velocity of the observer.

    Most large lumps of matter, such as galaxies, are nearly comoving, i.e., their peculiar velocities (due to gravitational attraction) are low.
    (ref. http://en.wikipedia.org/wiki/Comovin...roper_distance )

    This passage - especially the portion that states "...Thus isotropy, particularly isotropy of the cosmic microwave background radiation, defines a special local frame of reference called the comoving frame..." - helps to affirm the explanation offered in many of the previous posts in this thread that the CMB "...defines a special local frame of reference..." (depending, of course, on whether one considers Wikipedia to be a credible source of information).

    Chris

    Edited to correct spelling errors.
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    OK. Let me see if I've got this conundrum figured out.

    Lets suppose that a million years ago it takes 3x10^22 comoving observers with metersticks to measure the distance to a certain galaxy. Today it also takes 3x10^22 comoving observers to measure the same distance to the same galaxy - only the metersticks we're using today are 101 cm long instead of 100 cm long.

    A million years from now it once again takes 3x10^22 comoving observers to measure the same distance to the same galaxy - except this time their metersticks are 103 cm long instead of 101 cm long.

    Over this time the comoving distance to the galaxy remains the same as measured by comoving observers. The yardsticks they're using, however, increased in length by one cm during the first million years and increased by two cm during the second million years due to the scale factor of the universe.

    Thus, we say that the rate of cosmic expansion is increasing, but the comoving distance to the galaxy remains constant.

    If we look at a fixed (proper?) distance and measure how fast the galaxy is moving past that spot a million years ago we find that it's moving at 7x10^4 m/sec. (as an example)

    If we take the same measurement today, we find that a galaxy (not the same one) is moving past that same spot 7x10^4 cm/sec less than the one a million years ago (because our metersticks are one cm longer now).

    Likewise, if we measure the speed at which another galaxy goes past that same fixed spot a million years from now we find that it's moving at 14x10^4 cm/sec less than the one we just measured today.

    Thus, we say that the Hubble constant is decreasing.

    Is this more-or-less the right concept?

    Chris
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    I quickly removed a very inept and downright misleading explanation where I tried some math, which reminds me why I don't usually do that sort of thing! I don't know how I didn't spot the obvious mistake I had made before I posted! Luckily I spotted it soon after, hopefully before too many people read it!

    I'm tying myself in knots trying to explain it properly, I will try again later.
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    Quote Originally Posted by chinglu
    Therefore, to be at rest with CMB does not imply you are at absolute rest according to current theory.

    That is my point and this is the mainstream position.
    The CMB is a bunch of photons. It is impossible to be at rest with respect to a photon -- that would be a gross violation of relativity.

    You can adopt a local reference frame in which the CMB is isotropic, but that is all.

    According to current theory, general relativity, "absolute rest" is meaningless.

    You have no point. You have proved in this thread that you have no understanding of "the mainstream position".

    General relativity does not even admit ANY global reference frame, let alone one of "absolute rest". The decomposition of spacetime into "time" and "space", as is common in cosmology, is only a large-scale approximation, valid under the assumptions of homogeneity and isotropy -- assumptions valid only at the largest scales. In the real universe, which is neither homogeneous, nor isotropic, nor flat, there are only local reference frames.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by chinglu
    Therefore, to be at rest with CMB does not imply you are at absolute rest according to current theory.

    That is my point and this is the mainstream position.
    The CMB is a bunch of photons. It is impossible to be at rest with respect to a photon -- that would be a gross violation of relativity.

    You can adopt a local reference frame in which the CMB is isotropic, but that is all.

    According to current theory, general relativity, "absolute rest" is meaningless.

    You have no point. You have proved in this thread that you have no understanding of "the mainstream position".

    General relativity does not even admit ANY global reference frame, let alone one of "absolute rest". The decomposition of spacetime into "time" and "space", as is common in cosmology, is only a large-scale approximation, valid under the assumptions of homogeneity and isotropy -- assumptions valid only at the largest scales. In the real universe, which is neither homogeneous, nor isotropic, nor flat, there are only local reference frames.
    You can adopt a local reference frame in which the CMB is isotropic, but that is all.

    Now, we both know you can do this but over time, this does not work.

    Why is that.

    Because you are at rest with acceleration. I did not say we can currently can calculate it, but that is the theory.

    Now, if you claim a local reference frame in which the CMB is absolute, then you can claim you are at rest in an absolute sense.

