The beginning (13.75 billion BC): The Universe arises from the Big Bang, followed by a very short but rapid period of expansion ("inflation")
The following times are measured from the time of the Big Bang.
1 millionth of a second: Quarks combine to form protons and neutrons. The universe, initially infinitely small, is now roughly the size of the present Solar System
2-3 minutes: Nuclei of the light chemical elements, hydrogen and helium, are formed by fusion of protons and neutrons. Nuclear matter consists of 75% hydrogen and 25% helium by mass.
300,000 years: Protons combine with electrons to form neutral hydrogen, the first atoms
500 million years: Stars form from contracting clouds of gas and dust. Heavier elements are formed by fusion in stars and in supernova explosions. The first galaxies form from local inhomogeneities
4.6 billion BC: Our Sun is born in one of the spiral arms of the Milky Way galaxy, and 10-100 million years later the planets of our Solar System form from smaller colliding planetesimals
3.7 billion BC: Earliest life forms appear on Earth, initially limited to bacteria and archaea, and later eukaryotes
1 billion BC: The first multicellular forms of life appear
700 million BC: Primitive animals appear in the oceans
530 million BC: The first fish evolve - the earliest vertebrates
475 million BC: Simple plants and fungi evolve on land
400 million BC: Amphibians evolve from fish, and animals begin to appear on land
365 million BC: The first insects evolve
251 million BC: A catastrophic event causing rapid climate change leads to the greatest known extinction of the Earth's species - 90% of marine life and 70% of terrestrial life
220 million BC: The first mammals evolve from synapsid reptiles
200 million BC: The world's only supercontinent, Pangaea, begins to break up into all the continents that now exist
160 million BC: Birds evolve from theropod dinosaurs
70 million BC: Early primates appear
66 million BC: The Cretaceous-Paleogene mass extinction event due to an asteroid impact wipes out the dinosaurs as well as 75% of other plant and animal species, followed by the rise of mammals
6-7 million BC: Early hominids appear, with ape-like and human-like features
5-6 million BC: The human lineage diverges from that of chimpanzees
2 million BC: Homo habilis, the first creature to use primitive stone tools
1.8 million BC: Homo erectus, with more sophisticated tools and mastery of fire
200,000 BC: Archaic homo sapiens, our early human ancestors, appear and live contemporaneously with homo neanderthalensis (the neanderthals). The two species were descended from a common ancestor, homo heidelbergensis. Homo sapiens evolved in Africa, and the neanderthals in Europe.
120,000 BC: Homo sapiens sapiens evolve from the early homo sapiens. All modern humans belong to this subspecies.
40,000 BC: Rapid growth and migration of the world's human population
30,000 BC: The neanderthals become extinct
10,000 BC: End of the last ice age
The universe is expanding, and the rate of expansion is accelerating.
Our Sun is now a fairly typical, middle-aged star.
The beginnings of global heating on Earth due to greenhouse gas emissions, while the world's leading governments do almost nothing to control it. This could be near the "tipping point" - a runaway greenhouse effect, drastically changing the world's climate, and impossible to control.
The beginnings of the Earth's 6th mass extinction of numerous plant and animal species. The future of many of many species, including homo sapiens, is in doubt.
In 4 billion years our Milky Way galaxy will collide head-on with the Andromeda galaxy (currently 2.5 million light years away) and merge to form a new hybrid galaxy.
In 5 billion years, when the Sun's nuclear fuel is exhausted, it will become a red giant, eventually enveloping and destroying the inner planets, possibly including Earth, or at least making Earth uninhabitable after boiling away its oceans and atmosphere.
After about another 100 million years the Sun will produce little energy,
collapsing into a dense white dwarf the size of a small planet, while
cooling and growing dimmer.