Why do some scientists think there are aliens?
Good questions. Pierre Kerr, firstname.lastname@example.org, answers it with some help from Paul R.
Of course we've all seen movies about creatures from outer space, but so far no one has actually proven the existance of other intelligent life in the universe. However, some scientists spend a lot of time trying to find life on other planets. In our solar system, Mars appears to be the most promising planet for life to have existed at one time since there's evidence that shows that once water flowed on the surface.
In July and September of 1976, the Viking space crafts landed on Mars and did some experiments to see if there were any forms of life such as bacteria. Soil samples were taken and placed in a sort of soup. It was hoped that if there was life in the soil it would eat the soup and could be detected. Scientists are still not sure of the results. Some scientists believed that the experiment showed that there was life but others said that the experiment was faulty.
More recently, the spacecraft Clementine seems to have discovered water on the moon. Anywhere there is or was water is a good place to look for life.
Some scientists, rather than physically looking for evidence of life, use mathematics to calculate the probability of there being other life in the universe. Put simply, there are so many stars in the univers that there must be lot's of planets like ours and life can form on any of those.
Attached is a document that Paul Reid got from the InterNet that describes something called Drake's equation. Dr. Frank Drake came up with this formula and for almost 20 years, scientists have been discussing what the right values for the variable are. Dr. Drake is now the president of the SETI institute.
If you want to look for more information about extraterristrial life, you could look in the public library for books about SETI, that's an on-going study involving scientists from all over the world. It stands for Search for Extraterrestrial Intelligence.
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