    Otherwise, you are at rest with acceleration as I said in the first place.

    You are simply finally coming around to the understanding of what I said.
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    Quote Originally Posted by chinglu
    Quote Originally Posted by DrRocket
    Quote Originally Posted by chinglu
    Therefore, to be at rest with CMB does not imply you are at absolute rest according to current theory.

    That is my point and this is the mainstream position.
    The CMB is a bunch of photons. It is impossible to be at rest with respect to a photon -- that would be a gross violation of relativity.

    You can adopt a local reference frame in which the CMB is isotropic, but that is all.

    According to current theory, general relativity, "absolute rest" is meaningless.

    You have no point. You have proved in this thread that you have no understanding of "the mainstream position".

    General relativity does not even admit ANY global reference frame, let alone one of "absolute rest". The decomposition of spacetime into "time" and "space", as is common in cosmology, is only a large-scale approximation, valid under the assumptions of homogeneity and isotropy -- assumptions valid only at the largest scales. In the real universe, which is neither homogeneous, nor isotropic, nor flat, there are only local reference frames.
    You can adopt a local reference frame in which the CMB is isotropic, but that is all.

    Now, we both know you can do this but over time, this does not work.

    Why is that.

    Because you are at rest with acceleration. I did not say we can currently can calculate it, but that is the theory.

    Now, if you claim a local reference frame in which the CMB is absolute, then you can claim you are at rest in an absolute sense.

    Otherwise, you are at rest with acceleration as I said in the first place.

    You are simply finally coming around to the understanding of what I said.
    Notice you're the only one claiming anything to be absolute
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    Quote Originally Posted by chinglu
    [You can adopt a local reference frame in which the CMB is isotropic, but that is all.

    Now, we both know you can do this but over time, this does not work.

    Why is that.

    Because you are at rest with acceleration. I did not say we can currently can calculate it, but that is the theory.
    Word salad

    Quote Originally Posted by chinglu
    [[Now, if you claim a local reference frame in which the CMB is absolute, then you can claim you are at rest in an absolute sense.
    No one except you has claimed any absolute reference frame.

    Quote Originally Posted by chinglu
    Otherwise, you are at rest with acceleration as I said in the first place.
    "At rest with acceleration" is self-contradictory.

    Quote Originally Posted by chinglu
    You are simply finally coming around to the understanding of what I said.
    No one, nott even you, understands what you said.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by kojax

    A better way to say it would be to say that you are at rest with respect to the phenomenon that gave rise to the CMB. At least, you would at rest with respect to it, if the CMB had no net red or blue shift in any direction when you observe it.
    That makes even less sense than chinglu's statements. What, precisely, would it mean to be at rest with something that happened over 13 billion years ago ?
    If you look at a galaxy a billion light years away, you're looking into the past, at the state that galaxy was in a million years ago. It's quite possible that galaxy no longer exists, because a lot could happen in a billion years. Maybe a supermassive black hole ate it or something. However, we still see it now, and we can still use redshift to determine whether it was moving toward us or away from us at the time the light was emitted.

    The same goes for the photon cloud that emitted the CMB. The fact the cloud has ceased to exist in the time it took the radiation to reach us has absolutely no bearing on our measurements. We can compare our current heading and velocity against the heading and velocity of a photon cloud that once filled all of space.

    I guess it's still technically a "local" reference frame, but it's a weird kind of "local", considering that no other objects existed outside of that photon cloud against which its speed could be measured.
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    Minor, off-topic point, but supermassive black holes exist at the center of each and every galaxy (and only there). No galaxy will be eaten by one. (Even during a collision, a lot gets eaten, and the two black holes merge, but there's still a whole new galaxy of stuff left over.)

    On topic, time is just as local as space, so you can't meaningfully be at rest with something like that. Like DrRocket said, it's just (and exactly) the frame where you see the CMB as isotropic. Isotropic just means that you measure the red- or blue-shift to be the same in all directions. You wouldn't really be at rest relative to anything. Elsewhere and elsewhen, you'd have to accelerate to maintain that isotropy.
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    Quote Originally Posted by kojax
    Quote Originally Posted by DrRocket
    Quote Originally Posted by kojax

    A better way to say it would be to say that you are at rest with respect to the phenomenon that gave rise to the CMB. At least, you would at rest with respect to it, if the CMB had no net red or blue shift in any direction when you observe it.
    That makes even less sense than chinglu's statements. What, precisely, would it mean to be at rest with something that happened over 13 billion years ago ?
    If you look at a galaxy a billion light years away, you're looking into the past, at the state that galaxy was in a million years ago. It's quite possible that galaxy no longer exists, because a lot could happen in a billion years. Maybe a supermassive black hole ate it or something. However, we still see it now, and we can still use redshift to determine whether it was moving toward us or away from us at the time the light was emitted.

