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 7, Problem 35POS
Bizarre Forms of Life. Discuss some forms of life that have appeared in science fiction and that fall outside the general types of life that we’ve discussed in this chapter. Which forms seem most plausible, and why? Overall, do you think the definition of life we’ve used in this chapter is too constraining? Defend your opinion.
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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…
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.
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.
Chapter 7 Solutions
Life in the Universe (4th Edition)
Ch. 7 - Why do we expect the elements of life to be widely...Ch. 7 - How does the strength of sunlight vary with...Ch. 7 - Under what conditions does it seem reasonable to...Ch. 7 - Why is a liquid medium important for life? Why...Ch. 7 - Summarize the three major environmental...Ch. 7 - Why do the Moon and Mercury seem unlikely to be...Ch. 7 - Why is Venus so much hotter than Earth? How does...Ch. 7 - Why does Mars seem such a good candidate for life?Ch. 7 - Briefly discuss the possibility of life on Jupiter...Ch. 7 - With regard to habitability, how do the cases of...
Ch. 7 - What characteristics make some of the large moons...Ch. 7 - Briefly describe the prospects for habitability of...Ch. 7 - Describe and distinguish between space missions...Ch. 7 - For a few of the most important past, present, or...Ch. 7 - On the smallest moon of Uranus, my team discovered...Ch. 7 - New spacecraft images show lakes of liquid water...Ch. 7 - We are pumping water for our new Moon colony from...Ch. 7 - I was part of the first group of people to land on...Ch. 7 - We sent a robotic airplane into the atmosphere of...Ch. 7 - On a moon of Neptune, we discovered photosynthetic...Ch. 7 - We deposited bacteria (from Earth) that get energy...Ch. 7 - The drilled sample showed no signs of life on...Ch. 7 - We cut holes in the frozen surface of a methane...Ch. 7 - The drilled sample from Mars brought up rock that...Ch. 7 - Oxygen and carbon are (a) rarer than almost all...Ch. 7 - On an asteroid that is twice as far as Earth from...Ch. 7 - Compared to liquid water, liquid methane is (a)...Ch. 7 - Frozen lakes often have liquid water beneath their...Ch. 7 - Temperatures on Mercury are (a) always very hot;...Ch. 7 - On Venus, liquid water (a) does not exist...Ch. 7 - The reason Venus is so much hotter than Earth is...Ch. 7 - Life is probably not possible in Jupiters...Ch. 7 - Which of the following are you most likely to find...Ch. 7 - The Cassini spacecraft (a) flew past Pluto; (b)...Ch. 7 - Bizarre Forms of Life. Discuss some forms of life...Ch. 7 - Making a Living. Consider various methods by which...Ch. 7 - Solar System Tour. Based on the brief tour in this...Ch. 7 - Galileo Spacecraft. In 2003, scientists...Ch. 7 - Greenhouse Effect. The text (in Chapter 4) makes...Ch. 7 - Prob. 41IFCh. 7 - Understanding Newtons Version of Keplers Third Law...Ch. 7 - Understanding Newtons Version of Keplers Third Law...Ch. 7 - Earth Mass. The Moon orbits Earth in an average...Ch. 7 - Jupiter Mass. Jupiters moon Io orbits Jupiter...Ch. 7 - Pluto/Charon Mass. Plutos moon Charon orbits Pluto...Ch. 7 - Mission to Pluto. The New Horizons spacecraft took...Ch. 7 - Planetary Missions. Visit the web page for one of...
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- asap pleasearrow_forwardWhy are we limited to finding life on planets orbiting other stars to situations where the biosphere has created planet-scale changes?arrow_forwardIf 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_forward
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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?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_forwardPlease help me with this question. A=.2arrow_forward
- Imagine that we discovered a new planet that has the potential to support life. This planet has plenty of water on its surface and carbon dioxide in its atmosphere, and a nice, comfortable temperature similar to Earth. The only difference is that this planet orbits a star that produces green light only. If we took some plants from Earth and planted them on this new planet, would our plants be able to grow? Explain your answer.arrow_forwardIn 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_forwardWhat is the best way to determine if a exoplanet has life inside it? Group of answer choices Detect the star the exoplanet is orbiting and compare it to the Sun. Detect the exoplanet and determine if it is in the habitable zone of the star. Detect the exoplanet and study the atmosphere of the exoplanet. Detect the exoplanet and determine its age to see if it is similar to the age of the Earth.arrow_forward
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