Study Guide for the Final Exam -- Spring 1994

Overview:  The Final exam will be held on Monday, June 6 at 7 pm in 
Johnson 101 (not 8:30 pm as it says in the course schedule).  You 
will have the full 2+ hours to finish, but the majority of you should 
finish well before time is called (and everyone should finish in time, 
since I don't intend for the test to be that long).

The exam will consist of several short answer questions and 
perhaps three longer essay-type questions worth twice as much as 
the short answer questions.  You will be held responsible for all the 
material in the course, with a slight emphasis on the second half.  

1) Explain the concept that the easiest person to fool is yourself.  What 
   are some practical methods scientists use to avoid this problem?

2) Explain the difference between random and systematic error (see the 
   introduction to the skylabs for a discussion of this).  Why are errors 
   so crucial to obtain?

3) What is the difference between correlation and causation?  Give an 
   example from one of your assignments where there was correlation 
   but no cause for it.  

4) What are the four basic sources of scientific knowledge (include 
   personal experience as one of them), and how much do you (or should 
   you) trust each?  Explain why.

5) How is science like the process of induction?  Explain the concept of 
   the vulnerability of scientific ideas and why this is crucial.

6) Use a diagram to explain how the altitude of the North Celestial Pole 
   (marked by the North Star, Polaris) changes in the sky as your 
   latitude on Earth changes.

7) How does declination relate to latitude (you may explain with a 
   diagram)?  How does this help explain what you can and can't see in 
   the sky over the course of a year?

8) Use a diagram to explain how the offset of the Celestial Equator from 
   the Ecliptic causes seasons during the year.

9) Explain the difference between a sidereal and a solar day.

10) Be able to use a diagram to explain the difference between a lunar and 
    solar eclipse.

11) Use a diagram to explain why lunar and solar eclipses don't happen 
    every month.

12) Explain why the Moon appears to pass close to every other planet in 
    the sky over the course of one month.

13) Give an observation that contradicts the theory that seasons are 
    caused by the proximity of the Earth to the Sun (i.e. when the Earth 
    is closer to the Sun, we experience summer in Seattle).  Explain the 
    contradiction you find.

14) Why is the Sun at its highest maximum alititude in Singapore on March 
    21 and Sept. 21 as opposed to the solstice dates?

15) Explain why the days get longer in the summer the further North you 
    are in latitude (a diagram may be helpful).

16) Be able to draw the North Celestial Pole and the Celestial Equator on a 
    diagram similar to that in HW #2 if I provide you with a latitude.

17) Restate Kepler's Laws.  Be able to explain how the laws can be derived 
    from the concept of the conservation of angular momentum.

18) Explain how the tides are generated on the Earth (both on the near and 
    far side).

19) Why does the Moon always have the same face pointing toward the 
    Earth (i.e. why does the Moon's rotational period equal its orbital 
    period)?

20) Use a graph of a few sample continuous spectra to explain why bluer 
    stars are probably hotter then redder stars.

21) Describe the kind of set-up you would need to generate continuous, 
    emission-line and absorption-line spectra.

22) Why is it that we can see a pattern of just four of five lines in a 
    spectrum and unequivocally (or, with high confidence) determine the 
    composition of the gas we are looking at?

23) What is a Doppler shift?  How can we use Doppler shifting to tell 
    whether something is moving toward or away from us?

24) Know that Temperature is a measure of the random motions within a 
    gas.  Explain why hotter gases tend to have broader lines (both 
    emission and absorption).

25) Why is the "collision" theory for the origin of the solar system not 
    favored in the scientific community (two reasons)?

26) List several basic observations we have made about the solar system, 
    and show how the "nebular" theory of the origin of the solar system 
    explains some of them.

27) How does the principle of the conservation of angular momentum 
    result in the solar nebula collapsing into a disk rather than just a 
    single point?

28) Where do most volatile elements tend to be found in the solar system?  
    Why?

29) All objects we define as planets are differentiated.  Why is this?  

30) How is the differentiation within a planet different from the 
    differentiation between the inner and outer planets?

