ANNOUNCEMENTS. 2. EXTRA CREDIT HOMEWORK (if desired) DUE THURSDAY.

Transcription

1 ANNOUNCEMENTS 1. BOOKS REQUIRED FOR OBSERVING PROJECTS, SKYGAZER PLANETARIUM CDs AND BOOKS FOR IDENTIFYING TOPICS FOR THE RESEARCH PAPER ARE ON RESERVE AT GEOLOGY LIBRARY IN BENSON (across the hall!). 2. EXTRA CREDIT HOMEWORK (if desired) DUE THURSDAY. 3. DARK SKY TRIP. ONE WEEK FROM TONIGHT 6:30 10:30pm TO MOUNTAIN RESEARCH STATION ON NIWOT RIDGE. ELEVATION ~ 10,000 FEET IT WILL BE COLD REGARDLESS OF DAYTIME WEATHER IN BOULDER. 4. ECLIPSE SEASON!!! LUNAR ECLIPSE VIEWERS PLEASE USE 8:11pm AS TIME OF FULL IMMERSION INTO EARTH S UMBRA (darkest shadow); i.e., eclipse became total at that time. 5. HELP SESSION FOR ERATOSTHENES CHALLENGE OBSERVING PROJECT (measuring the circumference of the Earth): next Monday 2 4pm and Tuesday 3:30 5 pm Folsom Field Gate 5

2 Additional ANNOUNCEMENTS 6. ATTEND FISKE LIVE PRESENTATIONS FOR EXTRA CREDIT. WRITE ~ 1 PAGE ON WHAT YOU LEARNED. FIRST ONE THIS FRIDAY 7:30pm FOR PARENTS WEEKEND: THE ANTIKYTHERA MECHANISM: AN ANCIENT GREEK COMPUTER? (for PARENTS WEEKEND) 7. Stick with the Goat at hand a reminder about the addictive qualities of cellphone use. 8. UP FOR DISCUSSION TODAY: FULL MOON POSITIONS THROUGH THE SEASONS, MAJOR and MINOR LUNAR STANDSTILLS, INTRO. TO ECLIPSE PREDICTION

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5 A FEW INTERESTING LUNAR OBSERVING ODDITIES THE FULL MOON RISES and wow! LOOK HOW BIG IT IS much bigger than when it is up high in the sky! BLUE MOON?? A RAMMA DAMMA DING DONG A WOBBLY MOON??

6 FULL MOONRISE OVER THE TEMPLE OF POSEIDON NEAR ATHENS BIG AND REDDISH BUT SAME SIZE AS HIGHER IN THE SKY.

7 BLUE MOON??? MOON S THAT APPEARED BLUISH IN THE SKY ARE VERY RARE BUT ACTUALLY WERE OBSERVED IN ANTIQUITY. DUE TO A REDDISH SKY BACKGROUND FROM VOLCANIC ERUPTIONS (e.g. Krakatoa 1885) or INTENSE FOREST FIRES IN SCANDANAVIA. The Scream by Edvard Münch depicts such a sky in which a Blue Moon could have been seen.

8 BUT THEN BLUE MOON CAME TO MEAN, SIMPLY A VERY RARE OCCURRENCE. In 1890s Maine Farmer s Almanac redefined a BLUE MOON to mean when there were 4 FULL MOONS in the first 3 months of the year pushes Easter to be very late. In 1940s Sky & Telescope Magazine thought they were quoting the Maine Almanac correctly by saying that a Blue Moon is when there are more than one Full moon in any one calendar month. No one noticed the published correction and so this definition has become modern urban legend. Yet another reason to be skeptical of information provided by TV weathermen and women.

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10 WHY DOES THE MOON WOBBLE IN THE PREVIOUS SHORT VIDEO? A. THE MOON IS UNSTABLE AND IT WILL EVENTUALLY BREAK APART. B. THE CAMERA THAT TOOK THE PICTURE WAS WOBBLING C. THE MOON S ORBIT IS UNSTABLE AND EVENTUALLY THE MOON WILL FLY OFF INTO SPACE. D. SOMETIMES THE MOON IS CLOSER TO THE EARTH THAN OTHER TIMES. E. THE MOON IS CLOSER TO THE EARTH AT FULL MOON, WHICH YOU CAN SEE WHEN IT RISES. F. THE MOON S ORBIT IS ELLIPTICAL. G. WHAT S AN ELLIPTICAL ORBIT?

11 WHY DOES THE MOON WOBBLE IN THE PREVIOUS SHORT VIDEO? A. THE MOON IS UNSTABLE AND IT WILL EVENTUALLY BREAK APART. B. THE CAMERA THAT TOOK THE PICTURE WAS WOBBLING C. THE MOON S ORBIT IS UNSTABLE AND EVENTUALLY THE MOON WILL FLY OFF INTO SPACE. SOMETIMES THE MOON IS CLOSER TO THE EARTH THAN OTHER TIMES. E. THE MOON IS CLOSER TO THE EARTH AT FULL MOON, WHICH YOU CAN SEE WHEN IT RISES. THE MOON S ORBIT IS ELLIPTICAL. F. WHAT S AN ELLIPTICAL ORBIT?

