User talk:DVdm

— Welcome to my talk page — Please leave new comments at the bottom and sign them with tildes (~~~~) at the end. I will respond on this page. If I have left a message on your talk page, please respond there. I'll try to keep an eye on it. If you think I forgot to check don't hesitate to remind me here. "Watch out where the Huskies go, and don't you eat that yellow snow." "Remember there's a big difference between kneeling down and bending over." "Jazz is not dead, it just smells funny." "Everybody in this room is wearing a uniform, and don't kid yourself." vn-332This user talk page has been vandalized 332 times. — Canard du jour — As the light changed from red to greeen to yellow and back to red again, I sat there thinking about life. Was it nothing more than a bunch of honking and yelling? Sometimes it seemed that way. — Jack Handey This user has been on Wikipedia for 19 years, 6 months and 3 days. This user has earned the 100,000 Edits Award.

10 complement

Reliable source for what? 10 complement? If Wikipedia has a page with that title, that gives all it in details, why would I need to give any other source. The part was just diverting attention to that well-known but not mentioned case. — Preceding unsigned comment added by 95.34.4.122 (talk) 18:30, 3 April 2018 (UTC)

See wp:CIRCULAR: "Content from a Wikipedia article is not considered reliable unless it is backed up by citing reliable sources. Confirm that these sources support the content, then use them directly". Cheers. DVdm (talk) 20:21, 3 April 2018 (UTC)

Pair Production diagram

I have changed the Pair Production diagram because the old one is wrong. It might look better but it gives the wrong impression. Electron positron pair production does not occur when a photon hits a nucleus but in the electric field around a nucleus (or an atomic electron). Also the production opening angle is approximately zero not as shown in the old figure. I wrote all this in the Talk page of the Electron article. So I am reverting to the new figure. Chriskb19 (talk) 15:34, 16 April 2018 (UTC)

@Chriskb19: I find the the formula $\theta \approx 0^{o}$ a bit problematic. What does "approximately zero" mean exactly? Furthermore, I wouldn't call the angle in http://webhome.phy.duke.edu/~hsg/162/images/electron-positron-production-by-photon.html a small angle. When looking for images of e-p production, I can't find any with approx zero angles. I will leave a note at Wikipedia talk:WikiProject Physics, referring to your edits and to this here. You can respond there.

Also please note that when a Bold edit is Reverted, you are supposed to Discuss, not Revert-And-Discuss, as you did here - see wp:BRD. DVdm (talk) 18:35, 16 April 2018 (UTC)

As a reasonably new user, I didn't know that. Sorry. In my defence, I did explain my intention last December and your explanation for reverting was rather weak ("original was better"). I have added a full explanation and answers to your concerns on the WikiProject Physics page. That picture from phy.duke.edu does show a very small opening angle, in fact. This is a case of a photon converting after hitting an electron rather than a nucleus so the electron comes flying off but the nucleus (proton) hardly moves.

I have also looked at your Google picture search and this just shows that a non-expert can be easily confused by taking things out of context.

For example, top line from left to right: the first diagram is a Feynman diagram which does not show anything about angles; the next diagram is simply wrong; the third is a different process (photon-photon collision); the fourth is a pair of partial Feynman diagrams i.e. not complete Feynman diagrams. Second row: first diagram is another partial Feynman diagram; the second diagram is imprecise; the third is a bubble chamber photo and nicely shows the zero opening angle. Because a magnetic field acts on the produced electron and positron, they separate as they travel. If you track back to the production point, the two tangents to the arcs become one; etc, etc.

