The document discusses the history and cultural variations of timekeeping. It describes how early humans first began to measure time based on natural cycles like days, lunar months, and seasons. It then explains how different ancient cultures like the Egyptians, Babylonians, Chinese, and Mayans developed their own calendars and timekeeping methods based on their observations, religions, and needs. The document also discusses the development of mechanical clocks in medieval Europe and the eventual adoption of the Gregorian calendar.
1. About Time
OLLI/RISE Class – Fall 2015
Jim Isaak
HTTP://is.gd/Abouttime
2- Culture 3 Measuring 4 Cosmic 5 Future
2. What is Time?
• Past (memory) – Now – Future
• Second Law of Thermodynamics (Entropy)
– Heat dissipation – hot item loses heat to environ
[physic’s ‘non-reversible’ process]
– 1st
- conservation of energy (you can’t win)
– 3rd
–entropy approaches zero as temperature
approaches zero
• the indefinite continued progress of existence and events in
the past, present, and future regarded as a whole.
• Natural “periods”, defined “periods”
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3. Topics for our Consideration
• Time – The only show in town
– How and why humans started to keep time
• Cosmic Time – where were you 13.8 billion
years ago (on the night of Feb. 29th
?)
• Geological Time
• The drive for accuracy – what is “on time”
• Cultural Variations
• Relativity and Time
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4. Time – The only show in town
• Once upon a time, long, long ago, before TV,
radios, clocks, sundials … people lived in
caves, or temporary shelters migrating with
game and seasonal vegetation
• The evening activities were limited … stories
by the campfire, ceremonies, … and then
watching the sky
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6. So what is Time – way back when?
• Days --- pretty obvious
– Big yellow thing comes up, crosses sky, goes down
– Seems to be warm
– Sometimes it’s not as warm as other times
• Folks farther from Equator notice cold white stuff
– The cold/warm sequences seem to match animal
and vegetation changes
– All of this seems to repeat
• And some smart character notices the stars!
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10. Then there is that big white thing
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11. 28 Days
• And the Days and Moon
seem to be related
– Full moon 29.530589 days
• For those close to the
ocean, particularly those
feeding on low-tide
creatures, or on fish that
spawn on Spring Tides
(grunion)
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12. So the smart one(s) - observe
• Shaman’s – “one who knows”
– Perhaps “count the days” (marks on the wall)
– Realize that the Moon Cycle and Year are not
quite “right”
– 12 Lunations = 354.37 days
– Year is sort of 365 days
– And the shadows move, get longer/shorter
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13. People like Stories and Predictions
• When will winter come?
• When will the high tide / low tide come
• When will the monsoon’s start
• When will the birds return, the bison leave
• The moon and stars seem to hold the answers
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14. Astrology
• Is a natural attempt to relate the apparent
relationship between the events that govern
man’s life (and women as well) – and
synchronize with the motions of the heavens
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15. First step to becoming a Shaman
• “Gnomon” is also a term for one who knows
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16. Attach it to a piece of cardboard
• Spread your wings – it is stronger that way
– Ideally the angle of the “back” will be 42 degrees”
(our latitude) – but close is good enough
• It will take more than a 9” x 9” piece to have
all of the shadow “on the cardboard”
• Align your Gnomon North (point)/South
• Start marking the hours
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18. If you have a big open yard
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19. Vertical Gnomon
• Track the “top shadow” at noon (true noon) at
least once a month
• Note the sun-rise/set points for
– Equinoxes (first day spring/fall)
– And Solstices (winter/summer – longest day)
Does the sun set In the West or North on June 22?
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21. Cultural Variations
• What’s Important?
