Life in the Universe (4th Edition)
4th Edition
ISBN: 9780134089089
Author: Jeffrey O. Bennett, Seth Shostak
Publisher: PEARSON
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Chapter 6, Problem 53IF
Deep in Bacteria. In Cosmic Calculations 6.1, we calculated that the volume of bacteria after 120 doublings would be 1.3 × 1015 m3. The total surface area of Earth is about 5.1 × 1014 m2. Use these facts to calculate the average depth of the bacteria at that time, if we spread them evenly over Earth’s entire surface.
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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?
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 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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