AST 309LReview Questions for Fourth ExamSpring 2005This test covers Chapters 8 through 10 plus Contact. That means it covers the results for theDrake equation, communication, and travel. It will ask you for your values for N and r, and for ananalysis of the consequences of your numbers.A. Evaluation of the Drake Equation1. Two students have evaluated their Drake Equations. Happy Feller gets N = 2.5 × 1011,while Mr. Average Guy gets N = 9.4 × 105. Who will calculate the larger r? How manystars would one have to search before finding the nearest civilization, given each of theirestimates for N?2. Another student, Angela Angst, takes L = 100 years. Does Angela think two-waymessages are possible? What does it mean if your estimate for N is less than one?3. Given your estimate for N, would you expect your estimate for r to go up or down if theSun were closer to the center of the galaxy?B. Communication with Extraterrestrial Civilizations1. Describe the spectrum of electromagnetic radiation, identifying the various wavelengthregions. Indicate which are higher in frequency and shorter in wavelength.2. Why are radio waves generally favored as the wavelength region for interstellarcommunication? What range of frequencies is best? What are the arguments for thisrange?3. Explain three suggestions for “magic” frequencies.4. Draw a diagram, showing how a vertically polarized electromagnetic wave can produce analternating current in an antenna.5. Explain how a radio telescope works.6. Describe the problems of recognizing and decoding signals. What features should asignal have in order to make it easier to recognize and to be decoded? Explain AM, FM,analog, and digital signals.7. Make up a message by coding a picture into a series of 1’s and 0’s.8. Describe the pulsars and OH maser emission. Why don’t we think these are signalsfrom ETI?9. Describe the methods and results of Project Ozma and Project Ozma II.10. Describe the META and BETA projects.11. Describe the NASA search for extraterrestrial intelligence (ETI) and its successor, ProjectPhoenix. Explain the differences between the all-sky survey and the discrete sourcesearch.12. Describe the Allen Telescope Array and how it will extend the search.13. Describe the proposed Cyclops project. What would its capabilities be?C. Review Questions for Contact1. Describe the ARGUS facility discussed in Contact in as much detail as you can. Howmany telescopes, how many frequencies, how narrow were the filters?2. Describe the signal detected by ARGUS. What frequency was it detected at, what otherfrequencies did it show up at, what was the bandwidth, what was the intensity? How couldthe scientists in Contact tell it was not a terrestrial signal? How could they tell it camefrom Vega? What did they learn from the absence of a Doppler shift due to motion of thetransmitter around Vega?3. Describe the four levels of information coded into the signal received by ARGUS. Howwas each modulated and how was each decoded? What was the purpose of each level ofinformation? What is a palimpsest?4. When the ARGUS scientists were looking for the Primer, Ellie asked S. Hadden foradvice. Describe the various suggestions he gave. Which turned out to be correct?5. In Chapter 11 of Contact, various attitudes toward interstellar communication areexpressed at the meeting of the World Message Consortium. Describe the variousopinions and who expressed each one. Which is closest to your own attitude?6. Describe the journey taken by the people in the machine. What is Eda's theory for howthe transport system works (see Chapter 23)?D. Travel1. Give three motivations for interstellar travel. Use your estimates for factors in the Drakeequation to compute how many habitable planets there are in the Galaxy. Assume that aplanet remains habitable for 10 × 109 years.2. In what order did the following steps occur in exploration of our own solar system:missions with astronauts, flybys, landers, colonization, orbital probes, telescopicobservations? How would this sequence differ for interstellar travel? Why?3. Describe Project Orion and Project Daedalus. Give as much detail as you can.4. Describe two of the exotic ideas for interstellar travel. What are the problems with them?5. Give an example of time dilation.6. What is a Bracewell probe? What are its advantages and disadvantages for searching forETI?7. What are the implications of the view that colonization of the Galaxy is relatively easy forvery advanced civilizations?8. What is the Hart Hypothesis? Be sure that you can explain how this argument works andwhat its significance is. If you have a large estimate for N, you will have to have a goodcounter-argument to Hart. What are the Tipler and Zuckerman variations?9. What are the four categories of UFO's? What is a close encounter of the third kind?E. Broader Questions1. Some have argued that societies that develop the capability for interstellar communication,namely sophisticated technology, will also develop the tendency toward self-destruction,either by resource depletion or by nuclear war, thus ensuring a low value for L. What doyou think of this argument?2. Compare the pace of chemical, biological, and cultural evolution. Which sets the timescalefor the emergence of new technological
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