The Cosmic Perspective (9th Edition)
9th Edition
ISBN: 9780134874364
Author: Jeffrey O. Bennett, Megan O. Donahue, Nicholas Schneider, Mark Voit
Publisher: PEARSON
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Textbook Question
Chapter 24, Problem 53EAP
Nearest Civilization.
- Suppose there are 10,000 civilizations in the Milky Way Galaxy. If the civilizations were randomly distributed throughout the disk of the galaxy, about how far (on average) would it be to the nearest civilization? (Hint: Start by finding the area of the Milky Way’s disk, assuming that it is circular and 100,000 light-years in diameter. Then find the average area per civilization, and use the distance across this area to estimate the distance between civilizations.)
- Repeat part a, but this time assume that there are only 100 civilizations in the galaxy.
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Suppose 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?
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?
one hundred milli- (100 times one one-thousandth):
102 ✕ 10−3 = 10(2 + [−3]) = 10(2 − 3) = 10−1 = 0.1 (100 ÷ 1,000 = 0.1)
one hundred micro- (100 times one one-millionth):
102 ✕ 10−6 = 10(2 + [−6]) = 10(2 − 6) = 10−4
How do we write one hundred nano- (100 times one-billionth)?
102 ✕ 10−9 = 10
We write ten micrometers as follows.
10 ✕ 10−6 m = 10−5 m
How do we write ten nanoseconds?
10 ✕ 10−9 s = 10 s
Chapter 24 Solutions
The Cosmic Perspective (9th Edition)
Ch. 24 - Prob. 1VSCCh. 24 - Prob. 2VSCCh. 24 - Prob. 3VSCCh. 24 - Prob. 4VSCCh. 24 - Prob. 5VSCCh. 24 - Prob. 6VSCCh. 24 - Prob. 1EAPCh. 24 - Prob. 2EAPCh. 24 - Prob. 3EAPCh. 24 - Prob. 4EAP
Ch. 24 - How are laboratory experiments helping us study...Ch. 24 - Prob. 6EAPCh. 24 - Prob. 7EAPCh. 24 - Prob. 8EAPCh. 24 - Prob. 9EAPCh. 24 - Prob. 10EAPCh. 24 - Prob. 11EAPCh. 24 - Prob. 12EAPCh. 24 - Prob. 13EAPCh. 24 - Prob. 14EAPCh. 24 - Prob. 15EAPCh. 24 - Prob. 16EAPCh. 24 - Prob. 17EAPCh. 24 - For each of the following futuristic scenarios,...Ch. 24 - Prob. 19EAPCh. 24 - Prob. 20EAPCh. 24 - Prob. 21EAPCh. 24 - Prob. 22EAPCh. 24 - Prob. 23EAPCh. 24 - Prob. 24EAPCh. 24 - Prob. 25EAPCh. 24 - Prob. 26EAPCh. 24 - Choose the best answer to each of the following....Ch. 24 - Choose the best answer to each of the following....Ch. 24 - Choose the best answer to each of the following....Ch. 24 - Choose the best answer to each of the following....Ch. 24 - Choose the best answer to each of the following....Ch. 24 - Prob. 32EAPCh. 24 - Choose the best answer to each of the following....Ch. 24 - Prob. 34EAPCh. 24 - Choose the best answer to each of the following....Ch. 24 - Prob. 36EAPCh. 24 - The Turning Point. The end of this chapter...Ch. 24 - Prob. 39EAPCh. 24 - Prob. 43EAPCh. 24 - Prob. 45EAPCh. 24 - Prob. 46EAPCh. 24 - Prob. 47EAPCh. 24 - Prob. 48EAPCh. 24 - Prob. 49EAPCh. 24 - Prob. 50EAPCh. 24 - What’s Wrong with This Picture? Many science...Ch. 24 - Nearest Civilization. Suppose there are 10,000...Ch. 24 - SETI Search. Suppose there are 10,000...Ch. 24 - SETI Signal. Consider a civilization broadcasting...Ch. 24 - Prob. 56EAPCh. 24 - Prob. 57EAP
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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_forwardWould a human have been possible during the first generation of stars that formed right after the Big Bang? Why or why not?arrow_forwardWhat are the advantages to using radio waves for communication between civilizations that live around different stars? List as many as you can.arrow_forward
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