Talk:Equator

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Seasons[edit]

"Normal seasons can not occur at the equator."

Yet equatorial countries do have seasons. What is the explanation for this? Participation in non-local weather systems? -- The Anome

That's why I said "Normal" --- Karl Palmen


I deleted the sentence

"Normal seasons can not occur at the equator."

What constitutes a "normal" season is relative, and it is absurd to identify spring/summer/winter/fall as "normal" seasons just because many wikipedians live in temperate zones and are used to it. It's like saying, people in the tropics don't speak a normal language, because whatever they speak it isn't what I am used to. No, the seasons at the equator, just like the languages people speak, are indeed different from what you find in Nebraska (for example) -- but that doesn't make them abnormal. Indeed, people time all sorts of activities according to their seasons.

People who live on the equator identify all sorts of seasons and a good encyclopedia article will explore this. I don't know enough to do justice to it, but I hope my change is a step in the right direction. SR

Thanks to User:MPF for correcting my excess verbosity.  :) He's right, of course: an object doesn't have to be solid to have an equator. This is what I get for editing late at night after reading Jack Vance. ZorkFox 06:43, 30 September 2005 (UTC)

Pini[edit]

I deleted Pini island from the list as it is actually a handful of miles north of the equator (0.13 degrees north). Anagnorisis 19:26, 23 October 2005 (UTC)


Why should individual islands be deleted for all countries except Indonesia, Ecuador, and ST&P? --User:Lasunncty

Countries through whose waters the equator passes[edit]

How do we find out what waters belong to which nations? I am sceptical about Singapore being part of the list; the wiki page for it states that it is 137km north of the equator. How far do its waters stretch? --Spudtater 22:47, 13 February 2006 (UTC)

Definitely out of the 12 nautical miles denoted by the United Nations Convention on the Law of the Sea.

Crossing the line at the Prime Meridian[edit]

Note that this page currently calls sailors who cross at the point where the equator meets the Prime Meridian "Emerald Shellbacks" whereas the page Line-crossing ceremony calls them "Royal Diamond Shellbacks". Possibly both are correct. Could someone who knows about these titles edit either or both pages to show either the correct or both names. :-) Stelio 21:18, 8 April 2006 (UTC)

Also, "If the crossing of the equator is done at the 180th meridian, the title of "Golden Shellback" is conferred, recognizing the simultaneous entry into the realm of the Golden Dragon." But according to the other article, it's for the international date line (which coincides with the equator between 165°W and 180°) - does any crossing at any of these points give the title? What if the two are crossed on separate occasions, as "recognizing ... entry into the realm of the Golden Dragon" implies that it's just a combined title for the two crossings? --Random832 (contribs) 18:41, 22 July 2008 (UTC)

What about the water flow?[edit]

In the northern hemisphere the water drains clockwise and vice versa......

But what happens at the equator???

Do you cross a point where the waters direction changes automatically? Or is it a random changing?

This is an urban legand. In practice, the Coriolis effect is too weak to have such an effect except in very unusual circumstances. You can check out the references article and also do a search (I've seen some good discussion online Nil Einne 15:44, 21 June 2006 (UTC)

Presumably the "unusual circumstances" would be something along the following lines. Factors include whatever residual angular momentum the bather contributed to the water, any assymetries in the tub, and the Coriolis force at the local latitude, let's assume it to be 45 degrees for the moment. Although the last is always small, when all the other factors are small as well (extremely hard to arrange but certainly not impossible) there is a chance that they will all sum to much smaller than the local Coriolis force. In that case the choice should be pretty much random (even odds), and one should then be able to say that with the exact same setup at the equator the choice would be a little less random since the sum of the other factors would then be the negation of the Coriolis force at 45 degrees. Conversely when the factors sum to zero at the equator, then the choice would be made more randomly at the equator than at 45 degrees where there would be a (very slight) bias away from even odds. So circumstances could arise to make it a "random changing," but not necessarily at the equator: any latitude could be a candidate for such circumstances, however unlikely. Nor would one expect the equator to be a preferred candidate to any significant degree. --Vaughan Pratt (talk) 05:31, 4 February 2008 (UTC)

Equator History[edit]

What is the history of the name "Equator" for the latitude 0 line?

