motions in the sky
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Motions in the Sky
Watchers and Timekeepers
TheMilkyWayoverUtah
Felix Shih’s work
The First Science
Unless you were a troglodyte* thousands of years ago, you couldn’t help but notice that the sky changed, hour by hour, day by day, month by month, year by year
*someone who lives underground
The Sun rose and set and sometimes even disappeared;
The Moon also rose and set, changed shape, and occasionally turned red;
There were patterns in the night sky that came into view at different times of the year;
There were stars that defied the patterns and marched recklessly across the sky;
And there were often visitors in the heavens.
Astrologers: precursors to Astronomers
As in any population, there were a few geeks who took great interest in what was happening in the sky
These people never knew the cause of the events and phenomena they observed, but they did keep track of their periodicities
And they were good storytellers!
Great mysticism was attached to the goings-on in the sky
The people who recognized the repetition of celestial events and could make predictions of the next occurrence were therefore seen as shamans
Shamans in a society wield great power The ability to predict phenomena in the
sky extended back down to Earth and the supposed ability to foresee the future Often for personal gain!
Time Since celestial events happen with a
regularity, the shaman astrologers could use this periodicity to construct calendars (coming up in a minute)
Even today our calendars are closely attached to Astronomical phenomena
But it took millennia to iron out all the kinks
Months and Years
The most obvious cyclic events in the sky are the rising and setting of the Sun and the Moon
Important to realize is the fact that these rising and settings vary from day to day
Also critical is to understand that the Sun and the Moon cycles are not connected
The Sun rises in a different place every day
These four special days mark out many calendars
They are: Winter Solstice, Vernal Equinox, Summer Solstice, Autumnal Equinox
Northern Hemisphericocentric*
The Southern Hemisphere has equivalent days
The Sun’s rising position changes over a year, from south of East in December to directly east in March to north of East in June and back to East in September
And all points in between Same all year long on the equator
*not a real word
Effects
This changing rise position is caused by the tilt of the Earth relative to the Sun and by the motion of the Earth around the Sun
The tilt is what causes the Seasons* Ancient astrologers did not know about
the tilt or the orbit, but they knew the cycle repeated after about 365 days
*discussed in another ppt
Analemma
Not a regular path in the sky
Left: each picture was shot on a different day but at the same time over a year
Important Days
The four Astronomically important days delineated the four Seasons, although some cultures like the ancient Egyptians recognized only three
Please realize that ancient peoples did not necessarily have a December, March, etc., but the two solstices and the two equinoxes were recognized nonetheless
The Moon
Less ‘well-behaved’ than the Sun Rises in different places and much
different times every night, if it was visible at all
Changed shape as well, unlike the unchanging Sun
Phases
The Moon appears to change shape because of its position relative to the Earth and the Sun
In the bottom right there seems to be a problem; the Moon is there however!
The cycle takes about 29 days, an interval known to the ancients
Calendars (snapshots, only for comparison)
Egyptian 360 + 5 days Sothis 3 seasons 3 10-day weeks
Babylonian sexigesimal system 360 days, 12-30 day months, 4 seasons Begins with crescent Moon
Greek 4th C. BC Months 1-4 36 days, 5-10 35 days each
Roman (Julian) 12-month 355 day year D days per month Mensis Intercalaris month of 27 days
Chinese 12 Lunar months with alternating names
Mayan Many variants that synchronized, e.g. 260 day
Tzolkin with 365 day Haab Also lunar and Venusian cycles
Modern Western
Established by Pope Gregory 1582 Threw out lunar influence (almost) 365.24 days Leap year rules Still corrected for atomic clocks
Days of the Week
Like calendars, each culture had different names for the days of the week, number of days in a week, and number of hours in a day
Western names derive from celestial objects
English names span several languages
Sundials
The oldest known instruments for keeping track of time
First attempt at marking time ~ 5000 BC 2500 BC: Babylonian and Egyptian
obelisks By 250BC the Greeks produced complex
and more accurate sundials using their knowledge of geometry
Examples
Patterns in the Night
Constellations: “stars together” Different for different cultures (following
slides) Fanciful at best, but a good mnemonic to
find things Useful for calendars
Special Constellations
Zodiacal 12 Astrological signs Misleading: the sign
is not up at night during its reign
Circumpolar Never set Useful for navigation
Two Western Constellations
Orion is facing backwards for use with a celestial sphere
Egyptian Sky (interpretation of Greek view)
African Sky
Used the sky to explain myths
Chinese star map from the Tang Dynasty
Visitors in the Sky
The First UFOs! Unpredictable,
irregular Shooting Stars
Not! Small grains of dust
Comets “Bad Star”: Dis-Aster Harbingers of
catastrophe
Why Astrology is Not a Science Vague, untestable No account for time delay Wide constellations Twins
Which Horoscope is “Real”?
You have a relentless drive to get at the heart of things this Tuesday, whatever is under the surface or behind the scenes. Emotionally, you are also hot stuff, rushing into areas and handling subject matters that others would never come near. You may not like displays of emotion and pushy people, or at least find them challenging and thought-provoking. There is not much to slow your progress, however, and by this afternoon you are moving forward with your professional activities at full speed ahead. This evening is a good time to have a long talk with your partner about your future plans.
You have a good sense of where you stand in a group of people; exploit this at your gatherings this week. Nonetheless, your tendency to try to control any situation can get out of hand so rein in your urges in this area. There are those people who try to stand in your way, but they can be ready allies if you just give them a chance. Look to your social network resources to make this happen. Financially you should be conservative this week, but emotionally be liberal. By Friday your growing relationship will seem more stable and long-lasting. Listen to your best friend’s advice in these matters; it will be sound counsel.
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