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Across 3. two wds. the long axis of an ellipse 5. modern method for deriving the absolute scale of the solar system 6. one of the end points in the line 8. Italian fellow that made observations with a telescope 9. the square of the period= the distance ........ 11. "wanderer" 14. ratio between foci and major axis 15. planet that is 0.3 A.U. from Earth 17. Polish dude that came up with heliocentric model 18. keplers second- planets ......... out equal areas in equal time 19. 3 wds. what travels at 300,000 km per second 20. true shape of planetary orbits

Down 1. how kepler determined the distance to planets 2. Danish guy that recorded lots of planetary data 4. abbreviation for Sun to Earth average distance 7. refers to a planet making a complete 360 degree revolution 10. eccentricity for a circle 12. Sun centered 13. motion that is "backward" from our perspective 16. keplers second law deals with this at perihelion and aphelion