User talk:Ems57fcva/archive 2

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[edit] Time warping and time dilation

It kind of does occur during the turn-around phase. --EMS | Talk 16:18, 25 May 2005 (UTC)

Well, of course Stella shifts through Lorentz frames during the turn-around phase. During inertial motion the time-relationship of an object with its surroundings does not change, but during acceleration it does. I rather like the expression 'Lorentz boost' for the process of shifting from one Lorentz frame to another.

Recapitulating the basics: a shift from one Lorentz frame to another, does not only change the velocity of an object, it does not only change the space-wise relation with the surroundings, a Lorentz boost also changes time-wise relationship with the surroundings. (I didn't bother to recapitulate this before because it is so basic to relativity)

On the Time dilation talk page you wrote:

Gravity affects time through acceleration. --EMS | Talk 04:43, 26 May 2005 (UTC)

I suspected this is your view of GR, but here is the first place that I see you state it explicitly.

[...] since being accelerated means constantly switching inertial frames of reference, your view of "at the same time" keeps being changed and so you find that clocks at higher potentials are ticking faster and clocks at lower potentials are ticking slower.

That describes how I understand it in special relativity: if you draw planes of simultaneity in a space-time diagram then during acceleration the succesive planes of simultaneity are tilted with respect to each other.

I can see how this concept of accelerating with respect to the local inertial frame of reference can serve as a bridge between special relativity and general relativity. I have looked at that interpretation, but I found it on the whole unsatisfactory.

This is nothing more than Einstein's 1907 & 1911 view of time dilation in a gravitational field, done with the aid of the equivalence principle. Of course it is unsatisfactory. It was to Einstein too. You cannot go from SR to this view of inertial acceleration towards the center of a massive object without curvature. However, the goal was not to present GR is all of it's glory. It was to answer the question of how gravity causes time dilation. You don't need curvature for that.

To stay at the same distance from the center of the Earth, you are always being accelerated upwards in the viewpoint of relativity. (This acceleration is due to massive objects such as the Earth warping spacetime. BTW - You can choose not to be accelerated: The result is freefall.) --EMS | Talk 04:43, 26 May 2005 (UTC)

The Earth warps spacetime geometry. Because of this curvature of space-time geometry, an object that is stationary on the surface of Earth is accelerating with respect to the local inertial frame of reference. In other words: because of the curvature of space-time geometry, the local inertial frame of reference is accelerating towards the center of the Earth as seen from a frame of reference that is stationary with respect to the center of the Earth.

You describe that because of the acceleration with respect to the local inertial frame of reference, there is time dilation with respect to locations higher in the gravitational potential.

The warping of spacetime is mainly warping of time; in most circumstances the space-warping is negligable compared to the time-warping.

No it is not! Space is warped along with time, and by the same magnitude. Just look at the Schwarzschild metric:

$ds^2 = (1 - 2m/r)\, dt^2 - (1 - 2m/r)^{-1}\,dr^2 - r^2 \left (d\theta^2 + \sin^2 \theta \, d\phi^2 \right ).$

If there was no wapring of space, the

d r 2

coefficient (commonly refered to as

g r r

) would be -1. Instead it is the reciprical of

g t t

. The effects of space also being warped are seen in the amount of the gravitational bending of light, non-Newtonian orbital perihelion precession, and the Shapiro time delay.

According to your description gravitational time warping is to be seen as the first cause, and you describe gravitational time dilation as a final effect of that. The question then is: is there a difference between gravitational time warping and gravitational time dilation? Can this differnce be measured?
--Cleon Teunissen | Talk 09:38, 26 May 2005 (UTC)

See Einstein's 1911 prediction of the deflection of light passing the Sun, whre he assumed only time dilation as a cause for it instead of the full spacetime curvature. He got only 1/2 of the correct GR answer.

--EMS | Talk 14:47, 26 May 2005 (UTC)

P.S. Time warping is an oxymoron. It is impossible to curve a one-dimensional manifold.

--EMS | Talk 14:50, 26 May 2005 (UTC)

P.P.S. This is relativity anyway. You cannot treat time as something that is independent of space to begin with. --EMS | Talk 21:16, 26 May 2005 (UTC)

[edit] How to interpret the Schwarzschild metric.

Space is warped along with time --EMS | Talk 14:47, 26 May 2005 (UTC)

Yes, it was an error to use the expression 'time warping'. It's spacetime warping, space and time are equally affected.

I took the heuristic very literally. I equated the spacetime warping with its final effects. That is: I took the most symmetrical situation: a non-rotating planet, and clocks situated in towers of different heights, and I equated the spherically symmetrical time dilation pattern that can be measured in those circumstances with "time warping". That was incorrect.

Flow model
I came across a astrophysica article wit an intriguing interpretation of the Schwarzschild metric, River model of the Schwarzschild metric by Andrew J S Hamilton and Jason P. Lisle.

As we show in §II, the Gullstrand-Painlevé metric provides a delightfully simple conceptual picture of the Schwarzschild geometry: it looks like ordinary flat space, with the distinctive feature that space itself is flowing radially inwards at the Newtonian escape velocity.
[...]
The picture of space falling like a river into a black hole may seem discomfortingly concrete, but the aetherial overtones are no more substantial than in the familiar cosmological picture of space expanding [...].

Professor Max Tegmark of MIT has incorporated the river model in his General relativity teaching MIT Course 8.033, Schwarzschild metric & black holes

A natural interpretation of equation (2) (Hamilton 2004) is that space is flowing radially inward [...] and that particles can travel through this moving space according to the laws of special relativity [...] This is analogous to the FRW coordinates, where the “river” of space was expanding rather than flowing.

The background philosophy, as I understand it, is that the mathematics of General Relativity does not intrinsically enforce one interpretation or the other, so the interpretation of the theory is seen as a heuristic tool. The demands on the interpretation are that the interpretation is consistent with the mathematics, and free of self-contradiction.

As I understand Hamilton and Tegmark, the flow model is a heuristic tool, it allows a set of features of curved spacetime to be arranged in a coherent picture. As I understand it the flow model heuristic tool is seen as equally suitable for interpretation of the theory as other heuristic tools that are currently in use.

