INTRODUCTION TO ASTRONOMY

PHYS 206, FALL 2000

INSTRUCTOR: G. STACY

SOLUTIONS AND ANSWER KEYS

Answer Key to Test #1 (Given on Thursday, September 28)

• Part I. True or False
  1. F
  2. T
  3. F
  4. F
  5. T
  6. F
  7. T
  8. T
  9. F
  10. F
• Part II. Multiple Choice
  1. E
  2. B
  3. C
  4. B
  5. F
  6. A
  7. B
  8. B
  9. D
  10. B
• Part III. Short Answer
  1. Speed of light: Must have the proper units attached!
     c = 3 x 10^8 m/s = 3 x 10^5 km/s = 186,000 miles/s.
  2. Baton Rouge: longitude = 91 deg west, latitude = 30 or 31 deg north.
  3. Star in SW, 1/3 of the way above the horizon to zenith: azimuth = 225 deg, altitude = 30 deg.
  4. Diagram of the waning crescent Moon: should show a crescent on the "left-side" of the Moon as viewed from Baton Rouge, with the "right-side" in shadow.
  5. 3rd Quarter Moon at transit ==> 6 AM local time.
  6. Distance units ranked from smallest to largest: micron, km, AU, ly, pc, and Mpc.
  7. Planets visible to the naked eye (think of the days of the week): Mercury, Venus, Mars, Jupiter, and Saturn.
  8. 5:00 PM CDT = 4:00 PM CST = 10:00 PM UT (where UT = CST + 6 hours).
• Part IV. Short Problem
  • Given that a nautical mile is defined to be equal to the length of one arc-second of longitude at the Earth's equator, and is also equal to 1.85 km, determine the mean radius of the Earth.
    Can use the chord (or arc)-radius relation from geometry: s = r * theta , where s equals the chord or arc-length (one nautical mile = 1.85 km) and theta is the angle subtended by the arc (= one arc-minute, converted to radians). Re-arrange and solve for r = s / theta = 1.85 km / (1 arc-min / 60 arc-min/deg * pi/180 rad/deg) Find that r = 6360 km.
• Part V. Short Essay
  • Eratoshenes and the size of the Earth:
    Refer to the figure and explanation given on page 61 in our textbook.

gstacy@phys.lsu.edu