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{\bf 29:120 Introduction to Astrophysics II\\
     Spring 2009\\
     Second Hour Exam \ldots April 9, 2009\\
     SAMPLE}
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Start each question on a new page.  It allows me to make comments and generally keeps me in a better mood.  Write legibly. Explain what ideas you are using and what you are trying to do. There are 6 questions.  No whining.  I hate whining.  Good luck.
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{\bf Walk with Ursus!!!}
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(1) What is the {\em Schwarzschild Metric}?  Explain its mathematical content.  If you remember the approximate mathematical form, write it down and talk about the significance of the various terms. \\

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(2) Define what is meant by the term {\em interval} in General Relativity.  Explain the concept of the light cone.  What is the significance of the light cone? \\

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(3) Write down the expression for the {\em effective potential} acting on a mass $m$ in a close binary star system with stars of mass $M_1$ and $M_2$.  Even if you don't immediately remember this expression, you should be able to ``scope it out''.   \\

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(4) What is the argument as to why the temperature of an accretion disk is higher closer to the primary than it is further out?   \\

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(5) We speak of ``tidal disruption'' as a process in which tides can pull an object apart.  Explain what properties of tidal stresses can cause this disruption.    \\

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(6) In class, we discussed a theory for the retention of planetary atmospheres.  In the case of Mars, this analysis indicates that Mars should have completely retained a CO$_2$ atmosphere over the 4.5 Gyr history of the solar system.  However, there is independent evidence that the atmosphere of Mars {\em may have been} much denser billions of years ago.  What is a possible reconciliation of these two statements?     \\

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