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81 Cards in this Set
- Front
- Back
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rotation
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spin, motion about an axis
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revolution
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orbit, orbital motion
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synchronous rotation
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rotation period= orbital period
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celestial sphere
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earth at center
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horizon system
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altitude, azimuth
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altitude of pole star
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your latitute
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equatorial system
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right ascension, declination
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meridian
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semicircle through SCP, NCP
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observer's meridian
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circle through NCP, SCP, zenith, south point
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ecliptic
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apparent path of the sun on the sky
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equinoxes and solstices
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vernal equinox, autumnal equinox, summer solstice, winter solstice
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circumpolar stars
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always visible above horizon
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constellations
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groupings of stars in the sky. there are 88 constellations. constellations are named by brightness (ancient greeks)
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constellation
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a visual grouping of stars
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asterism
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perceived pattern (ex. great bear or big dipper/saucepan)
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use pointer stars
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use the big dipper to find the north star (polaris)
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cassiopeia
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looks like an M (near polaris)
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daily pattern
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the stars seem to revolve about polaris every 24 hours as earth rotates
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daily pattern
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polaris seems to stay in the same place because it is very close to the NCP
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at the north pole and south pole
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every star is circumpolar
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cassiopeia
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looks like an M
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Bootes
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looks like a question mark
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orion
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look for the belt
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leo
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looks like a lion
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cygnus
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looks like a cross
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ursa major
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big dipper
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circumpolar star
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dec > (90 - lat)
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stars never seen
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dec < -(90 - lat)
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stars that rise and set
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-(90 - lat) < dec < (90- lat)
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state college
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lat = 41o
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dec > 49o
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circumpolar
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dec < -49o
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never seen
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precession
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(p=26,000 years). caused by gravitation pull of sun & moon on earth's bulge
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nutation
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(p=18.6 years, saros cycle). happens because earth, moon, & sun are not always in a straight line
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lunar phases
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new, crescents, quarters, gibbous, full
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lunar configurations
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opposition, conjunction, quadrature
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lunar eclipses
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near full moon
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solar eclipses
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near new moon
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precession
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wobble of earth's axis of rotation (like a gyroscope)
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precession
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caused by gravitational pull of sun and moon on earths bulge, cycle period = 26,000 years
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nutation
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precession of the nodes (period = 18.6 years), same as saros cycle of solar eclipses.
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nutation
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occurs because the centers of earth, moon, and sun are not always in a straight line
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mean solar day
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24h
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sidereal day
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23h 56m
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synodic period
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29d 12h 44m (lunar month)
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sidereal period
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27d 7h 43m
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tropical year
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365.24 days
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sidereal year
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365.256 days
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gregorian calender
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modern calender
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solar day
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our system of time is based on this, rotation period of earth relative to sun
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apparent solar day
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length of solar day varies because the orbital speed of earth changes during the year
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mean solar day
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average length of a solar day (24 hours)
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equation of time
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apparent solar day - mean solar day (up to 17 minutes)
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time zone
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divide circumference of earth (360o) into 24 time zones. each time zone is (360o/24h) wide. 15o/hour
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sidereal day
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rotation period of earth relative to stars
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mean solar day
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sidereal day + 3m56s
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1 sidereal day
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23h56m4s
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sun rise / star rise
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sun rise - 4m later
star rise- 4m earlier |
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the analemma
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pattern of the sun's position in the sky.
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sun does not show up in the same place every day because
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earth's orbit is not a perfect circle (elliptical), earths axis is tilted by 23.5 degrees
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analemma
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difference between mean sun and apparent sun
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tropical year
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365.24 days, one full cycle of seasons. seasons are caused by the tilt of earths axis and orbital motion
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sidereal year
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365.256 days, period of earth orbital motion with respect to stars
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solar eclipse
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near new moon
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lunar eclipse
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near full moon
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total eclipse
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sun, moon, and earth are in straight line, every 18.6 years
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synodic period- superior planet
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time between successive oppositions
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synodic period- inferior planet
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time between successive inferior conjunctions
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sidereal period
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orbital period with respect to stars
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prograde motion
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counterclockwise from north. (same direction as earth)
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retrograde motion
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apparent backward motion of superior planet as seen from earth
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babylonians
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length of year, time, angular measurments
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ancient greeks
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named the constellations
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thales
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need to understand the universe
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pythagoras
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earth is round, circular motions
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plato
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circular motions
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aristotle
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physical laws govern universe. geocentric view. proof that earth is spherical
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eratosthenes
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accurate size of earth
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aristarchus
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heliocentric view (since sun larger than earth)
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hipparchus
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catalog of stellar positions. discovered precession. invented system to measure stellar brightness. COULD NOT MEASURE STELLAR PARALLAX.
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ptolemy
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used epicycles to explain motions of planets
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