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The big bang
!3.8 billion years ago the universe began from a tiny hot dense point, which rapidly expanded. -
Basic Elements Form
Protons and neutrons come together to form the nuclei of simple elements: hydrogen, helium and lithium. it will take another 300,000 years for electrons to be captured into orbits around these nuclei to form stable atoms. -
Radiaton Era
Most of the energy is in the form of radiation--different wavelengths of light, X rays, radio waves and ultraviolet rays. This energy is the remnant of the primordial fireball, and as the universe expands, the waves of radiation are stretched and diluted until today, they make up the faint glow of microwaves which bathe the entire universe. -
Matter Era
About this time, natural atoms are formed as electrons link up with hydrogen and helium nuclei. The microwave background radiation hails from this moment, and thus gives us a direct picture of how matter was distributed at this early time. -
First Stars and Galaxies
Gravity amplifies slight irregularities in the density of the primordial gas. Even as the universe continues to expand rapidly, pockets of gas become more and more dense. Stars ignite within these pockets, and groups of stars become the earliest galaxies. This point is still perhaps 12 to 15 billion years before the present. -
Our sun is born
The sun forms within a cloud of gas in a spiral arm of the Milky Way Galaxy. A vast disk of gas and this new star gives birth to planets, moons, and asteroids. Earth is the third planet out. -
Earth Forms
The Earth is thought to have been formed about 4.6 billion years ago by collisions in the giant disc-shaped cloud of material that also formed the Sun. Gravity slowly gathered this gas and dust together into clumps that became asteroids and small early planets called planetesimals. -
Earliest life
The earth has cooled and an atmosphere develops. Microscopic living cells neither planets nor animals, begin to evolve and flourish in earth's many volcanic environments.
