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PUZZLAH #8

PUZZLAH #8. If the universe is infinite in spatial extent, as we believe it to be, what fraction of its volume are our most powerful telescopes able to probe? (A) 90% (B) 50% (C) A very small amount, a few % (D) Zero. Introduction to the Sky.

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PUZZLAH #8

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  1. PUZZLAH #8 If the universe is infinite in spatial extent, as we believe it to be, what fraction of its volume are our most powerful telescopes able to probe? (A) 90% (B) 50% (C) A very small amount, a few % (D) Zero

  2. Introduction to the Sky

  3. Capella Sirius Aldebaran Orion Pleiades Comet Hale-Bopp

  4. Orion Mars Rigel Betelgeuse

  5. “Observation” is not “Looking”

  6. “Observation” is not “Looking” "You see, Watson, but you do not observe." --- Sherlock Holmes

  7. “Observation” is not “Looking”Instead: • Study carefully, comprehensively • Remember/record • Try to make connections • Identify systematic features

  8. Motivations for Observing the Sky • Curiosity • Practical applications • Navigation • Time-keeping • Calendar-keeping • Fear, religious belief • E.g. Astrology

  9. Polynesian Navigation

  10. Egyptian Pharoh Akhenaton and family communing with Sun God (ca. 1350 BC)

  11. Astronomical MeasurementsWithout Telescopes • Angles (quantitative) • Sky to Sky • Earth to Sky • Brightnesses (crude) • Colors, Shapes (crude) • Changes in above with time

  12. Isosceles triangle:

  14. Units of Angular Measure

  15. Naked Eye Instruments for Angular Measures 1580 AD 150 BC

  16. Naked Eye Instruments for Angular Measures Limiting accuracy ~ resolution of human eye ~ 1 minute of arc 1580 AD 150 BC

  17. 10 degrees 5 degrees Ursa Major (The Big Dipper)

  18. "Hand-y" Angle Measuring (crude)

  19. The Magnitude System(a brightness ranking)

  20. Example: Range of magnitudes in Big Dipper

  21. Star Colors (prism-dispersed image)

  22. Puzzlah #9 If you go out at 9 PM on a clear night, turn to the south, and look up at the sky, you will see a certain group of bright stars. How will the location of those stars in the sky change if you come back at midnight or several weeks later? (A) The locations of stars in the sky are always the same (they never change). (B) The locations change during the night but are always the same at a given time of night. (C) The locations change during the night and also change at a given time of night from month to month.

  23. Puzzlah #10 During the day, the Sun moves from east to west across the sky. In which direction do the stars move after the Sun has set? (A) The stars are stationary; they don't move (B) West (C) East (D) North (E) South

  24. Constellations • Constellations are the patterns formed by brighter stars on the sky • Patterns seem fixed (i.e. don't change over years) • Recognized for millenia, by all cultures • Associated with mythological figures, animals, instruments, etc

  25. Stick-Patterns

  26. Official Names

  27. "Classical" figures added

  28. Mesopotamian carved stone, ca. 1000 BC showing Sun, Moon, Venus, and constellations

  29. Greek amphora, ca. 400 BC, showing Leo, Aquila, Hercules, etc

  30. Orion, Taurus, Lepus in a classical celestial atlas.

  31. Orion in a modern star chart. Fainter stars don't participate in the pattern.

  32. Hevelius, Firmamentum 1690

  33. Hevelius, Firmamentum 1690

  34. Cellarius, HarmoniaMacrocosmica, 1661

  35. More modern constellations Bode, 1801

  36. "Asterism"

  37. Modern Constellations • "Official Constellations": 88 (est. 1930, IAU) • Boundaries of each well-defined • "Zodiac" = the 12 (13) constellations lying along the annual path of Sun through stars. (Names widely recognized but NOT all bright.)

  38. Significance of the Constellations? Not Much • Associations are arbitrary, man-made, culture-specific. • Not natural groupings: stars not necessarily close in 3D space. Shapes are specific to Earth's location in galaxy. • Constellations are transient because stars are all moving with respect to each other. • Used as convenient "address" for roughly locating objects in sky.

  39. Contemporary "constellations"

  40. Orion Projected View 3-D Distribution

  41. Motions in Big DipperOver 100,000 Years

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