    The same goes for the photon cloud that emitted the CMB. The fact the cloud has ceased to exist in the time it took the radiation to reach us has absolutely no bearing on our measurements. We can compare our current heading and velocity against the heading and velocity of a photon cloud that once filled all of space.

    I guess it's still technically a "local" reference frame, but it's a weird kind of "local", considering that no other objects existed outside of that photon cloud against which its speed could be measured.
    Youu are becoming more muddled, not more clear. This is even more meaningless that your earlier post. Word salad.

    You quite clearly have no idea what the CMB is.
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    Quote Originally Posted by kojax
    If you look at a galaxy a billion light years away, you're looking into the past, at the state that galaxy was in a million years ago. It's quite possible that galaxy no longer exists, because a lot could happen in a billion years. Maybe a supermassive black hole ate it or something. However, we still see it now, and we can still use redshift to determine whether it was moving toward us or away from us at the time the light was emitted.
    You sort of have the principles right here, although redshift never means anything is moving towards us. For that you need blueshift. I'm not so sure about the supermassive black holes either! But you are right that we see galaxies as they were, rather than as they are.

    Quote Originally Posted by kojax
    The same goes for the photon cloud that emitted the CMB. The fact the cloud has ceased to exist in the time it took the radiation to reach us has absolutely no bearing on our measurements. We can compare our current heading and velocity against the heading and velocity of a photon cloud that once filled all of space.
    Okay, back up just a little. The photon cloud IS the CMB, it didn't emit it. The photon cloud has permeated the universe since it was released, and as we detect those photons coming in from all directions, we assume other CMB photons, released at the same time but at a closer distance, will have been detectable in the past. Likewise, CMB photons released at the same time but at a larger distance will continue to be detectable in the future. Today, those photons have been redshifted into the microwave region of the electromagnetic spectrum by the expansion of the universe.

    A very simplified way to think of it is that before all those CMB photons were released, they dominated the universe, but everything was too hot for photons to be able to move freely without hitting something and scattering. The universe was opaque.

    When the universe reached the state where atoms could form, all those photons were released and the universe became transparent. The universe was filled with photons that could finally move freely for the first time, scattering in all directions. This is why the particle horizon is also known as the "surface of last scattering".
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    Quote Originally Posted by SpeedFreek
    Quote Originally Posted by kojax
    If you look at a galaxy a billion light years away, you're looking into the past, at the state that galaxy was in a million years ago. It's quite possible that galaxy no longer exists, because a lot could happen in a billion years. Maybe a supermassive black hole ate it or something. However, we still see it now, and we can still use redshift to determine whether it was moving toward us or away from us at the time the light was emitted.
    You sort of have the principles right here, although redshift never means anything is moving towards us. For that you need blueshift. I'm not so sure about the supermassive black holes either! But you are right that we see galaxies as they were, rather than as they are.

    Quote Originally Posted by kojax
    The same goes for the photon cloud that emitted the CMB. The fact the cloud has ceased to exist in the time it took the radiation to reach us has absolutely no bearing on our measurements. We can compare our current heading and velocity against the heading and velocity of a photon cloud that once filled all of space.
    Okay, back up just a little. The photon cloud IS the CMB, it didn't emit it. The photon cloud has permeated the universe since it was released, and as we detect those photons coming in from all directions, we assume other CMB photons, released at the same time but at a closer distance, will have been detectable in the past. Likewise, CMB photons released at the same time but at a larger distance will continue to be detectable in the future. Today, those photons have been redshifted into the microwave region of the electromagnetic spectrum by the expansion of the universe.

    A very simplified way to think of it is that before all those CMB photons were released, they dominated the universe, but everything was too hot for photons to be able to move freely without hitting something and scattering. The universe was opaque.

    When the universe reached the state where atoms could form, all those photons were released and the universe became transparent. The universe was filled with photons that could finally move freely for the first time, scattering in all directions. This is why the particle horizon is also known as the "surface of last scattering".
    We are disagreeing in the other thread, but we are agreeing here.

    Today, those photons have been redshifted into the microwave region of the electromagnetic spectrum by the expansion of the universe.

