Lecture 3 Flashcards
what did ancient civilisations rely on for time keeping
celestial observations - link lives to cycles in the sky. Intersected with superstitious beliefs, religious practices, power structures and social hierarchies
what is the oldest known time keeping instrument and who used them
sundial
Egyptians(1500 bce) divided days into hours by shadow clock
Chinese had sundials by 800BCE
old testament(700BCE) describes a sundial
british isles had the by 600 ce
who introduced months hours and minutes
Sumerians
explain the Sumerians introduction of months hours and minutes
12 lunar months, intercalary month to complete solar year every 2-3 years
each day was divided into 12 watch (~2hrs) then into 30 get (4 mins)
eventually adopted by Babylonian, Egyptian and Hebrew calendars
how did Egyptians and Indians independently develop the Sumerians calendar
the developed a 365 day calendar to track flooding
how did the myans track time
they had numerous cycles tracking the lunar solar and cycles of Venus into a long count calendar
what is heliacal rising
first appearance during the year of a star in the east just before sunrise
what is the brightest star in the sky and when is its heliacal rising
sirius, midsummer
what populations used Sirius to track time and what for
Mesopotamians - agriculture
Egyptians - nile flood season
where does the term wet moon come from, when does it occur, what did they use it to track
ancient Hawaiians - moon with horns pointing up. occurs at equinoxes, tracked wet and dry seasons, when it pointed up the moon was “holding the water up”
what are the 3 annual calendars and their features
Lunar - 12 months, 354 days
solar - 12 months of 30 days, 5 intercalary days
hybrid - periodically reconcile via intercalary month or leap month
examples of stone calendars
Stonehenge in england, aligned with solstice
maeshowe in Scotland , aligned with winter solstice
Nabta playa in Egypt - summer solstice
give info on warren field pits in Aberdeenshire
12 arranged pits, oldest known annual calendar, vary in size representing moon phase, standing in the pit and noting the moonrise allows you to tell the month. midwinter solstice marker resets calendar
what societies had one count calendars
olmecs, later adopted by mayans and other mesoamerican cultures
how did mayans adapt olmecs long count calendar
they accounted for both solar and lunar cycles and Venus period, could predict eclipses
how was the Gregorian calendar developed (our current calendar)
Caesar formed Julian calendar which introduces a leap year for the year being 365.25 days. 1079 khayyam of Persia measured the year to high accuracy
pop Gregory XIII then noticed Julian calendar has drifted so adjusted to skip leap years every so often.
who set up the current western astrology
babylonians, defined constellations. indicates location of sun in the sky for a given month
what is the precession of the equinoxes
the north pole circles like a tilted spinning top every 26k years, so sun sign shifts by one constellation. currently going from pisces to Aquarius.
how did stellar navigation work
using stars, sun, moon to determine direction and position
location on horizon for stars to rise/set changes very slowly
stars are used at night, sun used during the day
what groups used stellar navigation
Polynesian, Phoenicians(mediterranean) , vikings, Arabs
what is the zenith star
a star known to pass directly over a destination
navigate directly to where a zenith star passes overhead, either due east or due west of destination
used by Polynesians
what are common celestial events used to track time
comets. eclipses and supernovae
when do solar eclipses occur
moon positioned directly between earth and sun
what societies discovered solar eclipses
ancient Chinese, olmecs and mayans
how often do stars go supernovae and what groups noted them?
1 every 100 years.
in Middle Ages several appeared, noted by Arab, Chinese and Japanese astronomers
what is occams razor and prevalence in cosmology
simplest explanation that explains all the evidence is the best one, used to argue against dark matter and latter dark energy until evidence became overwhelming
what is the correspondence principle and prevalence in cosmology
Bohr argued that any successful theory of quantum physics must, at large scales, agree with classical physics
e.g. modified gravity cant screw up anything explained by current gravity
copernican principle and cosmology prevalence
humans do not occupy a special place or time in universe, nothing is special or unique such as earth, sun, galaxy, location.
principle is crucial for discovering the expanding universe
