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###### Life on Earth - Are We Alone?

For many years, humans have looked for evidence that life may exist elsewhere in the universe. In this activity you are to locate and evaluate evidence for the existence of life in the Universe beyond Earth.

The first thing to consider is "what is the likelihood that life exists beyond Earth?" Most scientists consider the requirements for life as the most important factors for finding other life forms. Therefore the following must exist: water, an atmosphere, and enough energy. While working at the National Radio Astronomy Observatory in Green Bank, West Virginia, a scientist named Dr. Frank Drake determined how to estimate how many technologically advanced civilizations might be in our galaxy. The equation does not have a definite solution, but it makes an interesting way to consider the topic. Here is the equation and an explanation of how it works:

Don't let this scare you! You don't have to actually DO the math unless you want to. Click on the equation to see what each part represents.

N = R* x fp x ne x fl x fi x fc x L

Just for fun, let's do an example and assume that there are currently 100,000,000,000 stars in the Milky Way. We plug that number into the equation for R*. For our example, we are going to have each of the fractions in the equation equal to 1/100 and assume that each solar system would have only one planet supporting life. Ignoring the length of time signals are released and the fact that stars are constantly dying and being born the equation looks like this:

N = 100,000,000,000 x 1/100 x 1 x 1/100 x 1/100 x 1/100

N = 1000

This means (according to our equation) there could be 1000 planets with technologically advanced civilizations! Could there really be a thousand intelligent civilizations in our galaxy? Is this number too high or two low? Try changing the fractions in the example above to 1/10 and see what happens. Mathematical models like this one are designed to show us that life elsewhere is probable.

Some scientists are searching for evidence that other planets exist. In recent years, astronomers have successfully shown that planets exist around many distant stars. The NASA Space Interferometer Mission (SIM) and Terrestrial Planet Finder Mission (TPFM) are designed to locate more Earth-sized planets around other stars in our galaxy.

One challenge for scientists is determining how life begins on a planet. Theories suggest that, given the right conditions, life may originate as complex combinations of molecules that can find and use energy to make copies of themselves. While progress has been made in combining molecules this way, no life forms have yet been produced in the laboratory.

One area of focus is the study of planets in our solar system to search for direct evidence that life existed in the past. The Mars Rover missions are searching Mars for evidence that past conditions could have supported life. Other missions have studied planets and moons to look for the presence of water. There are even NASA missions which study Earth and allow us to compare the features of Earth to other planets.

One area of exploration on Earth is the collection of evidence of visits by alien life forms to Earth. With the variety of presented evidence, the real challenge for people is to determine which evidence is real and which is less reliable. With this background information you are ready to look for evidence of life may exist elsewhere in the universe.

Materials:

• Library
• Textbooks
• Magazines
• Internet
• Paper
• Pen or pencil
• Computer

Procedure:

1. Search library books, school textbooks, magazines, and/or the Internet for evidence of life on other worlds.
2. Make sure that you write down the reference information for each form of evidence you discover.
3. Monitor your sources to determine the reliability of each source.
4. Possible Internet research sites:

Demonstrate what you know:
Present your knowledge. You may share your information as a written report, poster, multi-media presentation, video, or web page. Share your information with your friends, family, or peers.

This Sci-ber Text was developed by the Utah State Office of Education and Glen Westbroek.