Lecture 3

Science is built of facts the way a house is built of bricks, but an accumulation of facts is no more

science than a pile of bricks is a house.

- Henri Poincare’

Creation and development of the Earth

Webpage for course (daytime)

Webpage for course (nighttime)

Observations about our Solar System

1. planets, moons, asteroids form ring @ sun

2. all these revolve in same direction

3. most have similar orientations

4. most rotate in same direction, as does sun

5. many moons have same general features

6. distribution of planets

Terrestrial vs. Jovian

Nebula Hypothesis

Nebula Hypothesis

Earliest structure of the earth

unsorted mix of compacted gas and dust?

How did earth become molten?

Sources of heat- impact of meteorites- compression- radioactive decay

This history explains

Thin crust

Differentiation of earth by density

heavy material in middle of earth (core)

lighter material in crust

intermediate density in mantle

Formation of atmosphere

convection cells in mantle

Thin crust and convection cells in mantle help account for

- plate tectonics (continental drift)

- mountains

- erosion and deposition

Our earth is a very active planet

Nature’s Law is change; constancy is strange.