Q&A Hero

Q: What role did Frank Drake play in SETI?

Q: What is SETI? How is it being done?

Q: Contrast space flight and radio communication as possible means of SETI.

Q: How would the radio Earth appear to extraterrestrials?

Q: What is the "water hole"? Why is so promising to radio astronomers?

Q: Why are type O, A, and M stars considered poor candidates to find a technological civilization?

Q: Describe the reasoning leading to the idea that the number of technological civilizations in the galaxy is equal to the average lifetime of a technological civilization.

Q: Name each of the factors in the Drake equation.

Q: What happened to the dinosaurs? How does that enter into the Drake Equation?

Q: Define "technological civilization" according to Drake.

Q: What three classes of stars are most likely to house life like ours? Why?

Q: Why might the Cassini-Huygens probe to Titan be considered disappointing to exobiologists?

Q: What is meant by the idea life on Earth had an "interstellar origin"?

Q: What do we mean by "life as we know it"?

Q: Discuss the nature of the Miller-Urey experiments. What are the results of these experiments?

Q: Why is life difficult to define?

Q: Why does SETI concentrate on the water hole?

Q: Why is Earth a stronger radio emitter than the Sun?

Q: Which class of stars probably has too small a habitable zone for life to arise?

Q: Which classes of stars with large habitable zones probably don't last long enough for life to evolve to use them?

Q: What is the primary determinant of whether a planet resides in the "habitable zone" of a planetary system?

Q: Which factor in the Drake equation is the most uncertain?

Q: What evidence did probes to Mars find that makes it a prime candidate for life?

Q: Why does Europa's surface promise life of some kind?

Q: Compare the Copernican principle with the assumptions of mediocrity.

Q: What is an organic molecule based on? Why are they important?

Q: How did the Miller-Urey experiment attempt to recreate early conditions on Earth?

Q: If a star system 30 parsecs distant is found to be broadcasting intelligent radio signals, then their news is already approximately ________ years old.

Q: The water hole is important to SETI because it is a ________ part of the radio spectrum.

Q: The range of wavelengths for the "water hole" is ________ cm.

Q: As one of the strongest sources of radio waves in the solar system, the ________ has an observed period of about a day.

Q: The cheapest and probably most effective means of interstellar communication is ________.

Q: We believe binary stars to be the ________ likely to have an extraterrestrial civilization.

Q: As the average estimated lifetime of a technical civilization increases, then the distances between neighboring civilizations would ________.

Q: On average, the Milky Way forms about ________ stars per year.

Q: In a galaxy like ours, the best place for life to form would be in the ________.

Q: Compared to a G-type star, an F-type will have a ________ habitable zone.

Q: Besides comets and meteorites, we also find organic molecules in the ________ clouds in deep space.

Q: Cultural evolution has primarily taken place over the last ________ years.

Q: In the habitable zone, surface water must be at least partially ________ in phase.

Q: In addition to the proper chemistry, it is ________ that determines the feasibility of life on a given planet.

Q: The ________ equation was written to assess the probabilities of technological, intelligent life existing in the Galaxy.

Q: The Murchison meteorite in Australia was found to contain ________.

Q: Outside our Earth, the most likely places for life are the planet ________ and jovian moon ________.

Q: Single-celled life ruled the Earth from ________ to ________ billion years ago.

Q: Conducted in 1953, the ________ experiments were designed to show what types of complex molecules might have formed in the Earth's primitive environment.

Q: In the Miller-Urey experiment, the electric discharge was meant to simulate ________.

Q: Our earliest atmosphere, formed by outgassing, was much poorer in ________ than now.

Q: In addition to asteroids, ________ impacts also provided the primitive Earth with water and organics.

Q: Which of these radio waves would fall in the "water hole"? A) 15,000 cm in wavelength. B) 6.563 10-5 cm in wavelength. C) 19 cm wavelength D) 150 cm in wavelength. E) 243 cm in wavelength

Q: As a radio source, the period of "pulsar Earth" is A) 30 minutes. B) 23 hours, 56 minutes. C) 24 hours. D) 29.5 days. E) 365.25 days.

Q: An extraterrestrial observer would pick up the strongest radio signals when A) the Earth was at perihelion. B) North America was either rising or setting for the observer. C) North America was directly in front of the observers. D) at new or full moon. E) Saturday Night Live is on.

Q: Most SETI searches are done at A) X-ray wavelengths. B) infrared wavelengths. C) visual wavelengths. D) radio wavelengths. E) gamma wavelengths.