– Herd migrations
– Tides
– Storm patterns
– Annual floods
• “natural” periods (days, moons, years)
– Breaking daylight into “hours” is a contrivance
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22. Lunar Calendars
• Babylonians stuck with a lunar calendar,
knowing it did not yield a solar year –
discovered the 19 year “Metonic” cycle
– Alternated 7 years of 13 months, and 12 of 12
• Variations persist today
– Hebrew calendar follows this model
– Muslim – “star and crescent” allows the months
to flow independent of the years
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23. 73 is a prime number
• And so is 5
• Which means that 365 (=5x73) is not easily
divided into parts
• Consider “perfect” numbers (6, 28) which are
the sum of their factors (1+2+3=6…)
lots of choices for factoring … primes have
none, and products of primes just two
• i.e. for math oriented cultures, it is hard to
divide the year (even if it were exactly 365)
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24. • If a Lunation were exactly 28 days
• And the year were exactly 336 days
– 336= 12 x 28 = 2x6x28
Every culture would have lunar calendars and six
day weeks (28 and 6 being perfect numbers)
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25. Egypt (26° N Luxor –30 ° N Cairo)
• Flood driven 3 seasons – and good
observations yield a 365 day calendar
– 12 months of 30 days plus 5 ‘new year days’
– 36 ten day weeks + 5 [36 key stars]
• Driven by the helical rising of Sirius
(mid flood season)
• Wandering ‘year’ has 1460 year cycle
• 12 ‘decans’ of the night – asterisms rising
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26. Heliacal rising
For a given position, the star always rises at the same
point
And at the same time for a given day
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27. Babylonians (33° N Bagdad)
• Enamored of “60” divided the circle into 360 degrees, then 60
minutes and 60 seconds
(base 60 arithmetic)
– 5 “elements” and sacred “12”=>60
– But also “Fists above horizon”
• This was transferred into time-keeping
• And, prior to the introduction of “zero” (from India) decimal
arithmetic did not exist as we know it.
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28. But wait, there’s more
• Introduced 7 day week (perhaps 4/moon cycle?)
– Adopted by Jewish calendar, including names
aligned with 7 days of creation
• Alexander the Great embraced their calendar &
propagated it
• Creation cycle is 600 x 3600 years (2.16 MY)
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29. India (8-36° N New Delhi @ 28° )
• Not homogeneous – religion, language, geo
• Days into 60 Ghati (24 min), into 60 Pala (24 sec) into
60 vipala (.04 seconds)
• Months tied to timing of earth’s elliptical orbit – we
spend longer in Gemini (31.6 days) than Sagittarius
(29.4 days)
• Knew about polar precession, but ignored it
6 seasons named for weather, now off by 6 weeks
• 4.32 million year cycles of creation/destruction
last one started 18 Feb 3102 BC in this case
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31. Greeks (Athens at 38° N)
• Influenced by both Babylon and Egypt
• 36 star “decans” – source of “decimal”
– Each with 10 degrees of separation in circle
• Caught up in “geometric” models of the
cosmos, rather than observational reality
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32. Jewish Calendar
(Jerusalem at 31.7° N – 35.3° E)
• Lunar, with adaptations to align with years
• Starts 7 Oct. 3761 BC
– (compare to Bishop Usher’s
6 pm on 22 October 4004 BC)
• Calendars designed for
– Religious holidays (Holy days)
– Civil administration (collecting taxes)
– Agricultural cycles (etc.)
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33. China (Beijing at 39.9° N)
• The Emperor demonstrated his mandate of heaven
by his calendar – an imperial secret/right
• Jesuit’s brought clocks as gifts, lingered in
detention, but established credibility with the
solar eclipse of 21 June 1629
• Three divisions of the day:
– 12 ‘hours’ (double hours)
– 100 Ke (about 15 minutes each)
– 5 night watches
–
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34. Astrology
• In China, the critical “time” is the point of
conception, not birth
• The Emperor rotated concubines and wives on
a defined schedule so that the “Empress” had
the two nights (exclusively) of the full moon.
