1. Physics 112 Star Systems Lecture 2 Motions of the Heavens
Kevin H. Knuth
University at Albany
Fall 2015

2. "Who laid the foundations of the earth, that it should not be removed for ever.“
- Psalms 104:5

3. What day is it today?

4. Calendars
Calendars are how to know WHEN.

5. Calendars There are three basic components: Year Month Day
The year is divided into
12 months.
Each month has 28, 29,
30, or 31 days.
There are 365 days per year.

6. Why is it based on a YEAR? Why are our calendars based on a year?
Why don’t they just count the number of days since some starting point?

7. Why is it based on a YEAR? Why are our calendars based on a year?
Why don’t they just count the number of days since some starting point?
The annual cycle is important.
We need to know when to plant our crops.
When to hold certain festivals.
When other important events have been arranged

8. Mayan Calendar
Mayan Long Count counts the number of days since creation: Aug 12, 3113 B.C.
Batkun Count
Calendar Round
Cimi Kayab
Tzolkin (260 Day Calendar) Day (1-13) Sign (1-20)
Haab (Civil Calendar) Day (1-19) Month (1-19)
Batkun Count Batkun Katun Tun Uinal Kin
Kin = 1 Day Uinal = 20 kins Tun = 18 Uinals Katun = 20 Tun Batkun = 20 Katun

9. Northern Hemisphere
The modern civilizations mostly developed in the Northern Hemisphere, and our notions of time and seasons reflect this.
SUMMER – The Sun is high in the sky during the day
The days are long
WINTER – The Sun is low in the sky during the day
The days are short

10.  2009 Pearson Education Inc.

11. SEASONS
 2009 Pearson Education Inc.

13. Summer Solstice SUMMER SOLSTICE (about June 22)
The longest day of the year in the northern hemisphere
The Sun reaches its maximum height in the sky on this day
This angle (declination) is denoted the Tropic of Cancer
It is at (23° 27') latitude.
Sol = Sun
The word solstice comes from the Latin word solstitium meaning the point where the Sun stops.

14. Winter Solstice WINTER SOLSTICE (about Dec 21)
The shortest day of the year in the northern hemisphere
The Sun’s maximum height at noon, is as low as it will get
This angle (declination) is denoted the Tropic of Capricorn
It is at (-23° 27') latitude.
Sol = Sun
The word solstice comes from the Latin word solstitium meaning the point where the Sun stops.

15. Spring (Vernal) Equinox
SPRING EQUINOX (about March 21)
This is one of the midway points between the solstices.
Day and Night are both exactly 12 hours.
The Sun is directly over the Equator
The word equinox comes from the Latin word equinoxium meaning equality of night and day

16. Fall (Autumnal) Equinox
FALL EQUINOX (about September 23)
This is one of the midway points between the solstices.
Day and Night are both exactly 12 hours.
The Sun is directly over the Equator
The word equinox comes from the Latin word equinoxium meaning equality of night and day

17. Solstices and Equinoxes
The Solstices and Equinoxes enabled the ancients to tell the time of year to within the accuracy of a day.
They did this by carefully monitoring shadows.
Stonehenge 3100 BC – 1600 BC
El Caracol: The Mayan Observatory 600 – 1000 AD

19. Analemma
An analemma is the shape of the path that the Sun traces out in the sky over the course of a year.
It is found by noting the position of the sun at the same time each day.

20. Analemma on Mars

21. Excursion to Babylon

22. Babylon (56 mi south of modern Baghdad)
Sumer and Babylon
Babylon (56 mi south of modern Baghdad)
Sumer was the first civilization…home of the first cities.
First written language was probably in Sumer around 3100 BC
In 2500 BC, by Royal Edict, all weights and measures were standardized in Babylon.

23. Babylonian Measures Length 1 finger ~ 2/3 inch 1 cubit = 30 fingers
1 cord (surveyors rope) = 120 cubits = 3600 fingers
Weight
1 grain ~ 45 milligrams
1 shekel = 180 grains ( ¼ ounce)
1 talent = 3600 shekels (67 pounds)
You may note that these numbers are divisible by 6 and 10.
This is a recurring theme in the Babylonian system…

24. Babylonian Measures Angles 1 Circle = 360 Degrees
1 Degree = 60 Minutes of Arc
1 Minute of Arc = 60 Seconds of Arc
We still use these measures today!

25. Babylonian Measures Time 1 Day = 24 Hours 1 Hour = 60 Minutes
1 Minute = 60 Seconds
360 Days per Year
12 Months with 30 Days each
Every 5th year an extra month was added to keep the calendar aligned with the astronomical observations.

26. Babylonian Measures Time 1 Day = 24 Hours
1 Hour = 60 Minutes
1 Minute = 60 Seconds
360 Days per Year
12 Months with 30 Days each
Every 5th year an extra month was added to keep the calendar aligned with the astronomical observations.
Note that all of these ratios are divisible by 6.
Clearly 6 was important to the Babylonians.

27. Our Number System Look at the numbers 1, 13, 147
The symbol 1 means something different in each number. Its meaning depends on its position in the number.
1 = 1
13 = 1x10 + 3
147 = 1x x = 1x x x100
We call our number system, a Base 10 system since each symbol represents a number between 0 and 9 and is multiplied by the base 10 taken to the power of the place in the expression.
678,197 = 6x x x x x x100

28. Our Number System
John Napier of Merchistoun, Scotland (1550 – 4 April 1617) invented the Decimal Point enabling us to write fractional amounts efficiently.
1/2 becomes 0.5
1/10 becomes = 10-1
1/100 becomes = 10-2
1/3 becomes … (which goes to show that our system isn’t perfect either!)
We often use this to write very large or very small numbers.
The speed of light is 3.0 x 108 meters/second

29. Roman Number System Look at the numbers 1, 13, 147 again
The Romans used different symbols for different quantities.
1 = I
13 = XIII
147 = CXLVII
13 = = X + III
147 = = C + XL + VII
The Romans didn’t have a symbol for 0, which is why they had to use separate symbols for everything.