I find the 'flowing space-time' interpretation quite satisfactory. Take two observers: Hugh, who is high in the gravitational potential, and Lowe, who is low in the gravitational potential of the same planet. This planet is their primary. If they want to calculate the rate of proper time of Lowe with respect to the rate of proper time of Hugh, then the river model describes that Lowe is traveling more distance than Hugh (as expressed in proper time of Hugh), which corresponds to less proper time for Lowe compared to the proper time of Hugh.

I do not care much for the flow model myself. I have played with it as a gedanken, but in the end how does the extra space get created for the flow? Where does the flowed space go to?

When you get down to details, the flow model is not needed. For example, start walking on the surface of the Earth due east from a position north of the equator. If you only place on foot in from f the other, following the geodesic path, you will start heading more and more to the south. So where did this "southness" come from? Is it a "flow" from the north? Of course not. The surface of the Earth does not flow in response to you. Instead it is your motion along the geodesic that does the change.

In spacetime you are never at coordinate rest: You are always moving through time. The is the real flow, carrying us along from one moment to the next, carrying our atoms through eternity (or at least between major calamaties such as supernovas and nuclear explosions). Freefall is our inertia being deviated downwards as we go forwards through time due to the nature of curved spacetime. That way, no spatial flow is needed.

I do admit that the space flow model has some value. At the least, it gives you a framework for seeing how inertial frames of reference actually behave in a curved spacetime. However, I am beyond the need for something like that. --EMS | Talk 16:34, 28 May 2005 (UTC)

A flood of comments
I'm sorry about the way I have been flooding you with comments over the past months. Your Talk page is huge now. (My browser, Firefox, has problems displaying it.) I kept seeking contact because I just couldn't believe that communication can collapse so badly.

I will try hard to stay away from your Talk Page. Discovering that two leading astrophysicists endorse a flowing space-time interpretation resolves much of my uncertainties. I have a pretty good idea now of how I will explain the physics of general relativity to other people. (But not on wikipedia; I think explaining relativity is impossible on wikipedia, too many cooks spoil the broth.)
--Cleon Teunissen | Talk 14:08, 28 May 2005 (UTC)

In the meantime I have archived most of the past postings. I hope that your browser is happier now. --EMS | Talk 16:34, 28 May 2005 (UTC)

[edit] reply from pdn

Hi. I did not like that reference

"Reflections on Relativity (http://www.mathpages.com/rr/rrtoc.htm)." MathPages. Accessed on May 29, 2005A. An idiosyncratic semipopular introduction to some concepts of general relativity.

at all, but I hesitated to delete something somebody put there. The reference seems, to me, to be largely someone's attempt to show how one can arrive at GR after exploring many alternate paths. But it is just a recasting of one person's experiences. It will not help others, most of whom can't follow the labyrinthine reasoning. Sorry you do not fully believe black holes have been discovered. Pdn 02:28, 17 Jun 2005 (UTC)

Well, I might delete that odd gabby reference. Back to black holes. They are old-hat now (nothing to do with the man who mistook his black hole for a hat). Where's a reference to something recent and non-crank against them, please?

I will provide one to a book by Earman. That is fairly recent, and does a good job of expressing the misgivings. I will do a search and see what else I can find. Recent works the I have heard about include a work on how QM can keep a black hole from forming (which I personally classify under "how GR is not GR"), and another on how GRBs can be explained as the formation of a quark star. However, you need to realize that there is a certain amount of "crank"-iness in any anti-black-hole view or writing. The black hole is a theorem of GR! So I am essentially saying that GR is wrong. Personally I see GR as being correct enough that whatever the next theory is it must be based on it. However, I am also certain that there is something beyond it needing to be found (if I am not lucky enough to have found it, but since my original research is just that I am loathe to talk about it here).

Perhaps the big case against GR comes not from the black hole but instead for the inconsistency between it and QM. QM is much better verified than GR. The expectation really is that GR is what will give eventually, but noone can say for certain how it will give.

By the way, the stuff higher up on your page about space or time being curved is a bit specialized, I'd say, 'cause I hate to say "wrong.". There are some cases like static solutions (Schwarzschild, Reissner-Nordstrom, ...) where you can uniquely split space and time and define a world-time.

True, but what about the curvature? There is no curvature for a 1-dimensional manifold as time alone would be. Just try to compute it's Riemann tensor: For one dimension there can only be one value for it, and since the Riemann tensor is antisymmetric under certain exchanges of indices, that value must be 0.

So what is curved really is spacetime. Not space alone, and most definitely not time alone.

In more general cases, there is no global splitting possible and you would have no way to separate space curvature and curvature in the timelike dimension. Even in the Kerr metric, you have cross-terms between phi and t, so they are intertwined. Also remember any local observer can establish a "boost" to a local Lorentz frame of different velocity, and in that frame the constant-time sections are different. Wrong? Well, I mean that you are using one form of the Schwarzschild metric, but the are isotropic forms, and a form where the ingoing and outgoing null lines are used as axes (Kruskal-Szekeres metric [1])Pdn 03:57, 17 Jun 2005 (UTC)

As any observer always exists in a local Lorentz frame, a splitting of space and time can always be done (and as part of my research I have to do that ironically enough). But from a standpoint of curvature in GR, so what? I repeat: It is not space and/or time that is curved, but instead it is spacetime. --EMS | Talk 14:54, 17 Jun 2005 (UTC)

Sorry - I thought I was reading that you separated space and time curvature, but I guess it was someone else writing on your page. About that reference to a "web course" by Kevin Brown I think (as I wrote on Cleon Teunissen's page) it is mostly hogwash - so maybe someone will delete it. I changed the comments once and they were changed back so I am tired.Pdn 04:55, 18 Jun 2005 (UTC)

*Sigh*. Cleon tries, and is learning, but I think he understands relatively (no pun intended) little for this stuff. He may respect Kevin Brown, but that does not mean that this work deserved to be listed. In the meantime, that link has recently gone stale. So maybe this is a moot issue anyway.

