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 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
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.