• The ‘vermillion pens of the ladies secretarial”
recorded each liaison (since typically nine
concubines or secondary wives were present)
so subsequent birth’s would have accurate
data
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36. Mayan (Tikal at 17° N)
• Mayan: 260 day cycles
– Perhaps influenced by human gestation
– Or planting cycles, or cycles of Venus
• Solar year: 18 – 20 day periods with 5 “outside” days
• And no significant division of the day into parts
• Tracking eclipses was important, and did trigger
additional calculations/observations
• Cycle: 52 years (52x365=73x260)
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37. Aztec
(Mexico City
at 19.4° N)
• 5 Suns:
– Jaguar – destroyed
– Wind – some saved as monkeys
– Fire-rain – some saved as birds
– Water – some saved as fish
• We are now in the 5th
: “movement”
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38. Stonehenge (51.2° N)
• Sits at a unique latitude
• Primarily aligned:
– Summer Solstice Sunrise
to Winter Solstice Sunset
Orthogonal to
Winter solstice Sunrise
& Summer Solstice Sunset
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39. Inca (Cusco at 13.5° S)
• Aligned primary city on astronomical guides
– sun viewed over 328 “huaca” pillars from center
– Used “dark constellations” in sky view
• Milky way (river) as path for departed to
come/go
– The “door” closed due to precession of axis, an
event apparently predicted in Inca mythology
• June 9 (now) agra-calendar reset with Pleiades
– But with 37 “no time” days to make up for 365
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41. Inuit (69 ° 22’ N)
Month names for Igloolik
1. Sun is Possible
2. It gets higher
3. Premature birth of seal pups
4. Seal Pups
5. Bearded Seal Pups
6. Caribou Calves (image below)
7. Eggs
8. Caribou hair sheds
9. Caribou hair thickens
10. Velvet peels from antlers
11. Winter starts
12. Hearing
13. Great Darkness
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•Different villages, different month names
•“Aagjuuk” (Altair/Tarazed) is not recognized as asterism until mid-winter
•5 day & 5 night variable time divisions
•Associate activities with star/sun positions, not dawn/dusk
•Track years, moons, landmarks (births, deaths)
42. Rome (42° N) introduces finer
divisions
• AM/PM; then
• Morning, forenoon, afternoon, evening
• Then asserting 12 “temporary” hours during
daylight, and 12 at night (variable length)
• Water timers were used to limit speakers in
the senate or the court (we should be so wise)
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44. One other take on Cultural Time
• In Germany show up on time
• In Spain if you arrive at the hour suggested
you may embarrass your hosts who may not
be prepared
http://www.culturegrams.com/ (subscription)
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46. Who Owns Time?
• Compare Inuit (family time) to Roman (court time)
• The emperor, king, Inca, pope, …
– If someone controls your time …
• And how do you measure it?
– Why do you measure it?
• We move from AM/PM to hours to minutes…
• Religious observations is a leading factor
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47. Early Time
• Stars: Identify Meridian, when this star crosses
meridian then… (or appears above peak)
• Sun Dials
Shadow Clock, Egypt 1500 BCE
• Water Clocks (problem with variable hours)
as early as Egypt 1500 BCE
• Candles, oil, incense, .. Burn at given rate
Korean Examples (2 min)
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48. A Note on Incense
• Can be made to burn at constant rate
• Different ‘smells’ at different points on stick
(“it smells like 10PM” – no need to light the candle)
• Clock burns through
strings, balls drop
• Stick it between
your toes to wake up
• Partial sticks as
pill reminders
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49. Clock Requirements
Repeatable – ideally in terms of cycle measured
Measures useful increments
We think “fixed hours”, but not so with early
clocks (which was a problem since equal hours
is a bit easier)
Display result
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50. Mechanical Clock #30
• In the “Top 101 inventions of all time”
• 8- fire
• 7-Computer
• 6- Lever
• 5- Transistor
• 4- Steam Engine
• 3- Light Bulb
• 2- Printing Press
• 1- Wheel
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History Channel Shoiw with
Judges from Popular Mechanics
Your mileage may vary
51. Su Sung Clock
1088 CE. a water-driven escapement
(circa 725 CE.)
a bronze power-driven armillary
sphere for observations, an
automatically rotating celestial
globe, and five front panels with
doors to view manikins which rang
bells or gongs, and held tablets
indicating the hour or other special
times of the day.