    They are being red shifted on a continuous basis or so says the current theory.

    Therefore, to be at rest with CMB, you are at rest with acceleration or the accelerating expansion of the universe.
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    Quote Originally Posted by chinglu
    We are disagreeing in the other thread, but we are agreeing here.

    Today, those photons have been redshifted into the microwave region of the electromagnetic spectrum by the expansion of the universe.

    They are being red shifted on a continuous basis or so says the current theory.
    Actually, the theory does not say that, although a lot of popularisations describe it that way. In the theory itself, space has no intrinsic properties that cause the redshift, and it is most accurate to say the redshift is caused by difference in the frames of reference of the emitter when compared to the observer, in relation to the background metric.

    Quote Originally Posted by chinglu
    Therefore, to be at rest with CMB, you are at rest with acceleration or the accelerating expansion of the universe.
    Language issues again. If you are using english to describe scientific principles, you have to be specific in your wording in order to be understood. Your words say something different from your intentions here.

    CMB is radiation. It travels at c. You cannot be at rest with something travelling at c, as that would mean you would be travelling at c. So, you cannot be at rest with the CMB. This may seem a trifling matter, but it is important to be as clear as possible.

    If you are at rest in relation to the "rest frame" of the CMB, such that you measure all CMB to be redshifted by the same amount in all directions, then you are at rest in relation to the last random scattering of the light that filled the universe, in a universe a little over 1000 times smaller than today, nearly 13.7 billion years ago.

    It is considered a good approximation of a frame at rest in relation to the expansion of the universe.
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    Quote Originally Posted by SpeedFreek

    Quote Originally Posted by kojax
    The same goes for the photon cloud that emitted the CMB. The fact the cloud has ceased to exist in the time it took the radiation to reach us has absolutely no bearing on our measurements. We can compare our current heading and velocity against the heading and velocity of a photon cloud that once filled all of space.
    Okay, back up just a little. The photon cloud IS the CMB, it didn't emit it. The photon cloud has permeated the universe since it was released, and as we detect those photons coming in from all directions, we assume other CMB photons, released at the same time but at a closer distance, will have been detectable in the past. Likewise, CMB photons released at the same time but at a larger distance will continue to be detectable in the future. Today, those photons have been redshifted into the microwave region of the electromagnetic spectrum by the expansion of the universe.
    Ok, then I'm lost as to why it behaves like a perfect black body if it wasn't emitted by one.

    Why wouldn't the photons be distributed evenly across all possible frequencies, or homogeneous to just one frequency, instead of being distributed in a way that conforms to a black body? Most black bodies emit spectra based on the atoms that make them up, don't they? That's why I assumed the CMB had been emitted by a hot material object or cloud of some kind.


    A very simplified way to think of it is that before all those CMB photons were released, they dominated the universe, but everything was too hot for photons to be able to move freely without hitting something and scattering. The universe was opaque.
    Doesn't scattering give us a point of last emission?

    Suppose you were able to take a small slice of this photon-rich area of space and put it in the normal universe and let the photons go free. Wouldn't you be able to use red/blue shift measurements to determine whether you were approaching that patch of space, or receding from it?
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    Quote Originally Posted by kojax
    That's why I assumed the CMB had been emitted by a hot material object or cloud of some kind.
    Until about 300,000 years after the big bang, all of the matter in the universe was so hot that the universe was opaque. Then it cooled enough, due to expansion, that the universe became transparent. That last instant of opaqueness constitutes the "surface of last scattering and is the origin of the CMB.

    The "cloud" was all of the matter in the universe. All of it. It was not a photon cloud.

    Why are you assuming things ? You claim to have taken a bunch of physics courses. Try reading.
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    Yeah.... they tend to save the BBT for last. I'm more interested in fundamentals right now rather than cosmology anyway. (Besides that I don't even believe the BBT).

    What you're saying is that my understanding was correct. The CMBR was emitted by hot matter. Hot matter that filled all of the universe at that time. The fact that matter is no longer in the form it was in when it emitted the CMBR means absolutely nothing whatsoever as far as our ability to determine what our relative velocity and heading are now compared to what its velocity and heading was then. Redshift observations are always limited in that they only tell us how fast something was moving distance/C years ago compared to how fast we are moving this instant. A comparison between our speed then and its speed then would be a very tricky thing to accomplish. (I'm thinking it would require a third observer to measure both our speeds simultaneously relative to them, but maybe there's some other way to pull that off...)