It's originally from Latin, "circulus aequator diei et noctis", which means "circle equalising day and night". That referred specifically to the Celestial equator, but you can think of an "equator" as being something that splits a sphere into two parts that "equate"; i.e. two equal parts. 143.252.80.110 19:28, 21 June 2006 (UTC)

68.188.203.251 (talk) 15:21, 29 March 2013 (UTC) May the readers please have a history of equatorial movement in relation to geography? As geology presents more info as to the age of land masses, the equator is also defined. This site lack the normal information as to equatorial movement during the past 500 million years, altho it can be found by diligent effort culling thru web pages.

Comma[edit]

In many places in the world the comma is used as a decmil seperator instead of the period. I change the seperator of groups of three digits to a space to aliviate any confusion. I left periods as the decmil seperator for now. —The preceding unsigned comment was added by 75.14.55.227 (talk) S.D. ¿п? § 00:52, 2 February 2007 (UTC)

Among English-speaking countries, only Australia uses the SI style (see Decimal separator), and the article isn't written in Australian English. Furthermore, other numbers within the article used the comma. I've made the article consistently use the comma as the group separator, as is customary in a majority of English-speaking countries. Susan Davis 13:15, 2 February 2007 (UTC)
I agree: let people outside of North America, the United Kingdom, Ireland, etc., do as they please conerning numbers, but in this Wikipedia, we use commas in our numbers, like this: 123,456,789
Also, the use of the decimal point in numbers was introduced by and popularized by the British mathematician John Napier, who was also the inventor of the logarithm.

98.81.38.184 (talk) 23:58, 13 December 2010 (UTC)

citation for shellback award/ceremony[edit]

http://www.history.navy.mil/faqs/faq92-3.htm don't have time to put it in nicely cited, someone go ahead :) —Hobart 14:47, 8 March 2007 (UTC)

Worldwide view[edit]

This article is extremely biased towards Earthlings. I am not trying to be racist or anything, but there are gazillions of other planets, and this article is not paying much attention to that fact. It is written in a very Earth-centric way. May further edits please respect the diversity of the universe and not discriminate against the rest of the creation. Adriaan90 ( TalkContribs ) ♪♫ 17:31, 12 March 2007 (UTC)

I agree with this statement. -Indolences 23:10, 23 April 2007 (UTC)
In view of this alleged large number of other planets we earthlings are going to have to band together to protect ourselves from alien perspectives. Wikipedia is by earthlings for earthlings. Let aliens write their own stuff, and let us decide when the time is right to work on reconciling how we we think with alien perspectives, whatever they may turn out to be. If we run into aliens who do their best work at age five minutes and advocate euthanasia at ten minutes I for one would advocate steering clear of such lest they corrupt our impressionable youth. --Vaughan Pratt (talk) 11:51, 23 December 2007 (UTC)

Original mapping[edit]

I think it would be helpful and interesting to note how and when the equator was first identified, and how those people were able to do it. --Robertknyc 04:56, 24 March 2007 (UTC)

Exact length of the equator[edit]

I corrected and expanded the brief, unsourced, and slightly inaccurate claims by User Talk:Wikinger concerning the exact length of the equator, and moved them to their own section. Thanks to James Q. Jacobs ([[1]] and correspondence by phone and email) for the Moritz reference and insights into the origins of these numbers. (The slight inaccuracy was Wikinger's claim that the cited equatorial lengths were exact, which they clearly are not since integers are rational while π is not. Judging by the feedback at User Talk:Wikinger this was one of his better contributions.) --Vaughan Pratt 06:50, 15 August 2007 (UTC)

Nonsensical[edit]

"These rituals date back to the Middle Ages, though the current ceremonies are most likely derived from Viking traditions."

