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1. annular eclipse -
• the moon is not close enough to the earth to completely block the sun, so the sun rings the moon
2. autumnal equinox
• when the sun crosses the celestial equator in the fall season, directly over the earth’s equator
9. diurnal -
• The daily progression of the Sun, Moon, planets and stars across the celestial sphere
10. eclipse -
• event where one body passes in front of another, blocking the light from the light producing body
17. line of nodes -
• the lines where the plane of the Earth’s orbit and the plane of the Moon’s orbit cross
19. lunar phase -
• the apparent change of shape of the surface of the Moon as different amounts of the illuminated surface are visible
27. right ascension
• the position of any object in the celestial sphere east or west of a beginning point
31. sidereal month
• a month measured by the position of the Moon in the celestial sphere (measured by the stars)
39. tropical year -
• time it takes Sun to make one complete trip around the celestial sphere on the ecliptic
43. wane -
• when the size of the visible, illuminated surface of the Moon appears to shrink from one date to the next
45. wax -
• when the size of the visible, illuminated surface of the Moon appears to grow from one date to the next
1. Why is it important to astronomical science that the laws of physics as we know them apply equally well throughout the whole universe?
2. Why does the sun rise in the east and set in the west each day? Does the moon also rise in the east and set in the west? Why? Do the stars do the same? Why?
• The sun, moon, and stars rise in the east and set in the west because the earth rotates from west to east.
4. Why do we have seasons on earth?• The Earth’s axial tilt causes the Sun’s heat
energy to fall more directly and less directly on certain areas of the Earth at different times of the Earth’s yearly orbit.
5. Why do we see different stars in summer than in winter?• The night time side of the Earth faces
different directions in space at different times of the year.
6. At what phase of the Moon would you expect there to be the most burglaries? Why?
• At new moon it is darkest.
7. If one complete hemisphere of the Moon is always lighted by the sun, why do we see different phases of the moon? • The orbit of the moon around the Earth
causes the Sun’s rays to illuminate different areas of the surface of the Moon. We always see the same side of the Moon, so the fraction of that side that is illuminated changes.
8. What causes a lunar eclipse? A solar eclipse?
• Lunar - Earth between Sun and Moon.
• Solar - Moon between Sun and Earth.
9. What does the fact that there are both annular and total eclipses tell us about the Moon’s distance from the earth?• The distance from the Earth to the Moon
changes.
10. Why aren’t there lunar and solar eclipses every month?• The Moon’s orbital plane is at an angle to
the plane of the Earth’s orbit.
1. Cosmology –
• the study and descriptions of the universe
• for example, the geocentric model of the solar system (earth at the center) is one cosmology
4. epicycle -
• the smaller circle in the orbit of a planet, in addition to the deferent in the Ptolemaic solar system
• explained the retrograde motion of the planets
5. geocentric -
• the model of the solar system (cosmology) with the earth at the center
• everything orbited the earth
6. parallax -
• The apparent shift in position of an object as it is viewed from different positions.
• The lack of observable parallax in the stars was one reason scientists did not believe the earth was moving.
7. Ptolemaic model -
• Best geocentric model of the solar system.
• Consisted of 80 different circles.
8. retrograde motion -
• When a planet is observed to move from east to west from one night to the next.
• The opposite of direct motion.
9. solar system -
• The collection of all objects that orbit the sun.
• In the geocentric system, it was the collection of all objects that orbited the earth.
10. triangulation -
• Using angles, trigonometry, and parallax to determine the distance to an object.
1. What is parallax? Give an example.
• Parallax is the apparent shift in position of an object as it is viewed from different positions.
• When riding in a car, distant objects appear to be moving more slowly than nearby objects.
2. What are epicycles and deferents?
• The deferent is the orbit of a planet; the epicycle is the smaller additional circle.
• Used in the Ptolemaic solar system.
3. Give a brief description of the Ptolemaic model of the universe.
• The earth is at the center, geocentric.
• The planets orbited in deferents.
• The planets also orbited in epicycles to explain retrograde motion. (See question 2.)