1. Universal Gravitation Any two masses m 1 and m 2 separated by a distance R are attracted by a force given by F = G (m 1 m 2 ) / R 2 G = 6.67 x10 -11 Nm 2 /kg 2 g = 9.8 m/sec 2

2. Solar System Terrestrial Planets and Comparative Planetology

3. Variety of Planets Why so different? Why so different? “Terrestrial” planets “Terrestrial” planets “Jovian” planets “Jovian” planets (=Terr + gas!) (=Terr + gas!) The physics…. The physics…. neat stuff… neat stuff…

4. Neat stuff to understand What is meant by an atmospheric gas’ “temperature”? What is meant by an atmospheric gas’ “temperature”? Does “what goes up” have to come down? Does “what goes up” have to come down? Let’s see…

5. Put them together For planets plot v esc vs. temp v esc vs. temp For gases plot vs. temp vs. temp Problems with extrasolar gas giants.

6. The Earth Famous picture Famous picture Oblateness of 0.0034 (demo) Oblateness of 0.0034 (demo) Average density is ~5.5 g/cm 3 Average density is ~5.5 g/cm 3 Whereas surface rocks ~3… Whereas surface rocks ~3…

7. Seismology tells of interior Waves from earthquakes refracted at boundaries Waves from earthquakes refracted at boundaries Liquid and solid inner cores Liquid and solid inner cores Rotation of liquid core leads to … Rotation of liquid core leads to …

8. Magnetic Field Permanent magnet possible? Permanent magnet possible? Alternative: currents… Alternative: currents…

9. Magnetic Field “Dynamo” action of rotating liquid core “Dynamo” action of rotating liquid core Charged particles in liquid core move (and moving charges = a current) Charged particles in liquid core move (and moving charges = a current)

10. Interior structure Core heated in formation, kept hot from natural radioactivity Core heated in formation, kept hot from natural radioactivity Cools slower than smaller bodies like the Moon and Mercury (& babies) Cools slower than smaller bodies like the Moon and Mercury (& babies) Convection of lithosphere leads to seismic events and plate tectonics… Convection of lithosphere leads to seismic events and plate tectonics…

11. Plates of the Earth Action occurs along plate boundaries…

12. Volcanoes Mt. St. Helens…

13. Island Strings Hawaiian Islands How formed?

14. Hot Spots + Plate Motion xx xx

15. Earthquakes

16. Continental Drift If we back up…

17. Pangaea – 260 million years ago

18. Tides Differential gravitational force Differential gravitational force The Moon is twice as important as the Sun The Moon is twice as important as the Sun Result… Result…

19. Tidal distortion Earth itself stretches about 9 inches Earth itself stretches about 9 inches Tidal flow much larger Tidal flow much larger Two peaks (tides) per day Two peaks (tides) per day

20. Sun and Moon Together “Spring” tides when aligned “Spring” tides when aligned “Neap” tides when perpendicular “Neap” tides when perpendicular Extra-high when Moon near perigee and/or Earth near perihelion Extra-high when Moon near perigee and/or Earth near perihelion

21. Births and the Moon? Has anyone heard that birthrates depend on the phase of the Moon? Has anyone heard that birthrates depend on the phase of the Moon?

22. My Study

23. Nope. Nor ….

24. … plotted against perigee