I do not find the link stale: [2] . Are we on the same page (no pun)? The same "mathpages.com"? We should be so lucky it goes stale. Or more stale. There is a lot of wrong science or at least very unlikely science out there and it attracts the innocent. For example there is something called The Wu-Li Dancing Masters which promotes a hidden agenda of the Bohm hidden variables "theory" (ruled out I believe by Alain Aspect and others). There is probably not much wrong in the "mathpages" link, just fluff. Well, there are some odd remarks:"The real content of Einstein's principles is that light is an inertial phenomena (despite its apparent wavelike nature). " Pdn 02:59, 19 Jun 2005 (UTC)

I cannot get to it. I hit your link, and I get "article not found". I ask for mathgapes.com itself, and I get "access forbidden". To me, the site is down. If you like, you can ask the webmaster there what might be causing this. However, I repeat that for me it really is not there. --EMS | Talk 03:12, 19 Jun 2005 (UTC)

[edit] Re: Earman

I think it is getting too far afield and I regret asking for a reference, but thanks (I looked up Earman a bit on the Web).Pdn 04:57, 18 Jun 2005 (UTC)

It is afield. For most people, the black hole being a theorem of GR is good enough for them. That is good enough for me.

This discussion has made it so that documenting the difficulties with the black hole is now on my to-do list, but it is far down on the list of projects. Even though I hate it, I am not here to fight the black hole. Instead I am here to help fix up the GR part of Wikipedia, and to present the "Einsteinian" view of things in the process. Unlike others who seek to change GR, I have come into it having majored in physics, and with a great respect for the scientific community and it seems an ever greater respect for GR itself as time goes on. --EMS | Talk 02:47, 19 Jun 2005 (UTC)

[edit] Searching the web for info

Could you give me a hand with something? - black hole electron. [...] you have a knack for finding relevant sources. --EMS | Talk 03:54, 19 Jun 2005 (UTC)

Hi EMS, I appreciate the trust that you put in my searching.
Web-searching is tedious business, it takes a lot of motivation. The 'black hole electron' doesn't get my blood racing, I'm afraid, so I guess I won't be looking into that matter.

The aspect of relativity that attracts my attention these days is time dilation. Keep watching the Talk:time_dilation page. --Cleon Teunissen | Talk 18:51, 19 Jun 2005 (UTC)

[edit] reply on wrong page, I think

Hi You wrote: "I assure you that the physics as viewed in a rotataing/accelerated frame of reference has meaning, even if the bottom line is that the same results are obtained in either case. The ability of use an accelerated viewpoint is especially important in GR, where you can be in a spaceship moving intertially, but the effects of gravitation are such that the objects distant from you are being accelerated, and effects such as gravitational time dilation and red/blue shifting are none-the-less revealing themselves.

Relatitivy fundamentally is about how perceptions of the same events are changed by virtue of being in different frames of reference. In essesnse, changing frames of reference is a gedanken is nothing more than putting yourself is someone else's shoes. In that regard their state of motion (be it inertial or not) should not matter. -"

I agree completely. The assertion "My personal opinion is that the proper way to interpret the physics of the Sagnac effect is to look at the physics from the perspective of the local inertial frame of reference. I prefer the perspective of the local inertial frame of reference because that is the most symmetrical point of view.

By contrast: as seen from a point of view that is accelerating the speed of light appears to be non-isotropic, and I am rather suspicious about that.

I very much doubt that describing physics from an accelerating point of view has any meaning at all. EMS insisted that in the Sagnac effect article the physics should also be described as seen from a rotating frame of reference. I tend towards the opinion that describing physics from the point of view of a rotating frame of reference does not carry any physical meaning." was written by Teunisson, so it might be better to reply to him.

I will think more about the Michaelson-Morley experiment as related to acceleration. I think you are right - this cross dialogue is going too fast. But the idea was to detect differences in the "aether drift" as the apparatus turned (with the Earth). If it were in inertial motion the supposed drift would not show up as a fringe shift. A rotating reference frame is accelerated. Pdn 00:41, 21 Jun 2005 (UTC)

[edit] Physics and point of view

I assure you that the physics as viewed in a rotataing/accelerated frame of reference has meaning, even if the bottom line is that the same results are obtained in either case. The ability of use an accelerated viewpoint is especially important in GR, where you can be in a spaceship moving intertially, but the effects of gravitation are such that the objects distant from you are being accelerated, and effects such as gravitational time dilation and red/blue shifting are none-the-less revealing themselves.

[...] the physics as viewed in a rotataing/accelerated frame of reference has meaning [...]

To some extend it is a moot point; the same results are obtained either way. That implies that the matter cannot be decided by experiment, and it is not clear whether a matter that cannot be decided by either logic or experiment is worth scratching one's head over.

I choose to apply Occam's Razor: in this particular area I restrict my hypotheses to the minimal set of hypotheses that suffices to account for the physics taking place.

Relativity fundamentally is about [...] putting yourself in someone else's shoes. --EMS | Talk 21:08, 20 Jun 2005 (UTC)

I know what you mean by that, but personally I prefer to avoid any formulation that carries with it the suggestion that in relativity theory active participation of the observer matters for the physics taking place.

I prefer to formulate in such a way that it is clear that if the observers do not put themselves in the other guys shoes the same physics will take place. Whether the observer understands the physics or not, the same things will happen.

This is the crux of what I am saying. It is all the same, even though it is being viewed differently by the different observers. I do know that you know that. However, some of the subtler implications of that still escape you.

What I find intriguing about relativity is that there are the invariants, like the invariant space-time interval, that seem to suggest that there is an "arena" where these invariants exist, and that this is the true arena of physics. But every physical interaction, say a photon being detected and its frequency determined, occurs in such a way that space and time are split in a particular way. A photon may be emitted with an energy that corresponds to a light-wavelength of, say 400 nanometer, and the same photon can on absorption be detected to have an energy that corresponds to an 800 nanometer light-wavelength. For different observers space and time are split up differently, and we call that difference 'relative velocity'. I am inclined to think that the invariant qualities are closer to the true physics than the measurements, that are always subject to a particular split of space and time.

You seem to miss the point again. Both wavelengths are valid. It is just a matter of which frame of reference you are in.

With regard to the invariants, do realize that these are often locally measured or experienced quantities. For example, the invariant interval of a timelike path is the time experienced by a clock that travels that path. A clock at rest next to me may tick off 10 seconds along a world-line. For an observer moving at 87% of the speed of light, that same world like has a coordinate temporal length of 20 seconds. However, that same observer must also find that my clock ticked off only 10 seconds along it. So everyone has to agree that my clock ticked of 10 seconds along that world-line. However, they can disagree of the parameters of that world-line.

My main point if that there is an underlying physics to this, and it is no more valid in one frame than another, although there often is a frame where it is described the easiest.

