Early history of Earth By samg096 45 BCE Planetary Accretion 10 years is 1 billion years (?) The Earth started forming about 4.6 billion years ago. As meteors collided with one another. Period: 45 BCE to 35 BCE Planetary Cooling 10 years is 1 billion years 44 BCE Formation of the Moon 10 years is 1 billion years 38 BCE End of Heavy Bombardment 10 years is 1 billion years 37 BCE Core Formation 10 years
