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Chapter 24: Problem 28

Some scientists believe that humans may be the only advanced life in the galaxy today. If this is indeed the case, which factors in the Drake equation must be extremely small?

Short Answer

Expert verified
fl, fi, and fc must be extremely small.

Step by step solution

01

Understand the Drake Equation

The Drake Equation is used to estimate the number of active, communicative extraterrestrial civilizations in the Milky Way galaxy. The formula is: N = R* x fp x ne x fl x fi x fc x L where N represents the number of civilizations.
02

Identify the Factors

Each term in the Drake Equation represents a different factor: R* = average rate of star formation fp = fraction of those stars that have planetary systems ne = average number of planets that could potentially support life per star that has planets fl = fraction of planets that could support life where life actually appears fi = fraction of planets with life where intelligent life evolves fc = fraction of civilizations that develop technology to communicate across space L = length of time civilizations can communicate.
03

Determine Which Factors Must Be Small

If humans are the only advanced life in the galaxy, it implies that one or more of these factors must be extremely small. These factors are likely to be: fl (fraction of planets where life actually appears), fi (fraction of planets with life where intelligent life evolves), and fc (fraction of civilizations that develop technology to communicate). Any of these being small would significantly reduce the number of civilizations, including just ours.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Star Formation Rate
Understanding the Drake Equation begins with the star formation rate, denoted as \(R*\). This refers to the average rate at which new stars are born in the Milky Way galaxy.
Stars are essential as they provide the energy and conditions necessary for planets to form and potentially harbor life.
A high star formation rate increases the chances of planets forming. Conversely, a low star formation rate means fewer stars, and therefore, fewer opportunities for planetary systems to develop.
In the context of the Drake Equation, if \(R*\) were extremely low, it would drastically reduce the potential number of civilizations.
Planetary Systems
The next term, \(fp\), refers to the fraction of stars that have planetary systems.
Recent discoveries by astronomers show that many stars host planets, suggesting that \(fp\) might be relatively high.
However, if \(fp\) were small, it would mean that very few stars have planets, reducing the likelihood of conditions suitable for life.
  • The discovery of exoplanets has been pivotal in understanding \(fp\).
  • Planets can greatly vary in size, composition, and orbit.
The initial presence of planetary systems is crucial for any further steps in the development of life.
Intelligent Life Evolution
One of the most critical aspects of the Drake Equation is \(fi\), which indicates the fraction of planets with life where intelligent life evolves.
Even if life appears on a planet (\(fl\)), the development of intelligent life is not guaranteed.
  • Natural selection, environmental factors, and random events play roles in the evolution of intelligence.
  • Some believe that the emergence of intelligence may involve rare events or specific conditions.
A very small \(fi\) would significantly limit the number of civilizations that can develop advanced societies.
Extraterrestrial Life
Extraterrestrial life refers to any form of life that exists outside Earth. In the Drake Equation, this relates to \(fl\), the fraction of planets that could support life where life actually appears.
There are several factors affecting \(fl\):
  • The planet's location and environment.
  • Availability of water and essential chemicals.
  • Energy sources conducive to sustaining life.
If \(fl\) is very low, even with numerous planets, life might not develop, making human beings potentially unique.
Communication Technology Development
Finally, \(fc\) represents the fraction of civilizations that develop technology to communicate across space.
Even if intelligent life exists, the development and use of communication technology is not certain.
This could include radio signals, which humans have used to try to connect with possible extraterrestrial civilizations.
  • Advanced technology is needed to send and receive interstellar messages.
  • Constraints might include lifespan of civilizations or technical setbacks.
If \(fc\) is low, many civilizations might exist without being detected, as their technological advancements do not reach the level of interstellar communication.

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Most popular questions from this chapter

a. Go to the website for the Kepler space telescope (http://kepler.nasa.gov): click on "News" and "Planetfinding News." What is a recent discovery of a planet in the habitable zone? What is a recent discovery of a planet with an interesting atmosphere? b. Go to the website for the European Space Agency (ESA) Gaia mission (http://sci.esa.int/gaia). What are the science objectives of this mission? Click on "Exoplanets" on the left. How will Gaia identify new planets? What properties of the planet will it be able to measure? What are some recent results?

A mutation is a. always a deadly change to DNA. b. always a beneficial change to DNA. c. a change to DNA that is sometimes beneficial and sometimes not. d. a change to DNA that is not inheritable.

The study of life and the study of astronomy are connected because (select all that apply) a. life may be commonplace in the universe. b. studying other planets may help explain why there is life on Earth. c. explorations of extreme environments on Earth suggest where to look for life elsewhere. d. life is a structure that evolved through physical processes, and life on Earth may not be unique. e. life elsewhere is most likely to be found by astronomers.

During the Cambrian explosion a. the dinosaurs were killed. b. all the carbon that is now here on Earth was produced. c. biodiversity increased significantly. d. a lot of carbon dioxide was released into the atmosphere.

If the chance that a given molecule will mutate is one in \(100,000,\) how many generations are needed before, on average, at least one mutation has occurred?
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