Astronomy Test #3
This is a test for astronomy, #3 ! 8==D
Terms in this set (27)
Describe the relative positions of the sun moon and earth during a solar eclipse
sun - moon - earth in a straight line
Describe the relative positions of the sun moon and earth during a lunar eclipse
sun - earth - moon in a straight line
What is the phase of the moon during a lunar and solar eclipse?
Lunar - full
Solar - new
Compare and contrast the umbra and penumbra
Umbra - total shadow, thin
Penumbra - partial shadow, wide
Compare and contrast the ascending and descending nodes
Ascending node - point where the moon's path moves above the sun's apparent path
Descending - point where moon's path moves below the sun's apparent path
Why is there not a lunar and solar eclipse each month?
During a lunar eclipse the sun an moon must be close to opposite nodes and during a solar eclipse the sun and moon must be close to the same node. This does not happen every month.
Why can't the moon be eclipsed when it is halfway between the nodes of its orbit?
The shadow would fall way above or below the moon since the moon's oath is at a maximum deviation from sun's apparent path
How would eclipses be different if the moon's orbit were not tipped with respect to the plane of the Earth's orbit?
There would be a lunar eclipse at every full moon and a solar eclipse at every new moon
If a lunar eclipse happened at midnight, where in the sky would you look to see it?
Lunar eclipses occur at full moon. Full moon rises at sunset so at midnight it would be at the meridian.
Why are solar eclipses sometimes total and sometimes annular?
Orbits of Earth and moon are elliptical
When Earth is far from sun, the sun looks small and when moon is close to earth the moon looks big and there would be a total eclipse. When sun looks big and moon looks small there would be an annular eclipse.
How wide is the moon's umbral shadow during a total solar eclipse?
How often do solar eclipses repeat?
Saros Cycle is 18 years 11 1/3 days
When is the next solar eclipse that can be seen in the US? In NY?
Compare and contrast spring tide and neap tide?
Spring tide occurs during full or new moon when Earth, sun and moon are in a line. Causes tides to be extra low or high
Neap tide occurs during 1st or 3rd quarter moon when Earth sun and moon are at right angles, causes tides to be less extreme
How do tidal forces explain why we always see the same side of the moon?
Tidal locking. Since the tidal forces caused the moon to form in an oblong shape, the bulge eventually oriented itself so it always faces the Earth.
How long does it take for the sun to go from meridian to meridian?
24 hours = 1 solar day
How long does it take a star to go from meridian to meridian?
23 hours and 56 minutes = 1 sidereal day
Why is sidereal time useful to astronomers?
Astronomers can easily locate stars. For example when the sidereal time is 13 hours, a star with right ascension of 13 hours will be at the meridian so an astronomer can easily locate it.
If the earth rotated faster, would a sidereal day be longer, shorter or the same?
Shorter, since a sidereal day is approximately equal to the period of earth's rotation.
If the earth revolved faster, would a sidereal day be longer shorter or the same?
The same since a sidereal day only depends on rate of rotation, not on orbital period.
What are three evidences that ancient civilizations were interested in astronomy?
Artifacts, Monuments, Art, Written Records
Why were Ancient Civilizations interested in Astronomy? ( 3 reasons)?
Calendar, Time Keeping, Navigation, Religious Festivals, Planting/Harvesting
Who proposed that the planets should make music that we can hear?
Pythagoras - "Music of the spheres"
Summarize Ptolemy's geocentric model?
1. Earth is stationary. 2. The stars are on a celestial sphere that turns once per day. 3. The sun's sphere is tilted 23.5 degrees from the celestial sphere, and turns daily while the sun moves eastward around its sphere once per year. 4. The moon's sphere is tilted 5 degrees from the sun's sphere and rotates once every 24 hours and 50 minutes. 5. the spheres of the planets are spaced according to how long it takes them to move through the zodiac (moon, mercury, venus, sun, mars, jupiter, saturn)
How did Ptolemy explain retrograde motion?
Epicycle revolves around the equant which moves along the defernt
Why did geocentrism prevail over heliocentrism until the 1500's?
Tradition, Aristotle's reputation, The catholic Church, Adequacy of explaining and predicting motion of celestial objects
What are some evidences that the Earth moves?
Coriolis effect, Foucault pendulum, weather systems(hurricanes), photos from space, parallax