Life in the Universe (4th Edition)
4th Edition
ISBN: 9780134089089
Author: Jeffrey O. Bennett, Seth Shostak
Publisher: PEARSON
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Textbook Question
Chapter 6, Problem 50IF
Impact Movie Review. Watch one of the Hollywood movies concerning the threat of an impact to our civilization, such as Deep Impact or Armageddon. Based on what you have learned in this chapter, write a one- to two-page critical review in which you include discussion of whether the impact scenario is realistic.
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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.
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…
Briefly summarize the evidence linking human activity to global warming.
What are its potential consequences?
Chapter 6 Solutions
Life in the Universe (4th Edition)
Ch. 6 - What are the three lines of fossil evidence that...Ch. 6 - How do studies of DNA sequences allow us to...Ch. 6 - Based on current evidence, what locations on Earth...Ch. 6 - What was the MillerUrey experiment, and how did it...Ch. 6 - What do we mean by an RNA world, and why do...Ch. 6 - Briefly summarize current ideas about the sequence...Ch. 6 - Briefly discuss the possibility that life migrated...Ch. 6 - Why do we think that evolution would have...Ch. 6 - Briefly discuss the early evolution of life, from...Ch. 6 - How do we think that eukaryotes evolved? What time...
Ch. 6 - What was the Cambrian explosion? Briefly discuss...Ch. 6 - How and when did life colonize land? Why did it...Ch. 6 - How do we know that the early Earth could not have...Ch. 6 - Summarize the history of the oxygen buildup as it...Ch. 6 - What was the KT impact, and how is it thought to...Ch. 6 - Briefly discuss the evidence for other mass...Ch. 6 - Discuss the threat that future impacts may pose to...Ch. 6 - Describe several adaptations that evolved so...Ch. 6 - When did hominids arise, and when did modern...Ch. 6 - Briefly describe and clarify a few common...Ch. 6 - Prob. 21RQCh. 6 - Briefly describe two main approaches to creating...Ch. 6 - We discover evidence of life, in the form of a...Ch. 6 - We discover an intact fossil of a eukaryotic cell,...Ch. 6 - We discover a preserved, 3.5-billion-year-old...Ch. 6 - We discover clear evidence that life arose on a...Ch. 6 - We discover a fossil of a large dinosaur that...Ch. 6 - We discover that, contrary to present belief,...Ch. 6 - We discover a crater from the impact of a...Ch. 6 - We discover an asteroid about 300 meters across...Ch. 6 - We find fossil remains of an early primate that...Ch. 6 - The first life created in the laboratory has an...Ch. 6 - The origin of life on Earth most likely occurred...Ch. 6 - The earliest living organisms probably were (a)...Ch. 6 - Prob. 35TYUCh. 6 - RNA world refers to (a) the possibility that life...Ch. 6 - Early life arose in an oxygen-free environment,...Ch. 6 - The oxygen in Earths atmosphere was originally...Ch. 6 - The Cambrian explosion refers to (a) a dramatic...Ch. 6 - Prob. 40TYUCh. 6 - The hypothesis that an impact killed the dinosaurs...Ch. 6 - According to the fossil evidence, modern humans...Ch. 6 - Origin of Life Studies. We cannot go back in time...Ch. 6 - A Brief History of Life on Earth. Take all the...Ch. 6 - Geology and Life. In Chapter 4, we discussed the...Ch. 6 - Prob. 48IFCh. 6 - Prob. 49IFCh. 6 - Impact Movie Review. Watch one of the Hollywood...Ch. 6 - Artificial Life Review. Numerous science fiction...Ch. 6 - Bacterial Evolution. Suppose that a mutation...Ch. 6 - Deep in Bacteria. In Cosmic Calculations 6.1, we...Ch. 6 - Prob. 54IFCh. 6 - Human Population Growth. During the twentieth...Ch. 6 - Impact Energy. Consider a comet about 2 kilometers...Ch. 6 - The Missing Link. As we discussed in this chapter,...Ch. 6 - Evolution by Choice. Consider the technology we...
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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 Submit Skip (you cannot come back)arrow_forwardWhich of the following is least reasonable regarding the concept of a habitable zone? Group of answer choices M-type stars have wider habitable zones than G-type stars. It is a region around a star where liquid water could be found on a planet's surface. The habitable zone of a less massive star would be closer to the star. In the course of millions of years, our habitable zone will slowly shift from Earth to Mars. The Galactic habitable zone cannot be too close to the Galactic center because the radiation from the bright stars and supernovae in the crowded inner part of the Galaxy would probably be detrimental to life.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_forward
- The principle cause of our intense interest in Mars in the decades before the dawn of the space age was that Answers: A. a few astronomers believed that they saw evidence of an intelligent civilization on Mars. B. Mars has seasons just like the Earth and therefore should be inhabitable by humans. C. Mars has an unusual surface color and global dust storms, creating strange weather patterns. D. Mars has unusual orbital properties making our understanding of its motion around the Sun very difficult.arrow_forwardCO2 and planetary warming: understanding Earth’s complicated atmosphere Mars has an atmospheric pressure of 6 mbar (compared with Earth atmosphere pressure of 1013 mbar), 96% of which is CO2. The average calculated temperature of Mars is -57°C, whereas the actual average temperature is -55°C so that the amount of warming due to CO2 is only 2°C. On the other hand, the average calculated temperature of Earth, with 0.4 mbar of CO2, is -19°C, whereas the actual average temperature is 15°C so that the amount of warming due to CO2 is 34°C, much greater than that on Mars, which has higher CO2 concentration. Explain how this is possible.arrow_forwardPlease help me with this question. A=.2arrow_forward
- 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?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_forwardImpact Energy. Consider a comet about 2 kilometers across with a mass of 4 × 1012 kg. Assume that it crashes into Earth at a speed of 30,000 meters per second (about 67,000 miles per hour). a. What is the total energy of the impact, in joules? (Hint: The kinetic energy formula tells us that the impact energy in joules will be 1 × m × v2, where 2 m is the comet’s mass in kilograms and v is its speed in meters per second.) b. A 1-megaton nuclear explosion releases about 4 × 1015 joules of energy. How many such nuclear bombs would it take to release as much energy as the comet impact? c. Based on your answers, comment on the degree of devastation the comet might cause.arrow_forward
- Why do we think we would be able to decode a message deliberately sent to us by an alien civilization? Group of answer choices The message will probably be in video format, allowing us to watch it even without knowing the alien language. We can assume that aliens will also have 10 fingers and 10 toes and therefore that they can send a message that relies on this fact. They undoubtedly have already received our television broadcasts and would therefore be likely to send the message in English. The aliens presumably know the same laws of mathematics and physics as we do and therefore could develop a simple code based on these laws.arrow_forwardasap pleasearrow_forwardDefine energy. List at least four historic sources of energy. How are they different from energy sources of today?arrow_forward
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