User talk:Ywaz

About Cooper's relationship

Hi Ywaz,

I've been trying to figure out how to best use Cooper's relationship for declination. In the article Position of the Sun it is reported as:

$\delta _{\odot }=-23.44^{\circ }\cdot \cos \left[{\frac {360^{\circ }}{365}}\cdot \left(N+10\right)\right]$

even if in Cooper's original paper (The absorption of radiation in solar stills, 1969) is:

$\delta _{\odot }=23.45^{\circ }\cdot \sin \left[{\frac {360^{\circ }}{365}}\cdot \left(N+284\right)\right]$

In particular, I was wondering what N=0 meant. What instant does it represent? In this article it's written N=0 is midnight UTC between December 31st and January 1st. In Cooper's original paper is only written: "convenient approximate relationship for solar declination in terms of the day of the year n (i.e. 1st or 200th)".

I personally tried to do some calculations and I think the best thing would be to consider N=1 as the noon UTC on January 1st. I believe this minimizes the error. I would like to ask you why you changed your mind in making versions of article Declination in November 2011?

Also, however, don't you think that instead of "overestimates", "underestimates" should go? You could have a look here https://www.pveducation.org/pvcdrom/properties-of-sunlight/declination-angle

Sam X (talk) 23:09, 23 May 2020 (UTC)

Hi,

N=0 is exactly 10 days after the winter solstice, whatever time of day that was hence the 10. Then N can increase slowly to 1 for that first day in my formula. There are 365.25 days in a year, so the 365 should be 365.25, to be more precise (the reason we have leap years). -sin(A+B) = cos(A+B - 90), so the two formulas are the same, except Cooper does not allow for an N=0 to 1 to be a day, so he has 284 instead of the 285 implied by my formula. I changed to the cos() form to show its relationship to winter solstice. If I had not done that, I would not have remembered that. I may have changed the 23.44 to be more precise but I don't know if it's precise enough for 1/2 a day to matter. There may be some fudge in the 23.44. His 365th day will be Dec 31, all day. Mine will not be 365 until midnight that day (on non-leap year days). Even 365.25 is not exact, maybe it's something like 365.24. Here's another way to express what I'm saying:

$\delta _{\odot }$ = - 23.44 * cos(360 / 365.25 * N)

where N is the number of days after the moment the days start getting longer.

Ywaz (talk)

Now I see the article already says most of what I said, and I went back and read your comments more carefully. Yes, I should have said underestimates.

The initial equation comes from a 3D angle C = acos(cos(A)*cos(B)) where A & B are angles to 2 of the 3 x, y, & z axii in a 3D image. In terms of sin() this is:

declination = -(arcsin(sin(A+90) * sin(B+90)) - 90)

The link you gave above says "sun goes through 365 rotations" but it's actually 366.25 rotations because the orbit of the Earth around the sun cancels 1 rotation per year. This does not affect equation because it's already baked in.

Your statement that noon Jan 1st is probably correct since that's closer to 10 days after the average solstice.

I thought the 23.44 had a fudge factor, but now I see it's the precise tilt of Earth's axis.

The simplified equation is making use of sin(A) = A for small angles, but 23.44 is at all small. So maybe the simple equation should not be used.

I assume I did not continue "making versions for the declination" article because it's long discussions in place. Maybe it should be the other way around. Simply put the accurate equation in the sun position section with a link to the declination article that would have the full text.