The reason I produced the new diagram is that I was irritated when my own physics department was using the wrong diagram in Wikipedia in an exercise to create a LaTeX document about Feynman and anti-matter. Chriskb19 (talk) 21:37, 16 April 2018 (UTC)

Thanks for the reply here and at Wikipedia talk:WikiProject Physics. Cheers. - DVdm (talk) 10:29, 17 April 2018 (UTC)

You are welcome. However user MaoGo believes there is still a dispute here and has reverted my change. Can you tell him you are satisfied that the new figure is uncontroversial and illustrates the maths in the Pair Production page and what is seen in experiments where gamma rays convert in 'thin' materials? Chriskb19 (talk) 18:44, 19 April 2018 (UTC)

I agree with MaoGo that there is still a dispute. Please confine the discussion to Wikipedia talk:WikiProject Physics. Cheers and happy source hunting! - DVdm (talk) 18:54, 19 April 2018 (UTC)

Armento page

In my Mr. Armento page you quite rudely deleted, I actually ddid list why he was notable, I said he was the best math teacher in the world, which is quite notable Sand undertale (talk) 23:19, 17 April 2018 (UTC) sand undertale — Preceding unsigned comment added by Sand undertale (talk • contribs) 23:15, 17 April 2018 (UTC)

Please sign all your talk page messages with four tildes (~~~~) — See Help:Using talk pages. Thanks.

See wp:Notability for Wikipedia's take on notability. - DVdm (talk) 10:19, 18 April 2018 (UTC)

Richard Feynman scheduled for TFA

This is to let you know that Richard Feynman has been scheduled as today's featured article for 11 May 2018. Please check that the article needs no polishing or corrections. If you're interested in editing the main page text, you're welcome to do so at Wikipedia:Today's featured article/May 11, 2018. Ealdgyth - Talk 15:35, 23 April 2018 (UTC)

Precious

"Welcome, and thank you for experimenting with Wikipedia."

Thank you for contributions to quality articles related to physics and its people, such as Richard Feynman, restoring the quality of one of Wikpedias oldest articles in collaboration, for welcoming and warning countless new users, for formatting with constructive edit summaries, - you are an awesome Wikipedian!

--Gerda Arendt (talk) 07:21, 11 May 2018 (UTC)

Deleting sources because of the language

Hi! I can see you deleted a bibliography I have added in an article on Matter. It seems you don't like it because it is in French. And you give me a link in Wikipedia (Further reading) to learn. I am new in Wikipedia as contributor. After many years of being a passive reader, I decided that is time to help other readers. I have a PhD in Physics, and Professor at the University. I have written many journal articles and chapter books, so I know how important is to have good sources. At the same time, nowadays, you have to get information from other languages if you want to learn. Myself I can read/write/understand English, French, and Spanish. I use in my articles and books always references in many languages. So, I don't understand your criticism. At the same time, I went to the link you indicated me (and other sub-links there), and nothing says about sources in different languages. As I said, I am new in Wikipedia, and I need to learn how to improve Wikipedia. I will invest my time in learning, and in improving the wonderful idea of Wikipedia. I will appreciate your advise in this matter. But, also, I will appreciate in this punctual case that you can justify that the reference I have included is not useful. I read it, and it is perfect for general reference. I might try in the future to improve also the article on Matter. In the meantime, I am trying to make small and easy contributions, and references (I believe) are the easiest ones to make. Specially in those articles where the references are scarce. Please, revert the changes and include again the reference. Thank you. Triboscience (talk) 01:06, 4 May 2018 (UTC)

Please put new talk page messages at the bottom of talk pages. See Help:Using talk pages. Thanks.

@Triboscience: I think the entry that you added ([1]) is not useful, so I removed it. Also, note that adding the same reference (or similar ones, or titles by the same author) to different articles, is usually frowned upon in Wikipedia, and sometimes gets interpreted as wp:PROMO or even wp:SPAM. In this case, you just added a book title to the Futher reading list, not as a reference to article content. In this respect, note that per wp:FURTHER: "Any links to external websites included under "Further reading" are subject to the guidelines described at Wikipedia:External links", and in that respect, please see wp:ELNO.

