20140815 &  1. The Contents of the Universe
20060829 &  2. Scientific Notation
20060831 &  3. Timescales in the Universe
20060905 &  4. The Phases of the Moon
20060907 &  5. The Seasons on Earth
20060912 &  6. The Origin of the Moon
20060914 &  7. The Celestial Sphere
20060919 &  8. Planetary Orbits
20060921 &  9. The Scientific Method
20060926 & 10. Geocentric and Heliocentric Models
20060928 & 11. The Formation of the Planets
20061003 & 12. The Terrestrial Planets
20061010 & 13. The Jovian Planets
20061017 & 14. Waves and Light
20061019 & 15. Atomic Structure
20061024 & 16. Absorption and Emission
20061026 & 17. Stellar Temperatures
20061031 & 18. Nuclear Reactions
20061102 & 19. Binary Stars
20061107 & 20. The Hertzsprung-Russell Diagram
20061109 & 21. White Dwarfs
20061114 & 22. Neutron Stars
20061116 & 23. Black Holes
20061128 & 24. The Milky Way
20061130 & 25. The Expansion of the Universe
20061205 & 26. A Universe of Galaxies
20120814 &  2. Scientific Notation
20120815 &  3. Timescales in the Universe
20120816 &  4. The Phases of the Moon
20120809 &  6. The Origin of the Moon
20120817 &  7. The Celestial Sphere
20120808 &  9. The Scientific Method
20120811 & 11. The Formation of the Planets
20120818 & 14. Waves and Light
20120926 & 16. Absorption and Emission
20120928 & 17. Stellar Temperatures
20120831 & 19. Binary Stars
20120823 & 20. The Hertzsprung-Russell Diagram
20120924 & 21. White Dwarfs
20120819 & 22. Neutron Stars
20120820 & 23. Black Holes
20120821 & 24. The Milky Way
20120822 & 25. The Expansion of the Universe