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52. Korean Water Clock
• Animation
– 2 min
• Striking
– 20 sec
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53. The drive for accuracy – what is “on time”
• Early divisions of the day
created laments about the
intrusion of the hours,
dissecting one’s day
• Religion has played a
significant role with
expectations of prayers at
Dawn, Sunrise, Mid-morn,
noon… (Catholic)
or towards Mecca (Islam) 5
times a day
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54. Galileo & the Pendulum
• Recognizes the constant period of pendulum
based on length
• Suggests it might be used to keep time (1641)
• Applies knowledge to measure increments of
time --- determining the rate of fall of objects
• 13th
century early clocks existed
• 1656 - Huygens Pendulum Clock
• 1675 wall clocks – from ±15 Minutes to ±15 Seconds
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55. 17th
Century
• Era of massive innovation & discovery
– Telescope, and Galileo’s “Starry Messenger” (1610)
– (Sidereus Nuncius)
• Introduces “observational” science
displacing “dialog among experts”
• Observatories across Europe in last half
• But also – emergence of capital
– Caput (head) – Capital (cattle, and chattel)
(mercantilism economics based on fixed wealth: 1500 -1800)
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56. Time – By Jupiter!
• Best seen via binoculars … need wide field
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57. 1707 the Wreck of the Fleet
• 4 Royal Navy vessels sank
• 1550 sailors lost (including Admiral of the fleet)
• In ability to determine longitude (East West position)
• Triggered “Longitude” prize
• And 60 years of work to create and prove the first
marine chronometer by John Harrison
(some Commissioners of Longitude were competing
for the prize as well, or held pet theories – lunar
observation, Jupiter's moons..)
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58. The Equation of Time
• The difference between Solar Mean Time
and clock time ±16 minutes
• Sundial’s are ahead on Nov. 4th
(16 min)
and behind of Feb 12 (15 Min)
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Earth’s Tilt yields “long” axis of figure 8
Rotation of earth each day -> loops
the diurnal day > sidereal day (4 min)
Earth’s motion in orbit -> Asymmetry
and a key variation in “solar time”
59. Marshmallow (sidereal) Time
• You are the Sun!!
• The room is the celestial sphere (fixed stars)
• The marshmallow is the Earth (toothpick axis)
• Angle the axis so the upper point faces the
screen – it will maintain this orientation even
as it spins and orbits (23.439 °)
• Spin in place; now try a quarter orbit with a
full earth spin – notice it is not facing you!
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60. To Scale
• ½ inch Marshmallow
• Sun is 4.5 feet in diameter
(spread out your arms)
• And it’s 490 ft away!
(stretch real far!)
• Ask about what
causes the seasons!!
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61. Why do seasons happen?
Daylight hours Heat spread over larger area
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63. Why Measure Time?
• Daily religious observances
• Change of “watch”
• Galileo – scientific analysis, and related skills
like cooking, brewing, etc.
• The devices are delightful works of art
• Church Chimes – call to worship, and more
• The clock “eliminates the tyranny of the Sun”
But ….
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64. Emergence of “paid” work
• Industrial Revolution
– Factories want to start/stop on time
– Massive water driven mechanisms (or coal…)
– Perhaps even shifts of workers
(if sufficient light)
– For this, you want agreement (and conformance)
to “Local” time (noon is when sun crosses meridian)
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65. But – is this any way to run a railroad?
• Sandford Fleming – Canadian Railroad, unity advocate
– misses train in 1878
• Advocates universal 24 hour time at 1884 conference
• But concept of 15 degree time zones, while not
formally adopted is implemented by 1929
• Until Time zones
every station/town
had it’s own time
(sun passes our
meridian at noon)
No actual riots occurred
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66. Day light Savings Time
• An early advocate, Benjamin Franklin
(perhaps poking fun at his French hosts)
• First adopted by Germany April 30, 1916
– To improve war productivity
• US adopted in 1918 for the same reason
mostly repealed until 1942
• US Time Zones labeled “Eastern War Time” …
• But not uniformly adopted until 1966!
