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ANNOUNCEMENTS HOMEWORKS #4 & #5 handed out today. HAND HW#4 IN FOR CREDIT
NEXT THURSDAY
IF YOU WISH HAND-in #5 NEXT THURS TO REPLACE POOREST GRADE ON PREVIOUS HWs . Material from BOTH HWs will be covered on the Midterm Exam
Midterm exam 1.5 weeks from today in TUESDAY’S class on OCTOBER 13th in BESC 180.
OPTIONAL Observing night at SBO next Monday 7:30pm.
OPTIONAL “ERATOSTHENES CHALLENGE” HELP SESSION next Monday 2—4 pm or next Tuesday 3:30-5pm @ GATE #5 Folsom Field
OPTIONAL Dark Sky Field Trip next Tuesday 6:15pm meet at Fiske…dress very warmly. Pray for clear weather.
Eclipse video with possibly offensive language (my mother would have been offended; my son would not) will be shown in first 10 minutes of class period on Tuesday. Come late if you wish.
For how long have Humans had the ability to predict ECLIPSES of the Sun and the Moon?
Could all eclipses have been predicted in ancient times?
The Battle of Halys took place at the river Halys in Turkey) on May 28, 585 BCE between the Medes and the Lydians.
A Solar Eclipse occurred, was viewed as an omen from the gods and the war was ended!
First known Solar Eclipse prediction by Thales of Miletus….HOW DID HE DO IT???
Subsequently the Lydians and the Medes drew up peace accords.
Only a few dozen Solar Eclipses are mentioned throughout antiquity…these events are RARE in any portion of the world.
AND YET ANCIENT PEOPLE KNEW HOW TO PREDICT ECLIPSES !!!
*** this is why I want you to know what appears to be obscure details of the lunar orbit called LUNAR STANDSTILLS ***
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.
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
Moon’s path
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 !
Lunar Orbit not stable. Nodes & standstill
points move through the zodiac backwards
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). FULL CYCLE OF STANDSTILLS IS 19
YEARS (closest even number to the 18 and two-thirds year
cycle of the nodes.
These extremes are called: MAJOR LUNAR STANDSTILLS
IN ANALOGY WITH SOLSTICES, EXTREME LOCATIONS OF
THE SUN.
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 “ECLIPSE
SEASONS” ARE AT OTHER TIMES
Eclipse season at solstices
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
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
AT SOLID LINE IN CENTER, FULL MOON IS ON THE ECLIPTIC AND AN ECLIPSE OCCURS,
ONCE EVERY 9 YEARS A LUNAR ECLIPSE OCCURS on THE FULL MOON NEAREST THE SOLSTICE
FULL CYCLE OVER A 18 ½ - 19 YEAR PERIOD
next one: June 2025 last one: early July 2015
AT SOLID LINE IN CENTER, FULL MOON IS ON THE ECLIPTIC AND AN ECLIPSE OCCURS,
ONCE EVERY 9 ½ YEARS A LUNAR ECLIPSE OCCURS on THE FULL MOON NEAREST THE SOLSTICE
ECLIPSE SEASONS ECLIPSE SEASONS
NEAR EQUINOXES NEAR EQUINOXES
ECLIPSE SEASONS NEAR SOLSTICES
ECLIPSES
POSSIBLE ONLY
TWICE PER YEAR
DURING
“ECLIPSE
SEASONS”
WHEN FULL & NEW
MOONS OCCUR
CLOSE TO THE
NODES
In the year of a lunar
standstill (either
“major” or “minor”),
the Eclipse Seasons
are near the
equinoxes
ECLIPSE NUMEROLOGY: AN INTRODUCTION
ECLIPSE “SEASONS”: The possibility for one or more eclipses
happens twice per year when Full and/or New Moon occurs in or
near the Lunar Nodes.
Because nodes move “backwards” around the Moon’s orbit, these
eclipse seasons are LESS THAN ½ year apart: 173 DAYS to be
exact.
ECLIPSE SEASONS MOVE “BACKWARDS” through the
calendar at a pace of about 19 days per year…eclipse seasons
are ~ 19 days earlier than the previous year.