12 ELLIPTICAL ORBIT CIRCULAR ORBIT COULD ANCIENTS HAVE KNOWN?

13 ELLIPTICAL ORBIT XHALF HALF HALF HALF CIRCULAR ORBIT YES!! HIPPARCHOS OF RHODES KNEW BY TIMING DURATION BETWEEN WAXING AND WANING HALF MOONS (circa 150 BCE)

14 Synodic versus Sidereal Period of the Moon: 1. Synodic = Sun-odic the full cycle of the Moon relative to the Sun Measured using the phases of the Moon. New month either at each New Moon or at the siting of the first visible crescent moon days long the basis for almost all Lunar Calendars (Greek, Babylonian, Islamic, Jewish, Hopi, etc.) 2. Sidereal Period is the full cycle of the Moon relative to the stars. Measured using the position of the Moon in the stars specifically the Zodiac Constellations 27.3 days long the basis for the Inca lunar calendar new month every time the Moon passes the Pleiades

15 SYNODIC MONTH is THE MONTH OF THE PHASES SIDEREAL MONTH IS THE TIME PERIOD AFTER WHICH THE MOON RETURNS TO THE SAME ZODIAC STARS the 28 lunar mansions (NAKSHATRAs) of VEDIC ASTROLOGY e.g., Inca months set each time Moon passes the Pleiades.

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17 QUESTION: SURE, I KNOW ABOUT THE LUNAR PHASES and that THE POSITION OF THE MOON SHIFTS FROM WEST TO EAST AT SUNSET AS IT PROGRESSES AROUND ITS ORBIT. BUT WHAT ABOUT ITS LOCATION TO THE NORTH OR TO THE SOUTH ALONG THE HORIZON? DOES THE FULL MOON RISE: a). Always at about the same point on the eastern horizon regardless of the time of year? b). The moon s path is nearly along the ecliptic so it rises about where the Sun rose that same morning (i.e. to the northeast in summer and to the southeast in winter)? c). It s the Full Moon and so it rises in the opposite direction that the Sun set that same day (i.e., to the northeast in winter and to the southeast in summer)? d). It s the Moon and so its rising point is erratic.

18 THE SEASONAL CYCLE OF THE FULL MOON MOON ALWAYS STAYS WITHIN 5 DEGREES OF THE ECLIPTIC PLANE FULL MOON ALWAYS WITHIN 5 DEGREES OF DIRECTLY OPPOSITE THE SUN FULL MOON RISES WHEN SUN SETS WHEN SUNSETS FARTHEST NORTH OF WEST, THE FULL MOON RISES FARTHEST SOUTH OF EAST

19 BECAUSE FULL MOON IS ALWAYS NEARLY EXACTLY OPPOSITE TO THE SUN (FULL MOON RISES WHEN SUN SETS) IT ALSO SWINGS NORTH AND SOUTH DURING THE YEAR BUT OPPOSITE TO THE SUN S SWING: e.g., THE MIDWINTER FULL MOON IS THE HIGHEST IN THE SKY, RISES AND SETS FURTHEST NORTH OF EAST AND WEST & IS UP THE LONGEST!! BEAUTIFUL.

20 CELESTIAL LATITUDE OF SUN THROUGH THE YEAR SOLSTICES AND EQUINOXES IN GREEN RED MARKS SHOW APPROXIMATE LOCATIONS OF CROSS-QUARTER DAYS NOTE TWO SUNS PHENOMENON: SUN STAYS CLOSE TO SAME TWO LOCATIONS IN SKY OVER MUCH OF YEAR: SUMMER SUN AND WINTER SUN Time of changes SUMMER SUN Winter Sun Winter Sun CONTINUES

21 THE SEASONS OF THE FULL MOON:

22 TILT OF MOON S ORBIT RELATIVE TO SUN MAKES LOCATION OF MOON IN SKY SLIGHTLY MORE COMPLICATED. EXTREME POSITIONS THAN FOR THE SUN but Lunar Orbit not stable. Nodes move through the zodiac (and so backwards through the seasons with an 18 2/3 year period).

23 But recall that full moon is opposite the Sun so lowest Moon is in Summer (June/July);Highest Moon is in Winter (December/January). HARVEST MOON & HUNTERS Moon: Only Full Moons still named since these are most dramatic the darkness beginning to overcome the light!

24 EXTREMES OF THE LUNAR ORBIT Because the Moon s orbit is titled with respect to the ecliptic plane, the Moon sometimes gets up to 5 degrees NORTH of the ecliptic or up to 5 degrees SOUTH of the ecliptic. But for the Full Moon these extremes happen only once every 9.5 years (a northern extreme in winter is followed 9½ years later by a southern extreme for the Full Moon nearest the summer solstice). These extremes are called: MAJOR LUNAR STANDSTILLS IN ANALOGY WITH SOLSTICES, EXTREME LOCATIONS OF THE SUN.

25 NOTE WELL: THE ABOVE SKETCH IS QUITE SMALL IN COMPARISON TO THE SKETCHES AT LEFT. THE FULL EXTENT ABOVE IS ONLY A BIT OVER TWO THUMB LENGTHS IN THE SKY!!! AN ECLIPSE HAPPENS AT THE FULL MOON CLOSEST TO THE SOLSTICE IN THE YEAR DEPICTED AT CENTER ABOVE. OTHER YEARS ECLIPSES SEASONS ARE AT OTHER TIMES

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27 Why would we care about these Standstill points? Nodes are where eclipses occur Nodes are invisible and cannot be directly observed or tracked. Standstills are 90 degrees away from the nodes. In the year of a Lunar Standstill eclipses happen close to the equinoxes. Eclipse prediction!

28 ECLIPSE SEASONS: TWICE PER YEAR WHEN SUN IS NEAR THE LOCATION OF ONE OF THE TWO NODES ECLIPSE SEASONS WOULD ALWAYS BE AT SAME TIME OF YEAR except LUNAR ORBIT TWISTS IN SPACE MOVING NODES BACKWARDS (19 DAYS PER YEAR!!) NODE S PATH

29 NOTICE AT LEFT PROGRESSION OF SPRING ECLISPE SEASON: 1984 end of May 1985 beginning and mid May 1986 mid April 1987 late March 1988 mid March (year of a lunar standstill)