(expanded 1974 to conserve oil & in 2005)
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67. A “foot note” on the (North) Pole Star
• This week it
is Polaris
• And it will
be again in
26,000
years …
• The Earth
precesses
on it’s axis
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69. Cosmic Time
• Bill Bryson
– A Short History of Nearly Everything
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70. Creation
• Greek/Roman “thema mundi”: starting configuration
• Aboriginal “dream time” – serpent shapes land
• Asmat of New Guinea – creator kills to create life
young man is given fresh skull in coming-of-age ritual
• Balance of, often violent, competing forces are
foundation of creation – Mesopotamia, Navaho,
Hindu Vishnu
• Time is often a synonym for both creator and
destroyer of all things
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71. How Old is “Everything”?
• If there are stars everywhere, then we should
have light from all of them on earth – a ‘white
sky’
• Unless it takes time for light to reach us, they
are far away, and the intensity diminishes with
distance ….
• So the speed of light becomes a key way to
measure the age of the universe
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72. Speed of Light
• 1600’s folks considered how to measure it
Galileo – 1638 “purty darn fast”
• First estimates Romer, 1676 based on Jupiter
Moon eclipses tied to Earth’s position in orbit
• 1800’s getting to a fairly accurate estimate
“a hair under” 300k meters/second
• Newton determined same speed for all colors
• 1860’s ID’d as Electromagnetic wave
• 1887 Michelson/Morley fail to detect aeather
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73. Henrietta Swan Leavitt
• A computer at Harvard College Observatory
• 1912 “A straight line can readily be drawn among
each of the two series of points corresponding to
maxima and minima, thus showing that there is a
simple relation between the brightness of the
variables and their periods.“ (Cepheid variables)
• Later shown to be a result of helium isotopes
“containing” heat/light->expanding star
->condensing helium ->releasing light ->shrinking
star – i.e. – the stars pulse at a predictable rate
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75. Hubble discovers Galaxies
• 1922 Edwin Hubble identifies Cepheid
variables that must be outside of the Milky
Way
• In 1929 he uses red-shift data to demonstrate
that “they further away the faster they
recede” (Hubble’s law)
• Implies “big bang”
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77. Distance => Minimum Age
• Between Parallax, Cepheid variables, and Red
Shift – distances can be determined
• If a star is 15 light years away, it must be at
least 15 years old …
if a billion light years away, at least a billion
years old
• Furthest observed star/galaxy is
EGS-zs8-1 lies 13.1 billion light-years away
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78. Beyond the Galaxies
• The Cosmic Background Radiation
• The accidental discovery in 1964 by Arno
Penzias and Robert Wilson resulted in the
1978 Nobel Prize
• 2014
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81. Stratigraphic Layers
• Lyell – Darwin’s
Colleague
• (for Grand Canyon)
– Earliest rocks date
back 1.8 billion years
– Vishnu layer named
for the initial
documenting of this
layer in India
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83. Carbon Dating
Carbon 14 providing
dating back 60,000
years max
Other elements can
provide mechanisms
that go back billions
of years
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85. And the beat goes on…
Uranium-thorium -a twofer
U234 80k yr half life
U235 34.3 k yr half life
U238 4.5 billion yr half life
Samarium-neodymium
1000 billion yr half life
Potassium-argon dating method - 50
Billion yr half life
Rubidium-strontium
1.3 billion yr half life
Others:
argon-argon (Ar-Ar)
iodine-xenon (I-Xe)
lanthanum-barium (La-Ba)
lead-lead (Pb-Pb)
lutetium-hafnium (Lu-Hf)
neon-neon (Ne-Ne)
rhenium-osmium (Re-Os)
uranium-lead-helium (U-Pb-He)
uranium-uranium (U-U)
86. Scientists use “BP”
• Vs the “BCE, CE” – ‘current era’ euphemism
• BP = “Before Present” – i.e. Jan. 1, 1950
• Why that date?
