User talk:Pfalstad

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Hello, and welcome to Wikipedia. Thank you for your contributions. I hope you like the place and decide to stay. Here are a few good links for newcomers:

I hope you enjoy editing here and being a Wikipedian! By the way, you can sign your name on Talk and vote pages using three tildes, like this: ~~~. Four tildes (~~~~) produces your name and the current date. If you have any questions, see the help pages, add a question to the village pump or ask me on my Talk page. Again, welcome! CryptoDerk 18:49, Feb 13, 2005 (UTC)

why'd you unblock[edit]

he's blanking articles, and has been warned repeatedly.. what's the point? Pfalstad 19:16, 3 October 2005 (UTC)

Yup, that one seems to deserve a block, I've reblocked him. See WP:AN#Brian0918.27s_instant_blocks for why he was unblocked in the first place. --fvw* 19:24, 3 October 2005 (UTC)

Finite length unterminated transmission line[edit]

Take a look at User:Alfred_Centauri/sandbox#TL. The bottom line is (if I haven't made any mistakes) that there is no combination of waves on a finite length unterminated TL that give the constant voltage zero current condition as LC claims there is. Alfred Centauri 01:12, 15 October 2005 (UTC)

Your website is very impressive![edit]

THanks for pointing me to your website with the simulations. I am very impressed with all the work you have done there and it obviously shows a great knowledge of physics not to mention great skill in writing java applets!. Now that I have met you in person, so to speak, I have a better idea of how to put my arguments and statements. I assume that you too (like Alfred Centuari) are a lecturer in physics. I by contrast, I am but a poor ex EE.

However I still like to keep my mind active and hence I find discussions on WP to be useful (if a little time consuming).I also assume from your replies so far that you are a conventional physisict as far as EM theory goes (ie you accept all Maxwells stuff and the absolute necessity of vector calculus to prove any problem beyond doubt).

I shall hope therefore to learn a great deal from you by way of any future discussions. However, please remember that it is a great many years since I graduated, Many things have been forgotten, some teaching has changed, some things were never covered, and most importantly my degree was in Electronics engineering and not Physics. So I ask your patience if sometimes I seem a bit slow on the uptake. --Light current 17:48, 18 October 2005 (UTC)

(Do I reply here or on your page?) Thanks, glad you liked my website. I am not a lecturer, but just a programmer with an amateur interest in physics. I like to learn about electronics, but have not picked up a soldering iron since college. I certainly like to stick to conventional EM theory. But I have learned from our discussions; I've certainly been forced to put my own ideas in order! Like I said, I think Catt has some good ideas, but takes them too far. You certainly know a lot more about transmission lines than I, so I hope to learn there. I think it's important to have a rigorous mathematical theory behind EM, but that doesn't mean I like math, or am good at it; I'm better at coming up with computer simulations to see what's going on. And practical experience is nice too.  :) Pfalstad 18:39, 18 October 2005 (UTC)

Hey, I'm a physics major at Harvey Mudd College and I love your site. A few years back, your vector calculus applet saved my butt when I needed a physical interpretation of curl. I recently got a lot of use out of your quantum mechanics applet and I even showed it to my class to demonstrate tunneling. Basically, whenever I'm hopelessly confused by a subject, the first thing I'll do is turn to your website and see if there's a relevant applet there (and even if there isn't, it's a great way to waste time). Keep up the good work!-- 03:22, 29 July 2007 (UTC)


Yea, i was just joking too! >_<!!! You from the 'sota territory? Anyways, dos (thats two in spanish) questions for you, since you are more experienced and i am just a trawiki (wiki in training).

1) How do you upload an image and insert it into an article 2) How do you block those are being disruptful to articles, with repeated violations?