I am inclined to believe that relativity is fundamentally about the properties of Minkowski space-time, and more generally, about the properties of curved Minkowski space-time.

The ability of use an accelerated viewpoint is especially important in GR, where you can be in a spaceship moving inertially, but the effects of gravitation are such that the objects distant from you are being accelerated, --EMS | Talk 21:08, 20 Jun 2005 (UTC)

Yes, of course the ability to perform transformations between frames that are being accelerated with respect to each other is vital. In order to model the transmission of timing signals from a GPS satellite to a reciever on the ground, the following frame of reference is used: the non-rotating frame of reference that is co-moving with the Earth in its geodesic-following motion around the Sun. Both the GPS satellite and the reciever are moving with respect to that inertial frame of reference, so appropriate transformations need to be applied, and general relativity provides these transformations. --Cleon Teunissen | Talk 08:18, 21 Jun 2005 (UTC)

The ECRF [Earth-centered (inertial) Reference Frame] is a well known simplification for analyzing things in the vicinity to the Earth. However, its use does not invalidate the calculations done for an observer standing on the surface of the Earth. The issue is one of complexity, not correctness. --EMS | Talk 23:04, 21 Jun 2005 (UTC)

[edit] Pdn's criticism of Reflections on Relativity

As for the boson/photon business, I need more context to be sure of the mix-up, --EMS | Talk 17:31, 16 Jun 2005 (UTC)

I looked it up. As it turns out, it was Pdn himself who mixed up the sentence, Pdn's quote was garbled, the original sentence was correct.

By the way, I have never encountered any problem in browsing mathpages.com. I browse mathpages.com frequently, never a problem. It is unclear what makes the link appear stale to you.

In [chapter 2, section 1] it is written:

[...] photons are bosons, and hence not excluded from occupying the same state. In fact, the presence of one photon in a particular quantum state actually enhances the probability of another photon entering that state. (This is responsible for the phenomenon of stimulated emission, which is the basis of operation of lasers.)

--Cleon Teunissen | Talk 23:23, 21 Jun 2005 (UTC)

I wish I knew. I cannot get to it from my home computer, not that it matters too much. I should correct the entry though, now that I know that the problem is at my end and not necessarily theirs. --EMS | Talk 15:13, 22 Jun 2005 (UTC).

[edit] Pdn and the Michelson-Morley experiment

Pdn wrote:

I will think more about the Michaelson-Morley experiment as related to acceleration. [...] the idea was to detect differences in the "aether drift" as the apparatus turned (with the Earth). If it were in inertial motion the supposed drift would not show up as a fringe shift. A rotating reference frame is accelerated. Pdn 00:41, 21 Jun 2005 (UTC)

[...] If it were in inertial motion the supposed drift would not show up as a fringe shift. [...] Pdn 00:41, 21 Jun 2005 (UTC)

I get the impression that the reasoning of Pdn goes as follows:

"According to the 1905 theory of relativity, an inertially moving Michelson-Morley interferometer will not detect a fringe shift. Therefore I, Pdn, assume that the 1887 Michelson-Morley experiment was not designed to detect a velocity-related fringe-shift. I, Pdn, assume that the 1887 Michelson-Morley experiment was designed to test a higher order prediction of the 1905 relativity theory: that measurements taken with a device that is in accelerated motion will indicate a non-isotropy of propagation of light. I, Pdn's, draw the conclusion that the null result of the MMX tells us something about the physics of accelerated motion.

That is my tentative reconstruction of Pdn's reasoning.
--Cleon Teunissen | Talk 07:41, 22 Jun 2005 (UTC)

[edit] Chris Hillman's assessment of Kevin Brown

EMS wrote on the Talk page of Pdn

The other option is to drop Chris Hillman a line and see if you can get him to rule on it. My guess is that he will either yank it or justify it's presense after that. EMS | Talk 02:51, 17 Jun 2005 (UTC)

Hi EMS,

About the credentials of Kevin Brown, the author of Reflections on Relativity

I did a Google search of Newsgroups with the following search terms: "Kevin Brown" "Chris Hillman"

There were several threads in which both Kevin Brown and a Chris Hillman had posted. One thread was started by Kevin Brown in the newsgroep sci.physics.relativity.
Datum: 1998/05/10
Onderwerp: Loxodromic Aliasing

A Chris Hillman replied:

From: Chris Hillman <hill...@math.washington.edu>
Datum: 1998/05/10
Onderwerp: Re: Loxodromic Aliasing

On Sun, 10 May 1998, Kevin Brown wrote:
> When describing the appearance of a sequence of states we sometimes
> need to account for the phenomenon of aliasing.

Good grief, this is even more subtle that my Paradox Resolved post indicated! :-/ But, good point, Kevin, this is still another issue which needs to be explained by anyone presenting a relativistic starflight simulation.

This again shows the importance of superimposing on the star field say yellow Steiner circles (or loxodromic spirals as the case may be) showing the orbits of a given one parameter subgroup and say white circles of constant red/shift blue shift (which vary with parameter).
[end quote of message by Chris Hillman]

Considering this reply by Chris Hillman, and other replies, my impression is that Chris Hillman has a pretty good idea of Kevin Brown's level of competence, and that he considers Kevin Brown to be on equal par to himself in the field of theoretical physics.
--Cleon Teunissen | Talk 21:33, 11 July 2005 (UTC)

[edit] Religious Persecution by Muslims.

i just threw a massive edit on that piece. please let me know what you think. Hamster Sandwich 00:23, 21 July 2005 (UTC)

Thanks for the comment and observations. I agree that the article has a long way to go to offer even a partial overview of the issue. I am not an expert in theology by any stretch, but, when I see a valid topic possibly deleted for inane reasons, I feel compelled to make an effort at fixing some of the more obvious problems within the article. I know more about muffins than I do about Muslims. Regardless, I'll add to it when ever I find something relative to it. Thanks again! See 'round the wiki! Hamster Sandwich 01:10, 21 July 2005 (UTC)

[edit] Religious Persecution by Jews

Just left a comment for you on the VfD page. Summary is that I agree with everything you say about the need for copious citation and careful wording; apologize for not having the time to help out more right now; disagree with the claim that I'm ignorant of this material. Comment's still on the page. Take care. Babajobu 13:32, 21 July 2005 (UTC)