– Radio carbon dating introduced Dec. 1949
– Atmospheric nuclear testing after 1950
– Aligned with then current Astronomical Epoch
(as of 1984, moved to Jan 1, 2000– “J2000”)
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87. The Tale Tell Magnets
• Every 100k to 1M years
the magnetic poles
decide to swap
• With occasional hiccups
(41k years ago a 450
year decline/switch and
return – 75%+
reduction in field ->
more radiation -> more
carbon 14…)
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88. local magnetic fields sway as well
• Leaving imprints in ponds and other
sedimentary collections (that can be dated by
other means)
• And then in the pottery made from that mud
– Allowing locality of clay to be identified
– And also dating of the pieces
• A field called “microarcheology” dating objects
within decades vs. centuries….
(See “Witness to Armageddon”, Nov. 2015 Discover
Magazine)
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89. The Future of Time
Relativity and Time
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90. Einstein 1905
1. how to measure the size of molecules in a liquid
2. how to determine their movement
3. light comes in packets called photons—the
foundation of quantum (Nobel Prize)
4. special relativity (not fully accepted till after his death)
5. pointed that matter and energy can be
interchangeable at the atomic level: E=mc²
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91. Einstein
• 1905 – thought experiments
The speed of light is fixed for all observers
therefore time & measurements are relative
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92. Einstein’s Dream’s
(Alan Lightman –MIT)
• Short fictional scenarios exploring alternate
perspectives of time
– Circular – all things repeat – exactly
– Stream with eddies, some folks displace backwards
– Multiverse with every decision branches
– Live forever, or just one day, or known end
– Absolute everywhere, frozen at center, different
rates for different persons
– Flows backwards, visible dimension, only local…
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93. Time Travel
• In theory going faster than the speed of light
(superman movie), Startrek IV, etc …
runs the clock backwards
But – approaching the speed of light mass
increases approaching infinity -> ergo infinite
energy required to get to speed of light…
• BUT – since space/time is a continum
a worm-hole may connect one time to
another
• BUT - perhaps a different multi-verse … so ..
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94. Big Bang
Generally the laws of physics can be reversed
Entropy seems to be an exception
the one that defines the “arrow of time”
There are indications that the direction of this
arrow was a random aspect of the big bang
Prior to the big bang there was no time,
which is to say this statement starts with a
meaningless concept
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95. Hawking – A Brief History of Time
• Three Arrows of time (at least)
– Entropy (disorder, heat dissipation)
– Psychological – memory and perception
– Cosmological – expanding universe
• Psychological follows from the experience of
entropy in action (cups break, they don’t assemble)
• The anthropomorphic principle implies ‘if the arrow were
reversed, no intelligent creatures would exist to observe & ask
the question of why things were getting more ordered’
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96. A new take on time’s arrow
• Science News, 25 July 2015
• “Janus point”
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97. SciNews: Clocking in the Brain
• Different time keepers in the brain
– short term memory
– speed up recording -> slow motion with “high
octane” experiences,
– chemical modification
– disease impact (.2 sec for most folks, up to .4 for
persons with schizophrenia )
– sight merger at 24 frames/second vs
sound integration at 44000 cycles/second.
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98. SciNews – Life’s Cycles
• circadian time, in critters, but also in cells
• many life forms have 24 hour cycles, perhaps
to avoid oxygen (anti-oxidant cycles)
• some are lunar, some tidal
• many instances, no apparent single “mother”
11/17/15 http://is.gd/Abouttime 98
99. Time seems to slow down
• Extreme events seem to slow time down
an apparent illusion
The mind records more “frames per second”,
so in retrospect, things seem to have been
moving slower
• But, the difference between the .2 second
reaction time and .4 awareness time is the
critical element of mastery – pre-wired
responses
• (PBS Brain show and July Science News Issue)
