User talk:MOBle

From Wikipedia, the free encyclopedia

Contents 1 Links (continued from User_talk:131.215.6.88) 2 "Planetodesy"; ellipsoidal vs. elliptic geodesic? 3 Equations for a falling body 4 Schrödinger equation

[edit] Links (continued from User_talk:131.215.6.88)

Well, I don't watch E=mc2, so I don't know what your edits were there. You should probably take it to the talk page, where people will be able to give you specific feedback on why your edits were reverted. If you can reasonably explain the edits that you made, you may be able to reinstate them without them being reverted again. (I should note that if you made those edits from your IP, not from your new account, they may simply have been reverted along with your addition of the link, without the editor checking whether your other edits were useful.)

I agree that the link you added was relevant to some of the articles -- it just wasn't strongly relevant to many of them. Another editor clearly also saw the links as linkspam; s/he removed the links you added even on the pages where I thought they should stay. If you selectively choose a few articles to which the link is most relevant, and if you explain your addition of the link on the talk page or in your edit summary (give a good reason why it isn't linkspam), you again may be able to get the link to stay on those pages.

I'm glad to see you've created an account. Welcome to Wikipedia! Don't hesitate to get in touch on my talk page if you ever have any questions that I might be able to help you with. :) Good luck with editing! It can be a little discouraging at first sometimes, as you figure out the rules, because you will make edits that don't work for whatever reason and that will get reverted. If you ask nicely on the talk page, other editors will usually explain why they changed or reverted your edits. I hope you stick around -- we can always use more knowledgable specialists around here! :)

Hbackman 07:27, 22 February 2006 (UTC)

I will second this. I took the link out of places such as equivalence principle but left it in special relativity. However, another editor has obviously gotten annoyed with you and that link and just plain went on the warpath against it. I for one can't say that you did not ask for it. On the other hand, I found your (now restored) E=mc² edits to be reasonable, and you also seem to have done OK with metric tensor. So I strongly advise not worrying about you pet link and just help with the basic job of making this a better encyclopedia. --EMS | Talk 19:16, 22 February 2006 (UTC)

None of these files seem to be in Google cache at all. MOBle, did you just put this website up today? I see that you are at least at Cal Tech. We have a huge problem here at WP with anons sneakily adding links to crank sites, porn sites, completely irrelevant biz sites, etc. to legitimate articles on which dozens of editors have worked hard. So if this was a misunderstanding, we apologize. Until you get more wiki experience, it might be a good idea to first put proposed changes in talk pages, where you can get advice on whether the change is appropriate and if so how to execute it. Don't worry, basic wiki markups are very easy to pick up (very similar to html and latex)

Ed, if you can see these files at all, I'll go with whatever you think about how relevant they are.---CH 02:03, 23 February 2006 (UTC)

I'm sorry, but I don't think I understand this last comment. Are you referring to black-holes.org not being listed much at all in google? That's true. We haven't gotten any SEO to do anything for us. Are you unable to access the pages themselves?

I really think that this site has a lot of good content, at a level which I think even a high-schooler could understand, presented in a continuous tutorial format. (For those who disagree, please click through, especially to the numerous links under gravitational wave astronomy.) Thus, I believe that wikipedia users would be well-served by links to it. I thought links were unobtrusive and valuable enough that they wouldn't require discussion, and that there wouldn't be much blowback on this. Maybe one of the problems was that I mostly just linked to the home page, rather than the most relevant particular page. I honestly apologize for the upset this has caused, but I really believe that these were useful links. It seems as though I really don't see eye-to-eye with many people on here. MOBle 03:40, 23 February 2006 (UTC)

---

I am getting less and less pleased with those links the more I look at them. They are overly coy and often historically inaccurate. For example:

• The initial relativity page starts off talking about Ptolemy and Copernicus, and indicates that Copernicus replaced the circles of his original theory with ellipeses. That is wrong. Keppler did that.
• The second relativity page says that the interpretation of the Michaelson-Morely experiment was that the speed of light is constant. No it is not, at least not on its own. What that experiment did do was to call into question luminiferous ether theory, which was the dominant model for the behavior of light at the time. Yet you make no mention of that. (Also do note that Einstein never mentions this experiment in this article introducing special relativity.)

