# ملين سال اڳ

**ملين سال اڳ** - 10 لک سال اڳ (Million years ago)، جن کي مختصر طور تي "ميا" (Mya)، "مير" (Myr) (ميگا سال)، يا "ما" (Ma ميگا اينم) سڏيو ويندو آهي، وقت جي هڪ اڪائي آهي جيڪا 1,000,000 سال (6 10 1x سال يا تقريبن 31.6 ٽيرا سيڪنڊ (12 10 31.6x سيڪنڊ) جي برابر آهي.

## استعمال

"مير" (Myr) کي زميني سائنس ۽ ڪائنات جي شعبن ۾ عام استعمال ڪيو ويندو آهي. Myr کي Mya يا Ma سان پڻ استعمال ڪيو ويندو آهي. گڏجي اهي هڪ حوالو نظام ٺاهيندا آهن، هڪ مقدار ڏانهن ۽ ٻيو سال جي انگن اکرن جي نظام ۾ هڪ خاص نقطي ڏانهن. اهو موجوده وقت کان اڳ جو وقت آهي.

Myr کي ارضيات ۾ رد ڪيو ويو آهي، پر فلڪيات ۾ Myr معياري آهي. جڏهن "myr" کي ارضيات ۾ ڏٺو ويندو آهي، اهو عام طور تي "Myr" (ميگا سالن جو هڪ يونٽ) آهي. فلڪيات ۾، اهو عام طور تي "Myr" (ملين سال) آهي.

## بحث

In geology, a debate remains open concerning the use of *Myr* (duration) plus *Mya* (million years ago) versus using only the term *Ma*. In either case, the term *Ma* is used in geology literature conforming to ISO 31-1 (now ISO 80000-3) and NIST 811 recommended practices. Traditional style geology literature is written:

> The Cretaceous started 145 Ma and ended 66 Ma, lasting for 79 Myr.
>
>
>

The "ago" is implied, so that any such year number "X Ma" between 66 and 145 is "Cretaceous", for good reason. But the counter argument is that having *myr* for a duration and *Mya* for an age mixes unit systems, and tempts capitalization errors: "million" need not be capitalized, but "mega" must be; "ma" would technically imply a *milliyear* (a thousandth of a year, or 8 hours). On this side of the debate, one avoids *myr* and simply adds *ago* explicitly (or adds *BP*), as in:

> The Cretaceous started 145 Ma ago and ended 66 Ma ago, lasting for 79 Ma.
>
>
>

In this case, "79 Ma" means only a quantity of 79 million years, without the meaning of "79 million years ago".

## يونٽن جي بين الاقوامي نظام ۽ ممڪن حل سان تڪرار

The abbreviation mya does not comply with the International System of Units (SI) in three respects, each of which can be attributed to one of its letters:

1. (**m**illion): Neither *t* (in tya) nor *b* (in bya) are internationally recognized prefixes for units of measurement. The lowercase *m* (in mya) stands for milli, i.e., one thousandth, in the International System of Units (SI) and is therefore also not SI-compliant. It is therefore an attempt to approximate the International System of Units by using kya (kilo years ago) instead of tya and Gya (giga years ago) instead of bya.
2. (**y**ear): *y* is not a coherent SI unit. - Instead of *y* or *yr* (for year), the derived unit *a* (lat. **annus**, *year*) can be used, which is a multiple of the SI base unit second. This leads to the following formulations:
	1. 1 tya = “1,000 years ago” = “1 ka ago”
	2. 1 mya = “1,000,000 years ago” = “1 Ma ago”; alternatively, *bma* for “before million annos,” or 'bMA' for “before Mega annos”
	3. 1 bya = "1.000.000.000 years ago" = "1 ga ago"
3. Unlike units of time, this scale does not refer to a period of time, but to a point in time in the past.

Since it is often clear from the context that the time must be in the past, *mya* is often simply replaced by *Ma*. Physically, this means that a point in time is replaced by a period of time, but this does not necessarily pose a problem if a definition (such as the ISO 8601 standard for date notation) is agreed upon. This makes it clear why the abbreviation *mya* is still so popular: it stands for the phrase “so many years ago,” which makes it clear even without a definition that it must refer to a point in time so many years ago in the past.
If it is not clear from the context that it refers to the past, when replacing mya with Ma, a bp (for "before present") is added to the latter. This also makes it clear that it refers to a point in time and not a period of time. However, *Ma bp* does not necessarily mean exactly the same as *mya*.

## پڻ ڏسو

* نوري سال
* ارب سال اڳ
* ميگانم

## حوالا