If they date back to the middle ages why are people using Viking traditions, the Viking era being pre middle ages. Makes no sense. Someone just made this crap up. Wikiality. —Preceding unsigned comment added by 86.151.226.85 (talk) 01:01, 26 December 2007 (UTC)

You'll find that as commonly defined, for example in the respective Wikipedia entries, the Viking Age (ca AD 700-1100) is a part of the Middle Ages (ca AD 500-1500). However, I do very much doubt that the Equator-crossing ceremonies have anything whatsoever to do with vikings and took the liberty of putting a citation needed on the claim. 85.8.12.78 (talk) 16:21, 6 May 2008 (UTC)

More importantly there is no record of any European, Viking or other, crossing the Equator in the Middle Ages. This would mean they had reached southern Africa or South America!!!--Jack Upland (talk) 06:17, 27 November 2011 (UTC)

Map line[edit]

The red line on the map seems very 'thick' - as if the equator is a variable value between the top of the line and the bottom. I don't know much about the subject but surely this isn't the case ? Boomshanka (talk) 03:01, 21 January 2008 (UTC)

The equator is infinitely thin. Try drawing an infinitely thin line on a map - can't be done. The only way you can show where it is is by making it artificially thicker. Bazonka (talk) 10:42, 21 January 2008 (UTC)

Kilometre/mile conversion[edit]

"Despite its name, no part of Equatorial Guinea's territory lies on the equator. However, its island of Annobón is about 100 miles (200 km) south of the equator, and the rest of the country lies to the north" (emphasis added). This is taken from the section about which countries the equator passes through, but on this statement about Equatorial Guinea, the island of Annóbon is said to be 100 miles south of the equator, and then (in brackets) is said to be 200 km from it. Considering 100 miles ≠ 200 km (I think 100 mi is about 160 km), which one is it? 100 miles or 200 km? -- 80.41.149.192 (talk) 08:32, 24 May 2008 (UTC)

A quick play with the Google Earth ruler shows that it's about 97 miles or 155 km south. I'll fix the article. Well spotted. Bazonka (talk) 09:22, 24 May 2008 (UTC)

Prime Meridian[edit]

I added mention of the Prime Meridian to the table of coordinates, but was reverted. I think it's significant enough to warrant inclusion there. Andy Mabbett (User:Pigsonthewing); Andy's talk; Andy's edits 17:13, 22 September 2009 (UTC)

I reverted it because it's already there - in the introduction to the table: "Starting at the Prime Meridian and heading eastwards, the equator passes through:" We could add co-ordinates into that sentence, but that seems pretty pointless because they're exactly the same as the co-ordinates in the first line of the table. Bazonka (talk) 18:12, 22 September 2009 (UTC)

Closest Country[edit]

The article states The country that comes closest to the equator without actually touching it is Peru. Kiribati, with the landmass of Aranuka atoll, comes closer, without actually touching it (the latter, unless some water around the atoll is considered part of the country). Unlike Peru, Kiribati has parts north and south of the equator. Thus, a modified statement The country that comes closest to the equator without actually touching and being wholly either north or south of it it is Peru. But maybe that statement would be too specific for anyone to care about...--93.196.3.11 (talk) 19:43, 22 November 2009 (UTC)

Sorry, all wrong. Aranuka is 13 km north, but Peru is only 4.3 km south of the equator.--93.196.3.11 (talk) 19:54, 22 November 2009 (UTC)

Capitalization[edit]

While it's a little grammar nazi, whether or not equator is capitalized when referring to Earth's equator isn't clear cut [2]. Not the best ref in the world. Regardless, you clearly shouldn't capitalize equator in interwiki links or when it refers to equators in general. PirateArgh!!1! 05:36, 16 February 2010 (UTC)

I will agree with you on this case. However, I think it should be capitalised when preceding "the" in the same way that "the Prime Meridian" is capitalised. This can sort of be seen here and here. Also, this page on proper nouns supports it. So in short, I suggest that the term "equator" be capitalised in the phrase "the Equator" and left uncapitalised in all other cases, such as "Earth's equator" or "celestial equator" etc. Hope this helps. Set Sail For The Seven Seas 191° 37' 15" NET 12:46, 16 February 2010 (UTC)
I couldn't find anything definite either way, so that seems reasonable. PirateArgh!!1! 06:02, 17 February 2010 (UTC)
Speaking of capitalization, the word "Nazi" is always capitalized. Sadly, but truly. On the other hand, "fascist", "capitalist", "communist", and "dictorship" are usually common nouns and adjectives. We can make aa exception to that for "Fascist Italy". However, the term "Celestrial Equator" can be taken as a proper noun. 98.81.38.184 (talk) 00:07, 14 December 2010 (UTC)

Equatorial circumference[edit]

"The length of Earth's equator is 40,008.629 kilometres"

That looks like the polar circumference to me. WGS84 specifies 40075.16 km. Either way the figure probably needs a citation. —Preceding unsigned comment added by 217.40.148.115 (talk) 09:17, 6 October 2010 (UTC)

The motion of the Equator, over the course of a year, is not circular.[edit]

Over the course of a year, the drift, or wobble, of the Equator is not circular, but rather it is north-south.