    I think what confuses people here is that, not only is the hot matter's state of motion a past tense consideration, but the matter's state of being is also past tense. Clearly it has cooled quite a bit in the intervening billions of years since the CMBR was emitted. And.... that doesn't matter one bit. The present has no bearing on the past.
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    Quote Originally Posted by kojax
    What you're saying is that my understanding was correct. The CMBR was emitted by hot matter. Hot matter that filled all of the universe at that time..
    Did the last scattering surface emit the CMB, or was it simply the last thing to scatter it? The universe was already dominated by photons at the time.
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    Quote Originally Posted by kojax
    Yeah.... they tend to save the BBT for last. I'm more interested in fundamentals right now rather than cosmology anyway. (Besides that I don't even believe the BBT).

    What you're saying is that my understanding was correct. The CMBR was emitted by hot matter. Hot matter that filled all of the universe at that time. The fact that matter is no longer in the form it was in when it emitted the CMBR means absolutely nothing whatsoever as far as our ability to determine what our relative velocity and heading are now compared to what its velocity and heading was then. Redshift observations are always limited in that they only tell us how fast something was moving distance/C years ago compared to how fast we are moving this instant. A comparison between our speed then and its speed then would be a very tricky thing to accomplish. (I'm thinking it would require a third observer to measure both our speeds simultaneously relative to them, but maybe there's some other way to pull that off...)

    I think what confuses people here is that, not only is the hot matter's state of motion a past tense consideration, but the matter's state of being is also past tense. Clearly it has cooled quite a bit in the intervening billions of years since the CMBR was emitted. And.... that doesn't matter one bit. The present has no bearing on the past.
    No, your understanding, as usual, is way off base. You seem to fail to comprehend that we are talking about ALL the matter in the universe. It does not and dit not have a "heading" or a "speed".

    Maybe you should consider a different major.
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    Maybe I'll try again to clarify for Kojax and chinglu.
    After the Big Bang, the Universe has always been in a state of thermal equilibrium. The era we are interested in was approx. 10^6 yrs after the Big Bang, when expansion had cooled the universe to about 5000 deg. K. At this point the universe is filled with photons of the energy of 5000 deg K, and protons, neutrons and electrons ( just as today ) in thermal equilibrium. The neutrons snd protons can stick together but electrons cannot stick to the resulting ions because, as soon as they do, a photon comes along with the 5000 deg K energy, and knocks the electron loose. We have, in effect, conditions like in the sun, all the matter is in a plasma state composed of ions and free electrons in a sea of energetic photons. This permeates the whole universe and renders it opaque.
    As expansion continued, with the universe still in thermal equilibrium, the energy of the photons comprising this permeating radiation dropped below 4000 degK ( I haven't done the calculation for a long time but I think that's the appropriate temp ), at which point, the photons were no longer energetic enough to ionize, or free captured electrons, from forming atoms. This is the point in time when atomic matter as we know it and the permeating radiation can go their separate ways, and the universe becomes transparent ( called decoupling as photons and atoms no longer interact so severely ).
    The radiation still permeates all of the universe ( it is not emitted by anything kojax ) and its wavelength expands with universal expansion by a factor of about 10^3 ( somebody check my math ) so that presently its wavelength or energy corresponds to a temp of 2.7 deg K. No matter which direction you look at in the universe you expect to see the same temp since it still permeates all the universe and always will. However because of doppler effect, if we have a motion in a particular direction relative to the universe permeating radiation ( ie the universe or more aptly the causally connected, observable universe ), we will perceive a wavelength contraction ( blue shift ) towards our direction of motion, and a wavelength stretch ( red shift ) away from our origin of motion. I assme someone has already made these measurements as SpeedFreek provided us with values for our "absolute" motion ( note the parenthesis DrR ) in a previous post.