11/17/15 http://is.gd/Abouttime 99
100. A very good PBS series (2015)
The Brain with David Eagleman
1. What is reality?
2. What makes me?
3. Who is in control?
4. How do I decide?
5. Why do I need you?
6. Who will we be?
Addresses some aspects of perceived time
11/17/15 http://is.gd/Abouttime 100
101. Time Paradox (Book and TED talk)
• Philip Zimbardo – psychology of time
– Time is the medium in which you live
“No man ever steps into the same river twice,
for it’s not the same river and he is not the same
man” (Heraclitus)
• “Remember that time is money” B. Franklin
• ‘Only during the last thousand years have we
had “discretionary time”, and only in the last
hundreds have substantial segments of us
enjoyed it.’
11/17/15 http://is.gd/Abouttime 101
102. Pace of life
Walking speed, bank teller speed, talking speed:
- Fastest cities: Boston, NY and Northeast
- Slowest cities: South and West, LA as slowest
So what:
• Returning a pen someone ‘accidently’ dropped
• Helping a blind person across the street
• Donate to United Way
• More coronary disease
Rochester NY most helpful; LA not so good
11/17/15 http://is.gd/Abouttime 102
103. Future oriented/Now oriented
• The Marshmallow test
– Kids who resisted scored 250 points higher on SAT
better students, less trouble, self confident
• Time Perspective – individual, cultural…
– Present oriented – past positive/negative
– Past oriented - hedonist/fatalist
– Future oriented – life goal/ transcendental
RSA sketch talk on cultural time zones
but also revolution in time – affects kids/future
11/17/15 http://is.gd/Abouttime 103
104. Ideal Time Perspective mix
Past
Your Roots – Identify
Family, grounding
High on past positive Always low on
past negative
Present
Energy – explore people,
places, self
Hedonism - moderate Always low on
Present fatalism
Future
Your wings – soar to new
destinations & challenges
Moderately high
11/17/15 http://is.gd/Abouttime 104
Develop the discipline to shift time perspectives based on situation is key
105. Downside of excess
• Futures sacrifice family, friends, etc for
success
live for work, achievement, control
• Understanding your time perspectives, and
those of others, can facilitate resolution of key
interpersonal issues, but also addressing social
challenges such as drug abuse, PTSD, etc.
11/17/15 http://is.gd/Abouttime 105
106. Useful
• Money is time … given enough money, you
are free to do what you want with your time
(and insufficient money means others
dominate your time)
• “There is no present like time”
(Second Best Grand Marigold Hotel)
11/17/15 http://is.gd/Abouttime 106
107. The Long Term
• http://longnow.org/ fostering long term
thinking – sponsors:
• Long bets: http://longbets.org/
– 2+ year bets that will affect society
must have “both sides”, with explanations
– Money goes to winner's charity of choice
• http://www.10000yearclock.net/
Jeff Bezos & friends
11/17/15 http://is.gd/Abouttime 107
Midwinter sunset --- mid summer sunrise is just about the reverse
This very unusual photograph was recorded by Dennis di Cicco on a single piece of film that was exposed on 45 different dates throughout an entire year in a permanently mounted camera -- http://pages.uoregon.edu/klio/solarium/analemma.html
Wikipedia: The figure is an example of an analemma as seen from the Earth's northern hemisphere. It is a plot of the position of the Sun at 12:00 noon at Royal Observatory, Greenwich, England (latitude 51.48°N, longitude 0.0015°W) during the year 2006. The horizontal axis is the azimuth angle in degrees (180° is facing south). The vertical axis is the altitude in degrees above the horizon. The first day of each month is shown in black, and the solstices and equinoxes are shown in green. It can be seen that the equinoxes occur at altitude φ = 90° − 51.48° = 38.52°, and the solstices occur at altitudes φ ± ε where ε is the axial tilt of the earth, 23.439°. The analemma is plotted with its width highly exaggerated, revealing a slight asymmetry (due to the two-week misalignment between the elliptical apsides of the Earth's orbit and its solstices).