In another way of looking at it, the motion of the Equator is a far-more complicated curve than this -- but it is definitely not circular. 98.81.38.184 (talk) 00:12, 14 December 2010 (UTC)

Concerning the length of the Equator[edit]

Arguing about the length of the Equator down to the nearest centimeter of millimeter is a fruitless task.

On the surface of the Earth, the Equator goes uphill and down a great deal, especially in Ecuador and in Central Africa. None of the calculations in this article take this into consideration -- and for a good reason: that distance has never been surveyed. Among other problems, that would be a completely-impractical project in Ecudor, Brazil, and Central Africa.

As a general example, an absolutely straight highway between Washington, D.C. and San Francisco would have its length increased because of its crossing the the Appalachian Mountains, the Rocky Mountains, the Sierra Nevada, and all of the other hills and mountains in between the two. The shortest distance would require tunneling though all of them - at least mentally. 98.81.38.184 (talk) 00:23, 14 December 2010 (UTC)

Climate[edit]

"The climate in the area around the equator is hot." This is not necessarily true. Consider the climate in Quito, Ecuador, for example —Preceding unsigned comment added by 200.125.141.194 (talk) 06:04, 5 January 2011 (UTC)

That sentence was added on Oct 25. I'm surprised it has lasted this long, but it is now gone. --Lasunncty (talk) 06:34, 5 January 2011 (UTC)

Has it moved after the Earthquake?[edit]

Following the 2011 Sendai earthquake, it was said that Japan has moved by 8 feet and the Earth's axis has moved by 10cm. If we define the north and south poles as where the axis of rotation meets the surface of the Earth on both sides, then has the Equator also moved? We need an expert. - Richard Cavell (talk) 06:11, 24 March 2011 (UTC)

Yes, the Equator moved. But that's no big deal, it moves all the time. See for example, http://hpiers.obspm.fr/eop-pc/index.php?index=news and http://en.wikipedia.org/wiki/Chandler_wobble. The motion is irregular, but it's fair to say that a typical rate is 3 cm/day. To get around this situation, legal coordinates (including GPS) use a "conventional" pole = where the pole was about 1900-1905. --ExtonGuy (talk) 15:46, 30 May 2011 (UTC) (not an expert, but I have stayed at Holiday Inn Express)

French Guiana[edit]

French Guiana is not near the Prime Meridian. So why is it colored like a country that touches the Prime Meridian?? Georgia guy (talk) 17:03, 16 November 2011 (UTC)

French Guiana is part of France. --Lasunncty (talk) 09:58, 17 November 2011 (UTC)

Exact Length[edit]

The current length seems to underestimate the length by a factor of a million!!!!!!!!!!--Jack Upland (talk) 06:12, 27 November 2011 (UTC)

The length given in the Geodesy of the Equator section seems reasonable: 40,030.2 km. But the Exact length of the Equator section, which presumably is what you are referring to, is confusing and unclear. Also, it is totally unreferenced. I propose removing this section entirely - I don't think it adds anything meaningful to the article. Bazonka (talk) 09:20, 27 November 2011 (UTC)

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Image changing[edit]

I decided to change the Intiñan image and use one of the Quitsato Sundial. Not only there are sources who verify the sundial's precision, but also, because there are sources who indicates that at Intiñan, there are being performed non-scientifical experiments just for the amusing of the tourists and, even, they are not exactly at the Equator.

http://www.ems.psu.edu/~fraser/Bad/BadCoriolis.html http://www.badastronomy.com/bad/misc/egg_spin.html#badegg Gatoparlante (talk) 09:45, 26 June 2012 (UTC)

False statement was restored[edit]

Currently the section Geodesy of the Equator says

At the Equator, the rays of the sun are perpendicular to the surface of the earth on these dates [the equinoxes].

