Right Handed Spiral Galaxies are Preferred

Discussion in 'Astronomy, Exobiology, & Cosmology' started by danshawen, Nov 8, 2015.

  1. The God Valued Senior Member

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    3,546
    What is this?

    ......you are probably attempting to interpret the 'homogeneous' aspect of Dark Energy cc model. But don't you think some more reading about Dark Energy nature will help you and will keep you a bit away from making such word salad.
     
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  3. paddoboy Valued Senior Member

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    Forum clown? As you aptly described yourself?

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  5. Schmelzer Valued Senior Member

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    5,003
    I may have misunderstood, but I do not understand how you, in this case, distinguish "velocity through space" from other velocities. All I can do is to guess what you mean, and if something has no velocity through space, it seems reasonable to interpret this as rest. So, please explain the meaning of having some "velocity through space".
     
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  7. origin Heading towards oblivion Valued Senior Member

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    11,888
    The farthest galaxies that we observe have a recession velocity approaching the speed of light. That recession velocity is a result of the expansion of space. That means the recession velocity of that distant galaxy is not from movement through space. The milky ways movement through space is about 360 kps in the direction of the Virgo super cluster, relative to CMB. A galaxy 13.1 billion ly away would observe our recession velocity to be approaching 300,000 kps. Recession velocity is the apparent velocity for an observer due to movement of space as space expands.
     
  8. Schmelzer Valued Senior Member

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    5,003
    Nice, but it does not explain what is the "movement of space". Once, it seems, the galaxy can follow this "movement of space" (can it?), it should be some well-defined velocity, defined in each point (is it?).

    Of course, there is, at every point in the universe, the natural preferred velocity of the local CMBR frame, and the actual velocities relative to this natural preferred velocity will be of a similar order as for ourself. But from point of view of relativism, this preferred velocity is quite irrelevant, has no physical importance, but is simply the average velocity of the matter in our local environment (even if this "local" covers all the observable universe).

    So, naming this "movement of space" is nonsensical from point of view of GR in spacetime interpretation. You would have to rely on another interpretation of GR to make sense of this phrase.
     
  9. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    23,198
    I said: "Quite probably at about the same rate every where at the same time, but that AFAIK is not a known fact. It may be faster where "dark energy" is more concentrated, ..." and you say that is wrong. Why?

    Do you have some reason to think the density of DE is a constant through out the entire universe? Even if it is, I am still correct, not wrong. I said that universal uniform density of DE was "quite probable" but not AFAIK a known fact.

    If you are going to tell me I was mistaken on this "one issue" you should have more to back that up than just your opinion.

    I note the obvious:
    Gravity is in the modern view, a force of spacetime, but not a constant. Why must the force of DE be constant as you assume?
     
    Last edited: Nov 10, 2015
  10. The God Valued Senior Member

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    3,546
    There are a few models for Dark energy [http://arxiv.org/pdf/1212.4726v1.pdf].

    The most prevalent ones being CC (lambda based) and quintessence, lambda based offers homogeneous density nature of dark energy, while quintessence model is variable. But nonetheless both or rather none offers constant force type, whatever that means.
     
  11. origin Heading towards oblivion Valued Senior Member

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    11,888
    Recession velocity is discussed introductory astronomy! Do you really know so little about cosmology or are you just feigning ignorance?

    Here is a simple lecture from a college Astronomy 162 course. If you need some more help to understand I can get you some more links, let me know.

    From the lecture:

    What is the recession velocity?
    • NOT motion through space...
    • Expansion of spacetime: galaxies carried along.
     
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  12. The God Valued Senior Member

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    3,546
    I am getting a sense that you have some different ideas about this expansion of space......I am certainly unable to appreciate this uncontrolled expansion as explained in present form with possibility of recession velocity > c in remotest cases. Simple physics tells that anything which requires energy cannot violate SR. Something missing here too?
     
  13. Schmelzer Valued Senior Member

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    5,003
    So what?
    Thanks, and if you need a grammar, let me know.

    Note that if you would simply make some stupid error, I would probably not care at all about this. What has motivated me to comment was that you make a quite common error. An error shared also by your popular lecture:
    The error is that in GR, at least in their spacetime interpretation, there is no such animal as a distinction between motion through space and motion of spacetime. There is even no such thing as a "motion of spacetime". Spacetime is defined by the fields \(g_{mn}(x,t)\), but none of these functions defines a velocity of spacetime or something else usable to identify a "motion of spacetime".