Hey continued[edit]

Hey thanks for the response, i greatly appriciate it. I used to live in Edina too, thats where i grew up. I lived on Benton and Hansen Rd, if you know where that is. Anyways, thanks again, and enjoy!--Gephart 21:49, 25 October 2005 (UTC) Gracias por nachos for your time. Lequicho

Gephart 06:00, 25 October 2005 (UTC)

Thank you[edit]

I completely forgot about my merge suggestion of Total recall, thank you for completing it. Nihiltres 05:09, 12 November 2005 (UTC)

Einstein, Sr., Age Five[edit]

I had the same thought :-/ CH 23:40, 10 December 2005 (UTC)

Displacement current[edit]

Paul, Ive just been glancing at talk:Displacement current, and re-read your submission of 5 Oct 2005. I didnt really study it closely at the time as I and Alfred Centauri were in a heated discussion, but now I find that it concurs (as far as I can see) with my view of the interpretation of displacement current-- ie its not really a current(flow of charge or anything elese for that matter) but there is a magnetic field (associated with it?). Maybe there's only the magnetic and electric fields (the current is assumed). Thats what I think anyway - its all to do with EM radiation, not currents as such.

I think we all now realise that you dont need displacement current to explain the charging of a capacitor any more (See Ivor Catts article) and previous length discussion on talk:capacitor (Ithink). Would you concur with me on this? Also, are you happy that the article page now says what you think it should, or should I still be looking for 'errors' on the page. THanks! Hope you are well--Light current 22:45, 12 December 2005 (UTC)

I think I agree. I am happy with the displacement current page as-is. Feel free to look for errors anyway, though.  :) Pfalstad 23:55, 12 December 2005 (UTC)

Just come across another problem quoted by Nigel Cook. When a capacitor is in series with a load, how exactly does the energy get from one plate to the other. Does this need displacement current?. If so, how is this didsplaement current generated? --Light current 20:37, 19 December 2005 (UTC)

The energy is transmitted when the field goes across the places. And, the energy goes through the wires on either side of the plate. Pfalstad 20:43, 19 December 2005 (UTC)

Ahh but there can be no energy flow across (perpendicular to) the plates beacuse the Poynting vector points in a direction parallel to the plates-- no?. --Light current 20:52, 19 December 2005 (UTC)

Right you are! Interesting. Well, then the energy goes down the wires. It doesn't go across the plate. Pfalstad 20:58, 19 December 2005 (UTC)

What, and by passes the capacitors as if they werent there?--Light current 21:17, 19 December 2005 (UTC)

No, I meant it stops at the capacitors as if they were an open circuit. Pfalstad 21:53, 19 December 2005 (UTC)

If thats the case, how does energy get to the load?

                    | |
   -----------------| |----------------|
                    | |               |--|
 ac source                            |  | Load (resistor)
                                      |  |

--Light current 21:58, 19 December 2005 (UTC)

PS shall we move this to talk:displacement current to avoid clogging up your talk page?--Light current 21:59, 19 December 2005 (UTC)

Here is fine; my talk page is little-used. The energy gets to the load by the bottom wire. And to anticipate your next question, if you put another cap at the bottom, then I don't know what happens. There must be some energy flow across the cap... I can't simulate the fields with the resistor present, so I don't know what the poynting vector looks like in that case. Pfalstad 22:12, 19 December 2005 (UTC)
Ok, consider the case where there is a capacitor on either side of the load. Straighten everything out so the wire, caps, and resistor are in a line. Consider the time when current is maximum (voltages across each cap = 0). There is a magnetic field around the wire/caps/resistor. The electric field lines lead from the top wire to the bottom wire; near the resistor, they are parallel to the wire. If you work out the poynting vector, you'll find that it's pointing to the resistor. Energy is flowing from the wires into the resistor. It's not flowing across the caps, though; it just goes around them. Weird. Pfalstad 22:24, 19 December 2005 (UTC)

Interesting! Im going to think about that for a while. Needless to say, I dont know the answer.--Light current 22:30, 19 December 2005 (UTC)

Do you mean arrange cct as below: ?

