Wikipedia:Articles for deletion/Newcomb's formula

The following discussion is an archived debate of the proposed deletion of the article below. Please do not modify it. Subsequent comments should be made on the appropriate discussion page (such as the article's talk page or in a deletion review). No further edits should be made to this page.

The result was merge to Newcomb's Tables of the Sun. Spartaz ^Humbug! 18:27, 5 July 2011 (UTC)[reply]

Newcomb's formula

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This is a fork of Earth's rotation. It is also unreferenced and contains many errors. Jc3s5h (talk) 12:59, 19 June 2011 (UTC)[reply]

This is a key formula used everywhere in the world, for astronomy and spacecraft operations. As opposed to many other Wikipedia articles under this category (category timekeeping etc) it contains no nonsense! For this latter matter, see for example the discussion of Year

Stamcose (talk) 19:25, 19 June 2011 (UTC)[reply]

The problems with the article could be solved, but since the formula is an approximation to sidereal time, any mention of the formula belongs in that article, rather than devoting an entire article to one formula. Indeed, the Exact duration and its variation section in that article should be improved to show the most recent definition. A simpler approximation than Newcomb's formula is already in the "Sidereal time" article; whether Newcomb's formula ought to be included as an approximation intermediate between the one already in the article and the definitive version that can be found on pages B7–B9 of the Astronomical Almanac for the year 2011 (2010, published by the US Naval Observatory and the UK Hydrographic Office) is a matter for discussion at Talk:Sidereal time. Jc3s5h (talk) 20:09, 19 June 2011 (UTC)[reply]

Note: This debate has been included in the list of Science-related deletion discussions. — • Gene93k (talk) 02:00, 20 June 2011 (UTC)[reply]

Delete those wishing to convince wikipedia at large need independent third party references, not complex logic. Stuartyeates (talk) 09:58, 20 June 2011 (UTC)[reply]

Merge with sidereal time. Not enough to qualify for a standalone article. Owen× ☎ 11:31, 20 June 2011 (UTC)[reply]
Keep. Based on Google scholar and Google books search results, this is notable and it is not difficult to provide reliable sources. The formula is clearly of historical significance; the argument that in the 115 years that have since elapsed we have improved on it is irrelevant for its notability. There also appears to be enough material for expansion. --Lambiam 21:56, 20 June 2011 (UTC) (see below for my revised recommendation. --L.)[reply]
If enough references can be added, then keep, otherwise merge as per OxenX. - UtherSRG (talk) 23:27, 20 June 2011 (UTC)[reply]
I've never been called an ox, much less oxen, but I like the sound of it. :) Owen× ☎ 23:41, 20 June 2011 (UTC)[reply]
Move to Earth rotation angle and expand.
This identical formula appears in the Conventions document of several European Space Agency missions: [1] p.27, [2] p.51, [3] p.36, [4] p.29, etc. However, all of these documents call it the Greenwich sidereal angle within a section entitled Earth rotation angle obtained from GSA by adding a small nutation in longitude term. All mention the term Newcomb's formula in a historical sense: "The Greenwich sidereal angle moves with the daily rotation of the Earth and is calculated with the Newcomb's formula according to international conventions as a third order polynomial, ..." Newcomb's formula is too generic because it is used for at least four different formulas presented in Newcomb's Tables of the Sun [5] in, for example, the article [6]. IERS neglects the third order term, folds the small nutation in longitude term into the coefficient of T, and shifts the epoch from midnight to noon 2000 January 1, calling it the Earth rotation angle (ERA) in IERS Conventions (1996) p.76 (chapter 8), also see stellar angle on p.34 (chapter 5). The latest IERS Conventions (2010) only uses the term Earth rotation angle on p.52 (chapter 5). This appears in a slightly different form on page B8 of the 2011 Astronomical Almanac. It was developed in 1986 [7]. The concept of an angle is sufficiently different from a time to warrant a separate article. — Joe Kress (talk) 23:23, 22 June 2011 (UTC)[reply]
Regardless of the merits of the contents of the present article, I think the topic of Newcomb's formula is of considerable historic interest, and deserves to be treated in historical perspective (as opposed to merely listing somewhere the currently adopted formula as most recently determined by the IERS). I'm not an astronomer and I may be wrong, but it seems to me that the "original" Newcomb's formula was a formula for the right ascension of the mean Sun, and that other formulas dubbed "Newcomb's formula", such as for relating universal and sidereal time, are derived from it. I see many formulas in the article "Computing precise star co-ordinates" referred to above, but as I read it, only one is referred to as being Newcomb's formula, while other formulas are said to be computed by it. --Lambiam 08:50, 24 June 2011 (UTC)[reply]