Ywaz (talk) 11:03, 24 May 2020 (UTC)

Polysilicon a metal

Interesting. If true, please say so in the article to explain the "metal", in place of the current statement; but you'd need to cite a source. For now, I revert you. Dicklyon (talk) 16:58, 16 December 2008 (UTC)

Silicon is the most abundant metal on Earth and being in crystalline form does not change that. Maybe the article should say in all the various places that the technology has largely changed from a good conducting metal like aluminum to the poorly conducting metal polysilicon. I added a discussion topic on the article and hopefully someone will fix it in all the appropriate places. I was just browsing and that error stood out. Ywaz (talk) 00:58, 17 December 2008 (UTC)

Can you provide a source that says Si is a metal? It seems to me that you are wrong there (see e.g. http://www.chemicool.com/elements/silicon.html), and such a big change in an established article would indeed require a source. Dicklyon (talk) 01:17, 17 December 2008 (UTC)

You're right, as the wikipedia article on silicon says, it's a metlloid which is different from a metal. I looked at it earlier, but stopped reading at the word "metalloid" which I thought meant "metal".

That's why we ask for sources when people change what has previously been accepted. Thanks for correcting yourself. Dicklyon (talk) 03:59, 17 December 2008 (UTC)

February 2009

Welcome to Wikipedia. Although everyone is welcome to make constructive contributions to Wikipedia, at least one of your recent edits, such as the one you made to EEStor, did not appear to be constructive and has been automatically reverted by ClueBot. Please use the sandbox for any test edits you would like to make, and take a look at the welcome page to learn more about contributing to this encyclopedia. If you believe there has been a mistake and would like to report a false positive, please report it here and then remove this warning from your talk page. If your edit was not vandalism, please feel free to make your edit again after reporting it. The following is the log entry regarding this warning: EEStor was changed by Ywaz (u) (t) deleting 14553 characters on 2009-02-12T13:21:50+00:00 . Thank you. ClueBot (talk) 13:21, 12 February 2009 (UTC)

This notice was from trying to remove unreliable sources from EEStor article. The link above is not letting me report this ClueBot error.Ywaz (talk) 13:38, 12 February 2009 (UTC)

December 2010

Welcome to Wikipedia. We welcome and appreciate your contributions, including your edits to Johannes Kepler, but we cannot accept original research. Original research also encompasses novel, unpublished syntheses of previously published material. Please be prepared to cite a reliable source for all of your information. Thank you. There is an extensive literature on this passage that points out the distinction between Kepler's attraction between "cognate bodies" which is not universal gravitation and that his attraction is limited to a "sphere of influence" and does not extend indefinitely (as Newton's does). SteveMcCluskey (talk) 18:23, 2 December 2010 (UTC)

You're not telling the truth. Kepler: "If the attractive virtue of the moon extends as far as the earth, it follows with greater reason that the attractive virtue of the earth extends as far as the moon and much farther; and, in short, nothing which consists of earthly substance anyhow constituted although thrown up to any height, can ever escape the powerful operation of this attractive virtue."Ywaz (talk) 16:22, 5 December 2010 (UTC)

Please do not add original research or novel syntheses of previously published material to our articles as you apparently did to Astronomia nova. Please cite a reliable source for all of your information. Thank you. Your addition of material that was recently deleted from Kepler as original research shows a lack of concern for consensus. SteveMcCluskey (talk) 04:47, 5 December 2010 (UTC)

A quote from the book page being editing is not "original research". I agreed with the consensus (despite your claim) about my previous intro to the quote. I tried to exclude those comments that were not strictly from the source, which I cited. This is your second false and insulting post to my talk page. Unless you want to be honest, please stop spamming my talk page. Ywaz (talk) 14:18, 5 December 2010 (UTC)

I'm sorry you took offense at the implications in these standard messages that you might be new to Wikipedia. The authors of these templates assumed that it was wiser to assume first that people who didn't follow Wikipedia standards were new and didn't yet know those practices, rather than imply that these mistakes were deliberate. The issue at hand (as I've mentioned on the talk page) is interpretation of primary sources and the need to find secondary sources to support your interpretations. I hope you'll look carefully at this discussion. Best, SteveMcCluskey (talk) 18:16, 5 December 2010 (UTC)

My apologies if I'm being overly sensitive. As I was saying, I tried to limit my introductory comments to the quote so as to not go against the consensus. I've reduced them even more in my newest revision which I hope you'll allow. I moved it to the page for the book itself rather than Kepler's page because that's where it better belongs.Ywaz (talk) 18:25, 5 December 2010 (UTC)

Heliostat edits

Hi Ywaz:

I've just written a few paragraphs on the talk:Heliostat page about the edits you have recently made to the article. You asked what aspects I say are erroneous. I gave some examples.

