EBK THE COSMIC PERSPECTIVE
9th Edition
ISBN: 9780135161760
Author: Voit
Publisher: VST
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Chapter 24, Problem 54EAP
SETI Search. Suppose there are 10,000 civilizations broadcasting radio signals in the Milky Way Galaxy 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?
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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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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 24 Solutions
EBK THE COSMIC PERSPECTIVE
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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Need a deep-dive on the concept behind this application? Look no further. Learn more about this topic, physics and related others by exploring similar questions and additional content below.Similar questions
- asap pleasearrow_forwardSuppose 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?arrow_forwardSuppose there are 9000.0 civilizations broadcasting radio signals in the Milky Way Galaxy at the moment. On average, how many stars would have to be searched before a signal is heard? Assume that there are 8 × 1011 stars in the Galaxy and one civilization per star.arrow_forward
- What are the advantages to using radio waves for communication between civilizations that live around different stars? List as many as you can.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_forwardWhat is the difference between chemical evolution and biological evolution?arrow_forward
- Why are we limited to finding life on planets orbiting other stars to situations where the biosphere has created planet-scale changes?arrow_forwardWhich of the following seems least reasonable regarding life on Earth? Group of answer choices There is much scientific evidence suggesting that all creatures living on Earth today appear to have evolved from a common ancestor. Louis Pasteur discredited the concept of spontaneous generation by demonstrating that even bacteria and other microorganisms arise from parents resembling themselves. There is ample physical evidence that the earliest life forms on Earth were multicellular creatures, perhaps resembling some of our primitive fish. When the earth formed some 4.6 billion years ago, it was a lifeless, inhospitable place. Before the mid-17th century, most people believed that God had created humankind and other higher organisms and that insects, frogs, and other small creatures could arise spontaneously in mud or decaying matter About billion years into its development, the Earth it was teeming with organisms resembling blue-green algae.arrow_forwardWhich 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.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_forwardWhich of the following is not considered a likely solution to the question of why we are not currently aware of an extraterrestrial civilization? Group of answer choices There is no civilization because civilizations are not common. The civilization is probably undetectable to us because it makes use of technologies that do not obey the known laws of physics. There is no galactic civilization because civilizations do not leave their home worlds. There is no civilization because most civilizations destroy themselves before achieving interstellar travel. The civilization is deliberately avoiding contact with us.arrow_forwardThe Drake equation tells us that the number of technological civilizations in our Galaxy at this time is: Group of answer choices About 100,000. About 14 billion. About 200 billion. It cannot predict this number at this time. About 6,000. About 1 million. Somewhere in the range 1-10.arrow_forward
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