I amended it to

At any point on the Equator, the rays of the sun are perpendicular to the surface of the earth at noon on these dates.

but my revision was reverted with edit summary

I see what you're saying, but I think this wording could create some confusion.

(1) I don't see how the revised but reverted wording could possibly create any confusion -- it is precise, and it is true.

(2) The old and restored wording is, well, ludicrously false except at one point (the point experiencing noon). For examples, at any point on the equator experiencing sundown on the equinox, the sun's rays are 90° away from being perpendicular, and at a point at which it is 3:00 PM the rays are at 45°.

Let's come up with a wording that is true -- be my guest if you have a better one than mine. Duoduoduo (talk) 16:52, 29 November 2012 (UTC)

The equinox is an instant-- it doesn't last a day. So the sun is directly above one equatorial point at noon, not any equatorial point. (And that's noon solar time, not noon clock time, so might as well leave noon out of it.) Tim Zukas (talk) 18:07, 29 November 2012 (UTC)
Yes, that is what I was thinking. --Lasunncty (talk) 11:46, 1 December 2012 (UTC)

The word "equinox" is most generally and most usefully used in the "broader sense" stated in the lead of the Equinox article, ie it refers to a day rather than a precise moment. If you want to use it in a more restricted sense, please bear in mind that in general, for any particular point on the equator, noon never falls at precisely the right moment for the sun to be directly overhead at that time, so the equinox in that sense never occurs. --Ehrenkater (talk) 14:11, 1 December 2012 (UTC) (In more scientific language, at a given location on the Earth's surface, the Sun's right ascension and declination are never both precisely zero at the same time, as these are two degrees of freedom and time only provides one degree of freedom.)--Ehrenkater (talk) 14:44, 1 December 2012 (UTC)

Not that "useful" to speak of the equinox as a date rather than an instant. We agree it actually is an instant, so it won't happen on the same date for the whole world. Tim Zukas (talk) 16:51, 7 December 2012 (UTC)

Opening sentence[edit]

"An equator is the imaginary straight line that passes through a planet's center, and that is aligned with the planet's direction of rotation."

There are at least two things seriously wrong with this sentence:

  1. The equator is not a straight line; it's a curve
  2. The equator does not go through the planet's center; it follows the planet's surface

Can someone come up with a better definition? Julesd 02:36, 27 December 2012 (UTC)

  • i'm not sure about how you define a straight line, but on a sphere, if a line never changes angles, i would say it would be indeed straight; in the sense that its angle remains unchanged. The geometric term for this is either great circle or also "orthodrome". However you are right about the expression "going through"; although, geometrically speaking the equator does pass through the center of the circular sphere in a geometrical sense, we can still say that it "passes across" the planet's center. thanks for the observation. Maysarathustra (talk) 15:52, 27 December 2012 (UTC)
"Passes across" is very clumsy and unclear wording. Better to say that it shares its centre with the planet's centre. Bazonka (talk) 10:44, 5 January 2013 (UTC)

Not sure about these statements[edit]

1. "Places on the Equator experience the quickest rates of sunrise and sunset in the world since the sun rises and sets nearly vertically (exactly vertically at the equinoxes)."

It seems to me that this is almost correct in one interpretation, in that on the equinoxes a near-vertical trajectory extends all the way up to and down from the zenith, but misleading in another respect since at the time of sunrise and sunset the sun's trajectory is almost exactly vertical on every day, and no more so on the equinoxes than at any other time.


2. "Such places [= places on the Equator] also have a theoretical constant 12 hours of day and night throughout the year, though in practice there are variations of a few minutes due to the effects of atmospheric refraction and because sunrise and sunset are measured from the time that the edge of the Sun's disk is on the horizon, rather than the center of the disk."

