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4 BCE
Planetary Accretion (Planets Formation)
Early on, our Solar System was a disk of dust and gas in orbit around the proto-Sun. The solid materials collided with each other and accreted to form gradually larger bodies, until the Solar System's four terrestrial planets (Mercury, Venus, Earth, and Mars) were formed. -
4 BCE
Planetary Cooling
A planetary body, whether the body is a planet or a moon, has to cool off. The warmth contained inside a body controls what sort of surface activity, atmospheric activity, and interior activity which the body has. As planetary bodies cool slowly, heat diminishes, and the activities diminish to nothing. Examination of a body for various kinds of activities tells scientists what stage a body is in its history of cooling off. -
Period: 4 BCE to 3 BCE
Timespan of Planetary Formation
Approximately 4.6 billion years ago, the solar system was a cloud of dust and gas known as a solar nebula. Gravity collapsed the material in on itself as it began to spin, forming the sun in the center of the nebula. -
4
Heavy Bombarment
Early Earth suffered the constant threat of attack from the leftover planet-building material. From about 4.5 to 3.8 billion years ago, failed planets and smaller asteroids slammed into larger worlds, scarring their surface. Near the end of the violence, during a period known as the Late Heavy Bombardment, impacts in the solar system may have increased. The "Heavy Bombardment" wiped out a lot of living things, for example... Dinosaurs -
4
Earth Cored Formation
The inner core is Earth’s deepest layer. It is a ball of solid iron just larger than Pluto which is surrounded by a liquid outer core. The inner core is a relatively recent addition to our planet and establishing when it was formed is a topic of vigorous scientific debate with estimates ranging from 0.5 billion to 2 billion years ago. -
4
Fomation of the Moon
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
