1. Planet Earth What would alien astronomers observe? Chapter 4 Page 109-112

4. A Good Place to Live Position in the solar system Distance from sun, nearly circular orbit, axis tilt – Distance from Sun (Page 110) Average = 1.496 X 10 8 km (93,000,000 miles) Maximum = 1.521 X 10 8 km Minimum = 1.471 X 10 8 km Balance between size and intensity of the sun and the distance from the sun. Page 432 – Goldilocks- not too hot, not too cold, just right Too close= too hot Too far = too cold Just right for life as we know it.

5. Other Convenient Facts Orbital Eccentricity = 0.017 Very close to circular – No extremes of temperature Axis tilted 23.5 0 – “Smears” the climate

6. Diversity Large blue areas and brown areas Some green areas but these change Whirling clouds in the atmosphere Reflects 37% of incident sunlight – Pretty bright – Albedo 0.37 – Albedo varies with time White areas at poles – Change during the year

7. Active Seasonal changes – Polar ice caps – Green/brown Geologically active – Earth quakes – Volcanoes – River erosion – Mountain formation

8. Atmosphere Oxygen, Water, Carbon Dioxide But not too much – Nitrogen mostly Reflects and absorbs just the right amount of electromagnetic waves

9. Atmosphere ComponentSymbolVolume NitrogenN2N2 78.084% 99.998% OxygenO2O2 20.947% ArgonAr0.934% Carbon DioxideCO 2 0.033% NeonNe18.2 parts per million HeliumHe5.2 parts per million KryptonKr1.1 parts per million Sulfur dioxideSO 2 1.0 parts per million Methane CH 4 2.0 parts per million HydrogenH2H2 0.5 parts per million Nitrous OxideN2ON2O0.5 parts per million XenonXe0.09 parts per million OzoneO3O3 0.07 parts per million Nitrogen dioxideNO 2 0.02 parts per million IodineI2I2 0.01 parts per million Carbon monoxideCOtrace Ammonia NH 3 trace Nitrogen 78% Oxygen 21% Argon 0.93% Carbon Dioxide.03%

11. Troposphere 0 – 11 Km (approximately 7 miles) Sheet of paper wrapped around a globe Weather occurs here Jets fly at the top of this region Heat comes from the earth Temperature drops as you go up 218 K = - 55 o C =-67 o F 75% of mass of atmosphere

12. Stratosphere 11 – 50 km Contains the ozone layer O 3 Absorbs intermediate wave-length ultraviolet These rays are dangerous – – cause skin cancer, eye diseases Heats up because of this absorption Temperature rises as we go up in this layer 285 K = 12 o C = 50 o F Ozone layer has decreased due to chemicals – chlorofluorocarbons

13. Mesosphere Temperature again declines minimum of 200 K = -73 o C = -103 o F

14. Ionosphere Radiation from the sun heats and ionizes atoms in this layer Thermosphere Ions reflect radio waves (radio skip)

16. Atmosphere Oxygen, Water, Carbon Dioxide But not too much – Nitrogen mostly Reflects and absorbs just the right amount of electromagnetic waves

18. Lithosphere Ground surface fertile soil, valuable metals fuels

19. Atmospheric Windows (P 68)

20. Greenhouse Effect (P112) All wavelengths of electromagnetic radiation reach our atmosphere. Some is reflected back into space (albedo) Visible light, some ultraviolet and radio waves penetrate to surface and are absorbed. Earth is heated and then gives off infrared Infrared is absorbed by carbon dioxide, water vapor, and ozone This absorption heats the atmosphere

23. Complex Consequences Polar ice cap melting Rising sea levels Changes in ocean heating and circulation Changes in weather patterns More intense weather

24. Geologically Active

25. Alfred Wegener 1912-1915

28. Baby Earth Liquid – Space debris impacts – Radioactive elements – nuclear fission Dense material like iron settled to the center Less dense material floated to the surface Produced a layered structure

30. Magnetic Field

33. Phaser Shield (p119-120) Charged particles from the sun are deflected by the magnetic field. Some of the charged particles are captured by the magnetic field forming the “Van Allen” belts Sometimes when there are a lot of charged particles from the sun the particles get trapped in the magnetic field at the poles and cause aurora – Aurora Borealis at the north pole – Aurora Australis at the south pole