Talk:Annus

Does anybody happen to know how annus came to be neuter in this scientific usage? Google suggests that it actually is called annum here, but I wonder... It is definitely and solely masculine in classical Latin, and as far as I can see, in medieval Latin as well. So I suppose it must be fairly recent? Maybe taken from the accusative case, as in per annum? T.a.k. 4 July 2005 21:02 (UTC)

According to the Oxford English Dictionary, per annum first appeared in the early seventeenth century, and is derived from the Latin accusative case of annus. However, my knowledge of Latin is limited, so I'm not sure how that relates to being neuter. — Joe Kress 5 July 2005 07:41 (UTC)

It's not neuter. It's masculine. Masculine accusative has the same suffix as neuter nominative. Woodwalker 12:58, 5 June 2006 (UTC)

As such, I think the article should reflect that the etymology is the accusative because it was derived from it's use in the phrase "per annum," and at least state that the plural is annos or annums (rather than, for example, anna). Eebster the Great (talk) 03:33, 3 March 2009 (UTC)

I am trying to find out whether Ma means million years or million years ago. The definition here says its 'million years' but i always learnt it meant 'million years ago'. Which one is correct? -- 130.223.103.212 15:25, August 5, 2005 (UTC)

"Mega" means "million;" "Annum" means "year." Obviously, prima facie, "mega-annum" (Ma) means "million years." However, in an appropriate context we may interpret it to mean "million years ago." Be careful not to confuse the term with mya, which does mean "million years ago." -- FP ^{<talk><edits>} 05:02, August 7, 2005 (UTC)

Nothing should be implicit when it refers to units, IMHO. If "ago" is included it means "date". If it is not included, it means "age". Jclerman 12:07, 19 March 2006 (UTC)

Sorry Jclerman, but as you said nothing should be implicit in metrology. If "ago" is not included then Ma is a quantity of time (aka duration). To get a date from that you have to nail down one end of the quantity, i.e. '3.5 Ma B.P.' (where present is defined as 1950-01-01) or '15 d from today'.

Hi. Contrary to the assertion of Georgia Guy, Ka is a commonly used abbreviation in the scientific literature, particularly by earth scientists and geophysicists working on time scales of 10^3 to 10^5 years. As per Georgia Guys request, I submit proof that Ka is a commonly used term. These are the first ten references from a search in the ISI Web of Science indexing service that contain "Ka" in their title, abstract or keywords that use Ka in the sense of kilo-annum. The search retrieved some 14,000 articles. This selection of papers represented 10 of the first 15 hits (the other five used Ka in a different sense, for example, as k-alpha in x-ray spectroscopy), suggesting that over 9300 of the hits used Ka in the sense suggested in this article. Since the term follows logically from Ma and Ga (also commonly used terms), it should stay here and not be transfered to Millennium (although perhaps it could be included in Millennium).

Channell, J. E. T., 2006. Late Brunhes polarity excursions (Mono Lake, Laschamp, Iceland Basin and Pringle Falls) recorded at ODP Site 919 (Irminger Basin). Earth And Planetary Science Letters, 244(1-2): 378-393.

Clarke, M. L. and Rendell, H. M., 2006. Effects of storminess, sand supply and the North Atlantic Oscillation on sand invasion and coastal dune accretion in western Portugal. Holocene, 16(3): 341-355.

Cucci, L., 2005. Geology versus myth: the Holocene evolution of the Sybaris Plain. Annals Of Geophysics, 48(6): 1017-1033.

Li, S. H. and Sun, J. M., 2006. Optical dating of Holocene dune sands from the Hulun Buir Desert, northeastern China. Holocene, 16(3): 457-462.

Maher, B. A. and Hu, M. Y., 2006. A high-resolution record of Holocene rainfall variations from the western Chinese Loess Plateau: antiphase behaviour of the African/Indian and East Asian summer monsoons. Holocene, 16(3): 309-319.

