A101U Mid-Term Examination -- Autumn 1993

Instructions:  This exam consists of 12 short answer 
questions and 4 "long answer" questions.  Answer 10 of 
the 12 short questions and 2 of the 4 long questions on 
the exam or the paper I will provide you.  If you 
answer more than 10 of the 12 short questions, mark the 
10 you want me to grade (you may "x" out the 2 that you 
don't want me to grade, if you wish).  If you have more 
than 10 questions answered and have left me no marks, I 
will grade the first 10.  

Similarly, for the long questions, mark the 2 of 
the 4 that you don't want me to grade with an "x"
otherwise, I will grade the first two questions that 
you have attempted to answer.

The short questions are worth 7 points each.  Long 
questions are worth 14 points each.  For the short 
questions, I expect answers of 2-4 sentences or 1-2 
sentences with an accompanying diagram.  For long 
questions, I expect answers of 6-8 sentences (two 
paragraphs or so) or 3-5 sentences with an accompanying 
diagram.  You should have enough space to write in your 
answers on the exam, but if you need more paper or just 
some scratch paper, please raise your hand.

You should find that 2 hours will be ample time to 
finish this exam.  If you finish early, please leave 
quietly so as not to disturb others.  I encourage you 
to read back over your exam when you are finished to 
make sure you answered the correct number of questions 
completely.  I will periodically let you know how much 
time is left, so it should be easy for you to pace 
yourself to finish the exam in plenty of time.  You 
have the full 2 hours and 20 minutes should you need 
this much time.

When everyone has a copy of the mid-term, you may 
turn the cover page over and begin.  Note that each 
page has questions on both sides.

Part I -- Short questions (7 points each)

(1)  Imagine you are standing on the Earth's equator.  You 
     may use a diagram to help answer this question, but 
     only your written answers will be graded.  Of course, a 
     diagram might help you earn partial credit if you get 
     an answer wrong.
	(a)  At what altitude is the Celestial Equator with 
	     respect to your position?  
	(b)  As you walk South, how would the altitude of the 
	     Celestial Equator in the sky change?  
	(c)  What would the altitude of the Celestial Equator 
	     be once you arrived at the South Pole?
	(d)  Would the Celestial Equator be in the Northern or 
	     Southern part of the sky as you reached about halfway 
	     to the South Pole?

(2)  Draw a diagram showing the Earth and its North Pole.  
     Add to this diagram the locations in the sky of the 
     Celestial Equator and the Ecliptic.  Draw and label 
     locations on this diagram showing the position of the 
     Sun during the Winter, Spring and Summer (for the 
     Northern Hemisphere).


(3)  The two diagrams below represent the local horizons for 
     Pago Pago (latitude of 15 deg South or -15 if you prefer) 
     and Denton, Texas (my hometown, with a latitude of 33 deg
     North or +33 if you prefer).  Draw in the locations of 
     the North Celestial Pole and the Celestial Equator on 
     these diagrams.  You do not need to figure out the 
     actual angles; as long as you are in the correct 
     neighborhood in the sky for each, I will be happy.

[diagrams not included in ASCII version]

(4)  Explain why (in words or with equations, if you prefer) 
     orbiting bodies must move with slower speeds when they 
     are at larger distances away from the central massive 
     body.  Use this fact to help you remember Kepler's 3 
     Laws and restate these 3 Laws (if you've just memorized 
     them, that's fine, but it helps to be able to 
     understand where they come from).

(5)  Draw a diagram of the orientation of the Earth, Sun and 
     Moon during a lunar eclipse.  From this diagram, show 
     in what phase the Moon must be in order for a lunar 
     eclipse to occur.  Why don't eclipses happen every 
     month (answer in words or with another diagram, if you 
     prefer)?

(6)  Explain why the Moon's orbital period equals its 
     rotational period, resulting in the same face of the 
     Moon always pointing at the Earth.

(7)  Why is the Sun yellow?  Use a graph of the intensity of 
     continuous radiation versus wavelength to explain your 
     answer.  If the Sun suddenly got a lot cooler, would it 
     become redder or bluer?

(8)  Give two reasons why Jupiter is so large compared to 
     the terrestrial planets (Earth, Venus, Mars and 
     Mercury).

(9)  Why does Earth not have noticeable amounts of Hydrogen 
     and Helium present in its atmosphere (yet other gases, 
     like water vapor, carbon dioxide, molecular Nitrogen 
     are abundant)?

(10)  Briefly state the current most favored theory for the 
      origin of the Earth's Moon.  How does this theory 
      explain why the Moon is not "heavy enough?"

(11)  Why does the presence of an enriched layer of Iridium 
      in the soil 65 million years ago imply that there was 
      some kind of extraterrestrial cause for the extinction 
      of the dinosaurs?

(12)  What would happen to an asteroid if it were perturbed 
      into an orbit with a period that is exactly half as 
      long as the orbital period of Jupiter?  What are two 
      possibilities for the "ultimate fate" of this asteroid?  

Part II -- Long questions (14 points each)

(1)  James Randi has stated, tongue in cheek, "Scientists 
     have a remarkable ability to find exactly what they are 
     looking for."  What is he really trying to say about 
     the process of scientific investigation and bias?  Give 
     an example of an experiment that has been performed (or 
     that you might want to perform), and describe a method 
     that has been used (or that you might use) to overcome 
     this problem of bias.

(2)  The four basic sources of scientific knowledge are:  
     personal experience, eyewitness testimony from others, 
     a trusted authority telling you something, and 
     revelation in a spiritual sense (something just "comes"
     to you).  Rank these in order of reliability (I realize 
     that this is not a question everyone will or should 
     answer in the same way).  Explain your first and last 
     choices.

(3)  Describe the process by which Venus lost almost all of 
     the water vapor from its atmosphere.  As part of your 
     explanation, explain why the Earth managed to avoid (so 
     far) falling into the same "greenhouse trap" as Venus.  
     Why does the presence of an unusually large amount of 
     "heavy water" (water with Deuterium, or heavy Hydrogen, 
     in place of normal Hydrogen) with respect to normal 
     water vapor in the Venusian atmosphere help confirm 
     this hypothetical model?

(4)  Emitting gas clouds don't emit their specific pattern 
     of spectral lines at the exact wavelengths we expect.  
     These lines tend to be "broadened" or spread out 
     somewhat around their central wavelength (or the "rest 
     wavelength" we measure in the lab).  In fact (this is a 
     hint), it turns out that hotter gas clouds have broader 
     spectral lines than cooler gas clouds.  Explain this 
     phenomenon, including why the lines are broadened in 
     the first place and why the width (or amount of 
     broadening) depends upon the temperature.