chapter 3

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Astronomy & Astrophysics
Clifford Orwin

The Science of Astronomy (chapter 3) Scientic Thinking -based on observations and trial-and-error - Modern measures of time come from ancient observation of motion in the sky - Length of the day is the time it takes the sun to make one full circuit in the sky - Length of a month comes from the moons cycle of phases - Length of year comes from the seasons -Ancient people could estimate the time from the position and phase of the Moon - Positions of the stars can also indicate the tim, as long as u know the date -Egyptians divided the daylight into 12 equal parts A.M and P.M - Latin terms ante meridiem and post meridiem (before the middle of the day and after the middle of the day) The names of the seven days of the week are based on: -the seven naked-eye objects that appear to move among the constellations Egyptians -daylight summer hours were longer (112 of the daylight lasts longer) than the daylight winter hours -star clocks to estimate time of night -water clocks was the primary timekeeping instrument(greeks,romans,chinese) used to measure TIME by the ow of water through an opening of a size -stonehenge used for keeping track of seasons and as a social and religious gathering place -temple mayor(mexico) twin temples ***cities directions were north south east west representing miniature versions of the heavens** basic lunar calendar- 12months with some lasting 29days and others 30days - 354355 days (11days fewer than the sun calendar) - Muslims use lunar calendar which is why Ramadan begins about 11days earlier with the following year...example last year it start aug.20 so this year it will start aug.10 Metonic cycle- lunar phases repeat every 19years
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