                                   ____  C (Zo is very low)
                   Energy flow   |--|
                    ----->       |  |
                                 |  | R Load
         ac source(Zout=R)       |  |
                                   ____  C (Zo is very low)

I've drawn the Cs as little transmission lines to help us in thinking about this cct. This arrangement of components would indicate that the energy gets shared between the 3 components initially but we know that the Cs do not charge up and can therfore hold no energy. If they do not hold energy, they must reflect it.

Ah ha! Maybe the energy stolen by the capacitors in the first few ns (2 way transit time of TL) is given back to the load or source after reflection. Probably given back to the source actually assuming matched source and load resistances. (ie the capacitors introduce a small but positive mismatch to the source) Any reaction to my thoughts?--Light current 23:07, 19 December 2005 (UTC)

Well the capacitors definitely charge, and they hold energy when charged. I'm not sure I understand what you are saying. Pfalstad 23:16, 19 December 2005 (UTC)

No. The capacitors do not charge up because you have an ac source! (the voltage on each side of each capacitor is the same--roughly). Charging means holding separated charges on each plate and having a steady voltage diffrence between the plates (Q=CV)-- we dont have that here. In normal circuit theory, large capacitors act like a low impedance to the ac and so dont drop any voltage. In the em field representation, they dont drop any voltage because their characteristic impedance is so low compared with the resistance of the load. Understand so far?--Light current 23:43, 19 December 2005 (UTC)

There you go again, assuming the high-frequency limit without saying it. Ok, in that case the caps charge very little. I don't think I understand enough about your cap-as-TL model to say whether the energy is reflected or what happens to it. Pfalstad 23:52, 19 December 2005 (UTC)

Sorry. Yes I am assuming the capacitors heve low impedance compared to the resistor. But thats what you expect for coupling capacitors isnt it? OOPs looks tho I didnt mention that. But the argument still holds for any size capacitor.

Any way so far so good. What Im trying to show here is that energy can get to the resistor without the need for displacement current going from one plate to the other in the capacitors. EM energy can flow up and down the transmission line capacitors which are o/c at the far end of course. My propostion is that it all must happen by EM fields.

I don't think anyone disputes that the transmission of energy across the capacitor all happens by EM fields. I certainly don't. I don't understand how the TL representation helps. Of course I mentally picture a TL as a chain of caps and inductors. I suppose you have lots of experience with TL's, so perhaps they are more comfortable for you to work with.

Now in one limit, if we make the capacitors smaller and smaller the energy transferred to the resistor will tend to zero. In this case all the energy must be reflected back to the source by the capacitors. In the other limit, where C-->oo, none on the energy is reflected back to source. So the only effect the capacitors have is to decide how much of the incident radiation is reflected!

Current does NOT need to pass from one plate to another. Energy enters the resistor sideways. Energy enters the capacitors sideways and is reflected (to a greater or lesser degree). Nigel Cook is WRONG!! HA HA!! (See : Talk:displacement current to see what Nigel said).--Light current 00:19, 20 December 2005 (UTC)


It may be better to consider what happens if the source is a step of voltage to help work out the reflection scenario. Im not totally happy with what Ive said so far in that it doesnt completely explain the energy flow into and out of the capacitors. Im going to sleep on it! But I feel were on the right track here!!--Light current 01:03, 20 December 2005 (UTC)

The thing I have to be careful of is (as Alfred Centauri once said) not to mix a network approach with a field theroy approach as they can cause contradictions. So what Im going to do here is assume the field theory distributed component approach. This means that all connnections are TLs, capacitors must be considered TLs and the resistor... well just call it an ideal load for now.

