A Timeline of Everything
From the Big Bang to today — the milestones, each one sourced.
A tour across all nine eras: the origin of the universe, of life, of humanity, and the ideas and moments that shaped the modern world. Every event is backed by cited sources.
Events
- 13.8 billion years agoReputable source · 2 sourcesWell documented
The Big Bang
The universe began expanding from an extremely hot, dense state; space, time, matter, and energy originate here.
Why it matters: It is the origin of everything — the start of cosmic time and all subsequent structure.
How we know: The cosmic microwave background, the observed expansion of the universe, and Big Bang nucleosynthesis all converge on an age near 13.8 billion years.
Sources- NASA Science. The Big Bang · reference
- ESA. Planck reveals an almost perfect Universe (2013) · reference
- ~4.6 billion years agoReputable source · 2 sourcesWell documented
The Sun and Earth form
The Solar System condensed from a collapsing cloud of gas and dust; Earth accreted about 4.54 billion years ago.
Why it matters: Earth and the planets originate — the stage for all of geologic and biological history.
How we know: Radiometric dating of the oldest meteorites and lunar rocks pins the Solar System's age near 4.6 billion years.
Sources- USGS. How old is Earth? · reference
- NASA Science. Our Solar System · reference
- ~3.7 billion years agoPeer-reviewedDebated
Earliest life on Earth
Microbial life — or its chemical and structural traces — appears; among the oldest evidence are stromatolite-like structures in Greenland's Isua rocks.
Why it matters: The beginning of life, the root of the entire tree of living things.
How we know: Putative stromatolites and carbon-isotope signatures in ~3.7-billion-year-old rocks; the exact timing remains debated.
- ~539 million years agoReputable sourceWell documented
The Cambrian explosion
Over a geologically short interval, most major animal body plans first appear in the fossil record.
Why it matters: The rapid diversification of complex animal life that underlies today's biosphere.
How we know: Exceptional fossil beds such as the Burgess Shale and Chengjiang; the Cambrian begins ~538.8 million years ago on the international time scale.
Sources- Encyclopædia Britannica. Cambrian Period · reference
- ~66 million years agoPeer-reviewed · 2 sourcesWell documented
End-Cretaceous mass extinction
An asteroid roughly 10 km wide struck near Chicxulub, Mexico; about three-quarters of species, including the non-avian dinosaurs, went extinct.
Why it matters: Cleared ecological space for the rise of mammals — and, eventually, humans.
How we know: A global iridium-rich clay layer, shocked quartz, and the buried Chicxulub crater date the impact to ~66 million years ago.
- ~300,000 years agoPeer-reviewedDebated
First Homo sapiens
The oldest known Homo sapiens fossils, from Jebel Irhoud, Morocco, push the origin of our species back to about 300,000 years ago.
Why it matters: The emergence of anatomically modern humans.
How we know: Fossils and associated tools at Jebel Irhoud, dated by thermoluminescence to roughly 315,000 years; interpretations are still debated.
- ~10,000 BCEReputable sourceWell documented
The Neolithic Revolution
Humans in the Fertile Crescent and elsewhere began domesticating plants and animals, shifting from foraging to farming.
Why it matters: Farming enabled permanent settlements, food surpluses, and ultimately cities and civilization.
How we know: Archaeological remains of early domesticated crops, animals, and settlements from about 10,000 BCE onward.
Sources- Encyclopædia Britannica. Neolithic Revolution · reference
- ~3200 BCEReputable sourceWell documented
The invention of writing
Sumerians in Mesopotamia developed cuneiform, among the first writing systems, initially for administrative record-keeping.
Why it matters: Writing made complex administration, law, and the recording of history possible — the start of the written record.
How we know: Clay tablets from Uruk bearing proto-cuneiform accounts, dated to around 3200 BCE.
Sources- Encyclopædia Britannica. Cuneiform · reference
- 476 CEReputable sourceDebated
Fall of the Western Roman Empire
The Germanic leader Odoacer deposed Romulus Augustulus, the last emperor in the West, conventionally marking the end of the Western Roman Empire.
Why it matters: A traditional dividing line between classical antiquity and the European Middle Ages.
How we know: Contemporary and later chronicles record the deposition; 476 is the date historians conventionally assign.
Sources- Encyclopædia Britannica. Odoacer · reference
- c. 1440Reputable sourceWell documented
Gutenberg's printing press
Johannes Gutenberg introduced movable-type printing in Europe; the Gutenberg Bible followed around 1455.
Why it matters: Mass-produced books spread literacy and ideas, fueling the Renaissance, Reformation, and Scientific Revolution.
How we know: Surviving Gutenberg Bibles and printing records from Mainz.
Sources- Encyclopædia Britannica. Johannes Gutenberg · reference
- 1687Reputable sourceWell documented
Newton's Principia
Isaac Newton published Philosophiæ Naturalis Principia Mathematica, setting out the laws of motion and universal gravitation.
Why it matters: Founded classical mechanics and the modern mathematical description of nature.
How we know: The published work of 1687 and its documented reception in the scientific community.
Sources- Encyclopædia Britannica. Principia · reference
- 1859Reputable sourceWell documented
Darwin's On the Origin of Species
Charles Darwin published his theory of evolution by natural selection.
Why it matters: Unified biology and transformed humanity's understanding of life and its own origins.
How we know: The 1859 publication and the vast body of corroborating evidence gathered since.
Sources - July 20, 1969Reputable sourceWell documented
Apollo 11 Moon landing
Neil Armstrong and Buzz Aldrin became the first humans to walk on the Moon.
Why it matters: The peak of the Space Age and humanity's first steps on another world.
How we know: NASA mission records, telemetry, returned lunar samples, and a global live broadcast.
Sources- NASA. Apollo 11 · reference
- 1989General sourceWell documented
The World Wide Web
Tim Berners-Lee proposed the World Wide Web at CERN; the first website went live in 1991.
Why it matters: Made the internet broadly usable and reshaped communication, commerce, and knowledge.
How we know: CERN's archived original proposal and the first web server and website.
Sources- CERN. A short history of the Web · reference
- 2003Reputable sourceWell documented
Human Genome Project completed
An international effort produced the first essentially complete sequence of the human genome.
Why it matters: Launched the genomic era of medicine and biology.
How we know: The published reference sequence and the project records of the NIH's National Human Genome Research Institute.
Sources- NHGRI (NIH). The Human Genome Project · reference