Your edits to the content of the Wikipeidia pages are good, and they show that you have a good grasp of relativity theory. However, the web pages that you are so enamoured with are so error-strewn that they are more of a liability than an asset, even though they at times do a good job of introducing some of the theoretical underpinnings of relativity. --EMS | Talk 16:50, 27 February 2006 (UTC)

With regard to the "coyness" you point out, I think that is one of the strengths of these pages. The intent is not to give an encyclopedic account of the facts behind relativity, but to equip the reader with a basic understanding of the concepts. Some times, in the interest of teaching, it is best to sacrifice documenting the finer details for the sake of clarity. In this way, I think the site is complementary to Wikipedia; I wouldn't bother editing here if I thought otherwise.

The interpretation of the Michelson-Morley experiment was that the apparatus is at rest with respect to the local ether. Some of the theories dreamed up to explain this was that the ether may be dragged along with material objects, like the atmosphere with the Earth. Assuming a Copernican principle, this would imply that any material object would locally observe light's speed to be constant. This distinction could be drawn in the page you mention, but I don't think doing so would serve the reader. Nor would any mention of the ether, beyond "...came up will all sorts of ideas to explain the experiment's results, but none really succeeded as a scientific theory."

As for the Copernicus/Kepler point you make, that is a good one. Thank you. I'll see that it gets changed. Here again, though, the point is not to introduce a long list of contributors to astronomy--as would be appropriate in Wikipedia--but to contrast two basic ideas. If you note any other actual errors in the pages, please point them out to me, because I think your characterization of them as "error-strewn" is unfair. Remember, these pages are not meant to be Wikipedia entries, but a resource guiding people with no physics background through the basics of relativity.

Also, I don't see why these links are creating such problems, especially in comparison to some of the other links I see at the bottoms of the Wikipedia pages. In particular, I think black-holes.org fills a void which is not filled either by Wikipedia, or by other links I've looked at. -- MOBle 00:34, 28 February 2006 (UTC)

Einstein is often quoted as having said that things should be "as simple as possible, but no simpler". I fear that you are being somewhat misleading in your efforts to be simple. My complaint in that Michelson-Morley experiment (MMX) text is that you present the impression that the constancy of c was immediately obvious to people from it, when in fact it was 18 years between that experiment and Einstein's formulation of special relativity. It is fine to gloss over the luminiferous aether, but please at least make it clear that the MMX was not interpreted as evidence for a constant speed of light before Einstein presented that idea. --EMS | Talk 04:39, 28 February 2006 (UTC)

[edit] "Planetodesy"; ellipsoidal vs. elliptic geodesic?

Hiya MOBle!
Rather than "relating to planets specifically" shouldn't it be "relating to planets and other celestial bodies in general"?: See planetary science. It just seems that "geodesy" and related terms are inappropriately used (like geology of the Moon).
On a completely different (but related) note, while the geodesic (or planetodesic P=) follows the surface contour of an ellipsoid (e.g., if you pulled a string between two points, the string would follow the geodetic path), is there a name/term for an alternative geodesic that traces the globoidally (i.e., the spherical represention) delineated, elliptic distance——that is, you take the spherical "string path" and calculate the elliptic distance along it? ~Kaimbridge~ 00:18, 2 August 2006 (UTC)

Hey Kaimbridge!

I guess the specific wording doesn't matter much to me, but "planetodesy" is not the same thing as, for example, "heliodesy". This distinction wouldn't be clear if you included "other celestial bodies in general". Planets here refers to the more general notion of basically any small thing that orbits a bigger thing. My concerns are:

• Everything in an introduction should be brief and very much on topic. For example, mentioning planetology seems out of place.

Placement there isn't critical, I just placed it in the intro as an advisory, so that the reader realizes that the term technically applies to Earth——I'd have no problem putting it in its own section near the end (I just didn't think it was necessary).

I think the current intro serves that purpose.

• Geodesics, as referred to in that article are very general things, and include planetodesics as a subclass. Differentiating planetodesics from geodesics is artificial, in this sense.

