# Educator's Guide to Life Beyond Earth

Courtesy of the Jet Propulsion Laboratory

## Table of Contents

- Program History
- Signal Sources
- Detecting a Signal
- The Drake Equation
- Classroom Activities
- Contact Information

## Searching for Signs of Intelligence

Program History

In 1992, the Jet Propulsion Laboratory launched a survey of the sky using radio telescopes. The High Resolution Microwave Survey (HRMS) was designed to map the entire sky over the next several years. Part of the survey was the search for extraterrestrial intelligence, also known as SETI. This was not a wild-eyed search for the type of "aliens" that routinely turn up in supermarket tabloids. It was a careful examination of space around us. In fact, HRMS was designed to just "listen;" no signals were transmitted.

The HRMS was managed from the Ames Research Center in the San Francisco Bay area. JPL was a collaborating center. The JPL part of the project used radio telescopes of the Deep Space Network in California and Australia. Ames headed a search of selected targets with a huge 300-meter (1,000-foot) radio telescope in Puerto Rico. The extremely sensitive receivers began the search on Columbus Day, October 12, 1992.

However, Congress killed the program in October 1993 because of budgetary pressures. The SETI (Search for Extraterrestrial Intelligence) Institute, a privately-funded, non-profit organization that had been working on the HRMS, took over part of the effort aimed at discovering exterrestrial signals. The new effort is called Project Phoenix. NASA made its sophisticated equipment and facilities available to the SETI Institute's scientists and engineers.

Signal Sources

We already know that the sky is filled with radio energy. But Project Phoenix will also be listening for non-natural sources. Scientists have determined that the radio portion of the electromagnetic spectrum is one of the best places to search for signs of extra-terrestrial life. Radio waves, especially at some frequencies, appear much more powerful compared to the natural background of the sky. Visible light signals would have to be extremely strong at their source in order to be detected over even short distances. After all, stars are huge balls of glowing gas but none, except our own Sun, is even bright enough to cast a shadow.

Radio signals can travel through dust and gas clouds that would block out or scatter visible light. But this does not mean that our radio and television broadcasts would be detectable by an alien civilization or that we can expect to eavesdrop on their equivalent of soap operas or athletic shoe advertisements. Our radio, TV and radar transmitters send energy out in all directions. The signals get weaker as they get farther and farther from the transmitter.

The energy falls off by the square of the distance. If one receiver is twice the distance from a transmitter than another, the energy is not 1/2 but only 1/4! At three times the distance, it is 1/9, at four times it is 1/16 and so on. Very quickly, the signals get too weak to be casually detected. But, an alien intelligence that was interested in communicating would send out a focused beacon, perhaps like a lighthouse. The signal would be able to travel at the speed of light for many years. Of course, in order for their beacon to be detected, someone would have to be searching.

Searching is exactly what Project Phoenix will be doing. Using radio telescopes, the entire sky will be scanned. Unexpected or unusual signals will automatically be extracted from the data by computer. Scientists will then examine that data. If something intriguing turns up, a more detailed examination can be made.

Detecting a Signal

What will happen if signals suspected to be of extra-terrestrial origin are detected? Will the scientists keep it quiet? The project has given these questions careful consideration. The technical information will be given to independent observers so that they can confirm the findings. This will avoid embarrassment and confusion over misinterpretation. Then, the information will be released to the public.

Most likely, the finding will be that we have found something like a lighthouse beacon. The distance to the source is likely to be so great that conversations will be impossible. To communicate with a civilization on a planet 50 light years from Earth (right next door by astronomical standards) would take a century round trip. The signal we receive would already be 50 years old. Do the senders live longer than we? Did they send out a signal knowing that only their children and grandchildren might get a reply? Can we even hope to ever understand each other?

Project Phoenix will only cover a comparatively small portion of our galaxy. Our galaxy is only one of hundreds of billions of galaxies. Galaxies contain tens to hundreds of billions of stars. Project scientists might find signs of intelligent life, they might find interesting new natural objects, or they might find nothing at all. There might be life elsewhere in the Universe, or we might be completely alone. We will never know unless we take a look. It is a search for a golden needle in a cosmic haystack.