The place to discuss whether that particular entry would be appropriate in article Matter, is the article talk page (Talk:Matter). You can open an entry there (at the bottom) so other contributors to the article can join the discussion. Ultimately in Wikipedia everything is decided by wp:CONSENSUS and the best place to establish that, is on the article talk pages. Cheers. - DVdm (talk) 08:06, 4 May 2018 (UTC)

Removing of History of Cartamundi

Hi,

I saw you removed my history of Cartamundi. I work there and got all the information from them. I didn't use an external source that I can add to the article. Can I post without a source?

Thanks! Lotvanzwol (talk) 14:07, 8 May 2018 (UTC)

@Lotvanzwol: no, certainly not. No content without proper, reliable sources, preferably wp:secondary sources—see our policy wp:VERIFIABILITY. Also, as you work there, please see wp:Conflict of interest. - DVdm (talk) 14:13, 8 May 2018 (UTC)

Final thoughts on Twin Paradox

I am constructing an example where, by definition, the spaceships have the same maximum cruising a velocity and the same rate of acceleration, the only difference is the amount of time spent at that velocity. But I agree it is 100% beside the point. Initially I said:

'The risk is that the reader goes "oh, acceleration" and continues to not have even a basic grasp of length contraction'. To which you replied:

'So I think the article is fairly complete and balanced, and that balance is well reflected in the lead, and i.m.o. we don't need to worry about readers going "oh, acceleration"'

Then along comes a user who states: 'However, in the space twin's perspective, the acceleration phase explains everything (see Relativity of simultaneity), even if you imagine infinite acceleration. '

Which is pretty much "oh, acceleration". I don't know what to tell you, the article is continuing to perpetuate confused thinking.

Again, here is my proposed restructuring of the resolution section. First have a section on length contraction, as described by Wheeler and Taylor. Then, a section of planes of simultaneity to talk about it from a clock perspective. Then, a section on "acceleration" that can link the sources that use it in the resolution, but note that it isn't crucial to understanding the Twin Paradox at all. Bkennedy99 (talk) 14:41, 9 May 2018 (UTC) (forgot to sign)

The literature strongly disagrees with you. - DVdm (talk) 15:58, 9 May 2018 (UTC)

Oh yeah, and the guy that assumes "Oh acceleration" was the guy who started editing the article to talk about its "crucial role" outside of the "role of acceleration" section. Maybe you should take a look at that. And the literature fully supports my position, again see Taylor and Wheeler - or Roger Penrose, who makes it perfectly clear that acceleration can be accounted for by smoothing the spacetime diagrams, and is not central to the clock paradox. Here's a paper from the Australian Journal of Physics from 1957:

End of abstract: "The principle of equivalence is completely irrelevant to the analysis and discussion of the relative retardation of clocks unless there is a real gravitational field to be taken into account and, except in such a case, the general theory of relativity can add nothing of physical significance to an analysis correctly made using the restricted theory"

Then later on page 261 it concludes: "It must not be overlooked that the principle of equivalence was utilized (Tolman 1934) to resolve, by means of the general theory, the so-called paradox of the restricted theory. In effect, the "paradox" was resolved by denying the applicability of the restricted theory to the problem and then using instead conclusions that had been derived from the restricted theory by means of the principle of equivalence. This torturous procedure succeeded in hiding the paradox rather than in resolving it ; for it scarcely need be pointed out that the procedure would be quite invalid if the restricted theory were indeed not properly applicable to the problem considered. However, the resolution of the "paradox" in Section IV above and the subsequent discussion show that the general theory can contribute nothing of physical significance to an analysis properly carried out by means of the restricted theory except when there are permanent gravitational fields to be taken into account, as in the case analysed by Mikhail (1952)"

Again, you simply do not need acceleration / gravitational time dilation and general relativity. The literature supports this position quite clearly, and the journal article is correct in pointing out that talking about acceleration hides the solution rather than solves it. Bkennedy99 (talk) 21:33, 9 May 2018 (UTC)

