Life in the Universe (4th Edition)
4th Edition
ISBN: 9780134089089
Author: Jeffrey O. Bennett, Seth Shostak
Publisher: PEARSON
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Question
Chapter 1, Problem 14TYU
To determine
Growth of life on earth under current scientific understanding.
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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
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Chapter 1 Solutions
Life in the Universe (4th Edition)
Ch. 1 - Why are scientists interested in the possibility...Ch. 1 - People have long been interested in life beyond...Ch. 1 - Prob. 3RQCh. 1 - Prob. 4RQCh. 1 - What do we mean by a habitable world? Does a...Ch. 1 - What do we mean by the universality of physics and...Ch. 1 - Besides Earth, what worlds in our solar system...Ch. 1 - Prob. 8RQCh. 1 - Prob. 9RQCh. 1 - What do we mean by astrobiology? What are the...
Ch. 1 - An extrasolar planet is (a) a planet that is...Ch. 1 - A habitable planet is (a) a planet that has oceans...Ch. 1 - Prob. 13TYUCh. 1 - Prob. 14TYUCh. 1 - The correct order for the eight official planets...Ch. 1 - Today, the research known as SETI is conducted...Ch. 1 - Prob. 17TYUCh. 1 - Scientists today are interested in searching for...Ch. 1 - Based on current evidence, the object in our solar...Ch. 1 - Prob. 20TYUCh. 1 - Universal Laws. Briefly discuss how the idea that...Ch. 1 - The Science of Astrobiology. The study of...Ch. 1 - Conducting the Search. Given the large number of...Ch. 1 - Funding for Astrobiology. Imagine that you are a...
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- What is the difference between chemical evolution and biological evolution?arrow_forwardWhy are we limited to finding life on planets orbiting other stars to situations where the biosphere has created planet-scale changes?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
- If we do find life on Mars, what might be some ways to check whether it formed separately from Earth life, or whether exchanges of material between the two planets meant that the two forms of life have a common origin?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_forwardWhy is traveling between the stars (by creatures like us) difficult?arrow_forward
- Suppose a human generation is defined as the average time from birth to childbearing, which is about 20 years long. How many generations have passed in the 200,000 years during which anatomically modern humans have existed?arrow_forwardLife on Earth exists because of oxygen in Earths atmosphere. True false? Explain your answer.arrow_forwardWhat are the three requirements that scientists believe an environment needs to supply life with in order to be considered habitable?arrow_forward
- 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.arrow_forwardSuppose 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_forwardDoes all life on Earth require sunshine?arrow_forward
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