I hadn't worked much on this article until now. I had worked more on the Religious persecution by Muslims article. I'm making changes to the Jewish one as we speak. I know plenty of Jewish history, but I'll let you know if I think of something on which I'd like input. Regardless, I don't see being able to work much on this beyond today.Babajobu 14:49, 21 July 2005 (UTC)

Irishpunktom couldn't have created the series as cover for an antisemitic rant, because the article on Muslims was first. Anyway, it just occured to me: if you know anything about the experience of non-Jews living in the oblast that Stalin made officially Jewish, that'd be good. I can't even remember the name of the oblast. Babajobu 14:53, 21 July 2005 (UTC)

I know it still exists, but the Jewish proportion of the population is under ten percent. Stalin's purges didn't affect it, the purges affected members of the Communist Party and the oblast was populated by farmers induced to move (or deported) from the Pale of Settlement. Also, it was Stalin's idea in the first place. Anyway, the question is were there any notable persecutions of non-Jews in the region during the period when it was predominantly Jewish. Babajobu 15:10, 21 July 2005 (UTC)

The motivation in all these cases, and in all the cases in the other "Religious persecution by..." articles, could be described as political or military or cultural or economic or whimsical or whatever-the-fuck. "Proving" the nature of motivation is impossible, particularly because the motivation often incorporates elements of all these things. I've been defining "religious persecution" as persecution of a minority religious group by the majority religious group. I've not been tackling motivation. Anyway, I agree with you that these will be deleted no matter what happens from this point. We could have Elie Wiesel write the article, and the mufti of Mecca write the Muslim article, and the archbishop of Canterbury write the Christian one, and people would still dismiss them as anti-us trash.Babajobu 15:29, 21 July 2005 (UTC)

Yeah, you're right. Gotta run, won't be on Wikipedia for some time. Good luck. Babajobu 15:49, 21 July 2005 (UTC)

[edit] VfD

I'm understanding "religious persecution" as being the persecution of a minority religious group by a majority religious group. JDL doesn't qualify because a minority militant group is not capable of "persecution" as I'm defining it. The Kahane-ites were never part of the majority anywhere...except perhaps the ones in the West Bank, which would be covered under Israel. The Hasmoneans, as far as I know, could only qualify if they tried to Hellenize more traditional Jews. Even though they originally revolted against Hellenic occupation, they were pretty much Hellenized Jews themselves. That's my understanding. Babajobu 02:20, 22 July 2005 (UTC)

Incidentally, I'm science-y, too. You can see on my user page my primary interests are clinical medicine and diseases.

Right, I forgot, Herod was descended from forcibly converted Idumeans. Anyway, as I said previously, I don't have time to take this article on by myself. In future, hopefully. Babajobu 02:55, 22 July 2005 (UTC)

As per your suggestion I've cut-and-pasted the current article to my user page. I added a section heading on the Idumean conversion and removed the request for ("if possible"!) a section on the Jewish Autonomous Region, as apparently even in the early 50s this didn't have a Jewish majority. One thing I've learned from this slew of VfDs is that the phrase "religious persecution" (which I did not choose) is ambiguous and interpreted differently by different people. I interpret it to mean any persecution of a minority religious group by a majority religious group. Others interpret it to mean exclusively persecution motivated by religious or theological concerns, rather than economic, political, et cetera. Because motivation is so complex and multifaceted, I don't think the latter interpretation can be the foundation for an article. If the articles are deleted, any future versions will need a more carefully worded title. Anyway, I will contribute to these articles when I can; alas, for all my steamed talk, I'm not able to give as much time as I'd have liked. Babajobu 11:07, 23 July 2005 (UTC)

[edit] User page ?

Hi Ems. You may have had this trivial remark before: do you want to write something on (or create) your user page ? It would get rid of the only red link on my user page :) Mpatel (Talk).

[edit] VfD pollution

Ril enlisted Persecution by Muslims for VfD again, just 24 hours after the article withstood the first VfD. You might be interested to watch it. [3] --Germen (Talk | Contribs ) 10:19, 30 July 2005 (UTC)

[edit] GR

No confusion. I actually think that your overhaul of the GR article is cool. —AugPi 04:34, 2 August 2005 (UTC)

[edit] Fictitious force

Dear EMS, following your boldness at Inertial frame of reference, I've done something simliar at Fictitious force. I'm pretty sure you know about this stuff, and would be grateful for your opinion. William M. Connolley 14:43:48, 2005-08-02 (UTC).

[edit] The mathematics of coordinate transformation

William -
I took a quick look at the Coriolis effect article. At least at first glance it looks OK to me. --EMS | Talk 19:28, 2 August 2005 (UTC)

schematic, very simplfied representation of flow buildup around a low pressure area. Blue arrows: pressure gradient force, red arrows represent tendency to move in a particular direction, arising from the fact the the Earth rotates.

Currently, after the new edits, the coriolis effect article is contradicting itself badly. It is now a mosaic of fragments, written from incompatible points of view. William M Connolley acknowledges that the diagrams Image:Coriolis_effect10.png and the version Image:Coriolis_effect09.png are relevant for describing the formation of cyclonic flow, and his statements in the article indicate that he believes that the flow pattern is to be understood as a transformation from one frame of reference to another

CT, as usual, has completely misunderstood. I have never said this, and wouldn't. The flow *pattern* is clearly not to be understood as a transformation. Sigh. William M. Connolley 15:32:41, 2005-08-03 (UTC).

, the second frame rotating with respect to the first. (In the case of meteorology the transformation is invariably from a fixed-to-the-stars frame to a frame that is co-rotating with Earth, rotating around the Earth axis.)

I disagree with William's assertions on this matter.

Jolly good, since I disagree too. But perhaps we could talk about what I actually said, instead? William M. Connolley 15:32:41, 2005-08-03 (UTC).

The diagrams are relevant, which is why I manufactured them along with the animations, but nothing in the diagrams is related to coordinate transformation.

On a more general level: the underlying assumption of William M Connolley is that GRT has shown there is a one-on-one correspondence between relativity of linear velocity and relativity of angular velocity.
Given William M Connolley's reasoning, he will reject the content of the sagnac interferometer article, claiming that it violates GRT.
It has been months since William M Connolley and I have discussed this, his position may have altered since then. However, William's edits to the coriolis effect article do "breathe" the assumptions that also lead to the opinion that a Sagnac interferometer can only indicate a process of changing of angular velocity, but not angular velocity with respect to the local inertial frame of reference. --Cleon Teunissen | Talk 11:43, 3 August 2005 (UTC)

Cleon - I would be careful here. If, as I suspect, William is saying that the Sagnac fringe shift is due to an overall change in angular velocity, then he is correct.

