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PSY397H1 Lecture Notes - Lunar Phase, Photoperiodism, Solar Time

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Martin Ralph

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PSY397 Chapter 3
- two groups of clocks
o physical clocks
o biological clocks
- earth rotates every 23hrs 56mins
o in elliptical pattern
o reason for lag is that not only is the earth rotating but it is also
revolving around the sun
the rotation of the earth changes about 1degree with every
this is called the sidereal day
- our clocks focus on the solar day
- provides t8ime cues through photoperiodism
o caused by earthly movements
- a fixed tilt of 23.5 degrees and the elliptical pattern of rotation account for
the seasons
- tidal rythms are controlled by the moon
o revolves around the earth every 27.25 days (sidereal month)
- due to the rotation of the earth around the sun the duration from one moon
phase to the next is about 29.5 days (lunar month)
- ancient people had to predict when it was safest to get food, seek shelter and
their relationship with the “spiritual world”
o all rhythmic dependent activities
- consciousness of time occurred late in human history but developed quickly
o business and travel flourished
The Month and Year
- first measured time with emergence and disappearance of sun, moon and
- menstrual cycle is the almost the same as moon
o provided measure for pregnancy
- yet 12 moons is not a year
o not using the moon the Egyptians estimated the year to 365 days
based predictions on seasonal flooding of the Nile and the
appearance of Sirius in the Canis Major
4236 BC
- Stonehenge served as a type of calendar to indicate the the time of month
and year anchored by the summer solstice
- Caesar (in 45 BC) adopted the Egyptian Calendar but changed the year to
365.25 days long
- Pope Gregory XXIII (1582) changed the calendar by 10 days
o Day after Oct. 4, 1582 was Oct. 15, 1582
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