    But since this thread has stirred up alot of discussion, how about this. As we go back farther and farther towards time zero, we come across other decoupling events., such as the neutrino decoupling, where the original Big Bang neutrinos go their separate way. They would have created a background radiation pattern also ( although neutrinos are extremely difficult to detect ). Going further back we would have gluon decoupling where gluons and quarks go their separate ways ( probably the last time there were any free quarks ), and this may have created a gluon background radiation.
    Even further back, at what I believe is called the Planck time ( 10^-33 sec ) gravitational energy would have decoupled. I'm not sure what it would have decoupled from, what sort of background radiation this would have set up, or even if this makes any sense.
    It would be very interesting ( or fantasy ) if this could be related to the value of G ( gravitational constant ) in some way as I have read that G is inversely proportional to the square or cube ( don't recall which at the moment ) of the Planck energy ( Lisa Randall, MIT particle physics, only good looking physicist I know of ).
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    Excellent post there MigL. :-D

    Quote Originally Posted by MigL
    The radiation still permeates all of the universe ( it is not emitted by anything kojax ) and its wavelength expands with universal expansion by a factor of about 10^3 ( somebody check my math ) so that presently its wavelength or energy corresponds to a temp of 2.7 deg K.
    Yup, pretty much spot on. The last estimate I saw for that figure was z=1089, giving a scale factor (1+z) of 1090.
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    Quote Originally Posted by MigL
    ( Lisa Randall, MIT particle physics, only good looking physicist I know of ).
    Finally something I could understand.
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    Something I just ran across.

    Consider the following scenario. We ask two scientists to determine the rotation of the Earth. We ask Isaac Newton first, and he, with his notion of absolute space, sets up a pendulum and measures the procession of the plane of oscillation to detemine it. He would have inferred the rotation relative to a local inertial frame of reference. Next we ask Ernest Mach to make the same measurement, and being who he is, he makes use of a global determination. He looks at the farthest objects in the universe and, from the rotation of these stars and galaxies, determines the Earth's rotation. Again I stress the difference of the two methods, one being local and the other global, yet they both produce the same results such that there must be some causal relation between the two. Now it would be silly to infer that the local inertial frame affects the motion of distant stars such that the purely local pendulum can have any effect on the farthest reaches of the universe, however, the converse must be true, the far universe has an effect on the local inertia of the pendulum. The inertia of any body is determined by the distribution of the distant mass in the universe, is , in effect, Mach's principle. General Relativity does not satisfy Mach's Principle although Einstein was influenced by it. Accepted cosmological models of GR do, however, satisfy a special case of the principle such that, there is a preferred local frame of reference in which the distant galaxies of the universe are receding isotropically. We can consider the CMB to be anchored to its origin in the most distant regions of the universe, and these regions coincide with the reference frame of the isotropic universal expansion. In effect, the CMB provides us with a cosmic frame of reference determined by the large scale distribution of mass in the universe. The CMB has been measured to one thousandth of a degree kelvin, so blue shift in the destination direction and red shift in the origin direction give a measure of our net motion. Using this frame of reference, and allowing for Earth's, the sun's and the galactic motion in the local group, our net velocity has been measured to be 600 km/sec in the general direction of the Virgo Cluster and the supergalactic plane. The anisotropy of the CMB in effect, provides us with a local inertial frame and a modern interpretation of Mach's Principle.

    Paraphrased by me, from the book 'The Big Bang', Joseph Silk ( Astrophysics, U. of Cali @ Berkley ).
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  78. #77  
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    Quote Originally Posted by MigL
    Something I just ran across.

    Consider the following scenario. We ask two scientists to determine the rotation of the Earth. We ask Isaac Newton first, and he, with his notion of absolute space, sets up a pendulum and measures the procession of the plane of oscillation to detemine it. He would have inferred the rotation relative to a local inertial frame of reference. Next we ask Ernest Mach to make the same measurement, and being who he is, he makes use of a global determination. He looks at the farthest objects in the universe and, from the rotation of these stars and galaxies, determines the Earth's rotation. Again I stress the difference of the two methods, one being local and the other global, yet they both produce the same results such that there must be some causal relation between the two. Now it would be silly to infer that the local inertial frame affects the motion of distant stars such that the purely local pendulum can have any effect on the farthest reaches of the universe, however, the converse must be true, the far universe has an effect on the local inertia of the pendulum. The inertia of any body is determined by the distribution of the distant mass in the universe, is , in effect, Mach's principle. General Relativity does not satisfy Mach's Principle although Einstein was influenced by it. Accepted cosmological models of GR do, however, satisfy a special case of the principle such that, there is a preferred local frame of reference in which the distant galaxies of the universe are receding isotropically. We can consider the CMB to be anchored to its origin in the most distant regions of the universe, and these regions coincide with the reference frame of the isotropic universal expansion. In effect, the CMB provides us with a cosmic frame of reference determined by the large scale distribution of mass in the universe. The CMB has been measured to one thousandth of a degree kelvin, so blue shift in the destination direction and red shift in the origin direction give a measure of our net motion. Using this frame of reference, and allowing for Earth's, the sun's and the galactic motion in the local group, our net velocity has been measured to be 600 km/sec in the general direction of the Virgo Cluster and the supergalactic plane. The anisotropy of the CMB in effect, provides us with a local inertial frame and a modern interpretation of Mach's Principle.

