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4600 BCE
Start of the Solar System
Within the milky way, the solar system was originally a vast cloud of hydrogen, helium, and dust moving around in the galaxy. Nearby, a hot sun burned up its fuel and destroyed itself in an explosion (supernova), sending a shock wave that destabilized the cloud, causing it to gravitationally collapse. As a result, most of the mass became concentrated in the middle, forming the sun. Smaller concentrations of mass rotating around the center formed the planets, including Earth. -
Period: 4590 BCE to 4500 BCE
Planetary Accretion
In the first 100,000 years, dust collided into each other, creating little clumps. By the end, a kilometer-sized rock was enough to accrete/gather additional material, allowing it to grow, which continued on for roughly 10 million years. Later on, much larger objects started colliding with each other and the planetesimals formed to become the planets of the solar system. Including roughly four rocky planets in the interior, two gas giants; Jupiter & Saturn, and two ice giants; Uranus & Neptune. -
4540 BCE
Formation of the Moon
An asteroid the size of Mars smashed into Earth and the huge amount of energy from the impact melted most of Earth and the asteroid, knocking off some debris that stayed in orbit around Earth. Over time, the debris from both Earth and the asteroid smashed together and cooled into a spherical object, forming the Moon. Simultaneously creating the Earth-Moon system. -
4500 BCE
Earth's Core Formation
Earth grew from material that collided in its part of space. All the collisions caused Earth to heat up where rock and metal started melting. The molten material separated into layers where gravity pulled the denser materials into the center and the light elements rose to the surface. Earth’s core is mostly made of iron, the crust is mostly lighter materials, and in between, the Earth’s mantle is made of solid rock. -
Period: 4500 BCE to 4000 BCE
Late Accretion Stage
Pluto-like objects crash into other planets, depositing metal that stays at the surface in the process. -
4400 BCE
Planetary Cooling
Heat in the core trying to escape and the additional radioactive elements allowed the molten melt to remain there, probably the source of strong magnetic fields. It also broke up the surface of Earth, creating tectonic plates that began to move. As the planet cooled, solid crust was formed, then volcanos released gases, which eventually formed an atmosphere. As the atmosphere became denser, clouds formed and rain fell, eventually forming the oceans, setting the stage for life to begin on Earth. -
3800 BCE
End of Heavy Bombardment
Jupiter and Saturn migrated towards the inner planets, clearing out a lot more of the rocks, then migrated back out. During this period, comets and asteroids carrying water struck Earth, which might be the explanation of the existence of water/oceans on Earth.