    You can have, in other interpretations of the GR equations, some expressions which could define something like a "motion of spacetime". For example, in my ether interpretation of the Einstein equations of GR, there would be an ether velocity, defined by \(v^i(x,t) = g^{0i}(x,t)/g^{00}(x,t)\) in the preferred coordinates. And, of course, one can, with this interpretation as the background, also name this velocity as the one defining the "motion of spacetime" if one prefers such a misleading (in this interpretation) notion. Remarkably, the coordinates preferred by scientists are almost the same as those preferred by the ether interpretation, so the result would be, indeed, that the galaxies move together with the ether (the "spacetime").

    But from point of view of the spacetime interpretation a claim containing "expansion of spacetime" or "motion of spacetime" is meaningless, and an indication that the writer or does not really care about accuracy (quite typical for popular explanations) or simply does not know what he is talking about. In this case, the typical wish is to prevent misunderstandings which are much more wrong. Like the application of SR ideas ("recession velocity is greater than c, horrible!!!!!11!") in the domain of GR. For example here:

    Yes, you are missing that everything with expansion is not about SR at all but about GR (or some other metric theory of gravity).

    Then, even in SR you can use whatever coordinates you like, and in whatever coordinates you like the velocities may be whatever you like too.

    But, of course, scientists are lazy, and, therefore, use simple coordinates. The simple coordinates they use for an expanding universe are coordinates where the metric looks like \(ds^2 = d\tau^2 - a(\tau)^2 (dx^2+ dy^2 + dz^2)\). And in these coordinates all the galaxies everywhere have (coordinate) velocity 0, defined by the trajectory \(x=x_0, y=y_0, z=z_0, \tau=\tau\).

    (And if you apply the formula \(v^i(x,t) = g^{0i}(x,t)/g^{00}(x,t)\) for the ether velocity to this metric, you will find that it is also zero. So, the error made in this case - to sell the ether velocity of the ether interpretation they usually don't even know, but which is the only natural velocity here, as a diffuse "spacetime motion", is negligible in comparison with the "oh, recession velocity > c!!!!!" error.)
     
  14. origin Heading towards oblivion Valued Senior Member

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    11,888
    So you do not accept that the universe is expanding or that there can be superluminal recession velocities?
     
  15. The God Valued Senior Member

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    3,546
    Good one.

    Both these papers suggests possibility of recession velocity > c, and both the papers frown application of SR to limit the recessional velocity to c with a rider that it is not some kind of kinematics.

    You missed my point, i did say that this accelerated expansion requires energy, so called dark energy, so how can it be said that recession at > c does not violate SR. Expsnaion is all about GR, but can you be choosy that SR can be roughshod here, Both the papers rule out this expansion as non kinematics type, how can it be non kinematic when expansion energy is proposed?


    http://arxiv.org/pdf/astro-ph/0011070v2.pdf
    http://adsabs.harvard.edu/full/1977QJRAS..18..242M
     
  16. Schmelzer Valued Senior Member

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    5,003

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    Superluminal recession velocities are irrelevant coordinate velocities, moreover of coordinates nobody uses. But these recession velocities are, of course, superluminal for sufficiently large distances.

    And I prefer an interpretation in which galaxies remain on their places but our rulers shrink, so that we measure increasing distances between galaxies. But this is only a different interpretation. This does not mean any disagreement about anything measured. The same distance, measured with shrinking rulers, looks increasing in time, a triviality. Thus, if in your preferred interpretation the rulers cannot shrink, then, no problem, the universe is expanding.
    Sorry, but the accelerated expansion does not matter at all. If the universe is flat in space, the expansion may even decelerate, there will be always points far away which have now a velocity far greater than c. The only question if we can see them now. This may be not possible, simply because of insufficient time after the Big Bang. So, the universe we observe now is finite. So, one can compute the recession velocity of the oldest galaxies we can observe. Some time in the past their velocity would have been below c, and the answer would be also different if one would ask about the velocity now and then. AFAIU (I have never cared) what we actually see far away has recession velocities > c in above meanings.

    Whatever, an interesting point here is that even if such things would not be visible now, they would exist now and become visible in the future. Except in the case of a large enough acceleration. Then it would be possible to have a BB solution where 1.) we have a limit of the observable universe, not only of the part we see now, but even of the part we will see in future (this is a general property of accelerated expansion), and 2.) this part could be small enough that we would never see something with recession velocity > c.

