Horizons: Exploring the Universe (MindTap Course List)
14th Edition
ISBN: 9781305960961
Author: Michael A. Seeds, Dana Backman
Publisher: Cengage Learning
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Chapter 20, Problem 3DQ
To determine
To Explain:
About the outcome of the search of extraterrestrial intelligence.
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Check out a sample textbook solutionStudents have asked these similar questions
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?
Which 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.
Which 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.
Chapter 20 Solutions
Horizons: Exploring the Universe (MindTap Course List)
Ch. 20 - If life is based on information, what is that...Ch. 20 - How does the DNA molecule produce a copy of...Ch. 20 - What would happen to a life-form if the genetic...Ch. 20 - What would happen to a life-form if the...Ch. 20 - Give an example of natural selection acting on new...Ch. 20 - Prob. 6RQCh. 20 - Why do scientists generality think that liquid...Ch. 20 - Prob. 8RQCh. 20 - What is the significance of the Miller-Urey...Ch. 20 - Prob. 10RQ
Ch. 20 - Prob. 11RQCh. 20 - Why is it reasonable to suspect that travel...Ch. 20 - How does the stability of technological...Ch. 20 - Prob. 14RQCh. 20 - Prob. 15RQCh. 20 - Prob. 16RQCh. 20 - How Do We know? Why are scientists confident that...Ch. 20 - Do you expect that hypothetical alien recipients...Ch. 20 - Prob. 2DQCh. 20 - Prob. 3DQCh. 20 - A single human cell encloses about 1.5 m of DNA,...Ch. 20 - If you represent Earth’s history by a line 1 m...Ch. 20 - Prob. 3PCh. 20 - If a star must remain on the main sequence for at...Ch. 20 - Prob. 5PCh. 20 - Prob. 6PCh. 20 - Prob. 7PCh. 20 - Calculate the numb of communicative civilizations...Ch. 20 - The star cluster shown in the image in Figure UN...Ch. 20 - Prob. 2LTL
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- Why are scientists confident Earth has never been visited by aliens?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_forwardWhy is life unlikely to be found on the surface of Mars today?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_forwardSuppose 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_forwardTutorial 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…arrow_forward
- 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 Skip (you cannot come back)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_forwardWhen Mars is 90 million km (9 x 10^10 m) from Earth, a) How long would it take for a radio wave from a video camera mounted on the back of a Mars Rover to tell ground control on earth that the Rover is about to go over a cliff? b) How long would it take for a radio signal from Earth to reach the Rover saying "STOP". c) Why do our Mars Rovers have to be "intelligent" enough to figure out how to deal with obstacles themselves?arrow_forward
- 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_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_forwardWhat kind of evidence do you think would convince astronomers that an extraterrestrial spacecraft has landed on Earth?arrow_forward
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