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 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.
A radio broadcast left Earth in 1911. 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 0.20. How many possible planets with life could have heard this signal?
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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- What are the advantages to using radio waves for communication between civilizations that live around different stars? List as many as you can.arrow_forwardSuppose 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_forward
- Tutorial 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_forwardI don’t understand how that it was estimated as length of a mouse is 4 to 15 cm in length. Is that a guess and the answer just varies?also where did 10^-1 come fromarrow_forwardSuppose there are l0,000 civilizations broadcasting radio signals in the Milky Way GaIaxy right now. On average, how many stars would we have to search before we would expect to hear a signal? Assume there are 500 billion stars in the galaxy. How would the answer change if there were only 100 civilizations instead of 10,000?arrow_forward
- Most of the stars we can see with the unaided eye in our night sky are hundreds or even thousands of lightyears away from Earth. (The very closest ones are only a few dozen lightyears away, but most are much further.) The vast majority of stars in our galaxy are many tens of thousands of lightyears away. IF intelligent life existed on planets orbiting some of these stars – and that’s a huge IF! – comment on the likelihood and practicality of (a) visiting, (b) communicating with, or (c) verifying the existence of those life forms. Describe how you might go about approaching EACH of these three tasks, or if you think they are even possible. (One or two sentences for each part would be appropriate.)arrow_forwardThe evidence is overwhelming that the Grand Canyon was dug over a span of millions of years by the erosive power of the Colorado River and that river's tributary streams. Does this evidence support a catastrophic theory or an evolutionary theory?arrow_forwardIf you represent Earths history by a line that is 1 m long, how long a segment would represent the 400 million years since life first moved onto the land? How long a segment would represent the 4-millionyear history of humanoid life?arrow_forward
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