1. THE UNIVERSE

2. SUB-PART SOLAR SYSTEM A VERY SMALL PART – THE UNIVERSE MAY NOT BE INFINANT

3. SOLAR SYSTEM Sun at center 8 planets Planets move in ellipses Plane of rotation not same as plane of revolution Mathematically highly predictable Formed from space trash ~4.6 by ago

4. Why do (did) we need to know this stuff?? To learn this required extensive expenditure of time, energy, and effort

5. An answer -- maybe There certainty is no practical reason – at least not yet. An answer might be – human nature and the desire to ‘know’. There are some interesting philosophical questions in these thoughts.

6. Let’s take a look at the practical things that a early Homo might need to know

7. One Living in an equatorial region and hunting- gathering or early agriculture –No winter or summer seasons –There may be wet or dry seasons, however, along with plant changes and migration of selected animals

8. Two Living in a non-equatorial region and hunting-gathering or early agriculture –Climate –Seasons –Timing

9. Three What clues to changes and coming events—remember no one has a clock or a calendar until later on Astronomical clues –Phases of moon –Position of stars –Location of sun

10. BUT….. There is no need to know why. Then, why did Homo go looking for answers??

11. I don’t know…

12. What, then, are the tools for knowing astronomical things?

13. Eyesight and counting i.e. how may days has it been since the moon was full (or new)? What is the night-time pattern of stars? Is it the ‘’winter’ pattern? How many ‘moons’ has it been since the appearance of the ‘winter’ pattern? Has the sun set (risen) in the ‘winter’ notch (in yon mountains) yet?

14. Note, questions like “How long are the days?” doesn’t work—no clocks. But—are there lights in the sky that are not always in the same spot? Can they be used to tell seasons?

15. Devices for measuring angles The sextant, for example, and navigation Surveying instruments

16. Mathematics Along with the understanding of physics triangulation Parallax Inverse square law

17. triangulation

18. parallax

19. Inverse square law-1 Applies to any energy radiated from a point – spherical radiation Example – the radiant energy received by Venus compared to Earth; Earth = 1 AU, Venus = 0.72 AU 0.72 = 1/1.39; invert and square (1.39) 2 ; = 1.9 times more energy

20. Inverse square law-2 Energy received by Mars as compared to Earth; Earth = 1 AU, Mars = 1.52 AU 1.52 = 1/0.66; invert and square; (0.66) 2 = 0.44 (or 44% as much)

21. Inverse square law-3 Double the distance; the energy decreases to 1/4th Triple the distance; the energy decreases to 1/9th Take 1/2 the distance; the energy increases by 4 Take 1/3 the distance and the energy increases by 9

22. What, then, about Venus Near same mass as Earth – so has much the same mass and composition of atmosphere; never converted CO 2 to O 2 because much hotter! ~2x; and this conversion required plant life

23. What, then, about Mars Considerably less massive than Earth ~1/9 Hence unable to hold much of the lighter gasses Cold, thin atmosphere

24. Telescope First ~1608 Galileo heard about and made several about 1610; published observations and numerous discoveries; magnification ~30x After some fumbling around – leads to Solar System as we know it.

25. Kepler’s laws of Planetary motion 1619 Observed mathematical relationships –Ellipse –Equal areas –Periods and axes

26. 1687-Principia Newton’s laws of motion Newton’s law of gravitation A new mathematics invented

27. Newton’s first law - I “Every body continues in a state of rest, or of uniform motion in a straight line, unless it is compelled to change that state by forces impressed upon it.” Objects in motion remain in motion and objects at rest remain at rest, unless they are acted upon by an outside force.

28. II “The change in motion is proportional to the force impressed…..”

29. III “To every action there is always an equal and opposite reaction…”

30. Newton’s law of gravitation F = G (m 1 m 2 )/d 2

31. Photometry ~1900 with development of photography Use of photographs was first step to instrumental collection of data –Brightness (magnitude) –spectrometry

32. spectrometry ~1815 with discovery of Fraunhofer lines in spectra of sun The stars send us information—all we need to do is learn how to interpret it.

33. Spectra (continuous)

34. How atoms affect light

35. Fe in the sun

36. Telescopes of ‘other’ wavelengths Radio telescopes 1932 Other wavelengths Radar (~1950)

37. The Hubble telescope Outside Earth’s atmosphere Hence unaffected by atmospheric gases, dust, and light ~1985