EMS - please be careful, CT is misrepresenting, or more likely completely misunderstanding, what I've said. I've no idea about the Sagnac stuff and haven't commented on it at all! William M. Connolley 15:32:41, 2005-08-03 (UTC).

Then don't worry about it. There is an analogy here between it and how the Coriolis effect operates. Cleon is keying on it, and it is revealing that Cleon still has some misunderstandings here. If I understand his complaint properly, he is saying that your views mean that the Sagnac effect cannot determine angular velocities with respect to the local instantaneous inertial reference frame. In that case, you are the one who is correct. --EMS | Talk 16:08, 3 August 2005 (UTC)

However, if the is saying that the fringe shift is due to instantaneous angular acceleration (which I doubt), then he is mistaken. In any case, his position that there is a one-on-one correspondence between the relativity of angular velocities and the relativity of linear velocities (at least from a coordinate standpoint) is correct. (Only in the matter of centrifugal force is the inertial frame "priviliged", but even that issue is handled automatically by doing the coordiante transformations properly.)

I think what CT is talking about was the discussion of whether its possible to measure absolute rotation. He asserts it is. I can't see how that can be possible, as it would priviledge certain frames. William M. Connolley 15:32:41, 2005-08-03 (UTC).

Take a ball on the end of a string. If you just stand there, the string and ball dangle downward. However, if you start spinning in place, then there is a centrifugal force (in the view of your now rotating frame of reference) that pulls the ball outwards away from you. So right off the bat, that simple exercise measures "absolute" angular rotation, or rather rotation with respect to an inertial frame of reference.

This is not to say that you are totally wrong. Inertial frames are privilidged physically, but not mathematically. You can say that the ball is subject to a centripetal force pulling it in towards you and thwarting its desire move inertially at its current velocity just as well in your frame as you spin as in the frame of reference of your buddy who is standing off to one side watching all of this. As you remarked to Cleon in the talk pages, the same rules of physics apply in all reference frames. That is something that Cleon has had trouble with, and apparently seems to continue to have trouble with. --EMS | Talk 16:08, 3 August 2005 (UTC)

There is nothing wrong with setting up a Sagnac interferometer in a rotating frame of reference and declaring the fringes present in that state to be the unshifted state. In that frame of reference, derotataing the device with respect to the instantaneous inertial frame of reference is also a change of angular velocity, and will cause a Sagnac shift. (In essense this is the opposite of the shift that would have occurred had the device been set up in a non-rotating frame and then rotated into the initial frame of this exercise.)

So a Sagnac shift can only measure a change in angular velocity. To measure absolute angular velocity, you need to know where the fringes are when the device is not rotating, and that cannot be determined by the Sagnac effect itself. --EMS | Talk 15:17, 3 August 2005 (UTC)

I may have stated in the past that a Sagnac interferometer measures absolute rotation, but I have since retracted from that position. I now state the following things:

A sagnac interferometer measures its rotation with respect to the local inertial frame of reference. (The local inertial frame of reference being defined traditionally as a frame that is co-moving with free falling test masses. Since a Sagnac interferometer measurement of inertial motion is always seen to coincide with motion of free-falling objects Sagnac interferometry may itself become part of the definition of 'inertial frame')

No. A Sagnac fringe shift measures the change in the angular velocity of the aparatus. Normally, the aparatus is initially in a non-rotataing frame of reference, or rather one that is presumed to be non-rotating. (As a practical matter all of these devices initially have some slight rotation in them due to the rotation of the Earth.) Only if you know based on a careful analysis of the geometry of the experiment and the light source how the fringes should look when the experiment is inertial can you make any assertion about how a Sagnac device is rotating with respect to the local inertial frame of reference.

So your modified position is not that much of a modification. What you have done is to define what was meant by "absolute rotation", and that is a valid definition. The issue is that the Sagnac devices cannot measure that on their own. Instead, other means are needed to define the "inertial" state of the device. Then fringe shifts with respect to that state do measure rotation with respect to the local inertial frame of reference. --EMS | Talk 17:23, 3 August 2005 (UTC)
This can also be phrased as: a Sagnac device, like many other devices, effectively measures its own rotation with respect to local space.

See the above
general relativity predicts frame dragging. Frame dragging is so exceedingly rare and small that to this day no examples have been discovered (or are likely to be discovered) in astronomical observation. The Gravity Probe B experiment will, if succesfull, be the first demonstration.

Irrelevant, and also incorrect. The LAGEOS satellites have been used to measure it, but not as precisely.
In astronomical observation, there are no instances of observation that indicate that parts of the space of the universe are rotating with respect to the universe as a whole, even the possiblity is not considered, it would require massive frame dragging, for which not enough matter is present. It is just not an issue. (It may sound as if I ascribe material properties to space. However, I am carefull to avoid that, these statement are no more material than cosmological models that describe an expanding universe, with accelerating expansion, with the galaxies remaining in inertial motion with respect to local space.)
The separate points add up to: it is no coincidence that the local inertial frame of reference of the solar system does not rotate with respect to the fixed stars: that is because no parts of space of the universe rotate with respect to the universe as a whole.

This is true, but it is also irrelevant. Absolute rotation occurs with respect to the local inertial frame of reference. The stars can stay out of it. However, you may be interested in Mach's principle. Just don't read too much into it. --EMS | Talk 17:23, 3 August 2005 (UTC)

Of course, it is meaningless to talk about such a thing as whether the universe as a whole rotates. Only what can be observed can be meaningfully discussed. There are no known instances of parts of space rotating with respect to the universe as a whole, and the cosmological models do not allow for such a possibility.--Cleon Teunissen | Talk 16:28, 3 August 2005 (UTC)

[edit] The dynamics in meteorology

Yes, it would have been very strange indeed if that would have been your position.
So, for the umpteenth time we are back to square one, in a babylonian confusion of biblical proportion.

*You* are back to square one. You don't speak for anyone else. William M. Connolley 19:51:39, 2005-08-03 (UTC).

To understand that flow pattern there is no need to consider coordinate transformation, I just look at the physics. I am exclusively interested in the physics.

