The Cosmic Perspective Fundamentals (2nd Edition)
2nd Edition
ISBN: 9780133889567
Author: Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider, Mark Voit
Publisher: PEARSON
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Textbook Question
Chapter 15, Problem 9QQ
Choose the best answer to each of the following Explain your reasoning.
In the Drake equation, what would flife =1/2 mean? (a) Half the stars in the Milky Way Galaxy have a planet with life. (b) Half of all life forms in the universe are intelligent. Half of the habitable worlds in the gal axy have life.
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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…
Think of our Milky Way Galaxy as a flat circular disk of diameter 100,000 light-years. Suppose we are one of 1000 civilizations, randomly distributed through the disk, interested in communicating via radio waves. How far away in light years would the nearest such civilization be from us on average? Show your working. (Hint: Begin by calculating the area of the disk. Find the area of one of a 1,000 squares. Consider the separation of the centres of two adjacent squares.)
Which of the following is least reasonable regarding the difficulty in contacting extraterrestrial life using space flight and radio communication.
Group of answer choices
Space flight to the nearest star would take thousands of years with current technology.
Even if another intelligent civilization is within a few hundred light-years of us, conversations would be very slow with a turnaround time of decades or even centuries.
The spacecraft that NASA sent to Proxima Centauri a few years ago should be approaching its target within a decade or two, depending on solar wind conditions.
Earth has been broadcasting at radio wavelengths since the 1930's, so any civilization within a radius of about 100 light-years or so could have received the broadcast by now.
Without some major breakthrough, interstellar space flight is totally impractical.
Chapter 15 Solutions
The Cosmic Perspective Fundamentals (2nd Edition)
Ch. 15 - Choose the best answer to etch of the following....Ch. 15 - Choose the best answer to etch of the following ....Ch. 15 - Choose the best answer to each of the following...Ch. 15 - Choose the best answer to each of the following...Ch. 15 - Choose the best answer to each of the following...Ch. 15 - Choose the best answer to each of the following...Ch. 15 - Choose the best answer to each of the following...Ch. 15 - Choose the best answer to each of the following...Ch. 15 - Choose the best answer to each of the following...Ch. 15 - Choose the best answer to each of the following...
Ch. 15 - Choose the best answer to each of the following...Ch. 15 - Choose the best answer to etch of the following....Ch. 15 - Explain all answers clearly, with complete...Ch. 15 - Explain all answers clearly, with complete...Ch. 15 - Explain all answers clearly, with complete...Ch. 15 - Explain all answers clearly, with complete...Ch. 15 - Explain all answers clearly, with complete...Ch. 15 - Prob. 18SEQCh. 15 - Explain all answers clearly, with complete...Ch. 15 - Prob. 20SEQCh. 15 - Explain all answers clearly, with complete...Ch. 15 - Explain all answers clearly, with complete...
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