31) Explain the big difference in size between the inner and outer planets.

32) What are some of the different theories for the origin of Earth's Moon 
    and why are they not favored?  How does the "nebular" hypothesis of 
    solar system formation help support the so-called Giant Impact 
    model for the Moon?

33) What was the initial source of water for the Earth?  How come Venus 
    and Mars no longer have any noticeable water on their surfaces?

34) Why is Mercury the only terrestrial planet without a noticeable 
    atmosphere?

35) The atmospheres of Venus and Mars are laregely composed of Carbon 
    Dioxide, but for different reasons.  Describe briefly the history of 
    each atmosphere and explain how it ended up the way it is today.

36) Why don't the terrestrial planets have much Hydrogen or Helium in 
    their atmospheres?

37) How is Jupiter's system of satellites similar to the inner solar 
    system?  

38) Why didn't a planet form where the asteroid belt is today?

39) Describe how the Kirkwood gaps in the asteroid belt are formed.

40) What is the evidence that suggests that a giant impact 65 million 
    years ago resulted in the extinction of most of the dinosaurs (among 
    other species)?

41) Planets like Jupiter are large enough to cause the Sun to "wobble" 
    slightly about the center of mass between the two bodies (since 
    both bodies orbit the common center of mass).  How can we use this 
    principle to detect other planetary systems?

42) A planet like Jupiter would be about 22nd magnitude if we moved it to 
    the distance of Alpha Centauri.  This kind of object should be easily 
    imaged in some of our largest telescopes, so why can't we find 
    planets directly this way?

43) The main reason the search for other planetary systems has been 
    unsuccessful to date is believed to be the lack of good Infrared 
    technology.  What are two reasons why looking in the Infrared is 
    thought of as such a good idea these days.

44) How can we use the apparent and intrinsic (or absolute) brightness to 
    estimate the distance to an object?

45) Why is the sky blue?  Why are sunsets red?

46) Review in-class lab #3 and homework #4, paying close attention to 
    how bias is present in each.  What is a representative sample?

47)  Be sure you understand the concepts of flux, luminosity, apparent and 
     absolute brightness.  Know how each depends upon size and 
     Temperature of the star and how brightness varies with distance.

48)  What is Hydrostatic Equilibrium?  Construct a scenario in which the 
     pressure or gravity of a star is suddenly increased/decreased and 
     describe how the star returns to its original stable equilibrium.

49)  Why is there a lower limit to the mass of a star?  Can you think of a 
     reason why there would be an upper limit?  (Hint:  What happens in 
     the core as a star's mass increases?)

50)  Describe the basics of the p-p chain and show where the energy is 
     coming from that helps keep the star in equilibrium against gravity.

51)  If a photon is just being scattered in random directions, how does it 
     manage to escape the Sun after a long time (in other words, describe 
     how the "random walk" works)?

52)  Explain why the solar spectrum is an absorption spectrum.

53)  Why is the corona so hot?  Given the fact that temperatures in the 
     corona approach those found in the core of the Sun, why don't nuclear 
     reactions happen in the corona?

54)  What is it about nuclear energy generation that leads to the fact that 
     a star's lifetime _decreases_ as its mass increases?  (Hint:  how 
     does the change in fuel burning rate compare to the change in fuel 
     available for a star when you are determining its lifetime?)

55)  Explain why only the Hydrogen near the core of the Sun participates in 
     the fusion reactions while the star is on the main sequence.

56)  The expansion of the star into a Red Giant occurs before the core 
     ignites helium (the so-called "helium flash").  What is happening 
     before helium ignition to make the star expand so much?  What 
     finally causes the helium core to ignite?

57)  What are two reasons higher temperatures in the core are required in 
     order to fuse elements with higher atomic numbers that Hydrogen?

58)  What marks the boundary of a black hole (not just the name of it, but 
     the definition of the boundary)?  If you could squash it down to a 
     small enough space, could something as small as the Earth be 
     compressed into a black hole?  Explain.