It seems to me that places on the Equator do not even theoretically have exactly 12 hours of day, even disregarding the effects mentioned. 86.160.222.44 (talk) 01:56, 4 January 2013 (UTC)

You are correct about your first point. I will change it in the article. About your second point, however, the article is correct as is. Think about it this way: The equator is the only latitude where (theoretically) exactly half of every declination circle is above the horizon and the other half below. --Lasunncty (talk) 09:44, 5 January 2013 (UTC)
Thanks for your reply. I believe you are incorrect about the second point. You would be correct if the Earth was fixed in space, but the fact that the Earth orbits the Sun, combined with the Earth's tilt, causes very small variations in day length over the year. This is not the easiest thing to visualise, and a simple visualisation, such as the one you talk of, misses it. I also suspect that the sun does not rise and set exactly vertically, but the deviation is probably very small, and it may be satisfactory for the article to say "since the sun rises and sets vertically" as there is no mention of absolute exactness. 86.160.216.227 (talk) 03:37, 6 January 2013 (UTC)
I dropped a note at the Astronomy project page inviting further comments. 86.160.216.227 (talk) 03:48, 6 January 2013 (UTC)
However, the tilt of the Earth is actually centered on the equator, never changing with season (this is hard to visualize). There can be no deviation in day length at the equator for that reason. Wer900talk 03:52, 6 January 2013 (UTC)
I will get back to the tilt later when I have thought of a way to clearly explain what I am thinking – then maybe someone can demonstrate where it is wrong, if it is wrong. However, for now, even ignoring the tilt, would the ellipticity of the Earth's orbit not cause a slight variation? The Earth keeps on revolving on its axis at always the same rate, yet the effective rate at which it revolves around the sun varies depending on where it is in the orbit. Result: slightly varying day length throughout the year. 86.160.216.227 (talk) 04:19, 6 January 2013 (UTC)
OK, to illustrate the tilt effect, I have drawn a graphic at http://img845.imageshack.us/img845/2818/daylength.png .
This is a very exaggerated example of the effect, assuming a planet with an axial tilt of 80 degrees, and three days in a year. The orbit is assumed to be exactly circular.
The drawn globes are spaced at equal intervals of one eighth of the planet's sidereal day.
The black dot is a particular point on the Equator which we're interested in. The Equator appears as a narrow ellipse, with the obscured part shown dotted. The shaded hemisphere is night and the unshaded day.
The red and blue dots mark the exact points in the orbit where the black dot experiences sunrise and sunset respectively. (These do not exactly correspond in position to drawn globes, but it is easy to roughly interpolate by eye.)
As you can see, the distribution of red and blue dots is uneven, showing how the day length varies throughout the year. I believe the same effect occurs at the Equator on Earth, though the differences in day length are much smaller. Of course, the Earth has the added complication of having an elliptical orbit.
If you can see any error in this I would be most grateful to have it pointed out. 86.171.43.130 (talk) 01:01, 7 January 2013 (UTC)

You're thinking too hard. Just look at the arc the sun moves thru, viewed from the equator. When you're standing on the equator every star (including the sun) moves thru a 180-degree arc between its rise and its set. Polaris moves thru a very small semicircle, but it's still a 180-degree arc, and takes the same time as for all the other stars.

(This isn't exact, due to refraction and the earth's elliptical orbit and so on, but when you're on the equator in the middle of the ocean sunrise to sunset is always a few minutes more than 12 hours.) Tim Zukas (talk) 19:44, 7 January 2013 (UTC)

The sun is different from the other stars because the Earth is revolving around it. Even the sidereal day is obviously a different length from the solar day, so such simplistic comparisons are invalid. Please look at the diagram and say where it is wrong. 86.160.214.104 (talk) 20:53, 7 January 2013 (UTC)
By the way, the question is whether the day length at the Equator is theoretically exactly 12 hours every day, ignoring refraction and based on the time when the centre of the sun crosses the horizon. Exactly does really mean exactly. No one is questioning that the day length is 12 hours within a few minutes. 86.160.214.104 (talk) 20:59, 7 January 2013 (UTC)
"No one is questioning that the day length is 12 hours within a few minutes."
How many minutes variation during the year do you think there is?
"the question is whether the day length at the Equator is theoretically exactly 12 hours every day, ignoring refraction and based on the time when the centre of the sun crosses the horizon."
It isn't; hopefully the article doesn't say it is? Tim Zukas (talk) 22:21, 7 January 2013 (UTC)