Q: Considering both longevity and luminosity, which of these stars would be the most likely candidate for seeking extraterrestrial intelligence? A) Spica, a B3 main-sequence star B) 61 Cygni, a K2 main-sequence star C) Sirius B, a white dwarf D) Antares, a M3 supergiant E) Barnard's star, a M5 dwarf

Q: In Drake's equation, which of the following is the closest estimate for the number of stars that are formed in the Milky Way Galaxy? A) a star a day B) a star a month C) a star a year D) a star a decade E) a star a century

Q: How does Drake define a technological civilization? A) one that can get into space B) one that can communicate over interstellar distances C) one that has a written language D) one that can construct metal tools E) one that can have the intelligence not to destroy itself

Q: The Drake Equation is attempting to find A) the number of planets in the Milky Way Galaxy. B) the number of planets with life on them in the whole universe. C) the number of stars that might have planets orbiting them. D) the number of technological civilizations in the Galaxy at a given moment. E) the total number of terrestrial planets ever created.

Q: What is meant by the "habitable zone"? A) the zone in which water can be a liquid around the center of the Galaxy B) the region around each star in which terrestrial planets could have liquid water on their surfaces C) the zone in which terrestrial-sized planets could form around each star D) the region in dense atmospheres like Jupiter's in which water droplets could form E) the regions near the poles of Mercury in which liquid water might exist

Q: If we are optimistic in our assumptions about the development of life and intelligence, then the number of technological civilizations currently in the galaxy should equal the A) average lifetime of a civilization. B) number of stars forming per year. C) average number of planets per star. D) number of stars in the galaxy's habitable zone. E) average number of planets that produce life.

Q: Why do we feel type O and B stars are poor candidates for extraterrestrial life? A) They do not have a habitable zone. B) They don't produce enough yellow light. C) Their lifetime is too short. D) They don't produce a planetary system. E) Their habitable zone lies too close to the star.

Q: Assuming the conditions ripe for life and intelligence abound in the Galaxy, what factor limits the number of galactic civilizations currently in existence? A) the lack of metals for technology B) the number of supernova explosions C) the expansion of the universe D) the average survival time of the civilizations E) the speed of technological development

Q: According to our definition, we have been a technological civilization for about A) 1000 years. B) 10,000 years. C) 100 years. D) 10 years. E) 500 years.

Q: Which type of molecules, vital to our life, were found to have survived a fiery descent to Earth on meteorites? A) amino acids B) DNA C) lipids D) sugars E) vitamins

Q: What encouragement for life on Mars came from the Global Surveyor? A) spectral evidence for chlorophyll B) Hellas has a lake of salt water in its bottom. C) The ice of the south polar cap is water, not dry ice. D) strong photographic evidence for flowing and standing water on Mars in the past E) The face on Mars is an artificial construct.

Q: Which jovian moon has gotten the most attention from exobiologists? A) Io B) Ariel C) Triton D) Miranda E) Europa

Q: Large molecules found in meteorites and interstellar clouds are evidence that A) life is abundant in the galaxy. B) life has definitely formed in other places than Earth. C) chemical evolution has taken place elsewhere in the universe. D) organic molecules are extremely rare. E) life originated on Mars before Earth.

Q: The Murchison meteorite contained A) living cells. B) DNA. C) 12 amino acids. D) bacteria. E) RNA.

Q: How long ago did multicellular life forms appear in the fossil record? A) 4.5 billion years ago B) 3.8 billion years ago C) one billion years ago D) 63 million years ago E) 30 million years ago

Q: Which of the following appears least important in the evolution of life here? A) the stable luminosity of the Sun for billions of years B) the magnetic field of the Earth C) the presence of water and carbon atoms D) an Earth-like atmosphere E) the correct distance from the Sun

Q: How long between the evolution of single versus multicellular organisms? A) 4.5 billion years B) 2.5 billion years C) one billion years D) 600 million years E) 63 million years

Q: The simplest life forms appeared on Earth when it was how old? A) five million years B) one billion years C) 2.5 billion years D) 3.5 billion years E) 4.5 billion years

Q: Organic molecules are A) living cells. B) carbon-based. C) silicon-based. D) found only on Earth. E) not found outside our solar system.

Q: What important molecules of life did Miller and Urey brew up? A) RNA B) fatty acids C) lean acids D) amino acids E) antacids

Q: Which of the following appears most favored by natural selection? A) intelligence B) opposable thumbs C) bipedal locomotion D) binocular vision E) live birth

Q: As an artificial radio source, the spinning Earth would have a period of about a day.

Q: The Allen Telescope Array is one of the many radio searches for extraterrestrial life.

Q: The probes sent out of our solar system were carefully designed to hide any trace of their origin.

Q: The water hole is a region around Sun-like stars where liquid water can exist on the surfaces of terrestrial planets.

Q: The water hole is a radio region with very low background noise.

Q: Thanks to the far-flung Voyager and Pioneers, knowledge of our presence has now spread out over 30 light years.