30. Babylonian Writing System (Cuneiform)
The Babylonians wrote on soft clay tables which were then baked to make the writing permanent. (don’t make fun…we “burn” DVDs)
Their written number system (cuneiform) took advantage of this by using stencils with two basic patterns that are repeated to make more complex numbers.

31. Sexagesimal Number System (Base 60)
At 60, the pattern starts all over again…
72 = =

32. Problems with the Babylonian System
There is no symbol for zero.
So the number 60, is identical to the number 1…
60 =
61 =
83 =
There is no decimal point either, so ½ = 30/60 = Indistinguishable from 30

33. Benefits of the Babylonian System
All the simple fractions are easily expressed as a single number
1/2 = 30/60 =
1/3 = 20/60 =
1/4 = 15/60 =
1/5 = 12/60 = 1/6 = 10/60 =
Of course, 1/7 is going to cause some problems, but it does in our system too…
1/7 = …

34. Metric System Today’s metric system improves on the Babylonian system.
It is base 10, instead of 60.
But we have extra conveniences:
We use 0 to represent zero (nothing)
We use a decimal point to indicate a fractional portion
The name of the unit of measure indicates the scale
1 meter = 10 decimeters = 100 centimeters = 1000 millimeters
1 kilometer = 1000 meters
Our scientific notation takes advantage of this.

35. The Moon
When can you see the Moon?

36. The Moon When can you see the Moon?
It depends on state of the Lunar Cycle.
The Moon can be out in either the Daytime or the Nighttime.

37. Lunar Phases
The Moon goes through phases, which are subdivided into quarters

38. Timing of the Lunar Cycle
Lunar Cycle repeats about every 28 days.
Each month has just a little more than 28 days.
So the cycle repeats roughly every Month.
Dividing the cycle into 4 stages, gives us 7 days per stage.
Each seven day block is called a Week.
Since = 30 x 12
And ~ 28
There are a little more than 12 lunar cycles per year.
This is why we have 12 Months per Year

39. The Phases are a Lighting Effect

41. Sun-Based Calendar
We use a Sun-based calendar, so the lunar phases do not exactly coincide with the months.
The Jewish and Muslim calendars are Moon-based calendar, which is why Passover (and subsequently Easter) as well as Ramadan are on different days each year in our calendar. The Jewish calendar includes a leap month once every few years to help synchronize it with the solar year, so that Passover is on a different day each year in the Muslim calendar, as well.

42. Constellations
What is a constellation?

43. Constellations What is a constellation?
Constellation comes from the Latin constellationem, which means “set with stars”
A constellation is simply a group of stars defined by tradition.
We use them in Astronomy to denote a neighborhood in the sky. The constellation tells you about which direction to look in the sky.
Other groupings of stars are called Asterisms.
The Big Dipper is an Asterism, it belongs to the constellation Ursa Major (The Big Bear).

44. Constellations Lets go look at some constellations with Celestia
We will travel to some of the Stars and see what happens to the constellation

46. Constellation of Orion
Many Stars Have Names
Betelgeuse
Rigel
Saiph
Alnitak
Alnilam
Mintaka
Bellatrix
Star Names can be: Arabic
Greek
Roman
English
Named after Constellation
Catalog Number
Constellation of Orion

47. Constellation and Signs of the Zodiac
Constellations denote neighborhoods or directions in space
The Signs of the Zodiac are the constellations that the Sun passes through throughout the year.

49. Astronomy and Astrology
Astronomy and Astrology used to be the same study.
Both were used to predict when the seasons would happen, when eclipses would happen, when the lunar cycles would happen and so on.
But the two split when Astrology tried to predict too much from the motions in the sky.
To this day… Astronomy is a Science
Astrology is a Pseudo-Science

50. Planets
It turns out that the Sun is not the only one apparently moving through the constellations of the Zodiac.
Long ago, people noticed other “stars” that did this.
The Greeks called them Planets which means “Wanderers”
They were then named after the Gods of Olympus.

51. Planets Mercury Venus Mars Jupiter Saturn
Note that Jupiter was the King of the Gods. He was also called Jove or Zeus.
By Jove!
Zeus = Dios = God
Jupiter = God the Father

52. Days of the Week
Coincidentally, there are 7 main objects in the Sky These were associated with gods
More or less, we name the days of the week after them…
English Spanish French Object
Monday Moon’s Day Lunes Lundi Moon Tuesday Tīu’s Day* Martes Mardi Mars Wednesday Odin’s Day Miercoles Mecredi Mercury Thursday Thor’s Day Jueves Jeudi Jupiter Friday Frige’s Day*** Viernes Vendredi Venus Saturday Saturn’s Day Sabado** Samedi Saturn** Sunday Sun ‘s Day Domingo Dimanche Sun
*Tiu was the Germanic version of the God of War or Mars **In Hebrew Shabtai = Saturn, this is the origin of the word Sabbath
***Germanic equivalent of Venus

54. Planets Lets go look at some planets with Celestia
We will examine them from multiple viewpoints

55. References
M. Fowler, “Galileo and Einstein”
Earth Analemma
Martian Analemma
My apologies to those whose images I have neglected or was unable to reference.