In astronomy, geology, and paleontology, Gya is used as an unit of time to denote length of time before the present. Specifically, one Gya is equal to 10⁹ years ago. Lunar astronomy: the large crater is Daedalus, photographed by the crew of Apollo 11 as they circled the Moon in 1969. ... Geology (from Greek γη- (ge-, the earth) and λογος (logos, word, reason)) is the science and study of the Earth, its composition, structure, physical properties, history and the processes that shape it. ... A paleontologist carefully chips rock from a column of dinosaur vertebrae. ... The word unit means any of several things: Unit of measurement, a fundamental quantity of measurement Units (computer program), a popular program that does unit conversion Units conversion by the Factor-label method Functional unit, a component of a computer system such as the CPU Unit of action, a discrete... Watches are used to measure time Trying to understand time has long been a prime occupation for philosophers, scientists and artists. ... The present is the time that is perceived directly, not as a recollection or a speculation. ... A year is the time between two recurrences of an event related to the orbit of the Earth around the Sun. ...

A unit identical to Gya is bya (for "billion years ago"), which may be in more widespread use. However, some scientists prefer Gya because it uses the SI prefix giga- and thus avoids confusion over whether the short-scale billion (10⁹) or long-scale billion (10¹²) is meant, as well as avoiding preference for one of the two definitions of billion over the other. In [[hhehehe>12). ... The word billion and its equivalents in other languages refer to one of two different numbers, depending on whether the writer is using the long or short scale. ... The International System of Units (abbreviated SI from the French language name Système International dUnités) is the modern form of the metric system. ... Giga (symbol: G) is a prefix in the SI system of units denoting 109, or 1 000 000 000. ...

As a unit using an SI prefix, the first letter of Gya, the G, is usually capitalized, unlike the b of bya which is traditionally lowercase. G is the seventh letter in the Roman alphabet. ... For any word written in a language with whose alphabet or alphabet equivalent has two cases, such as those using the Latin, Greek, Cyrillic, or Armenian alphabet, capitalization (or capitalisation) is the writing of that word with its first letter in majuscules (uppercase) and the remaining letters in minuscules (lowercase). ... The letter B is the second letter of the modern Latin alphabet. ... Minuscule, or lower case, is the smaller form (case) of letters (in the Roman alphabet: a, b, c, ...). Originally alphabets were written entirely in majuscule (capital) letters which were spaced between well-defined upper and lower bounds. ...

In the scientific literature, the term Gya has been replaced by Ga (giga annum).

See also

• annum
• Before Present
• bya
• mya