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)