gigayears
Geological time units
A gigayear is one billion years, used in astronomy, geology, and cosmology for discussing deep time: The Earth formed about 4.5 gigayears ago.
The prefix giga- (billion) attaches to year as it does to other units.
Abbreviated Gyr or Ga.
The singular gigayear appears when the number requires it: one gigayear.
Immense spans of time
- epochsDistinct historical stretches
- agesExtended time spans
- millenniaThousand-year periods
- durationLength of existence
timescale · chronology · billions · magnitude · vastness · incomprehensible · astronomical · immense
Complete system or domain
- big bangLoud explosive noise
- cosmologyStudy of universal structure
- astrophysicsPhysics of celestial bodies
- expansionIncrease in scope
redshift · dark matter · galaxies · quasars · supernova · singularity · nebulae · space-time
Study of geological ages
- stratigraphyStudy of rock layers
- radiometric datingAge measurement via atomic decay
- paleontologyStudy of ancient organisms
- fossilsPreserved ancient organism traces
tectonics · sedimentation · isotopes · half-life · eons · Precambrian · Archean · Proterozoic
Life from inanimate matter
- mass extinctionLarge-scale species elimination
- speciationFormation of distinct species
- phylogenyEvolutionary relationships among organisms
- common ancestorOrigin point of descendants
tree of life · Cambrian explosion · prokaryotes · eukaryotes · multicellular · biodiversity · adaptation · natural selection
eons
Immense spans of time
duration · timescale · chronology · billions · magnitude · vastness · incomprehensible · astronomical · immense · scale
universe
Complete system or domain
- big bangLoud explosive noise
- cosmologyStudy of universal structure
- astrophysicsPhysics of celestial bodies
expansion · redshift · dark matter · galaxies · quasars · supernova · singularity · nebulae · space-time · inflationary
geochronology
Study of geological ages
- stratigraphyStudy of rock layers
- radiometric datingAge measurement via atomic decay
- paleontologyStudy of ancient organisms
fossils · tectonics · sedimentation · isotopes · half-life · eons · Precambrian · Archean · Proterozoic · deep time
abiogenesis
Life from inanimate matter
- mass extinctionLarge-scale species elimination
- speciationFormation of distinct species
- phylogenyEvolutionary relationships among organisms
common ancestor · tree of life · Cambrian explosion · prokaryotes · eukaryotes · multicellular · biodiversity · adaptation · natural selection · origin of life
gigayearsnanoseconds
Billionths of seconds
microseconds · picoseconds · femtoseconds · milliseconds · instants
gigayearslifetime
Duration of existence
generation · recorded history · moment · the present · now
year, years, yearly, yearling, yearlong, giga, gigabyte, gigabytes, gigahertz