Yes. In fact its become pretty obvious that you don't understand the maths. But if you want to calculate the flow pattern (rather than just wave your hands) you need to do the maths. If you're just waving your hands, then you can do it by saying "the force is perp to the flow..." etc; OR you can do it by "if you look down from the moon...". The two views are physically equivalent. You can only do the latter. William M. Connolley 19:51:39, 2005-08-03 (UTC).

The mathematics of the coordinate transformation is obvious and transparent. I do not see why coordinate transformation should be discussed at all in discussing meteorology, the coordinate transformation is just a mathematical tool.

Because all meteorologists use it? And the reason they use it is... because its by far the best way of doing it William M. Connolley 19:51:39, 2005-08-03 (UTC).

That has been my ongoing puzzlement. Why discuss coordinate transformation at all? As I said, the coordinate transformation involved is obvious and transparent, it is a mystery to me why William has kept explaining something that is A) glaringly obvious, and B) not involved in the physics.

The coordinate transformation explains why the Coriolis effect appears to us here on the Earth as a "force" that torques weather systems like that. It is a perfectly valid exercise, and is not "glaringly obvious" to everyone. This is the same kind of thing that I insisted on in the Sagnac effect page. If that is the issue, then I am squarely on William's side. --EMS | Talk 17:32, 3 August 2005 (UTC)

It has now been confirmed that the red arrows in the diagrams on the right are unrelated to coordinate transformation.

No. You really don't get it, do you? William M. Connolley 19:51:39, 2005-08-03 (UTC).

For the coriolis effect article I have been writing about what physics the red arrows represent, for that is very interesting physics.--Cleon Teunissen | Talk 17:01, 3 August 2005 (UTC)

I think two issues need to be treated separately. One is the difficulty in mentally imagining a rotation. For myself, I figure out what happens in the inertial frame of reference, then I mentally rotate that picture to what is seen from the rotating point of view. After a while that sort of exercise becomes transparent. I imagined an animation, from the two points of view, and when I made the animations it was exciting to see them come to life the way I saw them in my head. Possibly I underestimate how difficult it can be for others.

Here is a site with animations that shows puck sliding over a frictionless Earth The opening page The first animation Those animations use an approximation: the Earth as a perfect sphere. Unfortunately, that approximation is not valid in meteorology, in meteorology the oblateness of the Earth needs to be taken into account (and of course, the oblateness is (indirectly) represented in the equations of the big computer models, otherwise those computermodels would produce nonsense). It was the writing of the meteorologist Anders Persson that made me aware of this.

I'm not sure I subscribe to that. I'm pretty sure that the std met equations just incorporate the oblateness into the gravity/local vertical term. The horizontal terms just look like they would on a spherical earth. I think. William M. Connolley 19:51:39, 2005-08-03 (UTC).

So for me the interesting part is that dynamics. The animations by Mcintyre are no help in explaining the motion of air masses, on Earth the dynamics is different than that. --Cleon Teunissen | Talk 17:57, 3 August 2005 (UTC)

[edit] The Sagnac interferometer

I think the ring laser interferometer is the clearest demonstration of the Sagnac effect.

When a ring laser interferometer is not rotating with respect to the local inertial frame of reference, then then both counterpropagating flows of laserlight have the same frequency. When a ring laser interferometer is rotating with respect to the local inertial frame of reference, then there is a splitting of the frequencies, as described in the Sagnac effect article.

Some of the laserlight is diverted, and the two freqencies are brought to interference, leading to a beat frequency.

The university of Canterbury, new Zealand employs such a ring laser interferometer, one with a diameter large enough to measere the rotation of the Earth. The ring laser interferometer is in a deep cave, shielded as much as possible from any influence. The ring laser interferometer, is rotating with respect to space, so there is a splitting of the frequencies, resulting in a beat frequency of about 71 Hertz, consistent weith one rotation per sidereal day. The advantage of the ring laser interferometer for measuring the rotation of the Earth with respect to space is that small fluctuations in the beat frequency, related to Earth quakes, are picked up too.

Anyway, the point is: there are numerous ways to measure rotation with respect to local space, the ring laser interferomete is one of them, and because it works with light, I feel it is a bit more spectacular. --Cleon Teunissen | Talk 17:24, 3 August 2005 (UTC)

I could also mention: the advantage of the ring laser interferometer is that the instrument does not need any calibration. It works straight away. the Beat frequency depends on the followin things: the two frequencies in the laser cavity, the area that is enclosed by the laser ring, and the amount of rotation with respect to space, which is what is to be measured.

So there is no calibration involved, it just works straight away.--Cleon Teunissen | Talk 17:34, 3 August 2005 (UTC)

Months and months ago I mentioned the Sagnac interferometer to William, and he expressed doubts. --Cleon Teunissen | Talk 17:24, 3 August 2005 (UTC)

That is a very good example. The use of radio signals and a beat frequency is different than what I was thinking of, and I do see that it works and why it works. (In a sense, the device is self-calibrating, but that is almost semantic issue. You really do make you point here, and effectively.) I was just thinking of fringe shifts, as was done by Sagnac.

Let me repeat to you what I said to William: Inertial reference frames are privilidged physically, but not mathematically. You tend to lose track of the mathematical part. William seems to lose track of the physical part. --EMS | Talk 17:49, 3 August 2005 (UTC)

Let me try if I know your style well enough now that I can emulate it. (So I am going to mimic you know, ~~not quite my own thoughts~~ Oops that caveat does no longer apply, I tinkered it into a version that are my thoughts)

The tools of special relativity are the formulas that relate the frames of the symmetry-group of inertial frames of reference to each other. One of the things that general relativity does is that it extends this transforming ability to a much larger group of frames of reference, and the mathematical representation of the transformations are a unified form; the same structure of representation for any frame of reference.
By contrast: In the usual notation of newtonian dynamics we have the simplicity of f=ma in the context of an inertial frame of reference, and three terms: acceleration, a coriolis term, and a centrifugal term, in the context of a rotating frame of reference. --Cleon Teunissen | Talk 18:25, 3 August 2005 (UTC)

This isn't about GR. Although one Einstein's insights is involved here, invoking GR itself brings in so much extra baggage that it is not worth it. The Coriolis effect is best described using classical mechanics. Let's leave it at that. I also advise using your own style, just adopting it to new realities as you encounter them. Mimicing me allows you to say a lot of neat stuff, but it does not help you if you do not understand it.