    Then, accelerated expansion of the universe is something completely different from acceleration in a SR world which requires some energy and so on. It is a name for a"(tau)>0. The term in the Einstein equations which leads to such an effect has nothing to do with F=ma.
     
  17. origin Heading towards oblivion Valued Senior Member

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    11,888
    OK.
    That interpretation of yours is both odd and at odds with the physics community. I prefer the interpretation that that is held by the overwhelming majority of the physicist, which is that space is expanding.
     
  18. The God Valued Senior Member

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    3,546
    For ease, extract from one of the papers stated above..

    "The Friedmann-Robertson-Walker (FRW) metric [8] describes an homogeneous, isotropic universe. We are interested in only the radial components: ds2 = −c2dt2 + a(t)2dχ2. Radial distance along a constant time slice (dt = 0)
    is given by: D = aχ. Differentiating this physical or proper distance gives a
    two component velocity:
    vtot = ˙aχ + aχ˙= vrec + vpec"

    Shrinking of ruler when both peculiar and recession velocities are present can yield anomalous results. Secondly the differentiation is on proper distances, you cannot throw the recession velocity to dustbin by stating this as coordinate system gimmic. Moreover both the papers distinctly talk of > c recession velocities with GR perspective.

    Secondly in our local group, it is proposed that peculiar velocity dominates the recession velocity, some kind of neutralization, can we neutralize a non kinematic expansion with a kinematic effect (Gravity)? like Milky way and Andromeda heading towards each other, because peculiar velocity dominates. Thats why I said something is amiss here?

    Ps: It is not that I am a fan of this > c expansion, but I am not able to decipher whether you differ with mainstream on this or you are trying to establish that this is a popular faulty notion. You are not the one who will make mistake in understanding mainstream or will interpret it differently mistakenly and argue like a few fire brand posters here.
     
  19. Billy T Use Sugar Cane Alcohol car Fuel Valued Senior Member

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    23,198
    That works fine for linear functions, as you illustrate but not for measurements like density. For example the density of lead by menory is 13.6 gm/cc but when the ruler is 10 times smaller, each edge of that same old 13.6 gm lead cube is now 10cm and the volume of that 13.6gm cube of lead is now 1000 times greater so lead's density would fall to 0.0136 grams/cc. (The 13.6 grams now fills 1000 cc.)

    It is not just "interpretation" but a false POV unless 13.6gm becomes 13,600 grams. etc. Thus you need to postulate mass is a function of time also and to mention just one difficulty: Constantly increasing mass (and gravity values) would cause, is all the current satellites would crash.
     
    Last edited: Nov 10, 2015
  20. Schmelzer Valued Senior Member

    Messages:
    5,003
    Given that you have not proposed a single idea why my interpretation is odd, the only point is that the mainstream prefers another one, which reduces you to the paddoboy level of a mainstream follower. But, ok, that's your choice.

    But, unfortunately for you, the mainstream spacetime interpretation does not tell us anything about "space is expanding". This is nothing but sloppy speaking. Which is, of course, in this case also mainstream sloppy speaking, or accepted sloppy speaking. But it is nothing but sloppy speaking. Because in a four-dimensional spacetime all you have is - the four-dimensional spacetime. Without any splitting into space and time. In this sense, it does not even make sense to speak about space doing something like expanding.

    On the other hand, for mainstream followers it makes not much difference anyway. Once the mainstream is using such sloppy speaking, so what, one can use it too.
     
  21. Schmelzer Valued Senior Member

    Messages:
    5,003
    Nice point. What you forget is that all the things measured by physicists are well-defined by prescriptions about how to measure them. These prescriptions, of course, depend on using, in particular, standard rulers (as well as other standards, defined also by measurement prescriptions, which also depend on rulers, and so on). So, of course, if the rulers shrink, these other things change too. So, the same amount of matter which was 13.6 g in the situation with undistorted rulers may have a quite different weight with distorted rulers, already for the simple reason that the measurement device will be a different one, at least much smaller, now. In the simplest case you use, for example, a standard gram defined by a cube of x m of gold to measure mass. That this changes together with the rulers is obvious.

    How will all these measurement results be modified? This is a nontrivial question.

    But for all the matter we have, the theory we use to describe it is a covariant one. This is a postulate in GR. And such a covariant theory prescribes how to transform all the equations which describe the measurement with undistorted rulers into a measurement with distorted rulers. And the very point of covariance is that this is done in such a way that we cannot find out by observation that the rulers have been distorted.

