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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Chapter 17, Problem 42EAP
To determine
To discuss: The stars could have planet that harbor and advanced civilization like earth.
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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
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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…
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 17 Solutions
The Cosmic Perspective (9th Edition)
Ch. 17 - Prob. 1VSCCh. 17 - Prob. 2VSCCh. 17 - Prob. 3VSCCh. 17 - Prob. 4VSCCh. 17 - Prob. 1EAPCh. 17 - Prob. 2EAPCh. 17 - Prob. 3EAPCh. 17 - Prob. 4EAPCh. 17 - Prob. 5EAPCh. 17 - Prob. 6EAP
Ch. 17 - Prob. 7EAPCh. 17 - Prob. 8EAPCh. 17 - What will happen to Earth as the Sun changes in...Ch. 17 - Prob. 10EAPCh. 17 - Prob. 11EAPCh. 17 - Prob. 12EAPCh. 17 - Why cant iron be fused to release energy?Ch. 17 - Prob. 14EAPCh. 17 - Prob. 15EAPCh. 17 - Prob. 16EAPCh. 17 - Does It Make Sense? Decide whether the statement...Ch. 17 - Does It Make Sense? Decide whether the statement...Ch. 17 - Prob. 19EAPCh. 17 - Prob. 20EAPCh. 17 - Prob. 21EAPCh. 17 - Prob. 22EAPCh. 17 - Prob. 23EAPCh. 17 - Prob. 24EAPCh. 17 - Prob. 25EAPCh. 17 - Prob. 26EAPCh. 17 - Prob. 27EAPCh. 17 - Prob. 28EAPCh. 17 - Prob. 29EAPCh. 17 - Prob. 30EAPCh. 17 - Prob. 31EAPCh. 17 - Prob. 32EAPCh. 17 - Prob. 33EAPCh. 17 - Prob. 34EAPCh. 17 - Prob. 35EAPCh. 17 - Prob. 36EAPCh. 17 - Prob. 37EAPCh. 17 - Prob. 39EAPCh. 17 - Prob. 40EAPCh. 17 - Prob. 41EAPCh. 17 - Prob. 42EAPCh. 17 - Prob. 43EAPCh. 17 - Prob. 44EAPCh. 17 - Prob. 47EAPCh. 17 - Prob. 48EAPCh. 17 - Prob. 49EAPCh. 17 - Prob. 50EAPCh. 17 - Prob. 51EAPCh. 17 - Prob. 52EAPCh. 17 - Prob. 53EAPCh. 17 - Prob. 54EAPCh. 17 - The Speed of Supernova Debris. In the year 2001,...
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