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49 Cards in this Set
- Front
- Back
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ecliptic
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the aparent rout the sun takes against the constellations
the “projection” of earth’s orbit on the sky |
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vernal equinox
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(Spring, Mar 20)
sun crosses celestial equator going N. Intersection of celestial equator and ecliptic (p27) |
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autumnal equinox
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sun crosses celestial equator going S.
Also at intersection |
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Summer Solstice
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Sun is at its farthest north
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Winter Solstice (December 22)
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Sun is at its farthest south
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Earth's perihelion and aphelion
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The Earth is closest to the Sun in early January and farthest in early July. The relation between perihelion, aphelion and the Earth's seasons changes over a 21,000 year cycle. This anomalistic precession contributes to periodic climate change (see Milankovitch cycles).
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morning, evening star
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Mercury and Venus
They have small orbits, which make them appear to be close to sun in ecliptic |
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Zodiac (18º x 30º)
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denotes an annual cycle of twelve stations along the ecliptic, the apparent path of the sun across the heavens through the constellations that divide the ecliptic into twelve equal zones of celestial longitude
centered on planets (therefore, the ecliptic) |
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Year
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earth orbit
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month
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moon orbit
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day
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earth rotation
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week
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seven "planets" of greeks
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Sidereal day
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the time needed for Earth to complete one rotation around its axis, relative to the stars. It has a mean value of about 23 hours, 56 minutes,
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Julian calender
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created leap year
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gregorian calender
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refined julian calenter
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Synodic Period
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Phases of moon: 29.53 days
wax: new, crescent, 1st quarter, gibbous, full wane: full, gibbous, 3rd quarter, crescent, full |
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same side of moon faces earth. why?
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this is due to earth’s gravity pulling on the moon
the moon conserves energy by keeping slow rotation doesn’t stretch/relax.... |
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Spring tide
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highest high tide, lowest low
forces of sun and moon act together occurs at new moon and full moon |
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Neap
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lowest high tide, highest low tide
forces of sun and moon act against one another occurs at 1st and 3rd quarter |
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One to one phase lock
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the moon rotates on its axis at exactly the same rate as its orbit (sidereal)
this is due to the forces of the earth creating tides on the moon |
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Total Solar Eclipse
umbra |
moon projects small shadow(1 mile diameter) onto the earth
if you are in the umbra, you experience the total solar eclipse |
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Annular Solar Eclipse
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If eclipse occurs when moon is at farthest point on ellipse (orbit)
The umbra does not completely touch the earth This causes appearance of a solid ring of sun’s photosphere behind moon |
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Total Lunar Eclipse
umbra |
moon is completely in the umbra of the earth
moon appears to have reddish appearance this is due to earth’s atmosphere bending sunlight that passes through earth’s atmosphere reflects onto the moon |
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Penumbral Lunar Eclipse
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moon passes through penumbra
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nodes
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each month the moon crosses the ecliptic at two points
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SOLAR ECLIpSE, BASED ON NODES
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Occurs when the moon meets the sun near the same node
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Lunar eclipse, based on nodes
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Occurs when the sun and the moon are near opposite nodes
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Eclipse seasons
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Eclipse seasons occur each time the line of nodes (imaginary line connecting the moon’s nodes) points toward the sun
Can only occur twice a year |
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saros cycle
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Eclipse predictions
eclipse cycle starts over every 18 years and 11 and 1/3 days that is, the moon and the nodes of the orbit return to the same place with respect to the sun |
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Greek Astronomy: 4 elements
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fire, air, earth, water
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Aristotle: natural motions
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move towards proper place
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aristotle's theories
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earth at rest. objects fall at constant rates.
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parallax
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change in viewing object based on change in viewer's posish
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Aristarchus
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-sun centered
-earth rotates on access -circular orbits |
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Eratosthenes
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calculated radius of earth
calulated circumference within 10% of actual light shown down well in one area then observed shadow on a stick in a distant town on same day used simple geometry (triangle) to compute degree of angle then measured distance to town and used percentages |
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Hipparchus
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discovered precession
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Copernicus
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sun-centered
relative distances of planets retrograde motion explanation -flaw:still used circular orbits, not elipticals. |
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Galileo
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-accelerations
-objects in motion if no other force -jupiter in motion kept moons=earth can be in motion too |
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tycho brahe
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accurate measurements of stars
-devised better instruments |
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Kepler’s Three Laws fo Planetary Motion:
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1st law; elliptical orbits, sun at focus
2nd law; radial vector sweeps through equal areas at equal times 3rd law; harmonics - CP2 = a3 proportion C = 1, if P(yrs) and a(AU) |
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Newton 1st law
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inertia, momentum
inertia object will continue at rest or in uniform motion in a straight line unless acted on by some force |
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Newton
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acceleration - F = ma
measures how much force is required for acceleration of mass acceleration = a change in velocity velocity = a directed rate of motion (v = d/t) an object experiences acceleration if it’s speed or direction changes force is proportional to acceleration (F= ma) |
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Newton
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reaction
for every action there is an equal and opposite reaction NEVER the same object!!!! |
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3 exceptions to Newton’s laws:
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1. can’t describe motion of atoms, too small
2. extreme speeds (speed of light) 3. near the very massive (close to sun) |
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Law of gravity
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F = Gm1m2/d2
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What keeps the moon "up"?
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centrifugal, centripetal forces
weight, mass, and “weightless” |
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Newton's derivation of Kepler's laws
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1. Orbits are conic sections
ellipses, circles, parabolas, lines, points, hyperbolas |
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What evidence do we have that the Earth’s poles have changed direction many times in past?
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- as lava flowed out of the spreading sea floor the rocks hardened
- used magnet to measure polarity of rocks - found that the rocks changed n/s orientation over time - poles change about every million years |
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Explain plate tectonics
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Sea floor spreading is caused by lava coming to the surface.
The plates collide and create volcanoes and mountains |
