Test 3, 2019.6.13
Astronomy 123

Cosmological Constant Problem

Life in the Universe: Drake Equation, Fermi Paradox, & SETI

• What is the Drake Equation? What are the parts which comprise the Drake Equation? How well-determined are the parts to the Drake Equation? What are the most well-determined parts of the Drake Equation? The least well-determined? How well-determined is the overall solution to the Drake Equation? What parts of the Drake Equation can be determined from astronomical observation? What is likely to be the most well-determined term in the Drake Equation? What is the definition of the Habitable Zone? Can there be more than one type of Habitable Zones? Explain. What factors determine the size of the Habitable Zone? What are some other considerations that must be taken into account when discussing the habitable zone?
• Roughly how many extra-Solar planets have been discovered since 1995? Describe the methods used to discover planets. How were most of the planets discovered? What is the most common type of planet? Roughly, how many earth-like planets have been discovered? Roughly how many planets have been determined to fall in the habitable zone? What is Kepler? What is Tess? What is the origin of the oceans of the Earth? What is the origin of the oceans of Mars?
• How many extraterrestrial civilizations are there in our Galaxy based on the Drake Equation? Why are the results so uncertain?
• Describe the Gaia Hypothesis. Is the Gaia Hypothesis sensible? (Is there a mechanism which allows life on the Earth to play a role in the development of conditions suitable for life?)
• Describe the Faint Young Sun Problem. What is meant by equilibrium temperature? What is the solution to the Faint Young Sun Problem? Describe the Greenhouse Effect.
• Compare the evolution of the atmospheres of Venus, Earth, and Mars. Why did Venus and Mars turn out so differently from Earth?
• Mars, today, has a hostile environment for life as we know it. People suggest that in the past, things may have been different. What evidence and arguments do people propose to support this conjecture?
• Water plays a key role in our thinking about the development of life. On which planets (objects) have we discovered water? What key observations suggest that we have found water on these objects? On which objects have we perhaps discovered suitable replacements for water?
• On what bodies in our Solar System have we searched for life?
• What is meant by LAWKI? Is this a sensible guide to use when searching for extra-Terrestrial life?
• Describe the Viking biology experiments. Describe the results of the Viking Biology experiments. What is the current consensus as to whether life was found on Mars by the Viking landers? What are the issues to be addressed?
• What is ALH84001? Cite the evidence found from study of ALH84001 which suggests life may have existed on Mars in the past. How solid is this evidence? What is a good next step for the follow-up of the ALH84001 study?
• Titan: What is Titan? What makes Titan an interesting target for a search for extra-Terrestrial life? The conditions on Titan are such that methane is near its Triple Point. What does this mean and why is it interesting from an extra-Terrestrial life standpoint? Cite evidence that Titan may harbor extra-Terrestrial life. Titan may show that there are two habitable zones in planetary systems. Explain this statement.
• What is the Fermi Paradox? Describe the Fermi Paradox. Are there resolutions for the Fermi Paradox? What are Neumann machines?
• What is the major difficuty when considering interstellar travel? Cite examples of how difficult it will be. Describe the Twin Paradox. Describe the concept of a black hole? What is a wormohole? How would wormholes help up to explore the galaxy (or Universe)? What is a major problem with traversing a wormhole? How could the problem be overcome? Are clocks affected by whether a person is still or moving? Are clocks affected by the strenth of gravity about them? In both, if yes, what kind of effects are seen?
• We earlier defined Habitable Zone of a system as where the energy a planet receives from its pair is just so in the sense that it allows the planet to sustain large amounts of water in its liquid state. We now recognize that habitable zone concepts need modifiction. How do Europa and Enceladus suggest we expand our thinking on Habitable Zones? What is tidal forcing? Why are Europa and Enceladus now thought to be further interesting objects for studies of extraterrestrial life? What are the recent observations of Enceladus that suggest conditions for life exist on Enceladus? What is methanogenesis?
• Venus, Earth, and Mars were likely quite similar at birth and yet, today, they have grossly different atmospheres and surface conditions. Briefly sketch the atmospheric evolution of the Earth and then point out why Venus, Earth, and Mars turned out so differently.
• What evidence is that there Mars once had a much more lush environment in the past than today (that is, what is the evidence for water on Mars?
• Describe the Greenhouse Effect.
• What is the Faint Young Sun Problem? What is the likely solution to the Faint Young Sun Problem? What is meant by equilibrium temperature?
• What is the water trap?