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 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 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]
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 |