59)  What does the width of a spectral line tell us about a star's gravity?  
     How can we use this to estimate the star's overall size?

60)  Small stars rotate more quickly than large stars, so why can't we use 
     line widths from rotational velocities to determine sizes of stars?  
     (This is one for you to think about...we didn't cover it)

61)  Why do most stars on the H-R Diagram lie on the main sequence?

62)  What is the process that leads to the formation of a planetary 
     nebula?  What part of the star is left over and what do we call this?

63)  Describe the core structure of a very massive star late in its life, 
     just before the onset of Iron fusion.  You don't need to know the 
     specific elements being fused, but a general picture is sufficient.

64)  Why does the fusion of iron result in a supernova?  Describe the 
     process.

65)  Where does all the Iridium (atomic number 77) in the Universe come 
     from?  Explain how you know this fact.

66)  Why does the gas in the spiral galaxy collapse into a disk shape while 
     many stars continue to orbit in the halo?

67)  Why are there spiral arms in the disk of our galaxy (describe how they 
     form and how they are maintained)?  

68)  Why are spiral arms blue?

69)  What are two effects the inter-stellar medium (ISM) has on what we 
     see in the sky?  

70)  Describe the pattern of rotation in our galaxy that leads us to believe 
     that there is dark matter beyond the visible perimeter of the galaxy.

71)  Why are the spiral arms so bright even though they have a very small 
     overdensity of material compared to the rest of the disk?

72)  How is the Inter-Stellar Medium (ISM) changing over time, and what 
     is causing this change?  How does this enable us to estimate the 
     ages of stars?  

73)  Would you expect a hot, blue star to be high or low metallicity?  
     Explain your reasoning.

74)  How can we use the H-R Diagram to help us figure out the distance to 
     a globular cluster?  Describe the process and the reasons it works.

75)  What leads us to believe that ellipticals are the result of merged 
     galaxies?

76)  What is it about galaxy clusters that leads us to believe that dark 
     matter is present in them?

77)  Gravitational lenses have been used to argue that dark matter is 
     present in distant galaxy clusters, and they have been used to argue 
     that dark matter exists in the form of planets in our own Galaxy.  
     Describe the reasoning behind these arguments.

78)  Describe how one finds the Hubble constant.  How can our estimate of 
     the age of the Universe change if we suddenly realize we've made an 
     error in estimating the distances to a couple of galaxies?

79)  In homework #4, why are there so few very bright galaxies in our 
     sample?  Also, why are faint galaxies less numerous then medium-
     bright galaxies given the fact that we fully expect faint galaxies to 
     be the most numerous?

80)  What would your graph from homework #4 look like if the Universe 
     were contracting?  If it had no large-scale motion?

81)  Why is the night sky dark?

82)  Describe (in words) the microwave background radiation (MBR).  What 
     does the presence of the MBR tell us about the history of the 
     Universe?  

83)  How would the presence or absence of dark matter in the Universe 
     change our view of what the ultimate fate of the Universe will be?  
     Answer in terms of the critical density.

84)  Once you take out the motion of the Earth around the Sun, the rotation 
     of the Earth, and the rotation of the Sun about the center of our 
     galaxy, the MBR still is not perfectly uniform.  Explain why it is 
     generally bluer in one direction and generally redder in the opposite 
     direction.

85)  What is the importance of the small anisotropies in the MBR 
     discovered by the Cosmic Background Explorer (COBE) satellite?  
     What did these anisoptropies later become?

86)  What problem in cosmology is solved by inflation?

87)  Why was the Universe only able to create elements heavier than 
     Hydrogen during the first three minutes?

88)  Why did "recombination" coincide with the release of the MBR?

89)  State a few of the things that N (the number of intelligent, 
     communicative civilizations in the galaxy) depends upon.  Why does N 
     depend upon the lifetime of the civilization?

90)  Why do we search of ETI signals in the radio region of the spectrum 
     (two reasons)?  Explain how some scientists conclude from our lack 
     of detection (so far) that we are alone in the galaxy.