ECLIPSE SEASONS CYCLE THROUGH THE CALENDAR
ONCE EVERY 9 ½ YEARS…or TWICE IN 19 YEARS (“YEAR
OF METON”)
NOTICE AT LEFT PROGRESSION OF SPRING ECLIPSE SEASON:
1984 end of May
1985 beginning and mid May
1986 mid April
1987 late March
1988 mid March (year of a lunar standstill)
STONEHENGE: TEMPLE OR OBSERVATORY ? EARLIEST CONSTRUCTION c. 3200 BCE
STONEHENGE:
A MONUMENT CONSTRUCTED IN STONE AGE BRITAIN BUT BY WHOM AND WHY ???
90 MILES SW OF LONDON ON SALISBURY PLAIN AT THE INTERSECTION OF 2 HIGHWAYS.
SURROUNDED BY BARROW DOWNS (ANCIENT GRAVES)
STONEHENGE
INTERESTINGLY THERE WERE SEVERAL BUILDING PERIODS AT THIS SITE…. LATEST DATES SUGGEST STONEHENGE 1 WAS “ERECTED” PRIOR TO 3000 BCE, OVER 5000 YEARS AGO!
STONEHENGE 1 MORE INTERESTING ASTRONOMICALLY…
STONEHENGE 3 MORE INTERESTING FOR ITS ENGINEERING.
circa 3200 BCE
circa 2500 BCE
Circa 2400 BCE
THE “HEELSTONE”
SUMMER SOLSTICE SUNRISE “BACKSIGHT”
FORESIGHT AT CENTER OF SARCEN CIRCLE
STONEHENGE 1 STONEHENGE 2 & 3(c. 3200 BCE) (c. 2400 BCE)
“AVENUE” + DITCH MASSIVE STONES including56 HOLES FILLED WITH CHALK 5 “TRI-LITHONS” , “SARSEN FEW LOCAL STONES CIRCLE” & BLUESTONES
ONE OF 56 AUBREY HOLES EVENLY SPACED AROUND 3OO FOOT DIAMETER CIRCLE
THE EVIDENCE FOR ECLIPSE PREDICTION IS CIRCUMSTANTIAL but RELIES ON:
NUMEROLOGY: NUMBER 56 RELATED TO LUNAR NODE CYCLE AND HAS NO OTHER OBVIOUS CYCLES OR USE
GEOMETRY: ALIGNMENTS WITH EXTREME POSITIONS OF BOTH THE SUN AND THE MOON EXTREMES OF MOON GIVE LOCATIONS OF NODES !
REASONS WHY STONEHENGE 1 WAS LIKELY AN ECLIPSE PREDICTOR:1. 56 AUBREY HOLES: 56 = 18 2/3 X 3 (three
times the period of the nodes). The Classical World’s “Year of Meton”
2. Stonehenge 3 “Rectangle” accurately aligned with solstices and standstills to ± ½ degree. Stonehenge 1 circle is larger and so accuracy is better: ± ¼ degree ! (size of Sun and Moon in sky ≈ ½ degree
Stonehenge 1 accuracy good
enough to predict all eclipses.
3. Stonehenge Rectangle (summer
solstice sunrise and full moon rise
at major standstill in perpendicular
directions only within ± 150 miles
of Stonehenge.
THE STONEHENGE RECTANGLE
Only at the latitude of Stonehenge are the summer solstice sunrise point and the summer solstice Full Moon rise (at standstill) exactly perpendicular.
Already present in Stonehenge 1. evidence for eclipse prediction c. 3000 BCE
56 “Aubrey Holes” date to Stonehenge 1. (56 = 18 2/3 x 3…exactly 3 times the cycle of the nodes)
THEORIES ABOUT STONEHENGE CONTINUE TO ABOUND !!
NOTICE AT LEFT PROGRESSION OF SPRING ECLIPSE SEASON:
1984 end of May
1985 beginning and mid May
1986 mid April
1987 late March
1988 mid March (year of a lunar standstill)
SHORT ECLIPSE SERIES IN BETWEEN “SKIPS” (NO ECLIPSE)