    Paraphrased by me, from the book 'The Big Bang', Joseph Silk ( Astrophysics, U. of Cali @ Berkley ).
    1. "Mach's Principle" is so nebulous that no one, including Mach, has ever clearly defined it.

    2. The notion that distant galaxies have something to do with rotation sounds nice, but defies clear definition or supporting empirical data. The statement that "the CMB provides us with a cosmic frame of reference determined by the large scale distribution of mass in the universe" needs proof that is missing.

    3. Given the relativity of simultaneity and the lack of global definitions of either time or space it is not clear what "the large scale distribution of mass in the universe" even means. In most large-scale models the universe is homogeneous and so the distribution is uniform -- clearly an idealization.

    4. It is possible in principle to determine a local frame in which the CMB is isotropic. Global frames require idealizations that we know are, strictly speaking, invalid. So yes, you get a local frame that appears to be inertial -- a local inertial frame in GR is in free fall. Actually demonstrating the existence of a frame in free fall in which the CMB is isotropic would be rather difficult in practice. What this local frame has to do with a "cosmic reference frame" is not clear.

    5. I would be more impressed by a clear statement of a "modern interpretation of Mach's Principle" than by the statement that such an interpretation exists.
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    Quote Originally Posted by DrRocket

    No, your understanding, as usual, is way off base. You seem to fail to comprehend that we are talking about ALL the matter in the universe. It does not and dit not have a "heading" or a "speed".

    Maybe you should consider a different major.
    Why shouldn't it have had a heading or speed? Or vector, if you prefer? Just because it represents the complete set of all matter doesn't make it an infinite quantity, at least not in a finite universe. If it were an infinite amount, then I suppose the idea would be nonsense.


    Here's wiki on the subject we are discussing:

    http://en.wikipedia.org/wiki/Cosmic_...ole_anisotropy

    CMBR dipole anisotropy

    From the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 62722 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB) in the direction of galactic longitude l = 2763, b = 303.[57] This motion results in an anisotropy of the data (CMB appearing slightly warmer in the direction of movement than in the opposite direction).[58] The standard interpretation of this temperature variation is a simple velocity redshift and blueshift due to motion relative to the CMB, but alternative cosmological models can explain some fraction of the observed dipole temperature distribution in the CMB
    That suggests there is both a blue shift in one direction, and a redshift in the other, implying that the hot matter that emitted it was either stationary at the time of emission, or all moving in one direction together. If all frames are local frames, then we would certainly say that it had a heading and speed relative to whatever frame it is compared against.

    It just so happens I had read that article, even the specific part I'm citing before the topic was posted. I suppose I assumed you had read it also, or one like it, or maybe even one that was better, being as how you're the one accusing everybody of not having done their homework before they post. I do greatly respect your knowledge, but you need to get over yourself.
    Some clocks are only right twice a day, but they are still right when they are right.
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  80. #79  
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    If you look at pictures of the CMB, it's clear there are red and blue shifts in all directions. There is, by necessity, some point where those would even out to zero.
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  81. #80  
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    Quote Originally Posted by kojax
    Why shouldn't it have had a heading or speed? Or vector, if you prefer?
    How can it have a vector relative to nothing?
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    Quote Originally Posted by MagiMaster
    If you look at pictures of the CMB, it's clear there are red and blue shifts in all directions. There is, by necessity, some point where those would even out to zero.
    No, that is what I tried to teach Dr Rocket.

    You all have him pinned in a corner because I nailed him on the accelerating universe.

    He is either going to have to admit he is wrong to your group and that there is absolute motion and thus SR and GR are worthless flat earth theories or he will have to admit "at rest with CMB" implies you are at rest with acceleration and SR and GR are preserved.

    What will DR R choose?

    Either way, he will be wrong.
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    Quote Originally Posted by chinglu
    Quote Originally Posted by MagiMaster
    If you look at pictures of the CMB, it's clear there are red and blue shifts in all directions. There is, by necessity, some point where those would even out to zero.
    No, that is what I tried to teach Dr Rocket.

    You all have him pinned in a corner because I nailed him on the accelerating universe.