DOwenWilliams (talk) 22:15, 15 November 2011 (UTC)

Declination

Hi Ywaz:

I'm not sure that I agree with you about switching or not switching to cosine notation in the declination formula. If you consider its origin to be my Sunalign stuff, then it was definitely in cosine form back then.

However.... No big deal.

You may have seen that I have made an addition to the Equation of time page to include "our" kind of calculation.

DOwenWilliams (talk) 02:30, 22 November 2011 (UTC)

Equation of Time

I saw the edits you made today on the Equation of Time page. I guess most of them are matters of taste. I'll live with most of them. However, I have changed a couple of things back:

I replaced the nint(C) expression, which you had substituted with a bit of computer code. I imagine many people will use calculators, not computers. INT is not implemented on any calculator I have seen. However, anyone who is using a calculator will be able to subtract the correct nint(C) just by looking at the numbers.

I replaced a bit of explanation about the problem with Arctangent. Most non-mathematicians do not realize that it has many values.

I also noticed that you shifted the graph, saying you had improved its position. On my screen, it definitely looked better as I had left it. I'm not sure which position would be better on most people's screens.

You changed the title of my Equation of Time calculation, but you did not change the link I had put on the Declination page that points to it. I've fixed it.

You cut out a lot of little bits of explanation, presumably to save space. But how important is it to save space in Wikipedia?

DOwenWilliams (talk) 19:58, 1 December 2011 (UTC)

I think good writing begins with brevity, although it is usually the last step in the process. I think it also increases the chances of the content remaining. I changed "int" because i expect the vast majority interested will know what it means, and i gave context where they can figure it out. I've never heard of "nint".Ywaz (talk) 17:08, 2 December 2011 (UTC)

"Nint" is rare. That's why I explained it in the text. Explanation is generally better than hoping that readers will somehow figure something out on their own.

Incidentally, I moved that graph into the middle of the screen, and expanded it so the differences between the two curves are easily visible. How does it now look on your screen?

DOwenWilliams (talk) 16:21, 2 December 2011 (UTC)

But INT is not rare, not needing any explanation. The "nint" is what jumped out at me, evoking visions of a Monty Python scene. NINT appears to be Fortran (RINT in c). Now the graph is OK, except it's unusually large. I'm using FF on windows 7. Ywaz (talk) 17:08, 2 December 2011 (UTC)

INT is extremely rare, essentially unknown except to people who program computers. Maybe you lived through the time, as did I, when using a computer meant writing programs for it. But that is no longer true. The vast majority of computer users now just "get" (buy, steal, whatever) potted software, and depend entirely on it.

I wouldn't greatly object to using INT instead of nint if it were accompanied by an explanation. But explaining INT(C+0.5) would be more difficult than just explaining nint. KISS.

Incidentally, in some versions of Basic the nint function can be programmed as CINT (Convert to INTeger). However, that invites embarrassing typoes!

I tried several browsers (IE8, Chrome, Firefox, Safari) to check that the graph looked all right in its previous position, and they all showed it neatly. I'm using a Dell laptop with a regular-size screen. So I can't imagine why it didn't look ok on your screen. However, if the present position looks reasonably ok, let's keep it that way.

Someone left a post on the EoT Talk page this morning saying that the integer subtraction implied that the Equation of Time must be expressed in seconds, not minutes. Frankly, his logic completely escaped me, as our logic apparently escaped him. I wrote him a fairly detailed explanation. I don't know if that will help.

Monty Python... I used to watch every new episode.

DOwenWilliams (talk) 23:03, 2 December 2011 (UTC)

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