Look again at an edited version of the last part of what you wrote above:

In ... [N]ewtonian dynamics we have the simplicity of f=ma ... and three terms: acceleration, a coriolis term, and a centrifugal term, in the context of a rotating frame of reference.

What William's math is doing is showing how the extra terms arise. In that context, f=ma still applies, btw, just as it applies when you assume that gravity is a force. There is nothing GR-ish about this. This is a perfectly valid way of doing things in classical mechanics, and was in use long before GR came along. In fact, this kind of mathematical trick is what inspired Einstein to formulate one of the founding principles of GR.

[edit] Meteorology is really cool classical mechanics

Of course there is no reason at all to invoke GR in discussing meteorology, the things I wrote for the coriolis effect article are strictly classical mechanics. I wouldn't have it any other way.

The Ballistics section of the coriolis effect article is written by me, and other editers have left it the way it was. I wrote:

In the context of a rotating coordinate system the centrifugal and coriolis term perform the same job that F = ma performs in the context of an inertial frame of reference.

Anyway, that is all straightforward stuff.

The diagrams on the right, simplified as they are, are very relevant for understanding how cyclonic winds start, and the red arrows represent something, and the coriolis term in the equation of motion is unrelated to the red arrows in the diagrams.

The coriolis term is helpful when looking at motion that is a straight line as seen from one point of view (and thus curvilinear as seen from another, rotating point of view.) In the case of the diagrams on the right the motion with respect to the inertial frame of reference is curvilinear to begin with.

Reading the articles of the meteorologist Anders Persson made me aware of what the red arrows represent. It's really cool classical mechanics, worth looking into. --Cleon Teunissen | Talk 02:10, 4 August 2005 (UTC)

I kind of like meteorology myself, and am fascinated by hurricanes. (BTW - It looks like there might be a bumper crop of them this year in the Atlantic).

However, I am not interested in working on the Criolis effect page myself. I hope that both you and William have learned a few things, and can use that knowledge to tighten that page up in a way that is agreeable to you both. --EMS | Talk 02:37, 4 August 2005 (UTC)

It will be very very difficult. There's been a lot of buildup of hard feelings. I have poked William very hard, this time. I know a bit more now about why he believes the things he believes (but still not as much as I would like to)

The pattern of red arrows represents dynamic properties. In the diagrams the red arrows represent in what direction inertial motion would go. In this particular case, the pattern of the red arrows is preserved under transformation between coordinate systems. That is: the pattern is the same, both in the context of an inertial frame and in the context of a rotating frame.

To visualize that, I first visualize the system as seen from a non-rotating point of view, and then from a co-rotating point of view, for example a geostationary satellite.

To compare I visualize a non-rotating planet, with a low-pressure area, and air moving in to level the pressure. Obviously, no cyclones will form on a non-rotating planet. To see the direction of the wind, I visualize that balloons are being swept along with the wind. On a non-rotating planet, the air just moves straight in from all directions, towards the low pressure area. Seen from a rotating point of view, the whole picture is rotating, but the pattern of flow (just moving straight in to level the pressure) is the same in both contexts.

I can see in my head what those four different situations look like. Maybe I should try to make animations of those four situations, images tell more than words. --Cleon Teunissen | Talk 06:15, 4 August 2005 (UTC)

[edit] Contributors to general relativity

EMS, I know you think you are only trying to help, but you must have assumed (since you didn't even ask me before making the change) that I had no good reason for not wanting to make this change, at least not right now, but in fact I do have good reason not to want you to monkey with this. TIA, CH (talk) 00:31, 6 August 2005 (UTC)

This is Wikipedia, Chris. However, I think that you misunderstand what I am doing. Hopefully my last message to you has straightened this out. If not, then let me know what is going on. In the meantime I will lay off a while so that the dust can settle. My apologies for not asking and explaining this first. --EMS | Talk 00:42, 6 August 2005 (UTC)

EMS, please don't make huge changes without giving me time to respond/coment. 15 minutes is not enough, even if I am logged on (busy with other stuff, head in different place). And in fact I really loathe to appearance of the list you want to change my list to look like.---CH (talk) 04:30, 6 August 2005 (UTC)

[edit] Unhooking categories in Gen. Cov.- yes it's ok

Not a problem EMS, oh and ty for creating a user page :). ---Mpatel (talk) 11:16, August 8, 2005 (UTC)

[edit] Are slashes in article titles deprecated?

Hi, EMS, I have a wikicode question for you. Go to the "Exact solutions in general relativity" category and then follow the link to the article on "Aichelburg/Sexl ultraboost". While modifying another page, I noticed that I can't seem to get other articles to link correctly to this one. Looking at the url of the article, I see that the wikiserver may have interpreted the slash in the name as indicating a directory, which probably would not be good. Can you see how to link to this article? If not, can you see how to give it a name so that the slash appears to the reader, but the wikiserver can still link to it? If not, obviously, I'll have to change the name to "Aichelburg-Sexl ultraboost".

I have a preference for "Kerr/Newman" rather than "Kerr-Newman", and so forth, because hyphenated names are not unknown and can play havoc with the hyphen convention. However, if Wiki does not support this choice, I should know now, before I go and start trying to create lots of articles in the "Exact solutions in general relativity" category.---CH (talk) 19:53, 9 August 2005 (UTC)

[edit] Notification of request for arbitration

In response to your libelous false portrayal of my thoughtful and informative contributions to the cosmology article as NOT being thoughtful and informative, and furthermore as being mere diatribes, your use of a guise of being considerate so as to make your deceptions more convincing, and your act of giving small, nearly-insubstantial concessions in the guise of being considerare, so as to make more convincing the deception that other edits should not be allowed, thus demonstrating your malicious calculating nature, I have created a request for arbitration. Go ahead and make your statement on the arbitration page, not that it will make any difference. Your clever deceptions that I have pointed out are plain to see in the talk:cosmology page and the cosmology article history that they refer to, and the only way that the arbitrators will side with you is if they too have blind faith in the big bang belief, as well as the dominant temperament to suppress any facts that indicate that the big bang belief is anything less than a certain and obvious truth. --216.112.42.61

I have voted to reject the above, but would vote to accept if you feel 216.112.42.61 (talk · contribs) should be examined. Fred Bauder 21:35, August 10, 2005 (UTC)