I guess that's my point: Earth is pretty much exclusive in terms of planetary measurement, so discussion on planetary measure (planetodesy, planetodesic, planetodetic, planetographic, etc.) has just been denoted in Earth terms (geodesy, geodesic, geodetic, geographic), but now we are becoming more serious in measuring other planets——just Google planetodesy and planetodetic. Most of these sites are schools and government agencies. Thus, more properly, it would seem that geodesics is realy a subclass of planetodesics, not the other way around (one glaring discrepancy I do see is "geoid", which should be "planetoid"——which is pretty much another word for asteroid——or is it actually "planetooid"?!? P=)

I know that there's plenty of research which is self-described as "planetodesy", but I've only heard that word spoken in place of geodesy when a distinction needs to be drawn between that and "heliodesy"--or occasionally "bothrodesy". (And I spend far more time around space scientists than a healthy person should, so this comes up with some frequency.) Also, Earth isn't the context of the article. The article deals with the quite general notion of "straight lines" in any curved space, of any number of dimensions.

• While I agree that the origins of the words refer to earth, usage has transformed them into words which refer to many different types of bodies, and even abstract surfaces. Language evolves.

As I mentioned, though, a discussion of your concerns would not be out of place on pages dedicated to planetology, planetodesy, etc. I think it'd be a fine idea for you to start one or more.

As a curiosity, you also might be introduced in the following: There are several words with the -desy ending used in gravitational wave astronomy. Among them are geodesy, planetodesy, heliodesy, and bothrodesy. (The latter referring to the bothros, or sacrificial pit, symbolized by a black hole into which another body is falling.)

I don't know about heliodesy and bothrodesy, but I believe "geodesy" (be it dealing with distance, gravitation or whatever) is "Earth planetodesy".

Don't take this nitpick as a wildeyed rant, I just think that, being a credible reference, we should point out discrepancies and misrepresentations. P=)

It's just that the word has evolved away from the meaning of its roots. In this sense, it's neither a misrepresentation nor a discrepancy. Note, for example, that the first definition of geodesic in the New Oxford American Dictionary is "of, relating to, or denoting the shortest possible line between two points on a sphere or other curved surface".

In any event, I think that's all the discussion that the issue merits in the context of this article.

I'm not sure what you mean by elliptic distance or spherical "string path". Geodesics only really deal with a single surface at a time. An ellipsoid, as you say, will have well-defined geodesics independent of any sphere. Do you mean projection of a sphere's geodesic onto a related ellipsoid? If so, this depends entirely on how you take the projection. I can't think of anything else you might mean. --MOBle 01:23, 2 August 2006 (UTC)

I think so.

Consider a nice, small sphere with a radius of 20 cm. If you pull a string from a point on the equator, along the equator to the other side, the string will stay in position; if you pull that string between the two points, along a meridian, the same length of string will be used and the string will again stay in place: The same can be said for any transverse meridian (i.e., great circle) angled between the (upright) meridian and equator——i.e., the arc path. Now reduce the polar radius by half: Along the equator, the same amount of string will be required and it will, still, remain in place. But, while holding the endpoints in place, as soon as the string is nudged off of the equator, it will immediately loosen. As you pull out the slack, the string will angle closer and closer to the (upright) meridian, until it is taunt along the meridian (since that is the one and only antipodal geodetic path on an oblate spheroid). Now go back to the sphere and draw the 45° arc path (i.e., halfway between the upright meridian and the equator): As noted before, you can pull the string between two antipodal points along that path and it will stay in place. Now return to the half polar radius spheroid. Again, if you try to pull the string along that marked, 45° arc path, the string will slide off it, towards the pole. But one can see that 45° arc path (which, squashed down towards the equator, now elliptically goes from 75.96° → 75.12° → 72.88° → 69.85° → 66.74° → 64.35° → 63.43°), and one can travel along that globoidally/spherically delineated 45° arc path.

