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 1, Problem 5RQ
What do we mean by a habitable world? Does a habitable world necessarily have life?
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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?
can you imagine life without electricity? what would you be our if there is no advancement in technology like motors and generators?
Chapter 1 Solutions
Life in the Universe (4th Edition)
Ch. 1 - Why are scientists interested in the possibility...Ch. 1 - People have long been interested in life beyond...Ch. 1 - Prob. 3RQCh. 1 - Prob. 4RQCh. 1 - What do we mean by a habitable world? Does a...Ch. 1 - What do we mean by the universality of physics and...Ch. 1 - Besides Earth, what worlds in our solar system...Ch. 1 - Prob. 8RQCh. 1 - Prob. 9RQCh. 1 - What do we mean by astrobiology? What are the...
Ch. 1 - An extrasolar planet is (a) a planet that is...Ch. 1 - A habitable planet is (a) a planet that has oceans...Ch. 1 - Prob. 13TYUCh. 1 - Prob. 14TYUCh. 1 - The correct order for the eight official planets...Ch. 1 - Today, the research known as SETI is conducted...Ch. 1 - Prob. 17TYUCh. 1 - Scientists today are interested in searching for...Ch. 1 - Based on current evidence, the object in our solar...Ch. 1 - Prob. 20TYUCh. 1 - Universal Laws. Briefly discuss how the idea that...Ch. 1 - The Science of Astrobiology. The study of...Ch. 1 - Conducting the Search. Given the large number of...Ch. 1 - Funding for Astrobiology. Imagine that you are a...
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- In this chapter, we identify these characteristic properties of life: life extracts energy from its environment, and has a means of encoding and replicating information in order to make faithful copies of itself. Does this definition fully capture what we think of as “life”? How might our definition be biased by our terrestrial environment?arrow_forwardWhat are the three requirements that scientists believe an environment needs to supply life with in order to be considered habitable?arrow_forwardWhy are we limited to finding life on planets orbiting other stars to situations where the biosphere has created planet-scale changes?arrow_forward
- What is a habitable zone?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_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_forward
- 200 years has passed and now it is year 2220. The Earth is out of basic resourcesas they have been drastically drained in the past 200 years. The president of theUnited World Council (UWC) has approved you and your crew’s Mission toMars. You will pilot the most advanced spaceship the world has ever known, theExcelsior! It will carry equipment that will help to transform Mars so as toresemble the Earth, especially so that it can support human life.Before the mission can launch a few items need to be figured out. What is thecapacity of the fuel tank? How long should the fuel burn to achieve escapevelocity (otherwise the Excelsior will be stuck in the Earth’s gravitational pull)?How long will it take the Excelsior to arrive at Mars?1. The ground crew is filling the fuel tanks. You know tharrow_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_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
- Which 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 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 most promising places to look for other habitable planets would be orbiting stars similar to our Sun, or even dimmer than our Sun in our own solar system in other galaxies orbitin bright, giant stars like Betelgeusearrow_forward
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