Ok, now I see what you're getting at. Taking derivatives of the equation of time, we find that the fastest change is less than 30 seconds/day, so depending on time of year, the day/night would be between 11h59m45s and 12h00m15s (again ignoring the horizon and refraction effects). But the day and night would both remain about equal throughout the year, differing by no more than 0.4s. I also calculated the max variation in angle of sunrise/sunset and found it to be only ~0.06° from vertical (ignoring refraction). So the latitude with the fastest sunrise/sunset would vary within that angle of the equator, amounting to about 7km. Personally, I don't think all this explanation is necessary in the article (plus I calculated it myself rather than finding a source), but I will put a note explaining just how "exact" we mean. Someone can check my math if you wish. --Lasunncty (talk) 12:22, 8 January 2013 (UTC)

According to my theoretical calculations, assuming a circular orbit, and making all other simplifying assumptions discussed before, the day/night length at the Equator varies from the supposed 12h by up to +/- c. 11 seconds over the year. This is a purely geometrical effect, purely due to the fact that Earth's rotation axis is titled and the Earth is orbiting around the Sun. That +/-11 seconds is pretty close to your 11h59m45s and 12h00m15s; the discrepancy may well be due to the slight ellipticity of the orbit. I'm sorry, I do not understand what your 0.4 seconds refers to. Although the differences of a few seconds are tiny, it may be worth mentioning in the article since it seems to be a common misunderstanding that according to the theoretical geometry the day length should be exactly 12 hours. In my opinion the current comment "...this has little effect on the difference between day and night" is unclear. I don't think "the difference between day and night" is what was meant, or, if it was, I don't understand the point. 86.179.7.159 (talk) 01:21, 17 January 2013 (UTC)
Yes, The ±15s I came up with is a combined effect of the tilt and eccentricity. The 0.4s is the estimated max difference between daytime and nighttime on any given day. I changed the statement from "constant 12 hours of day and night" to "nearly equal day and night" to show that while the day and night may not be exactly 12 hours, they are always pretty close to half of the apparent solar day. If you think this point should be expanded/clarified, feel free to do so! --Lasunncty (talk) 09:07, 17 January 2013 (UTC)
Oh yes, sorry, I get the 0.4s now. My calculation gives a maximum difference of c. 0.17s, but again that's with a circular orbit. Since the text does not mention actual figures, and since 15s and 0.4s equally call for "very nearly exactly"-type wording, the following comment is somewhat redundant, but I believe that basing "nearly equal day and night" on the ±0.4s figure is misleading without further explanation since most people will naturally assume that day + night = exactly 24 hours by definition, so if day and night differ by max. 0.4s then day and night individually differ from 12h by max. 0.2s, which, as we know, is wrong. 86.160.87.95 (talk) 18:13, 21 January 2013 (UTC)

definition of the equator[edit]

Please check the following reverts [3] regarding the very definition of equator and participate with your opinion. the current version stays because two editors agreed that the revert definition was "dubious and confusing" in terms of wording, although i maintain that it is at least much clearer than the current one, and much more accurate and informative. The reverted definition, which i had contributed earlier, is also, imho, quite similar to many other definitions which i have read in other sources, like here for example [4] Thank you, Maysarathustra (talk) 18:24, 4 January 2013 (UTC)

Accurate and informative is obviously good, but the lead section of an article also "should be written in a clear, accessible style" (see WP:LEAD), and I don't think your version really achieved this. What exactly do you think is wrong with the current paragraph? Bazonka (talk) 18:31, 4 January 2013 (UTC)
"An equator is the imaginary great circle line that passes across a planet's centre, and that is aligned with the planet's direction of rotation."
"passes across a planet's centre" makes no sense. "aligned with the planet's direction of rotation" makes no sense.
"the line of the equator may be defined also as the linear area on a planet whose relationship with the Sun remains more or less constant through out the year"
Makes no sense.
As well as adding stuff that makes no sense, you have removed stuff that does make sense. I appreciate your good intentions, but your edit actually makes the article worse, not better. 86.167.19.105 (talk) 18:48, 4 January 2013 (UTC)