Pisias, N. G., Heusser, L., Heusser, C., Hostetler, S. W., Mix, A. C. and Weber, M., 2006. Radiolaria and pollen records from 0 to 50 ka at ODP Site 1233: continental and marine climate records from the Southeast Pacific. Quaternary Science Reviews, 25(5-6): 455-473.

Reid, E. and Thomas, M. F., 2006. A chronostratigraphy of mid- and late-Holocene slope evolution: Creagan a' Chaorainn, Northern Highlands, Scotland. Holocene, 16(3): 429-444.

Sinha, R., Smykatz-Kloss, W., Stuben, D., Harrison, S. P., Berner, Z. and Kramar, U., 2006. Late Quaternary palaeoclimatic reconstruction from the lacustrine sediments of the Sambhar playa core, Thar Desert margin, India. Palaeogeography Palaeoclimatology Palaeoecology, 233(3-4): 252-270.

Turney, C. S. M., Kershaw, A. P., James, S., Branch, N., Cowley, J., Fifield, L. K., :Jacobsen, G. and Moss, P., 2006. Geochemical changes recorded in Lynch's Crater, Northeastern Australia, over the past 50 ka. Palaeogeography Palaeoclimatology Palaeoecology, 233(3-4): 187-203.

Zhang, Z. H., Zhao, M. X., Eglinton, G., Lu, H. Y. and Huang, C. Y., 2006. Leaf wax lipids as paleovegetational and paleoenvironmental proxies for the Chinese Loess Plateau over the last 170 kyr. Quaternary Science Reviews, 25(5-6): 575-594.

Rickert 00:44, 7 May 2006 (UTC)

Rickert didn't specify if his search was case-sensitive. Checking the articles that are accessible, it is clear the usage is ka (as it should be), not Ka. Urhixidur 01:56, 16 March 2007 (UTC)

I would propose to merge this article with the articles Mya (unit), Bya and Gya. The suffixes do not make any difference to what the article is really about: the use of the unit annum in science. One article will be much clearer than three or four. We can have redirects on the other pages to cover the lot. Woodwalker 12:57, 5 June 2006 (UTC)

I totally agree.Rolinator 10:07, 29 October 2006 (UTC)

Are we sure that annum is the correct form? As mentioned above, annum is the nominative, and it would be far more regular to use the nominative, annus. The American Heritage Dictionary lists annus [1]. Unfortunately I do not have a copy of the ISO's Quantities and Units. Lesgles (talk) 05:22, 23 February 2007 (UTC)

Yes, except that the the expression is not "annum", but per annum. Per is a preposition that governs the accusative case. A simple English analogy might be "He is a man", but "I did this for him". JackofOz 01:40, 16 March 2007 (UTC)

This still leaves the question of whether, and why, the accusative is used here. 1 Ka is a thousand years, not "per thousand years". Septentrionalis PMAnderson 22:01, 10 July 2008 (UTC)

Quoting Gavin Betts in Teach Yourself Latin, 5 1/4, the accusative is used to express "time how long", or duration. Duos annos in Graecia eram means, "I was in Greece for two years". For emphases, the preposition per can be preposited, Per duos annos in Graecia eram.

Of course, this does not explain why the singular is used instead of the plural annos, but expecting anglophones to master all of niceties of Latin declension would be a bit much. That is why the nominative singular is usually used for all cases, with the nominative plural (antennae, ephemerides) sometimes thrown in to display erudition. Annum would seem to be something of a exception. "Data" is another kind of exception. For myself, I kinda like the expression, "one hectoannum, two hectoannos". Rwflammang (talk) 15:17, 28 October 2008 (UTC)

Why is this defined as an average Julian calendar year? It would seem to make sense to use the Gregorian since the Julian hasn't really been used in the west for about 250 years.... Does anyone know the rationale for this? 96.248.231.158 (talk) 04:51, 8 July 2008 (UTC)