BTW if I use a step waveform as input, that will cause the caps to charge eventually, so I dont want to do that. I must use a single frequency continuous wave (CW) as input. and estimate the standing waves on all transmission lines i suppose!--Light current 17:52, 20 December 2005 (UTC)

When the energy hits the capacitors (TLs) it induces counter propagating current in both conductors of the TL that cuold actually be measured. This current must be the same as that flowing thro' the resistor. Hence in a network theory sense, the energy can be considered to be transported across the capacitor by the em wave travelling down it. Now is that what you call displacement current? I call it em energy!--Light current 01:58, 23 December 2005 (UTC)

Why are you so fixated on displacement current? It's bad terminology, of course. You can call it em energy, em wave, displacement current whatever you want. Pfalstad 02:42, 23 December 2005 (UTC)

Well, I think the terminology that some people are using is confusing the issue and causing unneccesary arguments. I f its thought of as em energy I have no problem with it being able to travel across empty aspace. I DO have a problem with current (of any sort) traversing empty space. Any way, its not my only hobby horse. i do edit lots of other pages as well!--Light current 03:01, 23 December 2005 (UTC)

Well we agree then. I'm not even sure that "displacement current" is mentioned much in the textbooks I've seen. I see it when Maxwell's equations are introduced and that's about it. Pfalstad 03:19, 23 December 2005 (UTC)

Now, it should be possible to replace the phrase 'displacement current' on each and every occaision with the term 'em energy' without causing brain ache or contrdictions. May be this is what all the fuss has really been about?? Im going to try this and see if it still makes sense to me (Not in the articles!!).--Light current 03:34, 23 December 2005 (UTC)

That "yet" had better be a joke.. Pfalstad 03:37, 23 December 2005 (UTC)

Do you think Im stupid?? No dont answer that!--Light current 03:43, 23 December 2005 (UTC)

Ok sorry[edit]

I didn't realise at the time, won't make any further revisisions today

please dont kill me >_< --Mistress Selina Kyle 20:33, 19 December 2005 (UTC)

Electric susceptibility[edit]

I wonder if you could have have a quick look at Electric susceptibility. Im trying to rewrite the lead para in a non technical way and wanted to know whether you have any suggestions as to how to describe susceptibility simply but accurately.--Light current 18:49, 2 January 2006 (UTC)

stupid sort[edit]

Thanks for the heads-up. --cesarb 18:37, 11 January 2006 (UTC)

Danko Georgiev[edit]

Dear Pfalstad, I wish to ban Danko Georgiev from Wikipedia for his repeated accusations of Fraud to me regarding my experiment [1] on the talk pages. My experimental results were verified by faculty from Harvard and other schools. I will not allow this idiot to ruin my reputation. He must be repudiated by the Wikipedia community. Any help you can offer in this regard would be appreciated.-- Afshar 06:58, 3 March 2006 (UTC)

Edina Article[edit]

I gave you sources, or put them on the talk page, regarding Carl Pohlad living in Edina. I dont understand why you keep reverting and citing that no sources have been named. Please stop vandalising the article. Thanks.--Geppy 21:24, 7 March 2006 (UTC)

Chris Daughtry Page[edit]

Thank you for providing the source for the material I deleted. I was not saying that the information was untrue, but merely that it needed to be sourced. I grow tired of those pages that have information such as "fans have said blah blah blah" and the source comes down to some Joe Blow's posting on an internet blog. Thank you again for providing a solid source. Batman2005 02:40, 30 March 2006 (UTC)


Hey, I noticed you removed the part refereing to momentum as "the tendency for an object to continue in its direction of travel" or something - on the inertia page. I want to know what was "incorrect" about it. (btw, next time could you post something about deletions like that on the talk page, or the editors page - even if its a small comment?). We had a small discussion about how to conceptually explain momentum on its talk page. I finnally finnally came up with that conceptuality. Perhaps it doesn't really belong on inertia's article - but I'd like to hear your opinion anyway. thanks. Fresheneesz 09:14, 20 April 2006 (UTC)

Apology re. potential energy[edit]

I apologize for being too quick on the trigger reverting your re-addition of the gravitational potential energy equation example. However, even after figuring out what was actually going on in the example, I think it's best to replace it with something simpler instead of reverting my revert, as it managed to confuse at least three editors who considered themselves competent enough to change it or review the change made (myself included). I've put further comments at Talk:Potential energy. --Christopher Thomas 07:01, 27 April 2006 (UTC)

