Bya: Difference between revisions

From Wikipedia, the free encyclopedia
Jump to navigation Jump to search
VisualWikitext
imported>Drmies
Reverted 1 edit by 73.143.199.192 (talk): No
 
imported>Mz7
m Reverted edits by 37.39.191.127 (talk): editing tests (HG) (3.4.12)
 
Line 2: Line 2:
{{Other uses|BYA (disambiguation)}}
{{Other uses|BYA (disambiguation)}}
{{lowercase}}
{{lowercase}}
'''bya''' or '''b.y.a.''' is an [[abbreviation]] for "'''[[1000000000 (number)|billion]] years ago'''". It is commonly used as a [[unit of time]] to denote length of time before the present in 10<SUP>9</SUP> years. This [[Acronym#Nomenclature|initialism]] is often used in the sciences of [[astronomy]], [[geology]], and [[paleontology]].
'''BYA''', an abbreviation for '''"billion years ago"''', is a unit of time commonly used in disciplines such as '''geology''', '''astronomy''', '''paleontology''', and '''cosmology''' to denote events that occurred billions of years in the past. It is primarily used in the context of describing the age of the '''Earth''', '''Solar System''', '''Universe''', and major geological or biological milestones in Earth's history.


The "billion" in bya is the 10<SUP>9</SUP> "billion" of the [[Long and short scales|short scale]] of the [[United States|U.S.]],<ref name="Gale2009">Gale, Joseph (2009). ''Astrobiology of Earth: The Emergence''. Oxford: Oxford University Press, p. [https://books.google.com/books?id=64zn0nxDVUYC&pg=PA21 21.]</ref> not the long-scale 10<SUP>12</SUP> "billion" of some [[Europe]]an usage. Billion by this convention (10<SUP>9</SUP>) is often called a "thousand million" in the UK and a "milliard" in some other countries.<ref>Chartrand, Mark (2004). ''Satellite Communications for the Nonspecialist''. New York: SPIE Press, p. [https://books.google.com/books?id=MM0d2cMUWbEC&pg=PA73 73.]</ref> For this reason, there is potential for some confusion, and some scientists prefer the unit Gya, while others prefer [[Giga-annum|Ga]] (Giga-annum), however, bya remains in more widespread use.<ref name="Gale2009"/> In 1974, the UK switched from the long scale to the short scale.<ref name="Gale2009"/>
== Usage ==
The term "BYA" is often used to express time in billions of years before the present (where the "present" is generally considered to be '''1950 CE''', according to radiocarbon dating conventions).<ref name=":0">{{Cite book |last=Dalrymple |first=Gary Brent |title=The age of the earth |date=2007 |publisher=Stanford Univ. Pr |isbn=978-0-8047-2331-2 |edition=Nachdr. |location=Stanford, Calif}}</ref> For example:


Related units are [[Mya (unit)|mya]] ("million years ago"), and '''byr''' ("billion years"). These are traditionally written in [[lowercase]]. [[Giga-annum|Ga]] or Gya has a [[capitalization|capitalized]] first letter instead.
* The formation of the Earth is estimated to have occurred approximately '''4.54 BYA'''.<ref name=":0" />
* The Big Bang is estimated to have taken place around '''13.8 BYA'''.<ref name=":1">{{Cite book |last=Life |first=Committee on the Origins and Evolution |title=Astrophysical Context of Life |date=2005 |publisher=National Academies Press |others=National Research Council, Board on Life Sciences, Division on Engineering and Physical Sciences, Division on Earth and Life Studies, National Research Council, National Academy of Sciences |isbn=978-0-309-09627-0 |location=Washington}}</ref>
* Life is believed to have originated on Earth around '''3.5–4.0 BYA'''.<ref name=":2">{{Cite book |last=Knoll |first=Andrew H. |title=Life on a young planet: the first three billion years of evolution on earth |date=2015 |publisher=Princeton University Press |isbn=978-0-691-16553-0 |edition=New Princeton Science Library paperback |series=Princeton Science Library |location=Princeton Oxford}}</ref>
 
The abbreviation may also appear in scientific literature as '''Ga''' (from the Latin ''gigaannum'', meaning "billion years") or '''Gya''' (giga years ago), though these variants are more common in international and SI unit-compliant literature.<ref name=":0" />
 
== Alternative Notation ==
{| class="wikitable"
!Abbreviation
!Meaning
!Notes
|-
|'''BYA'''
|Billion Years Ago
|Non-SI, widely used in English-speaking regions
|-
|'''Ga'''
|Gigaannum
|SI-compliant, used in formal scientific literature
|-
|'''Gya'''
|Giga years ago
|Less common variant, similar to BYA
|}
 
== Context in Scientific Fields ==
 
* '''Geology''': Used to mark eras and events such as continental formation, mass extinctions, and plate tectonics.<ref name=":0" />
* '''Astronomy''': Used to describe the age of celestial bodies or cosmological events.<ref name=":1" />
* '''Paleontology''': Applied to the timeline of biological evolution, including the rise of multicellular life or the Cambrian explosion.<ref name=":2" />


==See also==
==See also==
* [[Chronology]]
* [[Geologic time scale]]
* [[Myr]]
* [[Year|Ga (unit)]]
* [[Before Present]]
* [[Before Present]]


Latest revision as of 07:17, 28 June 2025

Template:Short description Script error: No such module "other uses". Template:Lowercase BYA, an abbreviation for "billion years ago", is a unit of time commonly used in disciplines such as geology, astronomy, paleontology, and cosmology to denote events that occurred billions of years in the past. It is primarily used in the context of describing the age of the Earth, Solar System, Universe, and major geological or biological milestones in Earth's history.

Usage

The term "BYA" is often used to express time in billions of years before the present (where the "present" is generally considered to be 1950 CE, according to radiocarbon dating conventions).[1] For example:

  • The formation of the Earth is estimated to have occurred approximately 4.54 BYA.[1]
  • The Big Bang is estimated to have taken place around 13.8 BYA.[2]
  • Life is believed to have originated on Earth around 3.5–4.0 BYA.[3]

The abbreviation may also appear in scientific literature as Ga (from the Latin gigaannum, meaning "billion years") or Gya (giga years ago), though these variants are more common in international and SI unit-compliant literature.[1]

Alternative Notation

Abbreviation Meaning Notes
BYA Billion Years Ago Non-SI, widely used in English-speaking regions
Ga Gigaannum SI-compliant, used in formal scientific literature
Gya Giga years ago Less common variant, similar to BYA

Context in Scientific Fields

  • Geology: Used to mark eras and events such as continental formation, mass extinctions, and plate tectonics.[1]
  • Astronomy: Used to describe the age of celestial bodies or cosmological events.[2]
  • Paleontology: Applied to the timeline of biological evolution, including the rise of multicellular life or the Cambrian explosion.[3]

See also

References

Template:Reflist


Template:Measure-stub Template:Time-stub

  1. ↑ a b c d Script error: No such module "citation/CS1".
  2. ↑ a b Script error: No such module "citation/CS1".
  3. ↑ a b Script error: No such module "citation/CS1".
Retrieved from "http://debianws.lexgopc.com/wiki143/index.php?title=Bya&oldid=2060011"