Other astronomers provided formulas similar to Newcomb's. Newcomb's stand out as having been adopted by the entire astronomical community from the late 1800's through 1983. They might or might not stand out for the number and time span of observations used in the calculations; I'm not qualified to say anything about that. So if there were to be an article about Newcomb's formula(s) the article would need to explain what distinguishes Newcomb's from earlier equations of the same form.

By the way, no one is suggesting the technical Wikipedia procedure that prevents an article named "Newcomb's formula" from being created in the future. A possible course of action is to delete it for now and hope someone with sufficient interest will create a suitable article in the future. Jc3s5h (talk) 13:20, 24 June 2011 (UTC)[reply]

Also, the article "Computing precise star co-ordinates" is only mentioned by Lambian, so I can't tell which one it is. Jc3s5h (talk) 13:23, 24 June 2011 (UTC)[reply]

It is the article found at this link, given as an example above by Joe Kress. --Lambiam 13:41, 24 June 2011 (UTC)[reply]

I agree that the history of this formula should be included in the expanded article, including all of its historical forms, both its original form by Newcomb (whatever formula that was) as well as its Greenwich sidereal angle form prior to the advent of the Earth rotation angle. — Joe Kress (talk) 18:10, 28 June 2011 (UTC)[reply]

Relisted to generate a more thorough discussion so a clearer consensus may be reached.

Please add new comments below this notice. Thanks, J04n(talk page) 10:03, 27 June 2011 (UTC)[reply]

Keep. This article is not even a month old. It does need citations, it should have a stub tag and of course, if there really are errors they should be fixed). I don't see what is the rush. It's not hurting Wikipedia by being there. Give it some time. If you still think it's all that bad after a few months, resubmit to AFD. I concur with the conclusion below based on the new information given. --TimL (talk) 20:42, 27 June 2011 (UTC)[reply]

Divide and merge. The Explanatory Supplement to the Ephemeris (1961) gives this formula on page 75:

G.M.S.T. of 0^h U.T. = 6^h 38^m 45.836^s + 86 40184.542^sT_U + 0.0929^sT_U²

where "T_U is the number of Julian centuries of 36525 days of universal time elapsed since the epoch of Greenwich mean noon (regarded as 12^h) on 1900 January 0."

If this is restated for t_U (days rather than centuries) and stated in degrees rather than time it becomes

G.M.S.T. of 0^h U.T. = 99.690983° + 0.9856473354° T_U + 2.90°×10⁻¹³ T_U²

This formula is clearly related to the formula in the article. The difference in the constant term is expected due to different epochs. The reduction by about 360° in the linear term is because this formula is only valid at noon. ~~I can't explain the difference in the power of ten for the quadratic term~~. The power of 10 I calculated for the quadratic term coefficient nearly agrees with the European Space Agency documents cited by Joe Kress, and disagrees with the article. The formula in the Explanatory Supplement to the Ephemeris is exactly the same as the formula in Newcomb's Tables of the Sun for mean solar time, except 12 hours have been subtracted from the constant term and the subscript "U" has been added to T. Newcomb's formula for mean solar time has also been reproduced in Explanatory Supplement to the Ephemeris. So I would suggest the original form of the formula be merged to Newcomb's Tables of the Sun and any refinements in the formula that are noteworthy be placed in Sidereal time. Jc3s5h (talk) 13:13, 29 June 2011 (UTC)[reply]

Merge and redirect to Newcomb's Tables of the Sun per Jc3s5h – while referring to Sidereal time for updates. --Lambiam 22:28, 1 July 2011 (UTC)[reply]

The above discussion is preserved as an archive of the debate. Please do not modify it. Subsequent comments should be made on the appropriate discussion page (such as the article's talk page or in a deletion review). No further edits should be made to this page.