Lecture 5: Matter and Energy

Earth History Time Scale

• Age of sun & solar system ~ 4.57 Ga (Billions of years)
• Based on models of stellar evolution and dating of primitive solar system objects
• Example ﻿$\rightarrow$﻿ Carbonaceous chondrites (meteorites)
• Age of earth ~ 4.54 Ga
• Based on ages of terrestrial rocks + age of solar system + models of solar system formation
• Example ﻿$\rightarrow$﻿ Acasta Gneiss

The Nebular Hypothesis

• AKA the Nebular Theory of Solar Nebula Model explains the origin of the solar system
• Interstellar cloud inherits elements from previous generations of stars

Hypothesis Steps

1. Interstellar cloud of gas and dust
2. Rotates and ends up in a shape of flattened disc
3. High pressure and temperature creates Nuclear fusion in the Sun ﻿$\rightarrow$﻿ Solar nebula
4. Condensation of materials
5. Accretion of objects
6. Becomes a larger object
7. Differentiation
8. Segregates causing higher density to sink and lower density to rise therefore, it separates from one part to another
• Example ﻿$\rightarrow$﻿ The crust we live on has a lower density because the nucleus sank and the crust rose when the planet was formed.

Solar System

Jovian (outer) planets

• Huge
• Gaseous & icy

TerrestRial (inner) planets

• Small
• Rocky & metallic