It is both historical and mathematical. Both average Julian years and mean tropical years were used by Simon Newcomb, the director of the American Nautical Almanac Office within the United States Naval Observatory, during the nineteenth century for various astronomical calculations. For high precision, mean tropical years are not suitable because their value changes from year to year. The average Gregorian year could be used because its value is constant and is known precisely, but the average Julian year requires fewer digits. Throughout most of the twentieth century, variable tropical years were used. Possibly because Newcomb had preferred the average Julian year over the average Gregorian year, in 1976 the XVIth General Assembly of the International Astronomical Union required that average Julian years be used beginning in 1984 (several years advance notice was needed to prepare almanacs). Another reason may be that the smallest decimal multiple of the average Julian year is only 100 years (shifting the decimal point two places in calculations), whereas 10,000 years (four decimal places) are needed for Gregorian years. So the three multiples of 100, 1,000, and 10,000 Julian years provide greater convenience than the single multiple of 10,000 needed if average Gregorian years were used. — Joe Kress (talk) 03:19, 9 July 2008 (UTC)

The first link given does not discuss this unit, except to say Although there is no universally accepted symbol for the year, [the second link] suggests the symbol a; the second and third are broken; the fourth states that the halflife is 10¹⁵ years, and translates this as a "quadrillion years". I would like a source, both for the spelling and for usage; this article uses much stronger terms than suggests. Septentrionalis PMAnderson 22:07, 10 July 2008 (UTC)

I thank LeadSongDog for his link repair. Unfortunately the second link, ISO 80000-3, now leads to a pay site; the third link, the Unified Code, does not mention annum, just the symbol a in its several varieties.

Since kiloyear and kiloyears ago still are more frequent tham kiloannum, it may be simplest to say who deprecates kiloyear and the unambiguous kyr. Septentrionalis PMAnderson 20:01, 11 July 2008 (UTC)

(outdent)The term "deprecated" may be tough to source in this context, it may be OR. Usage of the hyphen in mega-annum seems to vary between sources.

• Pam Peters (2004). The Cambridge Guide to English Usage. Cambridge University Press. p. 72. ISBN 052162181X. Geologists bypass billion by estimating past time in terms of the mega-annum (Ma) or millions of years (variously abbreviated as my, my, m.yr). ...
• Edward J. Huth; et al. (1994). Scientific Style and Format: The CBE Manual for Authors, Editors, and Publishers. Cambridge University Press. p. 510. ISBN 0521471540. {{cite book}}: Explicit use of et al. in: |author= (help)
• David D. Pollard, Raymond C. Fletcher (2005). Fundamentals of Structural Geology. p. 124. ISBN 0521839270. {{cite book}}: Text "publisher Cambridge University Press" ignored (help)

One of the better written but perhaps less globally authoritative style guides using both notations is:

• Michael D. Hylland, William R. Lund (2003). Guide for the Preparation of Reports for the Utah Geological Survey. Utah Geological Survey. pp. 24–25. ISBN 1557916993.

I hope this will suffice until I can get my hands on the new ISO standard. LeadSongDog (talk) 03:49, 24 July 2008 (UTC)

This is some of the silliest shit I've read in Wikipedia, by the way. As if the quarter day matters on a geologic time scale. Anyhow, what's the plural? If it says in the article, I can't find it. --Milkbreath (talk) 23:43, 30 December 2008 (UTC)

Thanks for the informative analysis. For SI units, the plural is the same as the singular. A "6 second pause" or a "1500 metre race", for example. User:LeadSongDog come howl 18:23, 17 February 2010 (UTC)

but then annum is not an SI unit. Also, your examples have nothing to do with SI but with English apposition. It is "a 6 second pause" (nominal apposition), "a six seconds' pause" (genitival construction) or "a pause of six seconds" (prepositional phrase).

according to OED, annum is not an English word. The OED has per annum as an adverb, but this is not further analyzable within English. Annum is just the Latin accusative, and I am not sure what it is doing within an English text. --dab (𒁳) 19:10, 17 February 2010 (UTC)

