Some Things to Know for the Midterm Exam:

What are Gamma Ray Bursts?
How were Gamma Ray Bursts discovered?
How was it determined that Gamma Ray Burst's do not lie in the Milky Way's disk?
How was it determined that Gamma Ray Burst's are far away?
What is a redshift?
How do we know that the Universe is expanding?
What does the fact that Gamma Ray Bursts are far away imply about the amount of energy that they produce?
What is one possible explanation for Gamma Ray Bursts? Can this mechanism explain all Gamma Ray Bursts?

What was the Shapley-Curtis Debate about?
What positions did Shapley take?
What positions did Curtis take?
What are Cepheid variables and what is their significance?
What arguments did Shapley use to suggest 1) the Sun was far from the Galaxy's center, 2) the Milky Way was larger than previously believed, and 3) the spiral nebulae lay within our Galaxy?
What arguments did Curtis use to suggest 1) the Sun was at the center of a relatively small Milky Way and 2) the spiral nebulae are galaxies beyond our own?
How did Edwin Hubble help to resolve the debate?
On which debate points was Shapley correct?
On which debate points was Curtis correct?
What is the current picture we have about the size and structure of the Milky Way and of the other spiral nebulae?

What is the ``K-T Boundary'' and what is its significance?
What are foraminifera and what are their significance?
What is a dinosaur?
What are some of the reasons suggested for the disappearance of the dinosaurs?
Why is it so difficult to establish what killed the dinosaurs?
What is the scientific method?
What attributes does a really successful theory of dinosaur extinction require?
What is paleontology?
What is the impact theory of dino extinction and who discovered this theory?
What are some types of objects that may have caused the impact?
What is a comet, asteroid, meteor?
What are some of the reasons we think that impacts are common in the Solar System?
Why would an impact cause damage to the Earth?
How do we estimate how much damage is caused by an impact?
What are the predicted environmental effects (local and global) of an impact of a large, fast moving object on Earth?
What is the Greenhouse Effect?
What is Nuclear Winter, at least as applied to the death of the dinosaurs?
What are the specific predictions of the impact theory?
What is the evidence to date in support of the impact theory?
What is the iridium anomaly and its significance?
What are impact markers (spherules, shocked quartz, tektites) and their significance?
How would you estimate how often a species-destroying object impacts with the Earth?
What is the significance of Chicxulub?
What are some of the weaknesses of the impact theory?
What is the volcano-greenhouse theory?
What are the Deccan Traps and what is their significance?
What are hot spots and mantle plumes?
How do people think that the Hawaiian islands formed?
How might volcanic eruptions have killed the dinosaurs?
What are the consequences of increasing the CO₂ in the Earth's atmosphere?
What are the strengths of the volcano-greenhouse theory?
What are the weaknesses of the volcano-greenhouse theory?

What do astronomers mean when they say dark matter?
In general, what are the two ways that dark matter can be detected (on other words, how does dark matter affect the motions of objects and the path of light)?
How was dark matter discovered and by whom?
What is a cluster of galaxies?
What is a gravitational lens and how does it work?
What do you observe if you take a picture of a gravitational lens and why?
What is the rotation curve of a galaxy?
How do clusters of galaxies, rotation curves of individual galaxies, and gravitational lenses (either involving individual galaxies or clusters of galaxies as the lens) tell us about dark matter?
In what other ways could you use a telescope to determine if dark matter was present in the Universe?
How was Neptune discovered?
What is the precession of the perihelion of Mercury and what is its significance?
What important lesson can we learn about the dark matter problem from the discovery of Neptune and the precession of the perihelion of Mercury?
What is an alternate explanation for the effects normally attributed to dark matter?
What is the significance of dark matter for the fate of the Universe?
What are the Big Bang, Big Crunch, Big Rip, Hubble's Constant, Omega_{0, matter}, and the dark energy?
What is a mass-to-light (M/L) ratio? What is M/L for galaxies, for clusters of galaxies, for the nearby Universe?
How does M/L relate to Omega_{0, matter}? What must Omega_0,matter be to cause a Big Crunch (in the absence of dark energy)? To what M/L does this Omega_{0, matter} value correspond?
What are bulk flows and what is their significance?
How would you determine the amount of dark matter in the halo of a galaxy out beyond the visible stars of that galaxy?
How would you estimate the mass density of the Universe?
What are some of the uncertainties in estimating the mass density of the Universe?
What are some of the ways that astronomers estimate the mass of clusters of galaxies?
If bulk flow measurements suggest that M/L ~ 500-600 (Omega_{0, matter} ~ 0.3-0.4), and cluster mass measurements (on somewhat smaller scales) give only that M/L ~ 200-400, where might the additional mass lie?
What are low surface brightness galaxies and their significance?
What are quasars?
What is the Lyman-alpha forest and its significance?
What is baryonic dark matter and what are the possible components?
What is non-baryonic dark matter and what are the possible components?
What are black holes, neutron stars, white dwarfs, and brown dwarfs?
What are WIMPS?
What are MACHOS and how are they detected?
What are neutrinos, where do they come from, and how are they detected?
What is the evidence for non-baryonic dark matter?
What is the evidence for baryonic dark matter?
What is Big Bang nucleosynthesis and its significance?
What are some pieces of evidence for the Big Bang?
Why did astronomers eventually rule out the possibility that all elements in the Universe were produced either in stellar interiors or during supernova explosions?
What is a supernova?
What is the current theory as to how the elements (light and heavy) originated?
Why does nucleosynthesis tell us about the density of baryons (mass of baryons/volume of the Universe) today?
Why do nucleosynthesis predictions suggest that non-baryonic dark matter exists?
What are some of the problems inherent in assuming that a lot of dark matter is non-baryonic from nucleosynthesis predictions?
What is the significance of neutrinos having mass? What are neutrino oscillations?
What are the problems associated with using neutrinos to explain the dark matter?
What are some of the weaknesses of explaining dark matter with baryonic matter?
What are some of the weaknesses of explaining dark matter with non-baryonic matter?
What fraction of the mass of the Universe do we currently think is in baryons? In luminous matter? In dark matter?