So, how do you calculate the elliptic distance between two points along a meridian (which equals the geodetic distance)? You find the average value of M (the meridional radius of curvature) and multiply it by the angular distance, or central angle (), which (in this case) equals the latitude difference. Now let's make M "omniversal", O, so that it is the transverse meridional radius of curvature (or, more simply, the radius of arc). To find the elliptic distance between two points along the delineated 45° arc path, you find the average value of O between the two points (measured along the arc path, not north-south) and multiply it by the points' . Of course this isn't the true, surface conforming, ellipsoidal geodesic (i.e., the "string path"), but it is a legitimate elliptical distance——I call it the parageodesic (since it is related to the geodesic, like "paralegal", "parathyroid" or "parapsychology"), but given all of the different terms in geodesy and cartography (such as all of the different types of latitude), I would think that this "elliptic distance" would have a formal name. Are you familiar with Andoyer's approximation? This is actually an elliptic ("parageodetic") rather than ellipsoidal (true geodetic) approximation.  ~Kaimbridge~ 21:16, 2 August 2006 (UTC)

If I understand you correctly, this is just the projection of a spherical curve onto an ellipsoid centered on that sphere. Mathematicians just treat this parageodesic the same as any other curve. The length along any curve γ(t) (geodesic or not) is given by the formula

Here, t is just some parameter along the curve. You would give the mathematician a string path by naming a point γ(t) for every value of t. You would also have to give the metric, g. In the case of an ellipsoid in (flat) space, you could do this, for example, by expressing the radius of the ellipsoid as R in terms of the coordinates θ and φ, and plugging this function R(θ,φ) into the usual metric . (For a well-chosen ellipsoid, the function R would have no dependence on φ.) The mathematician would then take these, integrate the expression above, and tell you the length of the curve, which would agree with the length of a string you put along the curve. It looks like Andoyer's approximation is an approximation to this length by taking the simple curve (the projection), and using an approximate form for the metric and/or for the integral. In general the full integral will be pretty ugly.

I'm not sure about your above equation——and you may be saying the same thing——but the integral I use is quite simple and neat:

Where is the common ("planetodetic" P=) latitude, is the transverse colatitude (see central angle), is the globoidal/spherical azimuth at , is the globoidal/spherical arc path, and are the well known meridional, normal radii of curvature,

The "parageodetic" distance (DxG), then, is simply,

O (I believe) is the transverse meridional radius of curvature or radius of arc.

What you may find of particular interest is the elliptical form of O, where:

This is the "locally" elliptically adjusted azimuth (i.e., the elliptically azimuth adjusted for an infinitesimal length, )

Compare this with the radius of curvature of the normal section (where equals the ellipsoidal azimuth, which equals for ):

O is derivable (for distances) from the quasi-geodetic, elliptic loxodromic formula such as used by the FCC. ~Kaimbridge~ 16:16, 4 August 2006 (UTC)

There are innumerable approximations that you can make for simplifying the exact distance expression given above, and in the geodesic article. Especially in the important case of an ellipsoid, these approximations can simplify the problem greatly. --MOBle 19:25, 7 August 2006 (UTC)

[edit] Equations for a falling body

I was who tried to modify the Equations for a falling body section in Gravity yesterday. I talked than SCZenz, and he said that try to gathering more informaion. A emailed with the author, and he send me some pdf. In these pdf, there is an Simultaneous Fall Experiment with Different Materials from 110 m Height.

"[...] For an experimental verification of the difference between the inertial and the gravitational mass, the author has used only solid chemical elements Li/Be/B/C/ Al/Fe/Pb and has performed a simultaneous fall experiment in the 110 m high vacuum tube at the drop tower of ZARM, University of Bremen. The weights of the test bodies were between ~2 g and ~7 g. The purities were better than 98.8% in all cases.

The test bodies were freely placed at the middle of the safety glass cylinder. On the back plane of the experimental equipment, a cm scale was fixed with 0.0 cm at 130 Measurement of UFF Violation with Li/C/ Pb Compared to Al start, and with red marks for the fall distance prognoses according to Eq. (5). The relative movement of the test bodies was recorded with a standard CCD video camera. The camera was placed in front of the middle glass cylinder through a mirror arrangement in a distance (from the front of objective to the cm scale on the back ground) of ~ 60 cm directed to the height of 15 cm. The experimental equipment was fixed in the drop capsule falling freely in vacuum. The time resolution 0.04 s is to be calculated from 25 frames/s. From 256x256 pixels, the space resolution is in order of 1 mm for the quickest relative motion of Li. The time of fall was mirrored in by film exposure in 40 ms units. The time of fall with approximately free fall conditions and the relative fall distances in each time step can be read immediately from single pictures of film. The following sequence of four pictures shows the relative movement of the seven test bodies at fall times of 1.23 s, 2.43 s, 3.63 s and at 4.68 s, the end of the 110 m fall. [...]"