    He is either going to have to admit he is wrong to your group and that there is absolute motion and thus SR and GR are worthless flat earth theories or he will have to admit "at rest with CMB" implies you are at rest with acceleration and SR and GR are preserved.

    What will DR R choose?

    Either way, he will be wrong.
    I choose none of the above. Correctly.

    You don't know what you are talking about.

    SR and GR are just fine.

    There is no such thing as "at rest with acceleration". It is an oxymoron. You, on the other hand, are a regular moron.
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    Quote Originally Posted by DrRocket
    Quote Originally Posted by chinglu
    Quote Originally Posted by MagiMaster
    If you look at pictures of the CMB, it's clear there are red and blue shifts in all directions. There is, by necessity, some point where those would even out to zero.
    No, that is what I tried to teach Dr Rocket.

    You all have him pinned in a corner because I nailed him on the accelerating universe.

    He is either going to have to admit he is wrong to your group and that there is absolute motion and thus SR and GR are worthless flat earth theories or he will have to admit "at rest with CMB" implies you are at rest with acceleration and SR and GR are preserved.

    What will DR R choose?

    Either way, he will be wrong.
    I choose none of the above. Correctly.

    You don't know what you are talking about.

    SR and GR are just fine.

    There is no such thing as "at rest with acceleration". It is an oxymoron. You, on the other hand, are a regular moron.
    Let's see.

    You claim you are not at absolute rest with CMB with 0 diplole.

    Next, you claim you are not at rest with the accelerating universe (which is the correct answer) when you measure 0 light frequency anisotropy.

    So even though you have been check mated, what are you are rest with when you measure 0 light frequency anisotropy?
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    I think the answer, as has been stated several times, is that you aren't at rest relative to anything in particular. The CMB frame is just convenient in that you could be (nearly) at rest relative to the aliens in the next star system that are trying the same experiment.
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    Quote Originally Posted by kojax
    Why shouldn't it have had a heading or speed? Or vector, if you prefer? Just because it represents the complete set of all matter doesn't make it an infinite quantity, at least not in a finite universe. If it were an infinite amount, then I suppose the idea would be nonsense.
    Fer crisake, the CMB is isotropic, presumably everywhere with respect to some natural local coordinate frame, and with respect to the idealized decomposition of spacetiome used in most cosmological models. The distribution of mass, on the largest scale is uniform, and all mass (at the largest scale) is receding radially away from every point in the universe. What in the hell would you propose for a "heading" ?

    Are you sure that you actually passed any of those physics courses ? At what university -- that would be a good place to avoid.


    Quote Originally Posted by kojax
    Here's wiki on the subject we are discussing:

    http://en.wikipedia.org/wiki/Cosmic_...ole_anisotropy

    CMBR dipole anisotropy

    From the CMB data it is seen that our local group of galaxies (the galactic cluster that includes the Solar System's Milky Way Galaxy) appears to be moving at 62722 km/s relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB) in the direction of galactic longitude l = 2763, b = 303.[57] This motion results in an anisotropy of the data (CMB appearing slightly warmer in the direction of movement than in the opposite direction).[58] The standard interpretation of this temperature variation is a simple velocity redshift and blueshift due to motion relative to the CMB, but alternative cosmological models can explain some fraction of the observed dipole temperature distribution in the CMB
    That suggests there is both a blue shift in one direction, and a redshift in the other, implying that the hot matter that emitted it was either stationary at the time of emission, or all moving in one direction together. If all frames are local frames, then we would certainly say that it had a heading and speed relative to whatever frame it is compared against.

    It just so happens I had read that article, even the specific part I'm citing before the topic was posted. I suppose I assumed you had read it also, or one like it, or maybe even one that was better, being as how you're the one accusing everybody of not having done their homework before they post. I do greatly respect your knowledge, but you need to get over yourself.
    Which says only that the local proper motion of the Earth is such that the CMB is not quite isotropic wirh respect to an Earth-centered reference frame. This is rather well known.

    Of course you can compare the frame centered on the earth, or the solar system, or the galaxy with respect to a frame in which the CMB is isotropic, but that is both trivial and misses the point.

    The Wiki article mis-speaks in calling the frame in which the CMB is isotropic as being a "rest frame" for the CMB -- again the CMB is a bunch of photons. You cannot be at rest with respect to photons.

    Wiki is useful, but not definitive or even always accurate.

    Next time read the article and then take the time to understand it.
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