1,000,000,000 (one billion, short scale; one thousand million or one milliard, one yard, long scale) is the natural number following 999,999,999 and preceding 1,000,000,001. With a number, "billion" can be abbreviated as b, bil or bn. In standard form, it is written as 1 × 109. The metric prefix giga indicates 1,000,000,000 times the base unit. Its symbol is G. One billion years may be called an eon in astronomy or geology. Previously in British English (but not in American English), the word "billion" referred exclusively to a million millions (1,000,000,000,000). However, this is no longer common, and the word has been used to mean one thousand million (1,000,000,000) for several decades. The term milliard can also be used to refer to 1,000,000,000; whereas "milliard" is rarely used in English, variations on this name often appear in other languages. In the South Asian numbering system, it is known as 100 crore or 1 arab. 1,000,000,000 is also the cube of 1000. Sense of scale The facts below give a sense of how large 1,000,000,000 (109) is in the context of time according to current scientific evidence: Time 109 seconds (1 gigasecond) equal 11,574 days, 1 hour, 46 minutes and 40 seconds (approximately 31.7 years, or 31 years, 8 months, 8 days). About 109 minutes ago, the Roman Empire was flourishing and Christianity was emerging. (109 minutes is roughly 1,901 years.) About 109 hours ago, modern human beings and their ancestors were living in the Stone Age (more precisely, the Middle Paleolithic). (109 hours is roughly 114,080 years.) About 109 days ago, Australopithecus, an ape-like creature related to an ancestor of modern humans, roamed the African savannas. (109 days is roughly years.) About 109 months ago, dinosaurs walked the Earth during the late Cretaceous. (109 months is roughly years.) About 109 years—a gigaannus—ago, the first multicellular eukaryotes appeared on Earth. About 109 decades ago, galaxies began to appear in the early Universe which was then 3.772 billion years old. (109 decades is exactly years.) The universe is thought to be about 13.77 × 109 years old. Distance 109 inches is , more than halfway around the world and thus sufficient to reach any point on the globe from any other point. 109 metres (called a gigametre) is almost three times the distance from the Earth to the Moon. 109 kilometres (called a terametre) is over six times the distance from the