Can I send these pdfs to you for review? I am not the author and i am not good at physic so i dont know it is important or not.

Thanks, but I don't need to see the PDFs. What you (and apparently this Hungarian) claim contradicts established scientific thought. There is nothing wrong with testing theories, but a test needs to be accepted by more than a few people before it can be included in Wikipedia. If this experiment were believable, the author would have to find a fellow physicist to review the experiment up close, and in person. This is done by submitting a paper to a reputable journal. (Physical Review Letters would be the natural choice for this paper, if it were believable.) Once it is published in such a journal, it can be included in Wikipedia, but not before that. It doesn't matter how much you believe it, or I believe it. Something like this would need very careful review to be judged correct, and I am not willing to give it that review. Many other experiments have been published in well respected journals, using more sensitive techniques, and have not found the effect this experiment claims.

Now, just for your satisfaction, I find a few problems with the experiment. The only one I'll mention is this: The time resolution the author cites is 40ms over 4.68s; that is 0.9%. Roughly speaking, this means that no other number in the experiment should be believed to higher accuracy. All the numbers you wrote are within 0.9% of 1.0000, which means that your experimenter measured all the accelerations to be "correct" to within the experimental uncertainty. Also, I find it very suspicious that what you posted above says the author only tested solid Li, Be, B, C, Al, Fe, and Pb; in the article, you wrote data for every element from Hydrogen to Uranium.

Finally, I'll remind you that it doesn't matter how much you believe it, or how little I believe it. It only matters whether the results have been published in a scientific journal or not, and I have seen no evidence that the results were published. --MOBle 18:58, 27 October 2006 (UTC)

Thanks for the answer. I not correctly understood the authors's measures. He measured only once. And only the Li, Be, B, C, Al, Fe, and Pb. And there was problems wits the experiment. So he want another measure. (Nemethpeter 20:47, 29 October 2006 (UTC))

No problem. I didn't mean to discourage you from contributing to Wikipedia. However, please make sure that what you put in is true, and you can cite a reputable source to back up your claims. MOBle 04:08, 30 October 2006 (UTC)

[edit] Schrödinger equation

Hi MOBIe. I am a Wikipedia newby and at first put this text on your user page. Later I realized my mistake (sorry!) and moved it to here:

Generally I agree with your reverting the Schrodinger equation, but I have a remark that I don't want to edit in myself, because too many people have their fingers in this article as it is. I write it down, see if you like it, else discard it. --P.wormer 10:49, 21 November 2006 (UTC)

I would replace the sentences:

"For many real-world problems the energy distribution does not change with time, and it is useful to determine how the stationary states vary with position x (independent of the time t). The Schrödinger equation is often introduced without bra-ket notation in the following ways:

One dimensional time-independent, for a particle of mass m, moving in a potential U(x):"

with:

For many real-world problems the energy operator H does not depend on time. It can be shown that the time-dependent Schrödinger equation then simplifies^[1] to the time-independent Schrödinger equation, which—as we will discuss—has the well-known appearance Failed to parse (Cannot write to or create math output directory): H\Psi = E\Psi.

The simple one-dimensional time-independent equation for a particle of mass m, moving in a potential U(x) takes the form:

(and then the equation)

1. ^ In fact also an initial condition must be used here. At time zero the wavefunction must be an eigenstate of H.

Hi Paul. Good to see a new contributor -- especially one with such a great background. I reverted the anonymous edits because they destroyed the LaTeX (which I really don't think is helpful), removed a lot of content (which is rarely good), and destroyed the formatting suggested in the Wikipedia Manual of Style. At a brief glance, though, I thought some of the edits were good. In particular, the anon seemed to be making the article less wordy, which would be really useful -- especially in this particular case. Your proposed change also looks like it would make the article more understandable, so I think you should go right ahead and make the change.

By reverting, I didn't mean to endorse this article as it is. I think it needs a lot of work, and I think you should feel free to pitch in. Generally, even people with many fingers in the article will be happy to see constructive edits. --MOBle 18:17, 21 November 2006 (UTC)