3. Objectives: you should be able to… 1. Define hypothesis 2. Explain the protoplanet hypothesis 3. Explain how the earth’s oceans and atmosphere might have formed *proto = “earliest”, or “original”. What do you think proto-planet might mean?
4. What is a hypothesis? An educated guess, but…. A good hypothesis should: Explain known facts
5. Known facts 1. All planets revolve around the sun in the same direction 2. The orbits of the planets around the sun are all nearly circular. 3. Most of the orbits are in nearly the same plane. 4. The sun rotates (turns on its axis) in the same direction as the planets. 5. Most planets have moons, which revolve in the same direction as the planets.
6. Protoplanet hypothesis 5 billion years ago… A cloud of gas and dust rotated in space The cloud began to collapse… why? Gravity Explosion of passing stars Shrinking made the compressed cloud rotate faster. Compression made the interior very hot
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8. Protoplanet hypothesis, cont’d The center of the compressed gas cloud became hot and eventually, the core became the sun. Hydrogen fusion ~10% of the cloud formed a disk surrounding the sun Friction within the disk caused most of the mass to collect into eddies. These eddies were compacted and became planets and moons.
9. Review 1. Define hypothesis 2. Explain the protoplanet hypothesis 3. Explain how the earth’s oceans and atmospheres might have formed
10. Protoplanet hypothesis An enormous, rotating gas cloud begins to collapse Most of the material collects in the center, eventually becomes the sun What compressed the gas? Gravity, explosions Other, smaller, gas & dust masses shrank into protoplanets.
12. How did the oceans form? When the earth formed, there was no ocean Compression, radioactive minerals, and meteorite showers made the earth hotter. The heat melted the iron, which sank toward the center of the earth, and formed a core. The iron melted other materials that it touched, releasing water and other gases. The steam escaped to the surface in volcanic eruptions.
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14. How did the atmosphere form? What’s in the atmosphere? 78% Nitrogen 21% Oxygen 1% others (including CO2) Gases from volcanic eruptions: NO FREE OXYGEN! Break up of H20 molecules by sunlight Plants added oxygen through photosynthesis
15. Objectives 1. Define hypothesis 2. Explain the protoplanet hypothesis 3. Explain how the earth’s oceans and atmosphere might have formed