Well, I'd say it strongly agrees with me. But ignore it for a sec. What do you, someone familiar with the Twin Paradox, think? Does acceleration play a role in explaining the paradox? A crucial role? Or no role? Because if you say "crucial role", then this is all pretty pointless. Bkennedy99 (talk) 22:06, 9 May 2018 (UTC)

You still seem to think that invoking acceleration is equivalent to invoking general relativity. - DVdm (talk) 22:19, 9 May 2018 (UTC)

Solutions that attribute a crucial role to acceleration sometimes are using the (The Equivalence Principle), and therefore attributing the difference in clock time to gravitational time dilation. This stands opposed to using only relative velocity time dilation to account for the clock differences. An example of the former treatment is in the Ohanian textbook cited at the top of the article that flat-out says it's gravitational time dilation. Even in the main article, there is a big section on accelerated frames of reference and gravitational time dilation.

Yes, you can mention acceleration without invoking GR in order to make it clear that acceleration doesn't "break" SR, and that you can happily have one curvy world line instead of two angular ones. In these approaches, acceleration is not "crucial" in the sense that it explains the time gap, it just means it is being accounted for. Bkennedy99 (talk) 23:40, 9 May 2018 (UTC)

Yes, solutions that attribute a crucial role to acceleration sometimes are using the EP. Sometimes. The old-fashioned ones. Let them. - DVdm (talk) 08:30, 10 May 2018 (UTC)

I agree, let them - but not in the section called "Resolution of the paradox in special relativity". Solutions that talk about "acceleration" and "non-inertial frames" are wading into this territory. How about adding a section called "Resolution of the paradox in general relativity" in which the time dilation is conceptually caused by gravitational time dilation (via acceleration and the equivalence principle). Then the "Resolution of the paradox in special relativity" section would note that acceleration isn't crucial to that version of the solution, and in fact can be discarded as irrelevant (link to the the journal article I quoted above). Also, the next section called "A non space-time approach" talks about clock transfers from outbound to inbound travelers. This is a spacetime approach and should be under the "Resolution of the paradox in special relativity" section. Bkennedy99 (talk) 12:17, 10 May 2018 (UTC)

Yes,solutions that talk about "acceleration" and "non-inertial frames" are wading into this territory. Indeed, special relativity has no problem with acceleration or with non-inertial frames. Let them wade, as they belong there. You still seem to think that non-inertial frames belong in general relativity. - DVdm (talk) 13:14, 10 May 2018 (UTC)

(restarting indents) Right - but there is a *huge* difference between "special relativity has no problem with acceleration or with non-inertial frames" and "acceleration and non-inertial frames are crucial to explaining the paradox in special relativity". Do you see the distinction around this word "crucial"?

The reason why I am hammering on this is because the "paradox" to someone with a casual understanding of physics is something like "all motion is relative, so all effects should be symmetrical". Noting this, someone edited the article to then say "This acceleration, measurable with an accelerometer, makes his rest frame temporarily non-inertial. This reveals a crucial asymmetry between the twins's perspectives". No no no, this is completely misleading, and someone reading this will not understand how special relativity works. The asymmetry is actually that one twin is moving with respect to the start and destination, while the other twin is at rest with respect to the start and destination. Thus, each twin has a different observed distance of the journey. That's it! The "imagine a giant ruler" thought device makes this crystal clear. Once the reader has this basic picture, the rest is plain old special relativity. All the acceleration talk obscures this, and we know this because it's really easy to construct acceleration-free modifications that reveal that acceleration and non-inertial frames are not in fact crucial. This is the actual explanation that should be used in the "special relativity" section, and it will help readers get their heads around the paradox far more effectively than what is there now. Just making the first paragraph under "Resolution of the paradox in special relativity" an explanation along these lines would go a long way. How about I take a shot at rewording it? Bkennedy99 (talk) 14:26, 10 May 2018 (UTC)

