Diurnal Motion Focus Questions

 

 

1. Define diurnal.

    

2. Describe diurnal motion:
   • In which direction do the Sun, Moon, planets, and stars all generally move across the sky each day?
   • Where do they all generally rise roughly each 24 hour period?
   • Where do they generally set?

    

3. Is it fair to say that the diurnal motions of stars and planets would be explained by supposing them all to be attached to a giant celestial sphere which rotates around us once a day?

    

4. Complete the following definitions:
   • Rising time is the time when...
   • Setting time is the time when...

    

5. Rising or setting locations of fixed stars would enable sailors to determine their position... (choose one)
   ___ east or west in terrestrial longitude only
   ___ north or south in terrestrial latitude only
   ___ either in latitude or in longitude
   ___ sailors should content themselves with daytime sailing
   

    

6. A rotating sphere has two poles at each end of the axis of rotation, and an equator which bisects the sphere in a plane that is perpendicular to the axis of rotation. Use your planisphere (or a celestial globe) to determine if any stars are found near the north celestial pole.

    

7. Do any stars neither rise nor set at all from the vantage point of Shawnee, Oklahoma?

    

8. A circumpolar star is visible... (choose one)
   ___ all night long
   ___ every night of the year
   ___ both all night long and every night of the year
   

    

9. What circumpolar star enables you to determine which way is north?

    

10. On the assumption of a convex or spherical Earth, what would happen to the number of circumpolar stars a resident of Italy would see if he traveled:
    • northward?
    • southward?

     

11. How many stars would be circumpolar to Santa Claus at his home at the North Pole?

     

12. How many stars would be circumpolar to a penguin at the South Pole?

     

13. Would any of the circumpolar stars seen by Santa and the penguin in the two previous questions be the same?

     

14. A rotating sphere has two poles at each end of the axis of rotation, and an equator which bisects the sphere in a plane that is perpendicular to the axis of rotation. Use your planisphere (or a celestial globe) to determine if any stars are found on the celestial equator.

     

15. TRUE or FALSE?
    Stars located between the celestial equator and the poles daily follow circles parallel to but smaller than the celestial equator.

     

16. TRUE or FALSE?
    As seen from latitudes between the equator and the poles (e.g., from Shawnee), the celestial equator appears to intersect the horizon exactly due east and due west. Moreover, this remains true throughout each day and throughout the year.

     

17. Assuming that the earth is spherical, how will diurnal motion appear...
    • Facing east on the equator (sphaera recta)?
    • Facing east between the equator and the north pole (sphaera obliqua)?
    • Facing the horizon at the north pole?
    • Looking up toward the zenith from the north pole?

     

18. TRUE or FALSE?
    Because the celestial equator appears to bisect the celestial sphere, and because the celestial equator always intersects the horizon due east and due west at sphaera obliqua, one may validly infer that, compared to the distance to the stars, the earth is like a mere point, a dot in space, without appreciable size.

     

19. Altitudes of the North Celestial Pole and the Celestial Equator
    • What is the altitude of Polaris...
      • at 0 degrees latitude?
      • at 90 degrees north latitude?
      • from Shawnee, at 35 degrees north latitude?
      • from (x) degrees north latitude?

       

    • For a given latitude, does the altitude of the north celestial pole remain the same throughout the night and throughout the year?

       

    • What is the altitude of the celestial equator on the southern meridian...
      • at 0 degrees latitude?
      • at 90 degrees north latitude?
      • from Shawnee, at 35 degrees north latitude?
      • from (x) degrees north latitude?

       

    • For a given latitude, does the altitude of the celestial equator on the southern meridian remain the same throughout the night and throughout the year?

       

    • For a given latitude, does the angle made by the celestial equator as it intersects the horizon due east remain the same throughout the day or throughout the year?