Identify terms and things on the Celestial Sphere that you have assembled from your college astronomy kit from learning technologies.

1. North pole of the earth

2. North celestial pole

3. South pole of the earth

4. South celestial pole

5. Equator of the earth

6. Celestial equator

Now rectify the globe---this means set the latitude for where we are on the earth at Montgomery College (approximately 39). Use the protractor attached to the white Styrofoam block that the dowel is sticking in to do this correctly.

Think about how you would do this for the north pole, the south pole,

and the equator.

But do it for this latitude.

1. Locate the zenith on the celestial sphere.

2. Locate the nadir on the celestial sphere.

3. Locate the ecliptic, the path of the sun around the earth.

4. Locate the Vernal Equinox on the celestial sphere. Mark this point on your celestial sphere with the letters VE. What date does the vernal equinox occur on approximately? ________ Is this the beginning of a season, if so which one? ___________ What are the relative lengths of day light and night time on this date?
 

5. Locate the Summer Solstice on the celestial sphere. Mark this point on your celestial sphere with the letters SS. What date does the summer solstice occur on approximately? ________________ Is this the beginning of a season, if so which one? __________ What are the relative lengths of day light and night time on this date?
 

6. Locate the Autumnal Equinox on the celestial sphere. Mark this

point on your celestial sphere with the letters AE. What date

does the autumnal equinox occur on approximately? ________ Is this the beginning of a season, if so which one? _______________ What are the relative lengths of day light and night time on this date?
 

7. Locate the Winter Solstice on the celestial sphere. Mark this

point on your celestial sphere with the letters WS. What date

does the winter solstice occur on approximately? ___________ Is this the beginning of a season, if so which one? ______________ What are the relative lengths of day light and night time on this date?
 

8. If the ecliptic is the path of the sun around the earth in a year with respect to the stars, what about our modern view of the earth going around the sun instead of the ancient view of the sun going around the earth? Discuss this paradox that is not a contradiction in a couple of sentences!
 
 
 
 
 

9. Locate the Ecliptic North pole and the Ecliptic South pole on your celestial sphere. Mark them on your celestial sphere with the letters EN and ES. What is the EN and ES line the axis of? __________ How long does it take for the sun to appear to go around the earth with respect to the stars? __________ How far away in angle is the Ecliptic North pole and the Ecliptic South pole from the Celestial North pole and Celestial South pole? _________ Does this have anything to do with the seasons on the earth? __________ What if this angle between the Ecliptic axis and the Earth's rotation axis where a different amount, how would this effect the seasons?
 
 
 
 
 

Would we have seasons on the Earth if the two axis where aligned?
 

10. The ecliptic poles precess around the earth's rotation axis. How long does this precession take to make one full cycle? _________Will this make much of a difference on the seasons if the angle stays the same? _____________ Will this precession change the position of the equinoxes and solstices relative to the background stars? ______________ Your sun sign is the constellation along the ecliptic that the sun appeared to be in when viewed from the earth the day you were born. Does this change the sun signs of two people born on the same date, but several thousand years apart? _________ Mark on your celestial sphere the approximate circle that the ecliptic north pole takes as it precesses. Mark on your celestial sphere the approximate circle that the ecliptic south pole takes as it precesses.

11. Using the large 10 inch black globe in the class locate the Galactic equator. Where would the galactic equator be on your celestial sphere? Locate the Galactic North pole and the Galactic South pole. Mark them on your celestial sphere with the letters GN and GS.

12. What about the movement of the solar system within our Galaxy? How long does it take for the solar system to move around the Galactic center? __________years How far out from the Galactic center are we anyway? _________light years Won't all the star positions change as our solar system and all of the other stars on your celestial sphere move around the galaxy? _________ If your celestial sphere were sealed in a time capsule and opened in the remote future how long do you estimate it would be before an astronomy student of the future would notice that the stars were in the wrong place? __________ How long before the equinoxes and solstices would be in the wrong constellation along the zodiac _____________years.

Pages 13--18, Activity 3, The Celestial Sphere-Modeling The Sky, in Astronomical Instrument Kit for College Astronomy, Manual has another exercise for you to do. You should do it if you want to do well on the first test.