Life in the Universe (4th Edition)
4th Edition
ISBN: 9780134089089
Author: Jeffrey O. Bennett, Seth Shostak
Publisher: PEARSON
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Chapter 1, Problem 25IF
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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…
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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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?
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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- 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_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_forwardwhy do scientists generally think that liquid water is necessary for the origin of life? (astronomy)arrow_forward
- What are the three requirements that scientists believe an environment needs to supply life with in order to be considered habitable?arrow_forwardWhat evidence do scientists have that life on Earth began in the sea?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_forward
- Mars and Europa are two Solar System bodies that are considered possible habitats for Earth-like life. Why?arrow_forwardWhat is the difference between chemical evolution and biological evolution?arrow_forwardConsidering what you learned from the solar nebula theory, how likely do you think it is to find habitable planets in other solar systems? Visit NASA’s Kepler mission to learn more about this search, and write a ½ page summary on the mission.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_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_forwardKepler-444 is one of many stars with terrestrial planets that is over 10 billion a) What do you think the spectral type of Kepler-444 might be? b) How do stars of this spectral type end their lives? c) If evolution followed a similar course on a habitable pranet around a star similar to Kepler-444, it would be 5 billion years more advanced than we are. Let’s try to project our future and see what happens. In particular, suppose our civilization gets motivated enough to colonize another planet. Kepler indicates that most stars have potentially habitable (and colonizable) planets, so roughly how far away is the typical “nearest" planet? d) The New Horizons probe on its way to Pluto took 9 years to travel 30 AU. If we could send colony ships with the same average speed, roughly how long would it take to reach the typical nearest planet? уears old.arrow_forward
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