Edits by --Michael C. Price on Afshar experiment page[edit]

  • Dear Pfalstad, --Michael C. Price insists on using unsubstantiated claims without proper references on the article page. Regardless of the nature of his claims, I have requested that he does so, but instead he has produced at best irrelevant quotes from non-peer-reviewed sources. His edit follows:

Though Afshar's work is still the subject of ongoing interpretation and discussion, a significant portion of the scientific community is of the opinion that Afshar's experiment does not refute complementarity.

Some general criticisms are:

Bohr's philosophical views on the Complementarity Principle are generally seen in accordance with the Schrodinger wave equation. Since the latter is obeyed in Afshar's experiment it is not obvious how complementarity can be violated.[1][2]
The modern understanding of quantum decoherence and its destruction of quantum interference provides a mechanism for understanding the appearance of wavefunction collapse and the transition from quantum to classical. As such there is no need, in the decoherence view, for an a priori introduction of a classical-quantum divide as enshrined by complementarity. Any experiment that claims to violate complementarity needs to address this issue.

As Michael claims, those statments are supposedly "popular views" that preexisted my experiment, and as such must be present in peer-reviewed publication predating my work. All I have asked him to do is to provide such valid ref.s but he has persistently avoided doing so and instead engaged in personal attacks. He seems to have a lot of time on his hands to be on Wikipeida constatntly, but I don't. This is turning to oneupmanship, and I don't have time for such antcis. Maybe he would heed your request. Thanks!-- Prof. Afshar 13:51, 12 July 2006 (UTC)

P.S. I will be discussing this issue with Michael Price on the article talk page, and would highly appreciate if you could monitor our discussion and interject when you deem fit. I'm afraid it might get a little testy, as Michael has been persistent on personal attacks. Thanks very much for your help. Best regards.-- Prof. Afshar 17:02, 12 July 2006 (UTC)

Re: User:AntiVandalBot Edit[edit]

I LOLed. Hard!

Utilization of a revert tool[edit]

Please refrain from using a revert tool as you did here. Reverting with a tool like that is specifically meant to be used for reverting vandalism not good faith (if naïve) edits . Thanks. (Netscott) 16:56, 21 November 2006 (UTC)

Will do, sorry. I thought that might have been a bad idea. Pfalstad 18:09, 21 November 2006 (UTC)

Re: Martin Anderson.

I can live with that. Billollib 19:17, 29 November 2006 (UTC)

reverting images[edit]

"I love Wikipedia, and I'm puzzled why people like to trash it." Are you talking about yourself? Please do not respond. I'm not interested in reading it.--22:52, 24 June 2007 (UTC)Mbz1

Yes, I can see that from reading what's left of your talk page. Your new images are much improved. Pfalstad 03:50, 25 June 2007 (UTC)

Magnetic field talk page[edit]

"Get ready for a lengthy rant about an Orwellian cabal of fanatics dropping any traces of dissent down the memory hole.  ;-) Pfalstad 15:40, 18 July 2007 (UTC)"