    Of course, an ether interpretation of GR has to use the same postulates as GR too. It describes them possibly in other words, but these words do not change the equations, which remain covariant.
     
  22. origin Heading towards oblivion Valued Senior Member

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    11,888
    It is odd or more accurately it is absurd. Obviously (well I suppose it is obvious) not just the rulers are shrinking. Everything must be shrinking unless rulers have some special place in the cosmos. So that means that the earth must becoming more dense. The sun is becoming more dense as well so that would mean that the fusion at the core must be increasing - is that the cause of global warming??

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    That also means that the nucleus of atoms are contracting and the electrons are getting closer to the nucleus of the atom. So are the neutrons and protons shrinking or just getting closer together?

    So in the past 100 years the meter has shrunk about 7 microns!

    Now we have seen that the expansion of the universe is accelerating - oh no, that means that the shrinking rulers are shrinking faster and faster!

    Stop being absurd - resist the dark side.

    I couldn't help but be reminded of this Zoolander scene.

     
    Last edited: Nov 10, 2015
  23. Schmelzer Valued Senior Member

    Messages:
    5,003
    No. The shrinking rulers interpretation is nothing but interpretation. The physics remains unchanged. So it cannot lead to anomalous results not present in the mainstream interpretation.
    So what? Again, SR and GR are different theories. SR allows to derive global restrictions for velocities from local ones, because the local restriction v<c is the same everywhere, so that you can integrate it without problem and obtain a global restriction for relative velocities. In GR, this does not work, and global relative velocities have no such restrictions.
    Of course, in the center the recession velocity is zero by construction. Not really a hard job for peculiar velocities to dominate it.
    Ok, this is indeed subtle.

    The mainstream uses, to describe the expanding universe, the FLRW coordinates \(ds^2 = d\tau^2 - a(\tau)^2 (dx^2+ dy^2+dz^2)\). This is simply because these coordinates are preferable out of simplicity. Part of this simplicity is that in these coordinates space is homogeneous and isotropic even in its expression in coordinates. If the universe would be open or close, with nonzero spatial curvature, this would be different (one would use an ansatz which is not homogeneous in coordinates, but homogeneous as a metric), but observation suggests that we do not need this.

    Now the naive layman hears about an expanding universe, and the image he natural uses would be similar to an explosion, which would have a center. There is no such preferred center, nor in the mainstream interpretation, nor in my ether interpretation. In above interpretations, the universe is homogeneous. What corresponds to this misleading picture is all this recession velocity business. The recession velocity is a coordinate velocity in coordinates of type \( ds^2 = (d\tau - v_{rec}(r)dr)^2 - (dx^2+ dy^2+dz^2)\) (no warranty for this expression, too late and too high \(C_2H_5OH \) level, sorry) which nobody uses. I agree with the mainstream that to use these coordinates is stupid (other coordinates are simpler and better), and that to cry "for big r \( v_{rec}(r) > c\), horrible!!!!111!!" is completely off because this number means nothing in GR.

    Now comes the problem of every scientist of what one can explain a layman and what is too complicate and subtle. To explain him that there is no such animal as a center of the explosion of the Big Bang is something one can try to explain. And there is the balloon picture which can be used to illustrate it, even if it works only for a closed universe. But the point I have explained above, that GR restricts only local velocities, and for different points these different restrictions defined by different metrics \(g_{mn}(x,t)\) have nothing to do with each other, so that one cannot obtain any global restrictions for \(v_1(x_1,t)-v_2(x_2,t)\), contrary to SR where one can restrict this relative velocity, is, I would guess, to difficult for a layman. In this sense, I have not even a problem with a mainstreamer who does what the mainstreamers do, and become slightly inaccurate if they explain something to laymen.

    But even if I understand very well what justifies inaccuracies in popular descriptions, they remain inaccurate, thus, wrong. What is the inaccuracy here? The solution is homogeneous. Correct. One uses a picture - the expanding balloon - which preserves the symmetry, because it is also a homogeneous one. Acceptable. One describes this with a language which suggests that there is some animal named "space" or "spacetime" which expands in the same way as the balloon - error. Better, not really an error, but a use of another interpretation, something similar to an ether interpretation, where we have a well-defined velocity of the background, similar to the material of the balloon.
     

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