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13 BCE
Planetary Cooling (13.6 Billion Years Ago)
Earth began to form over 4.6 billion years ago from the same cloud of gas (mostly hydrogen and helium) and interstellar dust that formed our sun, the rest of the solar system and even our galaxy. In fact, Earth is still forming and cooling from the galactic implosion that created the other stars and planetary systems in our galaxy. This process began about 13.6 billion years ago when the Milky Way Galaxy began to form. -
4 BCE
Formation of the Moon (4.5 Billion Years Ago)
The giant-impact hypothesis, sometimes called the Big Splash, or the Theia Impact suggests that the Moon formed out of the debris left over from a collision between Earth and an astronomical body the size of Mars, approximately 4.5 billion years ago -
4 BCE
Planetary Accretion (Approximately 4.567 Billion Years Ago)
Accretion and Early Differentiation of the Earth and Terrestrial Planets - Home. Formation of the Earth and the other terrestrial planets of our Solar System (Mercury, Venus and Mars) commenced 4.567 billion years ago and occurred on a time scale of about 100 million years. -
3 BCE
End of Heaving Bombardment (3.8~4 Billion Years Ago)
3.8~4 billion years ago a period of intense comet and asteroid bombardment is thought to have peppered all the planets including the Earth. Many of the numerous craters found on the Moon and other bodies in the Solar System record this event.
One theory holds that a gravitational surge caused by the orbital interaction of Jupiter and Saturn sent Neptune careening into the ring of comets in the outer Solar System. The disrupted comets were sent in all directions and collided with the planets. -
1 BCE
Core Formation (1~1.5 Billion Years Ago)
There have been many estimates for when the earth's inner core was formed, but scientists have used new data which indicates that the Earth's inner core was formed 1-1.5 billion years ago as it 'froze' from the surrounding molten iron outer core. The inner core is Earth's deepest layer.