I deleted "exactly" before 365.25, because I think a year refers to a revolution of Earth around the sun, variously defined, but usually with respect to the rest of the Universe. If years were precisely 365.25 days of 24 hours each, that would avoid the necessity of altering the Julian calendar, but the actual duration of a year is not so exact; it depends on the mass and momentum of the earth and gravitational influences on it. So it's variable, and unrelated to the length of a day. Unfree (talk) 01:14, 17 June 2009 (UTC)

The article does not indicate where the definition came from. This is a serious flaw. --Jc3s5h (talk) 02:15, 17 June 2009 (UTC)

I'm removing the indefensible phrase about a revolution around the Sun, and adding a ref for the exact value of 365.25 days and 86,400 seconds per day. This information was already in Julian year (astronomy) which brings up the possibility that this article be merged with that article rather than year. — Joe Kress (talk) 20:40, 17 June 2009 (UTC)

Joe, I don't agree that the reference provided for the definition gives sufficient support for the definition. The reference says "Although there are several different kinds of year (as there are several kinds of day), it is best to regard a year as a julian year of 365.25 days (31.5576 Ms) unless otherwise specified." This seems more like a suggestion to astronomers rather than a definition. Since the word "annum" is widely used in law and finance, I don't think a suggestion aimed at astronomers can even be thought of as a suggestion to non-astronomers. --Jc3s5h (talk) 21:46, 17 June 2009 (UTC)

You have a point. Besides its use in astronomy, I was thinking of its use in dendrochronology and geology, which I doubt have precise year lengths. I completely ignored its use in law, where I believe various court cases have determined it to be a Gregorian calendar year, from a specified date in one year to the day before that date in the following year. Thus we may need several definitions, one for each area of use. Even in astronomy, a or annum is rarely used—yr is much more frequent, as it is in dendrochronology. I should emphasize that, at least in astronomy, only the symbol may vary. The exact value of 365.25 days was required by the IAU (1976) System of Astronomical Constants for use in ephemerides, implemented January 1, 1984. — Joe Kress (talk) 22:34, 17 June 2009 (UTC)

"For example, the dinosaur species Tyrannosaurus rex was abundant approximately 65 Ma (65 million years) ago "

"For example, the formation of the Earth occurred approximately 4.57 Ga (4.57 billion years) ago."

Should the "ago"s be moved inside the parenthesis so it reads "...approximately 4.57 Ga (4.57 billion years ago)."?

The article says that "ago" can be implied. I'm not a geologist so I don't know if something like "4.57 Ga" is almost never written with "ago" following it in the literature. If so, maybe it should be in the parenthesis to get the reader comfortable with it.He Flips (talk) 15:09, 7 July 2009 (UTC)

Although "ago" is implied in geology and paleantology and sometimes in celestial mechanics, the latter also predicts the motion of solar system bodies millions or billions of years into the future, so "ago" is definitely not implied there. — Joe Kress (talk) 20:48, 7 July 2009 (UTC)

apparently, from the references cited in the article, the paleontologists aren't sure what they should do themselves. Some insist that "kya" etc. is "deprecated" while others keep using it simply because no satisfactory alternative has been presented. --dab (𒁳) 13:58, 17 February 2010 (UTC)

This was raised above, but not answered.Why is the article located at "annum" when the Latin word is annus?Why does the article talk about "kiloannum", "meg[a]annum" etc., when the straightforward expansion of "ka" would be "kiloyears" or, if it absolutely must be Latin, "kiloannus" or "kiloanni"? Whose lead are we following here? I do not see any reference attached to the expansion "kiloannum". --dab (𒁳) 13:58, 17 February 2010 (UTC)

In my experience, ka, Ma, etc., are usually read as annum in the geological community even though this clearly incorrectly from the Latin root. Google searches like: [2] [3] show examples of this while the more logical annus form is almost never used (though some people recommend it), e.g. [4] [5]. Even more fun is the bastardized forms like kilo-annums, mega-annums. Dragons flight (talk) 00:00, 18 February 2010 (UTC)