"Apogee (PSF)" by Pearson Scott Foresman - Archives of Pearson Scott Foresman, donated to the Wikimedia Foundation→This file has been extracted from another file: PSF A-40005.png.. Licensed under Public Domain via Commons - https://commons.wikimedia.org/wiki/File:Apogee_(PSF).png#/media/File:Apogee_(PSF).png
http://www.wvup.edu/ecrisp/lecture2mesozoic.html
Most methods of radiometric dating are based on measurements of accumulation of stable daughter atoms produced by a parent radioisotope. When a mineral crystallizes, there are no radiogenic daughter atoms of the radioisotope contained within the mineral composition, i.e., the daughter to parent ratio is equal to zero (D/P=0). Knowing the decay constant (k) (which can be determined by measurement) of the parent radioisotope, it is possible to measure the ratio of daughter and parent isotopes (D/P) in a mineral sample (this is done with a mass spectrometer) and compute the age of the sample
========
Alpha decay an alpha particle (just like a helium nucleus), consisting of two protons and two neutrons, is ejected from the nucleus of a radioactive parent isotope, thus the atomic number decreases by two and the atomic mass number decreases by four for the daughter isotope.
Beta decay involves the emission of a high speed electron from the nucleus resulting in the conversion of a neutron to a proton, thereby increasing the atomic number by one without changing the atomic mass number for the daughter isotope.
Electron capture decay takes place when the nucleus captures an electron from the inner electron orbits of the atom; thereby converting a proton to a neutron; the atomic number daughter isotope decreases by one, but the atomic mass number is unchanged.
1. Usually only Igneous rocks can be dated radiometrically. 2. When a mineral crystallizes it has trace quantities of radioactive atoms and ideally no stable daughter products of the particular radioisotope/stable daughter isotope pair that we are using. 3. As the parent radioisotope decays, the stable daughter isotope increases in the mineral and cannot get out of the mineral crystal. 4. The decay rate (which is constant for a particular radioisotope) must be known. 5. The ratio of daughter to parent can then be used to calculate the age of the rock containing the mineral. 6. There is typically a plus or minus 1 to 2% analytical error for radiometric dates.
With a few exceptions (such as the K-Ar dating of sedimentary formed glauconite or volcanic ash deposites mixed with other sediment), radiometric dates are typically determined for igneous rocks and minerals. So, how do we date sedimentary rocks in an absolute way? The relative ages of the geologic events in a particular area must be worked out before radiometric ages can be applied. Once the relative sequence of events in a particular field situation is determined, radiometric dates can be obtained for igneous intrusions and/or extrusions (volcanic rocks) that bracket certain sedimentary strata, thus giving an age range for the sedimentary strata.
http://eesc.columbia.edu/courses/v1011/topic_4_2.htm
https://en.wikipedia.org/wiki/Geomagnetic_reversal
Laschamp event 41000 years ago, 450 year window, 250 year pole reversal/return
75% to 95% reduction in magnetic field strength, higher radiation …
GPS and other clocks
Cultural Time (invited for dinner in Germany, Spain, ...)
1905 papers:
Specific relativity (space time continuum, relative, and Lorenz contractions with near light speed)
But also: Brownian Motion (proved existence of atoms); black body radiation,
Science News TIME issue
Andrew Grant on Time’s Arrow, based on Barbour, Julian, Koslowski, Time and Mercati, Favio “Identification of a gravitational arrow of time” Physical Review letters, 31 Oct 2014
Also I this issue:
Laura Sanders on Clocking in the Brain –
Different time keepers in the brain … short term memory; speed up recording -> slow motion with “high octane” experiences, chemical modification, disease impact (.2 sec for most folks, up to .4 for persons with schizophrenia ), sight merger at 24 frames/second, sound integration at 44000 cycles/second.
Tina Hesman Saey on Life’s Cycles – circadian time, in critters, but also in cells; many life forms have 24 hour cycles, perhaps to avoid oxygen (anti-oxidant cycles), some are lunar, some tidal; many instances, no apparent single “mother”