But the article does not say that "acceleration and non-inertial frames are crucial to explaining the paradox in special relativity". I don't see any reason to make a change. - DVdm (talk) 16:00, 10 May 2018 (UTC)

The paragraph directly under "Resolution of the paradox in special relativity" says "Although both twins can legitimately claim that they are at rest in their own frame, only the traveling twin experiences acceleration when the spaceship engines are turned on. This acceleration, measurable with an accelerometer, makes his rest frame temporarily non-inertial. This reveals a crucial asymmetry between the twins's perspectives". And as I and various other sources have pointed out, this "crucial asymmetry" is not crucial at all with respect to SR. Specifically, this edit is the problem. I'm confused how you can not characterize this paragraph, which explicitly talks about the "crucial asymmetry" of acceleration, as anything but "acceleration and non-inertial frames are crucial to explaining the paradox in special relativity" given that it is in the lead paragraph of "Resolution of the paradox in special relativity" Bkennedy99 (talk) 16:28, 10 May 2018 (UTC)

Okay, I wouldn't mind undoing that edit by user Paolo.dL (hereby pinged). After all, it is not sourced. - DVdm (talk) 21:00, 10 May 2018 (UTC)

Do I need a source to say that the crucial difference between the two twins is that one of them stays an inertial observer throughout the experiment and the other does not? In other words, one twin "switches frames" and the other does not. If both twins were space twins, traveling at the same speed in opposite directions and coming back to Earth, both would need to "switch frames" and they would have the same age at the end of the trip.

Also, do I need a source to say that (in short) "inertial" means "not accelerating"? I am just using the definition of the term "inertial". In other words, you need acceleration (non-null net force) to switch frames. Paolo.dL (talk) 14:57, 12 May 2018 (UTC)

Hi Paolo, as far as I'm concerned, you don't have to undo the edit. It is user Bkennedy99 who objected to it, not me. But the more sources we have, the better. - DVdm (talk) 15:01, 12 May 2018 (UTC)

"Imagine a giant ruler" is a useful idea. I guess that the thought experiment would work even if Earth was accelerating together with the destination, i.e. even if the Earth twin was not an inertial observer. That's a generalized version of the thought experiment. The simplest version, in which Earth is not accelerating, is equally "paradoxical", but I am glad we have an elegant solution for the generalized version as well.

Then again, whatever version you study, when you describe everything from the space twin's perspective, you are forced to conclude that the phase in which the space twin accelerates to "switch frames" is the only part of the trip in which the Earth twin ages more quickly than the space twin (due to a change in simultaneous hyperplane orientation). During the constant speed phases, the Earth twin ages more slowly! In this perspective, it is misleading to say that acceleration plays no role. And this perspective is perfectly legitimate, by the principle of relativity.

Moreover, the paradox is not fully solved unless you explore both perspectives. The appearently paradoxical idea is that time dilation works both ways...

Paolo.dL (talk) 16:22, 12 May 2018 (UTC)

A cookie for you!

For beta testing these changes to the English Wikipedia's Huggle configuration. This would not have been possible without your help, and you have earned a permanent mention in the version history of this central configuration file. ~ ToBeFree (talk) 22:35, 13 May 2018 (UTC)

Glad to be able to assist! Yum!

Edited the page Yashika Aannand

I corrected a lot of mistakes and wrong information on that page it was all restored why ? I can provide with links for all the corrections made .mostly YouTube . Can you please revert back my changes . Was editing painstakingly for a long while only to see everything back to all the wrong information . Even her name is spelled wrong . Promanager101 (talk) 22:42, 20 May 2018 (UTC)

All I did was this: [2]. - DVdm (talk) 08:54, 21 May 2018 (UTC)

Length contraction

Dear DVdm

Thanks for your message. I uploaded the article in researchgate for more than 8 months. So far no one has refuted the outcome of the article, thus I thought it is acceptable to include it in Wikipedia. If you think my result is not correct then I am more than happy to accept its removal. But if it is right there is no justification for deleting it. Ziaedin shafiei (talk) 16:40, 21 May 2018 (UTC)