That's a safe bet!
I'm fascinated with this notion that the STR is sufficient to deduce the magnetic field. I'm sure that there is more than one way to show this. One realization that I came to this morning is that a relativistic four-force field must be four-velocity dependent. It cannot be any other way for the simple reason that, in the STR, the four-momentum and the four-force must be orthogonal and the only way to ensure this is four-velocity dependence. Thus, a 'magnetic' (i.e. 3-velocity dependent) 3-force must be part of any force-field compatible with the STR. Have I missed something here?
Further, since the four-force depends on the four-velocity of particle, a four-force 'field' good for any particle doesn't exist. Instead, we need a rank 2 anti-symmetric tensor field that, when contracted with a four-velocity, gives a four-force field for that particular four-velocity. Alfred Centauri 17:30, 18 July 2007 (UTC)
Don't ask me, I don't know much about STR... I just look up the references.  :) Trying to come up with proofs for these guys is a waste of time, since it's OR, and they won't believe your proofs anyway. Pfalstad 20:50, 18 July 2007 (UTC)
Oh, it's not for them, it's strictly for my own enjoyment. Thinking deeply about this subject is a hobby of mine, I suppose. Oh well, time to cut some grass. Later, Alfred Centauri 21:00, 18 July 2007 (UTC)
Paul, I think I've got it. I haven't seen this anywhere else but I'm certainly not smart enough to be the first one to see this. Here's the deal. Consider a general potential energy (and associated force field) that is a function of position only. It's easy to show (by inserting this into the relativistic Lagrangian) that this cannot be consistent with the STR (more specifically, it isn't consistent with the invariant speed of the four-velocity). The most simple modification is to ensure Lorentz invariance of the potential by taking the scalar product of the four-velocity and a general potential four-vector that is a function of position but has units of momentum - a potential momentum four-vector. When you put that term in the relativistic Lagrangian, you immediately get a force that is in the exact form of the Lorentz force - but this is for a general potential (momentum) function of position. No a priori appeal to any electric or magnetic phenomena. The bottom line is that the simplest force field consistent with the STR is of the form of the Lorentz force - that is, there is a velocity dependent component that is perpendicular to the velocity. Neat! Alfred Centauri 03:51, 22 July 2007 (UTC)

Alfred Centauri, I accept that you are fascinated with the idea that the magnetic field can be deduced from STR. But I fear that your fascination has been causing you to want to give too much primacy to the idea on a basic 'magnetic field' article.

I do also believe that you have been mislead and that magnetism cannot be derived from STR. STR is only a linear transformation with extra gamma and beta factors. To get Maxwell's equations you would need a curl/cross product operator in the transformation.

There are three ways that I know of that have been suggested, but I have spotted the flaw in all of them. Purcell produces an electric charge from a neutral current by doing differential Lorentz contractions on the particles of the wire. This derivation is bogus on quite a number of counts.

The one that you are talking about brings a current term in Coulomb's law simply by comparing it with the four vector that you talk about.

Then of course there is the Lorentz transformation on Maxwell's equations which restores the vXB term that Heaviside removed in 1884.

Even these three methods mutually contradict each other.

If you are really interested in magnetism, I genuinely believe that you should read more Maxwell. I think that relativity has mislead you.

Regarding the rant about the cabal, I do think that there was a sub conscious attempt on your part and that of a number of others, to delete material that is in general circulation but that somehow threatens your relativity vision of the magnetic field.( 22:37, 20 July 2007 (UTC))


Please see my comment here [2] —Preceding unsigned comment added by Gilisa (talkcontribs) 08:12, 19 September 2007 (UTC)

Moose /not unlike[edit]

Just letting you know I undid this edit [3]. I assume you did not notice that it was a direct quotation from a source. Beeblebrox (talk) 18:32, 30 May 2013 (UTC)

Upon further examination it seems clear you were scanning Wikipedia for all instances of this term and removing it wherever you found it. I don't see any reason for doing that, "not unlike" is a perfectly valid turn of phrase and is not perfectly synonymous with "like" as your edits would seem to imply. Beeblebrox (talk) 01:31, 31 May 2013 (UTC)
Wow, you must be even more bored than I am. Pfalstad (talk) 16:27, 3 June 2013 (UTC)

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  1. ^ "There is absolutely nothing mysterious about Afshar's experiment." "And of course, the conventional quantum mechanics is compatible with the principle of complementarity." Lubos Motl at [4]
  2. ^ "Bohr would have had no problem whatsoever with this experiment within his interpretation. Nor would any other interpretation of quantum mechanics. It is simply another manifestation of the admittedly strange, but utterly comprehensible (it can be calculated with exquisite precision), nature of quantum mechanics." Bill Unruh at [5]