  • I really can't see "why" they don't make sense, it seems like yours is a value judgment rather than an objective one. The current definition says absolutely nothing about the equator's relationship with the sun or the ecliptic (i.e. temperature and seasons), which is exactly what makes it relevant to most people reading about the Earth! imho. it does not even say that the equator is aligned with Earth's direction of rotation (which makes perfect sense to me!). it only explains where it is on the planet in terms of geometry, nothing more. the equator is not really a simple idea, and that's why its definition has got to bear some complexity, which may be understood by some, or require others to search further for more rudimentary information before they can grasp what it really is (such as the anon user needs to do imho). It's not my fault, it's not anybody's fault! What you have done is that you have avoided complexity altogether, by deleting all information that are directly relevant to its very definition. We do this in the simple English wikipedia, not necessarily here. Maysarathustra (talk) 18:57, 4 January 2013 (UTC)
There's nothing particularly wrong with the information that you're trying to include, but the lead is not the best place for it. Bazonka (talk) 19:10, 4 January 2013 (UTC)
Let me have a think about this (probably tomorrow) and I'll try to think of some alternative wording. Bazonka (talk) 19:22, 4 January 2013 (UTC)
All great circles "pass across" the earth's center-- or, better, none do. How is a circle supposed to "pass across" a point that it doesn't intersect?
"its definition has got to bear some complexity"
Its definition is pretty simple. There are halfway-complex things that are worth mentioning later on, but the definition should just be the definition. Tim Zukas (talk) 21:43, 4 January 2013 (UTC)
"it does not even say that the equator is aligned with Earth's direction of rotation (which makes perfect sense to me!)." That wording isn't awful, but it's easy to do better. How can a circle be "aligned" with a direction? The Tropic of Cancer is "aligned" with the earth's rotation just as much as the equator is. Tim Zukas (talk) 21:47, 4 January 2013 (UTC)
  • hi Tim, of course, any circle that is "perpendicular with the axis of rotation" is aligned with the direction of rotation. aligned does not refer to straight lines, it refers to angles. But if this is confusing to you then indeed i agree we should omit it. As a teacher myself, i find it very important to describe a fact from different angles so that, if one is not understood, the other would be. "perpendicular with the axis of rotation" is actually more complicated than to say that the line of the equator simply goes straight (i.e. aligned) with the direction of rotation. Tropic of Cancer is indeed thus aligned as well, but we are talking here about the equator. Anyways i wouldn't mind taking this "visual" statement off if you think it is confusing. As for the matter related to relationship with the sun, fine, if you think it shouldn't be in the definition (although i disagree), we should then think about adding the info in the section about seasons, which is very much inadequate imho. In it's current form, the article does not really explain "why" the equator has no seasons. To explain this, we have to describe matters related to constancy of equator's relationship with the sun despite of Earth's constant movement as it revolves around the sun in the ecliptic; which i have attempted to do in the definition section but might now need to move into the seasons sections. Most appreciatively, Maysarathustra (talk) 11:45, 5 January 2013 (UTC)
The concept of "constancy of equator's relationship with the sun" is an unclear one. There is nothing obviously more "constant" about the Equator in this respect than any other location on Earth. 86.160.216.227 (talk) 03:54, 6 January 2013 (UTC)

Diagram could be clearer[edit]

Seasons.svg

I am not a fan of this graphic. The areas marked as "low density" and "high density" appear on the diagram to have equal density. Just in case anyone with graphical ablities feels inclined to improve it... 86.171.42.159 (talk) 02:45, 29 January 2013 (UTC)

Seasons and climate[edit]

A couple of comments:

  1. It is unclear that there needs to be both an "Equatorial seasons and climate" section and a "Climate" section.
  2. The first paragraph of "Equatorial seasons and climate" talks about the general causes of seasonal variation, and then the second the says that there is little seasonal variation at the Equator, but there is no explanation of why, as if it is meant to be so obvious from the preceding explanation as to be not worth mentioning. I don't agree that it is so obvious, and I think those paragraphs should be better linked.
  3. "In many tropical regions people identify two seasons: the wet season and the dry season, but many places close to the Equator are on the oceans or rainy throughout the year." -- I find this sentence pretty confusing. It seems to be hedging its bets to the point of either contradicting itself or saying nothing worthwhile. Also "on the oceans" is an unfortunate phrasing that could mean on the coast or in the middle of the ocean. Whichever it is (my guess is the latter), what is being said about those places? That they do not have a wet season and a dry season because there are no people there so no one notices or cares? That they do not have a wet season and a dry season because the ocean affects the climate?

86.171.42.159 (talk) 03:07, 29 January 2013 (UTC)