Life in the Universe (4th Edition)
4th Edition
ISBN: 9780134089089
Author: Jeffrey O. Bennett, Seth Shostak
Publisher: PEARSON
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Textbook Question
Chapter 13, Problem 13RQ
Describe the coral model of galactic colonization. Why do we conclude that civilizations could have colonized the galaxy by now even with technology not much more advanced than ours?
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Tutorial
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…
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
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In a globular cluster, astronomers (someday) discover a star with the same mass as our Sun, but consisting entirely of hydrogen and helium. Is this star a good place to point our SETI antennas and search for radio signals from an advanced civilization?
Group of answer choices
No, because such a star (and any planets around it) would not have the heavier elements (carbon, nitrogen, oxygen, etc.) that we believe are necessary to start life as we know it.
Yes, because globular clusters are among the closest star clusters to us, so that they would be easy to search for radio signals.
Yes, because we have already found radio signals from another civilization living near a star in a globular cluster.
No, because such a star would most likely not have a stable (main-sequence) stage that is long enough for a technological civilization to develop.
Yes, because such a star is probably old and a technological civilization will have had a long time to evolve and develop there.
Chapter 13 Solutions
Life in the Universe (4th Edition)
Ch. 13 - Prob. 1RQCh. 13 - How does the speed of light affect the possibility...Ch. 13 - Prob. 3RQCh. 13 - Prob. 4RQCh. 13 - What is the rocket equation used for? Based on the...Ch. 13 - Prob. 6RQCh. 13 - Discuss a few ways of reaching the stars (other...Ch. 13 - How would time dilation affect space travel at...Ch. 13 - Prob. 9RQCh. 13 - What is the Fermi paradox? What two seemingly...
Ch. 13 - Why does it seem that other civilizations, if they...Ch. 13 - What arc Von Neumann machines? How do they affect...Ch. 13 - Describe the coral model of galactic colonization....Ch. 13 - Briefly discuss possible motives for galactic...Ch. 13 - Summarize the three general categories of possible...Ch. 13 - Briefly discuss the profound implications of the...Ch. 13 - What known problems were solved when Einstein...Ch. 13 - Prob. 18RQCh. 13 - Besides the idea that you cannot reach the speed...Ch. 13 - Prob. 20RQCh. 13 - Prob. 21TYUCh. 13 - Prob. 22TYUCh. 13 - Each of the following describes some futuristic...Ch. 13 - Prob. 24TYUCh. 13 - Prob. 25TYUCh. 13 - Prob. 26TYUCh. 13 - Prob. 27TYUCh. 13 - Prob. 28TYUCh. 13 - Prob. 29TYUCh. 13 - Prob. 30TYUCh. 13 - Prob. 31TYUCh. 13 - The amount of energy that would be needed to...Ch. 13 - The rocket engines of our current spacecraft are...Ch. 13 - Suppose that a spaceship was launched in the year...Ch. 13 - Prob. 35TYUCh. 13 - Prob. 36TYUCh. 13 - Which of the following questions best represents...Ch. 13 - Prob. 38TYUCh. 13 - Which of the following is not relative in the...Ch. 13 - Prob. 40TYUCh. 13 - Prob. 41POSCh. 13 - Prob. 42POSCh. 13 - Prob. 44IFCh. 13 - What's Wrong with This Picture? Many science...Ch. 13 - Large Rockets. Suppose we built a rocket that...Ch. 13 - Prob. 47IFCh. 13 - Solution to the Fermi Paradox. Among the various...Ch. 13 - Prob. 50IFCh. 13 - Cruise Ship Energy. Suppose we have a spaceship...Ch. 13 - Prob. 52IFCh. 13 - The Multistage Rocket Equation. The rocket...Ch. 13 - Relativistic Time Dilation. Use the time dilation...Ch. 13 - Testing Relativity. A + meson produced at rest has...Ch. 13 - Prob. 57IFCh. 13 - Prob. 58IFCh. 13 - Prob. 59IFCh. 13 - Prob. 60IFCh. 13 - The Turning Point. Discuss the idea that the...
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- Suppose astronomers discover a radio message from a civilization whose planet orbits a star 35 lightyears away. Their message encourages us to send a radio answer, which we decide to do. Suppose our governing bodies take 2 years to decide whether and how to answer. When our answer arrives there, their governing bodies also take two of our years to frame an answer to us. How long after we get their first message can we hope to get their reply to ours? (A question for further thinking: Once communication gets going, should we continue to wait for a reply before we send the next message?)arrow_forwardThink of our Milky Way Galaxy as a flat 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 would the nearest such civilization be from us (on average)?arrow_forwardWhy are upper-main-sequence (high-luminosity) host stars unlikely sites for intelligent civilizations?arrow_forward
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