@Ziaedin shafiei: your work will not be acceptable in Wikipedia before it is cited in the established literature. See wp:Primary sources, wp:Secondary sources, wp:UNDUE and wp:FRINGE. Give it a decade or so. Cheers. - DVdm (talk) 17:37, 21 May 2018 (UTC)

207.166.224.2

207.166.224.2 (talk · contribs · deleted contribs · logs · filter log · block user · block log)

Just came off of a six month block, went right back to vandalizing. --Guy Macon (talk) 15:03, 23 May 2018 (UTC)

@Guy Macon: could be another person with the same IP. Will report at wp:AIV if they continue. Thanks. - DVdm (talk) 15:24, 23 May 2018 (UTC)

Thank you

Apologies for the unsourced edit. Revised and sourced. — Preceding unsigned comment added by 205.172.134.229 (talk) 20:42, 23 May 2018 (UTC)

My pleasure. Thanks for the sourced redo. - DVdm (talk) 21:15, 23 May 2018 (UTC)

NPR Newsletter No.11 25 May 2018

Hello DVdm, thank you for your work reviewing New Pages!

ACTRIAL:

• WP:ACREQ has been implemented. The flow at the feed has dropped back to the levels during the trial. However, the backlog is on the rise again so please consider reviewing a few extra articles each day; a backlog approaching 5,000 is still far too high. An effort is also needed to ensure that older unsuitable older pages at the back of the queue do not get automatically indexed for Google.

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• Now that ACTRIAL is ACREQ, please be sure to look for tell-tale signs of undisclosed paid editing. Contact the creator if appropriate, and submit the issue to WP:COIN if necessary. There is a new global WMF policy that requires paid editors to connect to their adverts.

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Jefimenko edits

Hey, sorry if I'm putting this in the wrong place, it's been a while since i've been on wikipedia and I've forgotten most things :) Had a question re:https://en.wikipedia.org/w/index.php?title=Oleg_D._Jefimenko&oldid=prev&diff=842342751 - I'm not sure I understand why this needs a "solid second source" - this page is about Jefimenko and this is straight out of his book, why is a second source necessary? — Preceding unsigned comment added by Marquinho (talk • contribs) 00:19, 26 May 2018 (UTC)

Please put new talk page messages at the bottom of talk pages and sign your messages with four tildes (~~~~) — See Help:Using talk pages. Thanks.

@Marquinho: yes, that edit was mistaken, as I had explained in the edit summary of the revert of my undo, for the reason that in an article about the author, a factual statement with a wp:primary source is OK. However, in the artcle Alternatives to general relativity such a source is not sufficient ([3]). There we need wp:secondary sources. Cheers. - DVdm (talk) 07:38, 26 May 2018 (UTC)

The right of the Majority and the term KUKI

Hi,
  I appreciate your contribution but I would like to point out to you that you post incorrect information about the Kuki people. 

  Firstly , you are confuse about the term Kuki. You should know that Kuki and Chin are two different term and two different people though they are related by blood. You are also confuse about 'Mizos' and 'Zomis". These two terms were never use by any tribe in our history. These are new invented terms and have no connection with the Kuki Tribe(but with clans). 
  Secondly, when it comes to religion, Christianity is followed by 99% of the Kuki Tribes. Out of the remaining 1% half of them are Pagans- followers of their forefathers religion, Atheist , Agnostic and Judaism. Less than or about 0.5% of them believe that they are one of the lost tribe of Israel even though there is no proof. The fact that they claim to be the lost tribe of Israel defies logic and common sense. You are deliberately promoting this falsehood about 0.5% of the people and not the side of 99.5 %. Why promote internal division among us?
  I can only conclude that you are not a Kuki and clearly you have no idea of what you are posting here about my people-the Kuki People.