Is Anybody Out There?
And What if the Answer is "Yes"...?

There is no assurance that Project Phoenix will find evidence of extraterrestrial intelligence, but the search itself is certainly thought provoking. The SETI Institute is developing educational materials for elementary students.

The Drake Equation

One important aspect of the search is that it encompasses a very wide range of subjects and can be taught across the curriculum. A broad view of the topic can be found in the cornerstone of SETI, the "Drake Equation." Developed by astronomer Dr. Frank Drake in 1961, it is a way of organizing information to try to estimate the number of civilizations that might be emitting detectable radio signals. None of the values are really known now and estimates can vary by many orders of magnitude! Indeed, each one of the terms also raises thought provoking questions about nature and ourselves.

(Computer formatting prevents the use of subscripting. In the following equation and definitions the letter(s) following the first letter should actually be subscripts; R(subscript)star, f(subscript)p...)

N = Rstar x fp x ne x fl x fi x fc x L

Where:

N =
  the (estimated) Number of civilizations in our galaxy currently capable of communicating with others. "N" is an estimate since it is the product of estimates.
Rstar =
  the Rate of star formation during the period when our solar system was born. (How are stars born? How long do they live? How do they die?)
fp =
  the fraction of stars with planets. (Are planets routinely formed with stars or is our system a fluke?)
ne =
  the number of planets, per solar system, with an environment suitable for life. (Why are conditions on Earth suitable for life like ours? Why are conditions on other planets in our solar system so hostile?)
fl =
  the fraction of suitable planets on which life actually appears. (Are fertile conditions enough to allow life to get a start?)
fi =
  the fraction of life bearing planets on which intelligence emerges. (Life has been present on Earth for billions of years, but why is intelligence such a recent development?)
fc =
  the fraction of intelligent societies that develop the ability and desire to communicate with other worlds. (We have only had radio communications technology for a few decades. Is the desire to know about the universe a natural outgrowth of intelligence?)
L =
  the Longevity of each technological society in the communicative state. (Do societies develop the ability to destroy themselves or their environment soon after they develop communication technology?)

The product "N" might be a very large number or a very small one. All that we know for certain is that the value is greater-than-or-equal-to 1; after all, we are here and the fact that we can contemplate this is evidence of intelligence. Without quite a bit more information, it would be totally unrealistic to try to discuss each element of the equation in detail. But each variable can generally be used to point out important points about our Universe. Even defining terms like "galaxy" or "intelligence" will broaden student's views.

Classroom Activities

For classroom activities, students can be encouraged to make drawings of "aliens" and their worlds. They can write essays about what the impact of a detection of intelligent life would have on society or themselves, or on what message they would send to aliens. Research in astronomy, biology, geology, sociology, ecology, among a great many other sciences, can be given a SETI context.

Most science fiction stories deal with interactions with aliens. Television and movies often do as well--for example: Star Trek's four series, seven movies, and countless books and short stories. Often the plots involve current social issues. Even most of the cinematographic works featuring Arnold Schwarzenegger deal with interactions with aliens, although the sociological angles are often secondary.

Please remember that, although "N" may be greater than 1, the distances between stars is so great that it might very well be impossible to ever actually visit with aliens. After all, it took Voyager 2 twelve years to reach Neptune. Neptune is four hours away at the speed of light. The nearest star is over four years away at that speed! We may have to be satisfied with radio communications where decades pass between questions and responses.

Contact Information

Few children are disinterested by the idea of extraterrestrial intelligence. Many have had their views distorted by their exposure to supermarket tabloids. It is appropriate to harness their enthusiasm to the constructive use of science and the humanities. For more information, contact the SETI Institute at: 2035 Landings Drive, Mountain View, CA 94043 Tel.: (415) 961-6633.

Lesson Plans and Activities