Universe: Stars And Galaxies
6th Edition
ISBN: 9781319115098
Author: Roger Freedman, Robert Geller, William J. Kaufmann
Publisher: W. H. Freeman
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Chapter 27, Problem 20Q
To determine
(a)
The average lifetime of a technological civilization.
To determine
(b)
The consequence if there are
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The Drake equation In 1961 astronomer Frank Drakedeveloped an equation to try to estimate the number ofextraterrestrial civilizations in our galaxy that might be
able to communicate with us via radio transmissions. Nowlargely accepted by the scientific community, the Drakeequation has helped spur efforts by radio astronomers tosearch for extraterrestrial intelligence. Here is the equation:
NC = N # fp # ne # fl# fi# fc # fLOK, it looks a little messy, but here’s what it means:So, how many ETs are out there? That depends; valueschosen for the many factors in the equation depend onever-evolving scientific knowledge and one’s personalguesses. But now, some questions.a) What quantity is calculated by the first product, N # fp?b) What quantity is calculated by the product, N # fp # ne # fl?c) What probability is calculated by the product fl# fi?d) Which of the factors in the formula are conditionalprobabilities? Restate each in a way that makes thecondition clear.
The Drake equation attempts to calculate the number of communicative civilizations in the galaxy. What does the factor F S represent and why is it considered to be the most uncertain of all the factors in this equation?
The Drake equation tells us that the number of technological civilizations in our Galaxy at this time is:
Group of answer choices
About 100,000.
About 14 billion.
About 200 billion.
It cannot predict this number at this time.
About 6,000.
About 1 million.
Somewhere in the range 1-10.
Chapter 27 Solutions
Universe: Stars And Galaxies
Ch. 27 - Prob. 1QCh. 27 - Prob. 2QCh. 27 - Prob. 3QCh. 27 - Prob. 4QCh. 27 - Prob. 5QCh. 27 - Prob. 6QCh. 27 - Prob. 7QCh. 27 - Prob. 8QCh. 27 - Prob. 9QCh. 27 - Prob. 10Q
Ch. 27 - Prob. 11QCh. 27 - Prob. 12QCh. 27 - Prob. 13QCh. 27 - Prob. 14QCh. 27 - Prob. 15QCh. 27 - Prob. 16QCh. 27 - Prob. 17QCh. 27 - Prob. 18QCh. 27 - Prob. 19QCh. 27 - Prob. 20QCh. 27 - Prob. 21QCh. 27 - Prob. 22QCh. 27 - Prob. 23QCh. 27 - Prob. 24QCh. 27 - Prob. 25QCh. 27 - Prob. 26QCh. 27 - Prob. 27QCh. 27 - Prob. 28QCh. 27 - Prob. 29QCh. 27 - Prob. 30QCh. 27 - Prob. 31QCh. 27 - Prob. 32QCh. 27 - Prob. 33Q
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- Suppose there are 9000.0 civilizations broadcasting radio signals in the Milky Way Galaxy at the moment. On average, how many stars would have to be searched before a signal is heard? Assume that there are 8 × 1011 stars in the Galaxy and one civilization per star.arrow_forwardTutorial A radio broadcast left Earth in 1923. How far in light years has it traveled? If there is, on average, 1 star system per 400 cubic light years, how many star systems has this broadcast reached? Assume that the fraction of these star systems that have planets is 0.50 and that, in a given planetary system, the average number of planets that have orbited in the habitable zone for 4 billion years is 0.40. How many possible planets with life could have heard this signal? Part 1 of 3 To figure out how many light years a signal has traveled we need to know how long since the signal left Earth. If the signal left in 1923, distance in light years = time since broadcast left Earth. d = tnow - broadcast d = 97 97 light years Part 2 of 3 Since the radio signal travels in all directions, it expanded as a sphere with a radius equal to the distance it has traveled so far. To determine the number of star systems this signal has reached, we need to determine the volume of that sphere. V, = Vb…arrow_forwardTutorial A radio broadcast left Earth in 1925. How far in light years has it traveled? If there is, on average, 1 star system per 400 cubic light years, how many star systems has this broadcast reached? Assume that the fraction of these star systems that have planets is 0.30 and that, in a given planetary system, the average number of planets that have orbited in the habitable zone for 4 billion years is 0.85. How many possible planets with life could have heard this signal? Part 1 of 3 To figure out how many light years a signal has traveled we need to know how long since the signal left Earth. If the signal left in 1925, distance in light years = time since broadcast left Earth. d = tnow - tbroadcast d = light years Submit Skip (you cannot come back)arrow_forward
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